Content area
Present study examines the varying functionalities, antioxidant activities, pasting properties, and profiles of bioactive compounds in the four Kavuni morphotypes. Karuppu Kavuni identified as the superior morphotype, with the highest protein (11.27%), fiber (2.28%), and ash (0.89%) content, along with the highest total phenolic content (1055 mg GAE/100 g), making it an ideal choice for nutrient-dense foods. Karuppu Kavuni (24.3%) and Kavuni Nel (20%) exhibit intermediate amylose content and high gel consistency, while Sivappu Kavuni registers the highest Zn (23.6 ± 0.64 μg/g) and Fe (15.7 ± 0.57 μg/g) content. Pasting properties show that Sivappu Kavuni and Burma Kavuni are best suited for dishes requiring soft, pliable textures, such as puddings and porridges, due to their high breakdown viscosity (BDV) and low setback viscosity (SBV), respectively. In contrast, Karuppu Kavuni’s higher amylose content and high SBV provide greater structural stability, making it more suitable for dishes like rice cakes or sushi. Karuppu Kavuni also stands out with the highest resistant starch content (8.42%), which aids in managing glycemic response, positioning it as a functional food. GC–MS profiling identified 9,12-Octadecadienoic acid (Z, Z) as the major compound in Burma Kavuni (54.52%) and Karuppu Kavuni (50.76%), with potential benefits for reducing coronary heart diseases. Gamma-sitosterol, which has anti-diabetic properties, was detected exclusively in Sivappu Kavuni (4.28%) and Karuppu Kavuni (0.11%). These findings highlight the diverse and valuable applications of Kavuni rice landraces, from managing glycemic response to enhancing culinary uses, making them ideal for both consumer preferences and industry needs.
Introduction
Rice is a staple food and acts as a major vehicle for nutrient delivery to world’s half of the population. Around 90% of the world’s consumption of rice is consumed in Asia, followed by Africa, where it is the fastest-growing dietary staple1. Rice is preferred over other cereals due to its better digestibility, higher nutritional value in terms of minerals, and the absence of gluten2. However, the continuous consumption of polished white rice has led to protein-energy malnutrition, as it is comparatively deficient in protein and essential micronutrients3. Ironically, one out of seven people (14%, 189.2 million) suffer from hidden hunger in India and other developing countries4. Healthy diets remain unaffordable for many underprivileged individuals, where polished rice dominates their carbohydrate-rich diets5. As a result, the diabetic population worldwide is projected to reach 643 million by 2030 and 783 million by 2045 as per the International Diabetes Federation6. This underscores the pressing need to explore rice as a functional food to address global malnutrition and modern lifestyle disorders.
Landraces are known as the “treasure of breeders” as they offer a variety of traits, including cooking, pasting, nutritional, therapeutic attributes and the traits associated with biotic and abiotic stresses7. Pigmented rice landraces contain phytochemicals like phenols, flavonoids, carotenoids, and alkaloids, and have long been utilized in traditional Chinese medicine to address conditions such as anemia, diabetes, and edema, while also promoting better blood circulation, enhancing kidney function, and improving eyesight8. These varieties, known for their anthocyanin pigments and antioxidant properties, are recognized for their high biological value and are classified as functional food ingredients9,10, contributing to overall dietary health11,12. Recently, the cultivation of pigmented rice has gained increasing attention due to its richness in bioactive compounds and associated health benefits13, 14, 15–16. Linear association between pigmented rice consumption and the reduced incidence of coronary heart disease and certain cancers in Asian populations17 has prompted researchers to focus more on the nutritional potential of pigmented rice landraces.
While pigmented rice landraces are known for their high nutritional properties, it is essential to evaluate their overall consumer preference which is determined by a range of factors18,19. Rice quality includes various characteristics such as physical appearance, cooking behaviour, sensory qualities, chemical, functional and nutritional properties, all of which play a role in shaping consumer acceptance20, 21–22. Numerous studies have highlighted the importance of these factors, particularly regarding the nutritional, medicinal, and physicochemical properties, as well as the textural, rheological and pasting properties of rice and its flour23, 24, 25, 26–27. Understanding these factors together is crucial for developing rice varieties that satisfy both nutritional needs and consumer preferences, leading to better market acceptance.
Kavuni rice, a brownish-black medicinal landrace, has gained attention for its bioactive compounds such as flavonoids, anthocyanin, phenolic acids, lutein, and traceable levels of beta-carotene which has anti-diabetic, antioxidant, and anti-arthritic properties28. Its bioactive compounds inhibit alpha-amylase and alpha-glucosidase activity, aiding in managing type 2 diabetes29. Thus, it could be scaled up as functional food ingredients in composite blend with soya, alfalfa, and wheat flour for broader applications in the health food market. However, the market share and production trends of pigmented rice landraces in India, particularly Kavuni, remain underexplored. Despite their promising bioactive properties, pigmented landraces account for a minimal share of the rice production and consumption landscape in developing countries, with increasing interest in functional foods creating potential growth opportunities. Thus, detailed studies are necessary to assess their potential for inclusion in health-focused markets.
Preliminary studies have identified four major morphotypes of Kavuni—Karuppu Kavuni, Sivappu Kavuni, Burma Kavuni, and Kavuni Nel through morphological and molecular characterization. However, a comprehensive evaluation of their nutritive and functional properties is lacking, presenting a clear research gap. Thus, present study focuses on comparing the techno-functional, physico-chemical, and pasting properties of these Kavuni rice morphotypes, with an emphasis on their pharmacological activity and medicinal properties. These insights aim to facilitate the inclusion of Kavuni rice in future breeding programs, enabling the development of nutrient-rich rice varieties with good cooking quality to achieve food and nutritional security, as well as therapeutic benefits for modern lifestyle diseases.
Results and discussion
Characterization of morphotypes
The salient agronomic features of different morphotypes of Kavuni is listed in (Table 1). Karuppu Kavuni possesses purple basal leaf sheath colour and it also registered anthocyanin colouration on leaf blade whereas other morphotypes had green basal leaf sheath colour. The seeds and pericarp colour of Karuppu Kavuni were black in colour while Sivappu Kavuni had red colour. Brown coloured Burma Kavuni and straw coloured Kavuni Nel had black colour pericarp. Karuppu Kavuni and Burma Kavuni were found to have purple stigma rather than white stigma and exhibit photosensitivity. Except Kavuni Nel (77.5 cm), all other morphotypes found as tall in nature. Karuppu Kavuni had highest tiller number/plant (14). Burma Kavuni had highest 1000 grain weight (28.26 g) followed by Sivappu Kavuni.
Table 1. Details on different agronomic features, cooking quality parameters, protein, fibre, ash, mineral, phenolic content and antioxidant activity of Kavuni morphotypes studied.
Traits | Karuppu Kavuni | Burma Kavuni | Sivappu Kavuni | Kavuni Nel |
|---|---|---|---|---|
Basal leaf sheath colour | Purple | Green | Green | Green |
Leaf blade: P/A of anthocyanin colouration | Present | Absent | Absent | Absent |
Seed colour | Black | Brown (tawny) | Red | Straw |
Pericarp colour | Black | Black | Red | Black |
Lemma: Colour of apiculus | Purple | Purple | Red | Straw |
Stigma colour | Purple | Purple | White | White |
Days to 50% flowering | 88 | 91 | 84 | 96 |
Plant height (cm) | 115.3 | 115.5 | 147.5 | 77.5 |
Panicle number/plant | 14 | 8 | 12 | 12 |
Panicle length (cm) | 24.5 | 26.0 | 28.5 | 27.5 |
1000 grain weight (g) | 25.98 | 28.26 | 26.81 | 19.85 |
Photosensitive type | Photo sensitive | Photo insensitive | Photo sensitive | Photo insensitive |
KL (mm) | 6.8 ± 0.12a | 6.9 ± 0.14a | 6.5 ± 0.06b | 6.3 ± 0.11b |
KB (mm) | 2.5 ± 0.04a | 2 ± 0.01c | 2.5 ± 0.02a | 2.1 ± 0.03b |
L/B ratio | 2.72 ± 0.05c | 3.45 ± 0.15a | 2.6 ± 0.05c | 3 ± 0.11b |
KLAC (mm) | 9.9 ± 0.25a | 8.5 ± 0.18c | 9.4 ± 0.05b | 10.1 ± 0.38a |
KBAC (mm) | 3.3 ± 0.05a | 2.9 ± 0.12b | 2.9 ± 0.05b | 2.9 ± 0.08b |
LER | 1.5 ± 0.02a | 1.2 ± 0.04d | 1.4 ± 0.04c | 1.6 ± 0.01a |
ASV | 5 ± 0.01b | 3 ± 0.06c | 5 ± 0.08b | 7 ± 0.21a |
GC (mm) | 111 ± 3.70a | 58 ± 1.41d | 82 ± 0.59c | 105 ± 1.33b |
Amylose (%) | 24.3 ± 0.64a | 19 ± 0.33c | 19.8 ± 0.73bc | 20 ± 0.16b |
Resistance starch (%) | 8.42 ± 0.30a | 5.97 ± 0.21c | 6.47 ± 0.02b | 4.13 ± 0.13d |
Total starch (%) | 64.14 ± 2.60c | 84.06 ± 0.30a | 72.05 ± 2.66b | 73.77 ± 2.33b |
Total protein (%) | 11.27 ± 0.06a | 10.06 ± 0.07b | 9.62 ± 0.26c | 10.15 ± 0.11b |
Crude fibre (%) | 2.28 ± 0.05a | 1.56 ± 0.04c | 1.38 ± 0.02d | 1.93 ± 0.07b |
Ash content (%) | 0.89 ± 0.02a | 0.56 ± 0.02c | 0.5 ± 0.02d | 0.77 ± 0.03b |
Phosphorous (%) | 0.277 ± 0.01a | 0.243 ± 0.01b | 0.27 ± 0.01a | 0.193 ± 0.01c |
Potassium (%) | 1.346 ± 0.04a | 1.123 ± 0.03c | 1.098 ± 0.03c | 1.264 ± 0.03b |
Sulphur (%) | 0.95 ± 0.03a | 0.826 ± 0.02b | 0.874 ± 0.01b | 0.856 ± 0.04b |
Calcium (%) | 0.818 ± 0.02a | 0.585 ± 0.02c | 0.655 ± 0.01b | 0.68 ± 0.02b |
Magnesium (%) | 0.475 ± 0.01a | 0.333 ± 0.01b | 0.345 ± 0.01b | 0.33 ± 0.01b |
Zn (μg/g) | 18.8 ± 0.29b | 18.4 ± 0.1b | 23.6 ± 0.64a | 11.7 ± 0.28c |
Fe (μg/g) | 11.5 ± 0.04c | 12.6 ± 0.44b | 15.7 ± 0.57a | 11.7 ± 0.06c |
Total phenolic content (mg GAE/100 g) | 1055 ± 20.92a | 866 ± 5.46b | 687 ± 22.29c | 888 ± 25.61b |
DPPH scavenging ability (%) | 88.63 ± 1.76a | 88.15 ± 2.15a | 83 ± 2.62b | 82.11 ± 0.37b |
KL kernel length, KB kernel breadth, KLAC kernel length after cooking, KBAC kernel breadth after cooking, LER linear elongation ratio, ASV alkali spreading value, GC gel consistency, Zn zinc, Fe iron, DPPH 2,2-diphenyl-1-picrylhydrazyl. Values with the different letters are significantly different from each other (p > 0.05) by Duncan’s multiple range test.
Cooking properties of Kavuni types
The kernel length of the studied rice morphotypes ranged from 6.3 to 6.9 mm, while the kernel breadth ranged from 2.0 to 2.5 mm. Based on the standard evaluation system30, Sivappu Kavuni and Kavuni Nel were categorized under the medium grain group, whereas Karuppu Kavuni and Burma Kavuni, with kernel lengths exceeding 6.6 mm, fell into the long length category. The length-to-breadth ratio (LBR) ranged from 2.6 to 3.42 among the morphotypes. While Burma Kavuni was classified as slender due to its LBR exceeding 3.0, the other three morphotypes were categorized as medium, with LBR values between 2.1 and 3.0. Consequently, Burma Kavuni was classified as a long slender type, while the other morphotypes were categorized as long bold types based on kernel length and LBR.
The elongation ratio, a critical attribute influencing rice cooking properties, is a key determinant of consumer preference. Typically, consumers favor lengthwise elongation over breadthwise elongation31. In this study, Kavuni Nel exhibited the highest cooked kernel length (10.1 mm), followed by Karuppu Kavuni (9.9 mm). Breadthwise elongation did not vary significantly among the morphotypes; however, Kavuni Nel ranked highest in linear elongation ratio (LER) with a value of 1.6, while Burma Kavuni had the lowest LER. The alkali spreading value (ASV), an indirect indicator of gelatinization temperature (GT), categorized the morphotypes into low (Kavuni Nel) and intermediate GT groups. Intermediate GT rice is often preferred by consumers, as high GT varieties tend to become overly soft when overcooked32. Gel consistency (GC), which measures the hardness of cooked rice and depends on amylopectin fraction variations in the grain endosperm33, ranged from 58 to 111 mm among the morphotypes. All morphotypes, except Burma Kavuni, had GC values above 60 mm, placing them in the soft gel group, while Burma Kavuni exhibited medium gel consistency.
Amylose and resistant starch
Amylose content and resistant starch (RS) are two critical factors influencing the digestibility and glycemic response of rice. These components slow down starch breakdown and promote a controlled release of glucose into the small intestine, making them beneficial for managing blood sugar levels, particularly in diabetic patients. Resistant starch provides zero calories during digestion and offers significant health benefits, including reducing glycemic index (GI) and insulin response34. Amylose content in rice grains is categorized into waxy (0–2%), very low (3–8%), low (9–19%), intermediate (20–25%), and high (> 25%). Among the Kavuni morphotypes, Karuppu Kavuni (24.30%) and Kavuni Nel (20.00%) exhibited intermediate amylose content, while other morphotypes fell into the low amylose category. Amylose content is positively correlated with gelatinization temperature (GT) and plays a significant role in determining cooking quality and starch digestibility. Additionally, Karuppu Kavuni and Kavuni Nel demonstrated high gel consistency (GC) values, reflecting their desirable cooking properties.
Resistant starch normally constitutes around 3% of rice grains35, and its content in Kavuni morphotypes ranged from 4.13 to 8.42%. Karuppu Kavuni ranked highest in RS content (8.42%), followed by Sivappu Kavuni (6.47%). Foods with higher RS content are digested more slowly, resulting in a lower glycemic index, which is beneficial for individuals with type II diabetes36. RS and GI exhibit a negative correlation, while RS and amylose content show a positive correlation37,38. In comparison, Kavuni morphotypes had significantly higher RS levels, indicating their potential as functional foods for diabetic patients. Despite Karuppu Kavuni’s superior RS content, total starch content was highest in Burma Kavuni (84.06%), followed by Kavuni Nel (73.77%). These findings highlight the nutritional advantages of Kavuni morphotypes, especially Karuppu Kavuni, as a healthier rice option for managing glycemic response.
Protein, fibre and ash content
Rice’s nutritional quality depends on its protein content, which provides essential amino acids and helps address protein deficiency, making it vital for human diets39. Notably, all the Kavuni morphotypes studied exhibited high protein content (> 9%). Among them, Karuppu Kavuni recorded the highest protein content (11.27%), followed by Kavuni Nel (10.15%), Burma Kavuni (10.06%), and Sivappu Kavuni (9.62%) (Table 1). Protein in rice contributes not only to its nutritional value but also to its functional properties in various food applications, such as rice-based weaning foods and protein-enriched snacks.
The fiber content of rice, though generally low in milled rice (0.5–1.0%)40, is a vital dietary component for maintaining human health. The fiber content of the Kavuni morphotypes ranged from 1.38% in Sivappu Kavuni to 2.28% in Karuppu Kavuni, exceeding the standard levels found in conventional milled rice. Dietary fiber is known to offer numerous health benefits, such as improving bowel regularity, lowering cholesterol levels and regulating intestinal pH41. Furthermore, higher fiber content enhances the satiety value of rice, making it suitable for weight management diets. Ash content, an indicator of the mineral composition in rice, ranged from 0.5% to 0.89%. Karuppu Kavuni exhibited the highest ash content, followed by Kavuni Nel. These attributes make Karuppu Kavuni and the other Kavuni morphotypes valuable for consumers seeking nutrient-dense food.
Minerals
Minerals play a vital role in supporting metabolic functions and are necessary elements of a well-balanced diet. The range of minerals such as phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg) were recorded as 0.193 to 0.277%, 1.098 to 1.346%, 0.826 to 0.950%, 0.585 to 0.818%, and 0.330 to 0.475%, respectively. Amid the major minerals, Karuppu Kavuni exhibited the highest percentage of potassium (1.346%), followed by sulfur (0.95%), calcium (0.818%), magnesium (0.475%), and phosphorus (0.277%), surpassing other morphotypes in mineral composition. The elevated levels of K, Ca, and Mg in Karuppu Kavuni could play a significant role in improving muscle activity, particularly in patients experiencing muscle wasting42. Zinc (Zn) and iron (Fe) are essential micronutrients that promote immunity, wound healing, and nervous system development, and act as cofactors for metabolic enzymes. In this study, Zn content ranged from 17.8 to 23.6 μg/g, while Fe content ranged from 11.5 to 15.7 μg/g. Among the Kavuni morphotypes, Sivappu Kavuni exhibited the highest Zn (23.6 μg/g) and Fe (15.7 μg/g) content.
Total phenolic content (TPC)
Phenolic compounds, recognized as potent antioxidants in rice seeds, have been reported to play a significant role in reducing the risk of cardiovascular diseases43. They achieve this by lowering blood cholesterol levels and preventing atherosclerosis through the inhibition of low-density lipoprotein (LDL) oxidation. Additionally, phenolic compounds are associated with anti-carcinogenic, anti-mutagenic, and anti-metastatic activities, further emphasizing their importance in promoting human health44.
In the present study, Karuppu Kavuni recorded the highest total phenolic content (TPC) at 1055 mg GAE/100 g, followed by Sivappu Kavuni with 687 mg GAE/100 g. Among the morphotypes, black rice exhibited the highest TPC, ranging from 866 to 1055 mg GAE/100 g, significantly surpassing the red rice morphotype. These findings align with the observations of Nayeem et al.45, who reported a TPC of 730 mg GAE/100 g in black rice, compared to 650–680 mg GAE/100 g in red rice. Similarly, Murdifin et al.46 demonstrated that black rice consistently possesses higher TPC than red rice. The superior phenolic content in black rice, including Karuppu Kavuni, underscores its potential as a functional food ingredient, contributing to health benefits such as reducing oxidative stress and mitigating the risk of chronic diseases. This makes it a valuable dietary choice for promoting overall well-being.
Antioxidant property
The ability to scavenge free radicals is a vital indicator of antioxidant properties in rice bran. Among the various methods available, the DPPH radical-scavenging assay is widely regarded as one of the simplest and most effective. This assay evaluates antioxidant activity based on the transfer of electrons from a donor molecule to neutralize free radicals. In the present study, Karuppu Kavuni exhibited the highest scavenging ability (88.63%), followed by Burma Kavuni (88.15%) and Sivappu Kavuni (83.00%). Our findings are consistent with the reports of Ghasemzadeh et al.47, Sompong et al.12, and Pengkumsri et al.48, who noted that black rice extracts exhibited superior DPPH activity compared to red and brown rice extracts. This enhanced antioxidant capacity in black rice is attributed to its higher levels of anthocyanins and phenolic compounds, which are potent natural antioxidants. Such findings highlight the potential of pigmented rice varieties, particularly Kavuni morphotypes, as a valuable source of bioactive compounds for promoting health and preventing oxidative stress-related disorders.
Ultrastructure of starch granules
The starch samples of Kavuni morphotypes were morphologically compared with SEM (Fig. 1). The flours of Karuppu Kavuni and Burma Kavuni possess the loosely packed irregular spherical shape granules whereas Sivappu Kavuni had round shape granules. Kavuni Nel had compactly packed polygon shape starch granules. Starch granules of Karuppu Kavuni were smooth, whereas the granules of Burma Kavuni and Sivappu Kavuni possess the pitted surface. The uniform starch granules were highly suitable for milling49. Kavuni Nel is highly suitable for milling as it possesses harder and uniform starch granule with surface with low damaged starch content than other morphotypes. All the morphotypes except Kavuni Nel were observed as chalky it might be due to the air space between the starch granules which induce low grain hardness.
Fig. 1 [Images not available. See PDF.]
Morphological structure of starch granules of four different morphotypes of Kavuni.
Pasting properties
Rapid visco analyzer, a proven tool to access the pasting properties viz., pasting viscosity (PV), trough viscosity (TV), breakdown viscosity (BDV), final viscosity (FV) and setback viscosity (SBV) of starch which directly influences the cooking quality of rice and rice products26,50. Pasting properties of rice flours serve as essential parameters for determining their suitability in diverse food applications, including evaluating the quality of cooked rice, rice cakes, rice bread, and rice-based extruded products26,51. Sivappu Kavuni exhibited the highest PV, TV and BDV, followed by Karuppu Kavuni. However, Sivappu Kavuni had a low PT while Kavuni Nel displayed the opposite trend (Table 2). The high PV and TV observed in Sivappu Kavuni and Karuppu Kavuni suggest that these morphotypes possess excellent water absorption and starch swelling capacities, leading to a higher viscosity during the gelatinization process52,53. However, starches with high peak viscosity are often associated with high breakdown values, indicating weak gel structures51. This positive correlation between PV and BDV suggests that such starches are prone to breakdown under prolonged shear and heat, resulting in reduced stability. However, such properties make these starches ideal for liquid and soft-textured food products, such as gravies, salad dressings, puddings, and soft cakes, where a creamy texture and quick thickening are desirable54. In contrast, Kavuni Nel, with its higher PT and lower PV, TV, and BDV, indicates greater resistance to gelatinization and higher thermal stability. This suggests a slower water absorption process and reduced swelling of starch granules, making it better suited for products requiring prolonged cooking or structural stability, such as noodles, baked goods, or extruded snacks.
Table 2. Pasting property analysis through RVA.
Genotypes | PV (cP) | TV (cP) | BDV (cP) | FV (cP) | SBV (cP) | PT (min) |
|---|---|---|---|---|---|---|
Karuppu Kavuni | 3516 ± 352.18 | 2339 ± 455.82 | 1178 ± 103.63 | 5245 ± 1211.28 | 2907 ± 755.46 | 84.4 ± 0.65 |
Burma Kavuni | 2516 ± 507.49 | 1930 ± 387.98 | 586 ± 119.51 | 3088 ± 793.28 | 1158 ± 405.30 | 83.3 ± 0.01 |
Sivappu Kavuni | 3851 ± 357.67 | 2424 ± 291.56 | 1427 ± 66.11 | 5106 ± 424.64 | 2682 ± 133.08 | 77.5 ± 1.89 |
Kavuni Nel | 1513 ± 51.38 | 1522 ± 275.68 | 506 ± 72.46 | 3471 ± 744.78 | 1950 ± 469.10 | 84.4 ± 0.65 |
PV pasting viscosity, TV trough viscosity, BDV breakdown viscosity, FV final viscosity, SBV setback viscosity, PT pasting temperature.
Burma Kavuni exhibited the lowest SBV and FV, which are indicative of good cooking quality. A low SBV suggests that the rice remains soft and does not harden upon cooling, a desirable trait for culinary applications55. SBV reflects the tendency of starches in rice flours to reassociate and retrograde upon cooling. It is a critical parameter that correlates with the gelling ability of starches to form semi-solid pastes. The amylose content of rice plays a significant role in influencing these pasting properties. Specifically, amylose content is directly proportional to SBV56 and inversely related to breakdown viscosity (BDV)57. The higher amylose content observed in Karuppu Kavuni contributes to its high SBV. Higher SBV indicates a greater propensity for retrogradation, which can lead to firmer and less stable gels51. Starches with low SBV and FV are often associated with good cooking quality, as they produce softer rice that retains its palatability and texture after cooling55. Moreover, high BDV is positively correlated with good gel consistency, enhancing the mouthfeel and structural integrity of rice-based dishes. In this study, Sivappu Kavuni (high BDV) and Burma Kavuni (low SBV and FV) were identified as superior cooking quality morphotypes and represent ideal choices for consumers and industries prioritizing soft-textured rice with high culinary versatility59. These traits make them ideal for applications requiring soft, pliable textures, such as puddings, porridges, or steamed rice dishes. Conversely, the high SBV observed in Karuppu Kavuni, driven by its higher amylose content, indicates a firmer texture upon cooling, which may be more suitable for dishes requiring structural stability, such as rice cakes or sushi.
Metabolome profiling
Four Kavuni morphotypes were subjected to metabolome analysis using GC–MS. A total of 104 compounds were detected from the four morphotypes using chromatographic analysis of the grain metabolome. Amid four morphotypes analysed, Kavuni Nel had highest compounds (47) followed by Karuppu Kavuni (43), Sivappu Kavuni (41) and Burma Kavuni (37) (Fig. 2). With the help NIST library, the unknown components spectrum was compared with the known spectrum of components and the name, chemical formula, structure and molecular weight were found. 9,12-Octadecadienoic acid (Z,Z)- (50.76%), n-Hexadecanoic acid (16.58%), Tetradecanoic acid (2.62%), Methyl linolelaidate (2.37%) and Eicosyl 2-ethylbutanoate (2.22%) were the major compounds ascertained in Karupu Kavuni (Supplementary Table S1) which contributing 74.55% of total compounds identified. 9,12-Octadecadienoic acid (Z,Z)- was identified as a major compound of Burma Kavuni (Supplementary Table S2) with 54.52% followed by n-Hexadecanoic acid (31.52%), Methyl linolelaidate (2.66%), 9-Octadecenoic acid, methyl ester, (E)- (2.14%) and Ethyl Acetate (2.05%). These five major compounds were corresponding to 92.89% of total compounds found. Five major compounds of Sivappu Kavuni (Supplementary Table S3) Viz., 9,12-Octadecadienoic acid (Z, Z)- (26.14%), Isopropyl peroxide (19.49%), n-Hexadecanoic acid (12.22%), Gamma-Sitosterol (4.28%) and Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester (4.02%) were accorded 66.15% of total compounds discovered. In case of Kavuni Nel (Supplementary Table S4), 9-Octadecenoic acid, (E)- (22.07%), Ethyl Acetate (18.25%), n-Hexadecanoic acid (13.21%), 9,12-Octadecadienoic acid (Z,Z)- (9.47%) and Methyl linolelaidate (3.12%) were identified as the major compounds contributing 66.12%.
Fig. 2 [Images not available. See PDF.]
GC–MS chromatogram of methanol extract of (a) Karuppu Kavuni (b) Burma Kavuni (c) Sivappu Kavuni and (d) Kavuni Nel grains.
The number of metabolites commonly present or differing among the four morphotypes was studied and is shown using a Venn diagram (Fig. 3, Supplementary Table S5). All four morphotypes showed 12 metabolites in common, and each landrace had its own special metabolites. A Venn diagram showed that 25 metabolites were specific to Kavuni Nel, 18 to Sivappu Kavuni, 17 to Burma Kavuni, and 16 to Karuppu Kavuni.
Fig. 3 [Images not available. See PDF.]
Venn diagram showing number of the commonly shared and differing metabolites among the four Kavuni morphotypes.
The MetaboAnalyst software was used to conduct MSEA to observe the trends of the main chemical class sets. Figure 4 shows that fatty acyls, pyridines and derivatives and benzene and substituted derivatives were the most common chemical classes found in the Kavuni morphotypes. Colors of the bar chart are based on p-value. For dot plot, the color and size of each circle are based on p-value and the enrichment ratio, respectively. A pathway topology analysis was conducted to determine the prominent metabolic pathways, and the results identified a total of 25 important metabolic pathways which were depicted in bubble chart (Fig. 5). Fatty acid biosynthesis pathway had the highest log (p) value of 4.1533 followed by cutin, suberine and wax biosynthesis pathway with 2.6713 and the unsaturated fatty acid biosynthesis pathway with a value of 2.3361 (Supplementary Table S6). Cutin, suberine and wax biosynthesis, pyruvate metabolism, glycerolipid metabolism, glycolysis, valine, leucine and isoleucine biosynthesis, carbon fixation in photosynthetic organisms, fatty acid biosynthesis, cysteine and methionine metabolism and biosynthesis of unsaturated fatty acids pathways had a higher impact value. Living organisms undergo complex metabolic processes that are regulated by several genes and proteins. These components interact together to create complex networks and pathways that regulate and influence one another’s functions60. To explain the differently expressed metabolites in each of the Kavuni morphotypes, we painstakingly mapped out and arranged pathways in our analysis.
Fig. 4 [Images not available. See PDF.]
Overview of metabolite sets identified from Kavuni morphotypes. Each colour and size are determined by p-value and the enrichment ratio, respectively.
Fig. 5 [Images not available. See PDF.]
Metabolic pathways identified among the Kavuni morphotypes. An individual metabolic pathway is represented by each bubble in the plot, and the abscissa and bubble size together show the amount of the pathway’s impact factors in the topological analysis. (A). Cutin, suberine and wax biosynthesis (B). Pyruvate metabolism (C). Glycerolipid metabolism (D). Glycolysis/Gluconeogenesis (E). Valine, leucine and isoleucine biosynthesis (F). Carbon fixation in photosynthetic organisms (G). Fatty acid biosynthesis (H). Cysteine and methionine metabolism (I). Biosynthesis of unsaturated fatty acids.
The current study was carried out to decipher the grain metabolome of the well-known nutritious and therapeutic rice varieties. Profiling of the bioactive compounds in pigmented landraces are the prerequisite to be utilized in the breeding programmes. Pigmented rice grains are rich in both primary and secondary metabolites. Primary metabolites help in the production of macromolecules required for yield and quality attributes. A wide variety of secondary metabolites, including phenolic acids, flavonoids, terpenoids, steroids, and alkaloids in rice exhibit beneficial properties for humans, including antioxidant, anti-inflammatory, cytotoxic, anti-tumor, and neuroprotective properties60.
Fatty acids are a class of lipids that are important sources of energy as well as having important structural, functional, and biological roles. Polyunsaturated fatty acids, including omega-3, omega-6, and omega-9, which are present in traditional rice varieties, cannot be synthesised by the human body. The risk of cardiovascular disease and blood cholesterol levels can be decreased by omega-3 and omega-6 fatty acids61. 9,12-Octadecadienoic acid (linoleic acid) is one of the significant omega-6 fatty acids present predominantly in Burma Kavuni (54.52%) followed by Karuppu Kavuni (50.76%) and Sivappu Kavuni (26.14%). The identified major bioactive compounds with their biological activity were listed in (Table 3). Monounsaturated fatty acids like oleic acid can lower blood cholesterol, increase the permeability of cell membranes, and protect against arteriosclerosis and cardiac blockage60,62. Oleic acid (0.14%) was accumulated only in Burma Kavuni. The two fatty acids, oleic and linoleic acid, which together account for 75% of the unsaturated fats in rice bran oil, are mostly in charge of lowering cholesterol levels63. Furthermore, a plethora of research has demonstrated that these two naturally occurring fatty acids mitigate the risk of coronary heart disease64,65. Therefore, consuming Burma Kavuni and Karuppu Kavuni, linoleic and oleic rich morphotypes, on a regular basis may protect against coronary heart disease.
Table 3. List of the Bioactive compounds identified through GC–MS profiling.
Compound name | Compound class | Structure | Biological activity | References |
|---|---|---|---|---|
9,12-Octadecadienoic acid (Z,Z)- | Fatty acid | Reduces coronary heart diseases (CHD), Anti-inflammatory, nematicide, hypocholesterolemic, hepatoprotective, insectifuge, antihistaminic, antieczemic, antiacne, 5-Alpha reductase inhibitor, antiandrogenic, antiarthritic | 69 81 | |
n-Hexadecanoic acid | Fatty acid | Throat disorders, anti-asthmatics, anti-pruritic, anti-psoriatic, anti-epileptics, anti-convulsant, anti-migraine and increases the risk of cardiovascular diseases | 68 69 | |
Tetradecanoic acid | Fatty acid | Antitumor activity, anti-spasmodic, anti-asthmatics, Antifungal, nematicide, Lubricant, Antioxidant, hypercholesteraemic | 70 | |
9-Octadecenoic acid, methyl ester, (E)- | Fatty acid | 5-Alpha-Reductase-Inhibitor, Anemiagenic, Antialopecic, Antiandrogenic, Antiinflammatory, Antileukotriene-D4 (Anti-platelet activating factor), Choleretic, Dermatitigenic Flavor, Perfumery, Propecic, Hypocholesterolemic, Insectifuge Irritant, Percutaneostimulant, | 69 | |
Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester | Fatty acid ethyl ester | Antioxidant | 71 | |
Hexadecanoic acid, methyl ester | Fatty acid methyl ester | Anti-oxidant, decrease blood cholesterol, anti-inflammatory, hypocholesterolemic nematicide, pesticide, antiandrogenic flavor, hemolytic, 5-Alpha reductase inhibitor | 70 | |
7,9-Di-tert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione | Flavonoids | Antioxidant | 71 | |
2,4-di-tert-butylphenol | Benzene and substituted derivatives | Antioxidant, Antifungal | 72 | |
Diethyl Phthalate | Benzene and substituted derivatives | Antifungal, Antimicrobial | 74 | |
Dibutyl phthalate | Benzene and substituted derivatives | Antimicrobial | 75 | |
Gamma-Sitosterol | Phytosterols | Anti-diabetic | 73 | |
Oleic acid | Fatty acid | Reduces cardiovascular risk by reducing blood cholesterol | 65 | |
L-( +)-Ascorbic acid 2,6-dihexadecanoate | Vitamin | Antiallergic, Antianemic, Antianxiety, Antibacterial, Antibronchitic, Anticarcinogenic, Anticataract, Anticoagulant, Anticonvulsant, Antidiabetic | 82 |
Tetradecanoic acid, a long-chain saturated fatty acid which is also called myristic acid directly influences pathways that control important metabolic processes in the human body as well as post-translational protein changes66. Tetradecanoic acid was found three times higher in Karuppu Kavuni than that of other morphotypes. The amount of omega-3 long-chain fatty acids in plasma phospholipids is increased by modest myristic acid ingestion, which may improve human cardiovascular health indicators67. n-Hexadecanoic acid (Palmitic acid) can increases the risk of cardiovascular diseases68. The highest percent (31.52%) of n-Hexadecanoic acid was ascertained two-fold higher in Burma Kavuni than of other morphotypes. Compared to the previous study64, pigmented rice varieties studied possess two to three times lower level of palmitic acid than the non-pigmented varieties. Therefore, consumption of traditional rice grains that have been pigmented may shield consumers against cardiovascular diseases.
9,12-Octadecadienoic acid (Z, Z), Tetradecanoic acid and 9-Octadecenoic acid, methyl ester, (E)- was found to have properties that may help reduce coronary heart diseases69,70. Tetradecanoic acid, Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester, methyl ester, 7,9-Di-tert-butyl-1-oxaspiro [4.5] deca-6,9-diene-2,8-dione, and 2,4-Di-tert-butylphenol helps to reduce oxidative stress71,72. Flavonoid 7,9-Di-tert-butyl-1-oxaspiro [4.5] deca-6,9-diene-2,8-dione was found higher in Kavuni Nel (0.29%) and Sivappu Kavuni (0.28%). Gamma-sitosterol possess anti-diabetic properties73 that predominantly present in Sivappu Kavuni (4.28%) which was 39 folds greater than Karuppu Kavuni (Table 4). Benzene and substituted derivatives of Diethyl phthalate74 and dibutyl phthalate75 act as an anti-microbial agent whereas 2,4-Di-tert-butylphenol serves as an anti-fungal compound72.
Table 4. Comparative profiling of different bioactive compounds in Kavuni morphotypes.
S. no | Compound name | Area (%) | |||
|---|---|---|---|---|---|
Karuppu Kavuni | Burma Kavuni | Sivappu Kavuni | Kavuni Nel | ||
1. | 9,12-Octadecadienoic acid (Z,Z)- | 50.76 | 54.52 | 26.14 | 9.47 |
2. | n-Hexadecanoic acid | 16.58 | 31.52 | 12.22 | 13.21 |
3. | Tetradecanoic acid | 2.62 | 0.89 | 0.9 | 0.27 |
4. | 9-Octadecenoic acid, methyl ester, (E)- | 1.62 | 2.14 | 1.64 | 2.21 |
5. | Hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester | 0.39 | 1.06 | 4.02 | 6.82 |
6. | Hexadecanoic acid, methyl ester | 0.96 | 0.57 | 3.02 | 2.53 |
7. | 7,9-Di-tert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione | 0.17 | 0.07 | 0.28 | 0.29 |
8. | 2,4-di-tert-butylphenol | 0.05 | 0.03 | 0.07 | 0.19 |
9. | Diethyl phthalate | 0.06 | 0.02 | 0.29 | 0.12 |
10. | Dibutyl phthalate | 0.06 | 0.12 | 0.19 | 0.21 |
11. | Gamma-sitosterol | 0.11 | – | 4.28 | – |
12. | Oleic acid | – | 0.14 | – | – |
13. | L-( +)-Ascorbic acid 2,6-dihexadecanoate | – | – | 2.6 | – |
Conclusion
The present study aimed to explore the biochemical and therapeutic properties of traditional Kavuni morphotypes, revealing their remarkable nutritional and health-promoting potential. Kavuni morphotypes demonstrated significantly higher levels of protein, fiber, ash, amylose, and bioactive compounds compared to widely consumed polished rice. These unique attributes suggest that Kavuni rice offers significant health benefits, including mitigating oxidative stress, managing diabetes, and contributing to a balanced diet. Additionally, the high resistant starch content and phenolic compounds further highlight its potential role in reducing the risk of chronic diseases such as cardiovascular disorders. Landraces like Kavuni serve as invaluable reservoirs of genetic diversity, housing numerous beneficial traits. However, their widespread adoption faces challenges due to limitations such as poor agronomic performance, photosensitivity, and low yield potential compared to modern high-yielding varieties. Addressing these challenges requires strategic approaches, including the introgression of Kavuni’s desirable traits into mega varieties to enhance their nutritional and therapeutic value without compromising yield. This study underscores the potential of Kavuni morphotypes as donors for genetic studies, trait mapping, and targeted improvement programs. Future efforts should prioritize leveraging molecular breeding and genomic tools to unravel the genetic basis of these traits. Additionally, exploring the pharmacological properties of Kavuni rice could pave the way for developing therapeutic rice varieties with superior nutritional profiles and enhanced agronomic performance. By integrating traditional biodiversity with modern breeding techniques, Kavuni morphotypes could contribute to addressing the dual challenges of nutritional security and sustainable agriculture.
Methods
Plant materials
Four distinct Kavuni morpho-types namely, Karuppu Kavuni, Burma Kavuni, Sivappu Kavuni and Kavuni Nel (Fig. 6) were utilized in the present study (Table 5). All the four Kavuni morpho-types seeds used in the current study are owned by Tamil Nadu Rice Research Institute (TRRI), Aduthurai, Tamil Nadu, India. Experimental research and field studies on plants, including the collection of plant materials in the current study, was carried out in compliance with relevant institutional, national and international guidelines and legislation. Field experiments were carried out in a paddy field in the TRRI, Aduthurai (10.99° N and 79.48° E) during Kharif 2020. A 21-day old seedlings were transplanted as two seedlings per hill with three replications in randomized block design with spacing of 20 × 20 cm. The recommended package of practices for rice was followed for the proper establishment and growth of the crop. The salient agronomic features of the selected morphotypes on 12 characters were recorded. The well dried seeds were dehusked using hulling machine and powdered for the analysis of nutritive compounds identification.
Fig. 6 [Images not available. See PDF.]
Morphological features of panicle and grain types of Kavuni morphotypes.
Table 5. List of the plant materials used and its features.
Kavuni morphotypes | Accession number# | Plant type | Special features |
|---|---|---|---|
Karuppu Kavuni | ADLR-20 | Landrace, cultivated | Best for puttu preparation, grow well in sodic and water logged soils. At maturity the grains are black interspersed with light yellow colour |
Burma Kavuni | ADLR-03 | Landrace, cultivated | High fibre, suitable for alkaline soils and sustain in water logged conditions. Photo insensitive, long slender grain longer than Karuppu kavuni |
Sivappu Kavuni | ADLR-27 | Landrace, cultivated | Red rice, Bold grain rich in antioxidant. It is a multipurpose rice suitable for consumption as tiffin, sweets and savouries. Suitable for water stagnated condition and alkaline soil |
Kavuni Nel | ADLR-29 | Landrace, Cultivated | Black rice. Suitable for flaked rice. Suitable for both transplanted and direct sowing |
#Accession number of the germplasms conserved at Tamil Nadu Rice Research Institute, Aduthurai, Tamil Nadu, India.
Cooking parameters
Kernel length, kernel breadth and length breadth ratio were measured using graph sheet and the mean was expressed in millimeters (mm). Based on average length, kernels were classified using Standard Evaluation System (IRRI, 1996). Kernel length, breadth after cooking and linear elongation ratio were calculated. Gel consistency and alkali spreading value were also estimated33
Proximate chemical analysis
Grain protein estimation
Grain protein, crude fibre and ash content were estimated according to standard methods of AOAC76. Micro Kjeldhal method using KELPLUS automatic nitrogen estimation system were used to determine grain protein content. A 200 mg of rice flour were added with 3 g of catalyst mixture in digestion flask followed by 10 ml of conc. H2SO4. The samples were digested in the tube for 3 h at 420 °C and then cooled. 40 ml of water added to the cooled digestion tube and kept it for distillation around 8 min. During this time boric acid + double indicator turns from brick red colour to green colour. Titrated the mixture against 0.1 N H2SO4 (colour changes from green to brick red). Percentage of nitrogen (N) was calculated using the following equation: where (S–B) = Titration value, D = Dilution factor, W = weight of sample, V = volume of the sample, 0.014 = Constant value.
Crude protein was estimated using the formula
Crude fibre estimation
FIBRA PLUS automatic fibre estimation system was used to estimate the crude fibre content in samples as per the method described in AOAC76 method No. 32-10. Difference in weight of the sample before and after ash gives the weight of crude fibre.
Ash content estimation
The ash content was estimated by following the methodology developed by AOAC76 method No. 08-01. The ash content in each rice flour sample was estimated by keeping samples in a muffle furnace at a temperature 550 °C till white, grey residue is obtained.
Amylose content estimation
Amylose content of Kavuni morphotypes were analysed using the method of Juliano33 with slight modifications. In brief, 10 ml (1 ml of 95% ethanol + 9 ml sodium hydroxide) mixture were added into 100 mg rice flour and this mixture was heated in water bath and cooled down for 1 h. The final volume of 100 ml was made up with the help of distilled water. 5 ml of this aliquot was taken and 1 ml of acetic acid (1 N) and 2 ml of freshly prepared iodine solution were added into it. Absorbance of the solution was measured at 620 nm after 20 min of incubation.
Resistant starch (RS) estimation
Megazyme kit (Megazyme International Ireland Ltd, Bray, Ireland) was used to estimate the RS content. A 100 mg of rice flour was digested with 4 ml of pancreatic alpha amylase (10 mg/ml) containing amyloglucosidase (3300U/ml) and kept it in water bath for 16 h at 37 °C, with shaking at 100 strokes/min. A 4 ml of ethanol (99.00%) added into the mixture and centrifuged 1107 g for 10 min. The pellet was suspended with 8 ml of 50% ethanol and then centrifuged at 3000 rpm for 10 min. The supernatant was decanted and pellet was resuspended with 2 ml of 2 M KOH and kept the tube immediately in ice water bath for 20 min with shaker (40–45 strokes) and then 8 ml of 1.2 M sodium acetate buffer (pH 3.8) and 0.1 ml of amyloglucosidase (3300U/ml) were added. The tubes were then placed in water bath at 50 °C for 30 min, after shaking followed by centrifugation at 3,000 rpm for 10 min. 0.1 ml of supernatant was transferred into glass tubes in duplicate and 0.3 ml of GOPOD reagent were mixed and kept 50 °C for 30 min. The absorbance was measured at 510 nm (Spectrophotometer, Model 4001/A, Thermo Spectronic, USA) against the reagent blank. The RS percentage was calculated by following formula: where, ΔE = OD Value, F = 100/Std. Glucose OD value, W = Weight of Sample taken (100).
Determination of mineral contents
The mineral contents such as Phosphorous (P), Sulphur (S), Potassium (K), Calcium (Ca) and Magnesium (Mg) were determined using the triacid extracts (9:2:1 ratio of nitric, sulphuric and perchloric acid). Phosphorous content was estimated by vanado-molybdate yellow colour method. Flame photometer was used to estimate the K content. Calcium and Magnesium were estimated by titration method with the presence of indicators.
ED-XRF (energy dispersive X ray florescence) method of Fe and Zn estimation
Oxford Instruments X-supreme 8000 was used to estimate Fe and Zn content in the brown rice. 5 g of dehusked and cleaned sample were taken in sample cups for analysis. For each set of samples, it has taken 3.1 min which included 60 s acquisition time for the separate Zn and Fe conditions as well as 66 s ‘dead time’ during which the XRF will establish each measurement condition. Scans were conducted in sample cups assembled from 21 mm diameter and the cup combined with polypropylene inner cups was sealed at one end with 4 μm Poly-4 XRF sample film. Concentration was expressed in microgram per gram (μg/g).
Total phenolic content
One gram of methanol extract was added to 15 ml of 50% methanol and allowed for maceration for 2 h. The extraction was done three times and then filtered and make up the volume to 100 ml with 50% methanol. 1 ml sample was diluted with 10 ml of distilled water followed by 1.5 ml Folin Ciocalteu’s reagent was added and kept incubation for 5 min at room temperature. Then 4 ml of 20% Na2CO3 was added and makeup the volume upto 25 ml with distilled water. The absorbance at 765 nm was measured with the help of UV/VIS spectrophotometer (Singleton and Rossi, 1965). Total phenolic content was calculated from the standard curve and expressed as mg Gallic Acid Equivalent (GAE) per 100 g of rice (mg GAE/100 g).
DPPH radical assay
Antioxidant activity was measured by DPPH radical scavenging assay77. A 3 ml of mixture (0.2 ml methanol extract of seed sample + 2.8 ml 60 μM DPPH) was kept in dark place for 30 min before analysis. The scavenging ability was estimated with the help of absorbance measured at 515 nm using UV VIS spectrophotometer.
Scanning electron microscopy
Starch granules of Kavuni morphotypes were compared by scanning electron microscopy (SEM). Rice flour was sputtered with gold at 30 kV and the coated samples were observed under TESCAN VEGA3, Czech Republic with an accelerating voltage of 15.0 kV, 100 s photo time, and 1000 × and 5000 × magnification with the same SEM.
Pasting property estimation
Rheolgical properties of starch was estimated using Rapid Visco Analyser (RVA-2, Perten, Sweden). A sample of 3 g of rice flour was transferred into a canister, and approximately 25 mL of ultrapure water was added. The pasting properties were determined based on a procedure reported by Juliano et al.78. The peak viscosity (PV), trough viscosity (TV), breakdown viscosity (BDV), final viscosity (FV), and setback viscosity (SBV), peak temperature (PT) and RVA pasting curves were recorded.
GC/MS analysis
Metabolite profiling in the grains of Kavuni morpho-types were studied by using GC/MS (Gas chromatography/Mass spectrophotometry). In brief, 30 mg of finely ground rice flour was extracted with the help of methanol79. 50 μl of internal standards such as ribitol and nonadecanoic acid were added and then filtered with 0.22 μm PVDF syringe filter. Then sample (1 μl) was into GC injection port (AI3000 II, Thermo Fischer Scientific, USA) connected to a GC/MS (TRACE™ GC Ultra with DSQII Quadrupole mass spectrometer and capillary column of 30 cm in length, 0.25 mm diameter and 0.25 μm film thickness-Agilent, DB-5 ms Ultra Inert, 122-5532). AMDIS (Automated Mass Spectral Deconvolution and Identification System Program) was used to determine the deconvolution of peaks, extraction of the baseline corrected mass spectra, retention time of each component. The MSTs (Mass Spectral Tags) were compared with the NIST library and the best spectral match was selected and metabolite name was assigned.
Statistical analysis
Analysis of variance for physio-chemical properties were analyzed and compared with Duncan Multiple Range Test (DMRT) (p < 0.05) using R software using “agricolae” package80. The data was depicted as mean ± standard deviation.
Acknowledgements
The authors acknowledge with thanks the NABARD sponsored project for financial support for this research. The authors thank Tamil Nadu Rice Research Institute, Aduthurai, TNAU, Tamil Nadu and India for conducting experiments.
Author contributions
SD: Conceptualization, Funding acquisition. SD &PR: Investigation, Project administration, Writing—review and editing. TP: Experimental analysis, Methodology, Data curation. PR, SR & MR: Formal analysis, Methodology, Validation, Writing—review and editing. SA: Experimental analysis, Data curation, Writing—original draft. SP: Formal analysis, Writing—review and editing.
Data availability
All data generated or analysed during this study are included in this published article (and its Supplementary Information files).
Declarations
Competing interests
The authors declare no competing interests.
Research involving plants
A diverse panel of rice landraces of South Indian origin were collected and conserved at Tamil Nadu Rice Research Institute (TRRI), Aduthurai, Tamil Nadu Agricultural University, Tamil Nadu, India. From the genotypes, four morphotypes of Kavuni accessions were utilized for this study.
Supplementary Information
The online version contains supplementary material available at https://doi.org/10.1038/s41598-025-95747-8.
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
1. Futakuchi, K et al. History and progress in genetic improvement for enhancing rice yield in sub-Saharan Africa. Field Crop Res.; 2021; 267, 108159. [DOI: https://dx.doi.org/10.1016/j.fcr.2021.108159]
2. Owolabi, IO; Chakree, K; Yupanqu, CT. Bioactive components, antioxidative and anti-inflammatory properties of soaked and germinated purple rice extracts. Int. J. Food Sci. Technol.; 2019; 54, pp. 1-13. [DOI: https://dx.doi.org/10.1111/ijfs.14148]
3. Zhao, M; Lin, Y; Chen, H. Improving nutritional quality of rice for human health. Theor. Appl. Genet.; 2020; 133, pp. 1397-1413. [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/31915876][DOI: https://dx.doi.org/10.1007/s00122-019-03530-x]
4. World Health Organization. The state of food security and nutrition in the world 2020: transforming food systems for affordable healthy diets. Food Agric. Org. (2020).
5. Kowsalya, P; Sharanyakanth, PS; Mahendran, R. Traditional rice varieties: A comprehensive review on its nutritional, medicinal, therapeutic and health benefit potential. J. Food Compos. Anal.; 2022; 114, 104742. [DOI: https://dx.doi.org/10.1016/j.jfca.2022.104742]
6. International Diabetes Federation. IDF Diabetes Atlas 10th ed, Brussels, (accessed 19 October 2022); http://www.diabetesatlas.org.
7. Shanmugam, A et al. Unraveling the genetic potential of native rice (Oryzasativa L.) landraces for tolerance to early-stage submergence. Front. Plant Sci.; 2023; 14, 1083177. [DOI: https://dx.doi.org/10.3389/fpls.2023.1083177] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/37275250][PubMedCentral: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10232957]
8. Deng, GF et al. Phenolic compounds and bioactivities of pigmented rice. Crit. Rev. Food Sci. Nutr.; 2013; 53,
9. Bhat, FM et al. Status of bioactive compounds from bran of pigmented traditional rice varieties and their scope in production of medicinal food with nutraceutical importance. Agronomy; 2020; 10,
10. Raman, P et al. Elucidation of nutritional properties and cooking quality traits of under-exploited pigmented rice (Oryzasativa L.) landraces. Indian J. Genet. Plant Breed.; 2024; 84,
11. Mbanjo, EGN et al. The genetic basis and nutritional benefits of pigmented rice grain. Front. Genet.; 2020; 11, 229. [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/32231689][PubMedCentral: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7083195][DOI: https://dx.doi.org/10.3389/fgene.2020.00229]
12. Sompong, R et al. Physicochemical and antioxidative properties of red and black rice varieties from Thailand China and Sri Lanka. Food Chem.; 2011; 124,
13. Rathna Priya, TS; Ann, EN; Ravichandran, K; Antony, U. Nutritional and functional properties of coloured rice varieties of South India: a review. J. Ethnic Food; 2019; 6,
14. Reddy, CK; Kimi, L; Haripriya, S; Kang, N. Effects of polishing on proximate composition, physic chemical characteristics, mineral composition and antioxidant properties of pigmented rice. Rice Sci.; 2017; 24,
15. Saleh, AS; Wang, P; Wang, N; Yang, L; Xiao, Z. Brown rice versus white rice: Nutritional quality, potential health benefits, development of food products, and preservation technologies. Compr. Rev. Food Sci. Food Saf.; 2019; 18, pp. 1070-1096. [DOI: https://dx.doi.org/10.1111/1541-4337.12449] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33336992]
16. Sanghamitra, P et al. Evaluation of variability and environmental stability of grain quality and agronomic parameters of pigmented rice (O.sativa L.). J. Food Sci. Technol.; 2018; 55,
17. Hudson, EA; Dinh, PA; Kokubun, T; Simmonds, MS; Gescher, A. Characterization of potentially chemopreventive phenols in extracts of brown rice that inhibit the growth of human breast and colon cancer cells. Cancer Epidemiol. Biomark. Prev.; 2000; 9,
18. Anjali, KU; Kamatchi, AR; Haripriya, S; Kumar, A; Reddy, CK. Varietal differences in the physical and engineering attributes of underutilized pigmented and non-pigmented paddy and rice landraces. Food Sci. Eng.; 2023; [DOI: https://dx.doi.org/10.37256/fse.4220232342]
19. Nadaf, A; Mathure, S; Jawali, N. Scented Rice (Oryza sativa L.) Cultivars of India: A Perspective on Quality and Diversity; 2016; Springer: [DOI: https://dx.doi.org/10.1007/978-81-322-2665-9]
20. Fitzgerald, M; Mccouch, ASR; Hall, RD. Not just a grain of rice: the quest for quality. Trends Plant Sci.; 2009; 14,
21. Jamal, S; Qazi, IM; Ahmed, I. Comparative studies on flour proximate compositions and functional properties of selected Pakistani rice varieties. Pak. Acad. Sci.; 2016; 53, pp. 47-56.
22. Zhou, H; Duo, X; Yuqing, H. Rice grain quality-traditional traits for high quality rice and health-plus substances. Mol. Breed.; 2020; 40, pp. 1-17. [DOI: https://dx.doi.org/10.1007/s11032-019-1080-6]
23. Devi, LM; Badwaik, LS. Variety difference in physico-chemical, cooking, textural, pasting and phytochemical properties of pigmented rice. Food Chem Adv.; 2022; 1, 100059. [DOI: https://dx.doi.org/10.1016/j.focha.2022.100059]
24. Karim, MD; Abuhena, M; Hossain, MD; Billah, MM. Assessment and comparison of cooking qualities and physio-chemical properties of seven rice varieties in terms of amylose content. Food Phys.; 2024; 1, 100014. [DOI: https://dx.doi.org/10.1016/j.foodp.2024.100014]
25. Mudgal, S; Singh, N. Physicochemical, functional, pasting, and amino acid compositions of milled rice, and extrusion behavior of milled rice from basmati and non-basmati varieties. Cereal Chem.; 2024; 101,
26. Nakamura, S; Katsura, J; Maruyama, Y; Ohtsubo, KI. Evaluation of hardness and retrogradation of cooked rice based on its pasting properties using a novel RVA testing. Foods; 2021; 10,
27. Tangsrianugul, N; Wongsagonsup, R; Suphantharika, M. Physicochemical and rheological properties of flour and starch from Thai pigmented rice cultivars. Int. J. Biol. Macromol.; 2019; 137, pp. 666-675. [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/31252009][DOI: https://dx.doi.org/10.1016/j.ijbiomac.2019.06.196]
28. Raveendran, M; Valarmathi, R. Molecular tagging of a novel genetic locus linked to accumulation of lutein—A therapeutic carotenoid in rice grains. Indian J. Genet. Plant Breed.; 2020; 80,
29. Valarmathi, R; Raveendran, M; Robin, S; Senthil, N. Unraveling the nutritional and therapeutic properties of ‘Kavuni’ a traditional rice variety of Tamil Nadu. J. Plant Biochem. Biotechnol.; 2015; 24,
30. IRRI. Standard evaluation system for rice: International rice research institute. PO Box; 1996; 933, 1099.
31. Golam, F; Prodhan, ZH. Kernel elongation in rice. J. Sci. Food Agric.; 2013; 93,
32. Singh, SK et al. Studies on character association and path analysis studies for yield, grain quality and nutritional traits in F2 population of rice (Oryzasativa L.). Electron. J. Plant Breed.; 2020; 11,
33. Juliano, B. O. Criteria and test for rice grain quality. 2nd Edn., American Association of Cereal Chemists, Rice Chem. Technol.. 17–57 (1985).
34. Mondal, D et al. Evaluation of indigenous aromatic rice cultivars from sub-Himalayan Terai region of India for nutritional attributes and blast resistance. Sci. Rep.; 2021; 11,
35. Atkinson, F; Foster-Powell, K; Brand-Miller, JC. International tables of glycemic index and glycemic load values: 2008. Diabetes Care; 2008; 31,
36. Cummings, JH; Edmond, LM; Magee, EA. Dietary carbohydrates and health: do we still need the fibre concept?. Clin. Nutr. Suppl.; 2004; 1,
37. Deepa, G; Singh, V; Naidu, KA. A comparative study on starch digestibility, glycemic and resistant starch of pigmented (‘Njavara’ and Jyothi) and non-pigmented (‘JR 64’) rice varieties. J. Food Sci. Technol.; 2010; 47,
38. Kumar, A et al. Resistant starch could be decisive in determining the glycemic index of rice cultivars. J. Cereal Sci.; 2018; 79, pp. 348-353. [DOI: https://dx.doi.org/10.1016/j.jcs.2017.11.013]
39. Febina, M; John, D; Raman, M. Physicochemical properties, eating and cooking quality and genetic variability: a comparative analysis in selected rice varieties of South India. Food Prod. Process Nutr.; 2023; 5, 49. [DOI: https://dx.doi.org/10.1186/s43014-023-00164-x]
40. Oko, AO; Onyekwere, SC. Studies on the proximate chemical composition, and mineral element contents of five new lowland rice varieties planed in Ebonyi state. Int. J. Biotechnol. Biochem.; 2010; 6,
41. Fuentes-Zaragoza, E; Riquelme-Navarrete, MJ; Sánchez-Zapata, JA; Pérez-Álvarez, MJEJA. Resistant starch as functional ingredient: A review. Food Res. Int.; 2010; 43,
42. Deepa, G; Singh, V; Naidu, KA. Nutrient composition and physicochemical properties of Indian medicinal rice–Njavara. Food Chem.; 2008; 106,
43. Xia, M; Ling, WH; Ma, J; Kitts, DD; Zawistowski, J. Supplementation of diets with the black rice pigment fraction attenuates atherosclerotic plaque formation in apolipoprotein E deficient mice. J. Nutr.; 2003; 133,
44. Hu, C; Zawistowski, J; Ling, W; Kitts, DD. Black rice (Oryzasativa L. indica) pigmented fraction suppresses both reactive oxygen species and nitric oxide in chemical and biological model systems. J. Agric. Food Chem.; 2003; 51,
45. Nayeem, S; Venkidasamy, B; Sundararajan, S; Kuppuraj, SP; Ramalingam, S. Differential expression of flavonoid biosynthesis genes and biochemical composition in different tissues of pigmented and non-pigmented rice. J. Food Sci. Technol.; 2021; 58,
46. Murdifin, M et al. Physicochemical properties of Indonesian pigmented rice (Oryzasativa Linn.) varieties from South Sulawesi. Asian J. Plant Sci.; 2015; 14,
47. Ghasemzadeh, A; Karbalaii, MT; Jaafar, HZ; Rahmat, A. Phytochemical constituents, antioxidant activity, and antiproliferative properties of black, red, and brown rice bran. Chem. Cent. J.; 2018; 12,
48. Pengkumsri, N et al. Physicochemical and antioxidative properties of black, brown and red rice varieties of northern Thailand. Food Sci. Technol.; 2015; 35, pp. 331-338. [DOI: https://dx.doi.org/10.1590/1678-457X.6573]
49. Han, Z et al. Structural variations of rice starch affected by constant power microwave treatment. Food Chem.; 2021; 359, 129887. [DOI: https://dx.doi.org/10.1016/j.foodchem.2021.129887] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33964655]
50. Li, Y; Shoemaker, CF; Ma, J; Moon, KJ; Zhong, F. Structure-viscosity relationships for rice varieties during starches from different heating. Food Chem.; 2008; 106,
51. Oppong, D; Panpipat, W; Chaijan, M. Chemical, physical, and functional properties of Thai indigenous brown rice flours. PLoS ONE; 2021; 16,
52. Waewkum, P; Singthong, J. Functional properties and bioactive compounds of pigmented brown rice flour. Bioactive Carbohydr Diet. Fibre; 2021; 26, 100289. [DOI: https://dx.doi.org/10.1016/j.bcdf.2021.100289]
53. Ye, L; Wang, C; Wang, S; Zhou, S; Liu, X. Thermal and rheological properties of brown flour from Indica rice. J. Cereal Sci.; 2016; 70, pp. 270-274. [DOI: https://dx.doi.org/10.1016/j.jcs.2016.07.007]
54. Pradipta, S; Ubaidillah, M; Siswoyo, TA. Physicochemical, functional and antioxidant properties of pigmented rice. Curr. Res. Nutr. Food Sci. J.; 2020; 8,
55. Asante, MD et al. Starch physicochemical properties of rice accessions and their association with molecular markers. Starch-Stärke; 2013; 65,
56. Xuan, Y et al. Amylose content and RVA profile characteristics of noodle rice under different conditions. Agron. J.; 2020; 112,
57. Liang, J; Xueyun, D; Pingrong, W. Rice RVA profile characteristics and correlation with the physical/chemical quality. Acta Agron. Sin.; 2008; 34,
58. Yan, CJ et al. Performance and inheritance of rice starch RVA profile characteristics. Rice Sci.; 2005; 12,
59. Pang, Y et al. Relationship of rice grain amylose, gelatinization temperature and pasting properties for breeding better eating and cooking quality of rice varieties. PLoS ONE; 2016; 11,
60. Nandhini, DU et al. Metabolomic analysis for disclosing nutritional and therapeutic prospective of traditional rice cultivars of Cauvery deltaic region India. Front. Nutr.; 2023; [DOI: https://dx.doi.org/10.3389/fnut.2023.1254624]
61. Kris-Etherton, PM; William, SH; Lawrence, JA. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation; 2002; 106,
62. Yoshida, H; Yuka, T; Yoshiyuki, M. Lipid components, fatty acids and triacylglycerol molecular species of black and red rices. Food Chem.; 2010; 123,
63. Wilson, TA; Lynne, MA; Carl, WL; Mark, HD; Robert, JN. Comparative cholesterol lowering properties of vegetable oils: beyond fatty acids. J. Am. Coll. Nutr.; 2000; 19,
64. Ashokkumar, K et al. Comparative profiling of volatile compounds in popular south Indian traditional and modern rice varieties by gas chromatography–mass spectrometry analysis. Front. Nutr.; 2020; 7, 599119. [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33363195][PubMedCentral: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7755633][DOI: https://dx.doi.org/10.3389/fnut.2020.599119]
65. Priore, P et al. Oleic acid and hydroxytyrosol inhibit cholesterol and fatty acid synthesis in C6 glioma cells. Oxid. Med. Cell. Longev.; 2017; [DOI: https://dx.doi.org/10.1155/2017/9076052] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/29435099][PubMedCentral: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5757140]
66. Ruiz-Núñez, B; Dijck-Brouwer, DJ; Muskiet, FA. The relation of saturated fatty acids with low-grade inflammation and cardiovascular disease. J. Nutr. Biochem.; 2016; 36, pp. 1-20. [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/27692243][DOI: https://dx.doi.org/10.1016/j.jnutbio.2015.12.007]
67. Dabadie, H; Peuchant, E; Bernard, M; LeRuyet, P; Mendy, F. Moderate intake of myristic acid in sn-2 position has beneficial lipidic effects and enhances DHA of cholesteryl esters in an interventional study. J. Nutr. Biochem.; 2005; 16,
68. Fattore, E; Fanelli, R. Palm oil and palmitic acid: a review on cardiovascular effects and carcinogenicity. Int. J. Food Sci. Nutr.; 2013; 64,
69. Hema, R; Kumaravel, S; Alagusundaram, K. GC/MS determination of bioactive components of Murraya koenigii. J. Am. Sci.; 2011; 7,
70. Mujeeb, F; Bajpai, P; Pathak, N. Phytochemical evaluation, antimicrobial activity, and determination of bioactive components from leaves of Aegle marmelos. Bio. Med. Res. Int.; 2014; [DOI: https://dx.doi.org/10.1155/2014/497606]
71. Chandrasekar, T et al. GC-MS analysis, antimicrobial, antioxidant activity of an ayurvedic medicine, Nimbapatradi choornam. J. Chem. Pharm. Res.; 2015; 7,
72. Varsha, KK et al. 2, 4-Di-tert-butyl phenol as the antifungal, antioxidant bioactive purified from a newly isolated Lactococcus sp. Int. J. Food Microbiol.; 2015; 211, pp. 44-50. [DOI: https://dx.doi.org/10.1016/j.ijfoodmicro.2015.06.025] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/26164257]
73. Balamurugan, R; Stalin, A; Ignacimuthu, S. Molecular docking of γ-sitosterol with some targets related to diabetes. Eur. J. Med. Chem.; 2012; 47, pp. 38-43. [DOI: https://dx.doi.org/10.1016/j.ejmech.2011.10.007] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/22078765]
74. Mangamuri, U et al. Bioactive metabolites produced by Streptomyces Cheonanensis VUK-A from Coringa mangrove sediments: isolation, structure elucidation and bioactivity. 3 Biotech; 2016; 6,
75. Roy, RN; Laskar, S; Sen, SK. Dibutyl phthalate, the bioactive compound produced by Streptomycesalbidoflavus 321.2. Microbiol. Res.; 2006; 161,
76. AOAC. Official Methods of Analysis, 17th Edition. Washington: Association of Official Analytical Chemists (2000).
77. Brand-Williams, W; Cuvelier, ME; Berset, CLWT. Use of a free radical method to evaluate antioxidant activity. LWT-Food Sci. Technol.; 1995; 28,
78. Juliano, B. O. Rice quality screening with the rapid visco analyser. Applic. Rapid Visco Anal. 19–24 (1996).
79. Fiehn, O et al. Metabolite profiling for plant functional genomics.Nature biotechnology 18(11), 1157–1161.https://doi.org/10.1038/81137 (2000).
80. Mendiburu, F. D. & Yaseen, M. Agricolae: statistical procedures for agricultural research. R package version 1.4. 0 https://cran.r-project.org/package=agricolae (2020).
81. Tian, C et al. Chemical compositions, extraction technology, and antioxidant activity of petroleum ether extract from abutilon theophrasti medic leaves. Int. J. Food Properties; 2018; 21,
82. Igwe, OU; Okwunodulu, FU. Investigation of bioactive phytochemical compounds from the chloroform extract of the leaves of Phyllanthus amarus by GC–MS technique. Int. J. Chem. Pharm. Sci.; 2014; 2,
© The Author(s) 2025. This work is published under http://creativecommons.org/licenses/by-nc-nd/4.0/ (the "License"). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.