Nutritional Composition, Bioactive Compounds, Food Applications, and Health Benefits of Pigeon Pea (Cajanus cajan L. Millsp.): A Review

Abstract

Pigeon pea is one of the most multipurpose grain legumes in the tropical and subtropical world. It is highly resilient to climate change due to drought tolerance. It ranks sixth following common beans, chickpeas, field peas, cowpeas, and lentils globally. Pigeon pea is an excellent source of high-quality protein, essential amino acids, and minerals. Furthermore, pigeon pea is endowed with valuable water-soluble vitamins such as thiamin, ascorbic acid, riboflavin, and niacin. With low levels of saturated fat and sodium and being cholesterol free, pigeon peas emerge as a nutritious dietary choice. Pigeon peas are rich sources of bioactive compounds with various potential health properties, including anti-inflammatory, antibacterial, antioxidant, anticarcinogenic, and antidiabetic effects. Pigeon peas can be consumed in diverse forms, including whole seeds, split seeds (known as dhal), vegetables using green seeds, and fresh pods. Moreover, pigeon peas find application in a variety of food products, including bread, pasta, noodles, snacks, and biscuits. Despite their nutritional and medicinal properties, pigeon peas remain among the least utilized legumes globally. This review paper aims to provide up-to-date information on the nutritional compositions, bioactive compounds, food applications, and health benefits of pigeon peas.

Introduction

Pigeon pea (Cajanus cajan L. Millsp.) is a paramount component of the human diet in developing countries, particularly those that live in tropical and subtropical regions (Miano et al. 2020). It belongs to the fabaceae family and is one of the oldest grain legumes (Torres et al. 2007; Varshney et al. 2011). Pigeon pea is one of the six important legumes produced in the world after common beans, chickpeas, field peas, cowpeas, and lentils (Gerrano et al. 2022). According to FAOSTAT, approximately 5 million tons of pigeon peas are produced every year from 6.1 million hectares of land globally. India, Myanmar, Malawi, Kenya, and Tanzania are the top producers of pigeon pea in the world (FAOSTAT 2021). Asia, Africa, and America share 90.5%, 3.7%, and 5% of the total world production of pigeon pea, respectively (FAOSTAT 2021; Gerrano et al. 2022).

The pigeon pea presumably originated in South Asia and emerged around 2000 BC in West Africa, which is thought to be the second major center of origin. Then it was brought to West India through the slave trade, where it was used as feed for pigeons, which led to the name of pigeon pea (Singh, Upadhyaya, and Bisht 2013). This legume is known by various names, namely, red gram, Congo pea, gungo pea, and no-eye pea (Singh, Rai, and Singh 2020). Pigeon pea is a perennial grain legume that reaches heights of 1–4 m. Its pods are flat, commonly green in color, hairy or streaky, or dark purple with two to nine seeds or pods. The seeds of pigeon pea are widely variable in color and usually weigh 4–25 g/100 seeds (Sharma, Agarwal, and Verma 2011).

Pigeon peas are very drought-tolerant legumes that are impervious to climate change (Emefiene, Salaudeen, and Yaroson 2013). Owing to its higher yield in extreme environmental conditions such as heat, drought, and poor soil fertility, pigeon pea has a noteworthy potential positive impact on the lives of poor people when compared to other legumes (Negi et al. 2021). As a result, pigeon peas are attractive legumes for resource-poor farmers. Furthermore, it provides numerous benefits to smallholder farmers, for instance, protein-rich food, animal feed, firewood, fencing material, and improved soil fertility through nitrogen fixation (Sharma, Agarwal, and Verma 2011). The deep taproot system of pigeon peas helps to fix nitrogen from 40 to 250 kg ha⁻¹, which contributes to the reduction of soil erosion (Namuyiga et al. 2022). Pigeon pea is usually cultivated together with yam, millet, sorghum, and cassava, among other crops (Simion, Ersulo, and Fikre 2022). Pigeon pea is an ideal crop in dryland areas where it is intercropped or grown in a mixed cropping system with cereals or other short-duration annuals (Joshi et al. 2001).

Pigeon peas can be consumed in different forms, including seeds (whole grain), dhal (split seed without seed coat), and green seeds as vegetables and fresh pods (Abebe 2022; Jeevarathinam and Chelladurai 2020). Currently, pigeon pea flour is used as a unique ingredient in various food products such as pasta, noodles, biscuits, and sausages because of its high fiber and protein, gluten-free status, low glycemic index, high antioxidant levels, and functional properties like water absorption and water-holding capability (Keshav 2015; Singh 2022). According to Karri and Nalluri (2017), pigeon pea products combined with cereals provide a nutritious human diet and can be used as a potential source of protein to alleviate protein deficiency and malnutrition.

As elaborated by Susmitha et al. (2022), pigeon pea is the main source of protein for more than billions of people in regions such as Asia, Africa, South America, Central America, and the Caribbean. Also, it serves as an essential cash crop to support the livelihoods of millions of resource-poor farmers in these areas. The nutritional composition of pigeon pea is similar to that of other legumes. It has a low-fat content and high protein. As numerous findings indicate, pigeon pea contains 20%–22% protein, 65% carbohydrate, 3.8% ash, and 1.2% fat (Sarkar et al. 2020; Sharma, Agarwal, and Verma 2011; Sun et al. 2020). Pigeon peas have two to three times more protein than cereals specifically rich in lysine (Jawalekar et al. 2020; Olalekan and Bosede 2010). It is a good source of dietary fiber, vitamins, and minerals (Atuna et al. 2023; Talari and Shakappa, 2018a, 2018b).

Presently, there is an increasing demand for vitamins, essential minerals, and animal-derived proteins; nonetheless, the costs of these items are on the rise, particularly impacting individuals in developing nations (Singh 2022). This legume is an affordable alternative to animal-derived protein sources such as beef, dairy products, seafood, fish meat, or poultry for low-income farmers (Singh, Rai, and Singh 2020). According to the review by Talari and Shakappa (2018a, 2018b), pigeon pea, when combined with cereals, give a well-balanced diet that is analogous to other dense protein sources like whey and soy. According to the report of Anitha et al. (2020), including legumes like pigeon peas in diets offers all essential amino acids, vitamin B, vitamin C (ascorbic acid), carotenoids, magnesium, and iron.

Apart from this high nutritional value, pigeon pea is used as a traditional medicine in India, China, the Philippines, and some other nations (Saxena, Kumar, and Gowda 2010). It is used for curing measles, smallpox, chicken pox, sickle cell anemia, fever, dysentery, hepatitis, and malaria (Abebe 2022; Singh 2022). Pigeon pea has a good number of health-promoting bioactive compounds, like phenolic compounds, flavonoids, tannins, saponins, and phytic acid. These compounds have countless useful properties like anti-inflammatory, antibacterial, antioxidant, anticarcinogenic, and antidiabetic effects (Oluwole et al. 2021; Pal et al. 2011; Rani et al. 2014; Singh 2022).

Despite its potential to enhance food security, particularly protein intake in developing countries, as previously mentioned, pigeon peas remain one of the least-utilized legume crops compared to others like soybeans. International researchers have paid relatively little attention to this crop, as evidenced by studies (Abebe 2022; Simion, Ersulo, and Fikre 2022). Indeed, it falls within the category of underutilized crops, a term denoting those receiving scant attention from researchers, farmers, marketers, and consumers alike. This neglect stems from various factors encompassing agronomic, genetic, economic, environmental, and cultural considerations (Fatokimi and Tanimonure 2021). The perception of underutilized crops varies depending on geographical location, as noted by Padulosi, Thompson, and Rudebjer (2013), who highlighted the significant potential of such crops in improving global food accessibility and protein intake. Further exploration of pigeon pea's food applications could stimulate its cultivation and address the growing demand for high-quality plant-based protein from sustainable sources. However, despite its potential, there is a lack of comprehensive, up-to-date reviews on pigeon pea. Hence, this review aims to fill this gap by providing current insights into its nutritional composition, bioactive compounds, food applications, and associated health benefits.

Review Approach

The foundation of this review paper rests upon a wide range of scholarly databases, including Google Scholar, Research Gate, Web of Science, and Scopus. By employing targeted keywords such as “Antioxidant, Legumes, Nutrition, and Pigeon pea,” pertinent and insightful information was meticulously gathered. The review synthesizes findings from a comprehensive database comprising over 121 scientific sources, sourced from reputable outlets spanning various disciplines, as outlined by the paper's headings and subheadings. The articles referenced in this review span from 2001 to 2023, providing a contemporary perspective on the subject matter.

Nutritional Compositions of Pigeon Pea

Legumes are highly recommended for inclusion in diets due to their exceptional nutritional value, as reported by Maphosa and Jideani (2017). These legume seeds boast an array of bioactive compounds that offer significant health benefits, underscoring the importance of incorporating them into our daily diets. Among these legumes, pigeon pea stands out for its rich nutrient profile, encompassing fats, ash, carbohydrates, lipids, and proteins. However, it is crucial to note that variations in proximate compositions may arise from factors such as different varieties, environmental conditions, storage, and processing methods, as discussed by Anaemene and Fadupin (2022). Notably, carbohydrates and proteins emerge as the predominant constituents of pigeon pea, as evidenced in Table 1, surpassing other nutritional components, according to the USDA (2022).

TABLE 1 Proximate composition of pigeon pea.

Proximate (%)	Olalekan and Bosede (2010)	Benítez et al. (2021)	USDA (2022)
Moisture	8.45	—	10.59
Protein	24.46	22.63	21.70
Fat	4.78	3.87	0.38
Fiber	1.10	6.53	15.00
Ash	4.58	3.96	3.45
Carbohydrate	56.63	63.02	62.78
Energy (kcal/100 g)	369.39	—	343(kcal/kJ)

Proteins

Pigeon peas are widely recognized as a primary source of protein, providing essential macro and micronutrients (Saxena, Vijaya Kumar, and Sultana 2010). Protein, a fundamental macronutrient comprising amino acids crucial for human growth and development, plays a pivotal role (Semba 2016). Reported protein content in various studies ranges from 16.7% to 26.8%, with wild pigeon pea varieties showing levels as high as 30% (Amarteifio et al. 2002; Benítez et al. 2021; Jawalekar et al. 2020; Olalekan and Bosede 2010; Upadhyaya et al. 2013). This protein content surpasses that of cereals by threefold. Moreover, pigeon pea protein is of exceptional quality, particularly rich in lysine, making it a crucial complement to cereal- and root-based diets (Odeny 2007). Additionally, Akporhonor, Egwaikhide, and Eguavoen (2006) contend that combining pigeon peas with other crops can yield higher protein content than soybeans, even exceeding other essential amino acids. Pigeon pea proteins consist of four main segments, commonly referred to as albumins, globulins, prolamine, and glutelins (Saxena, Reddy, and Saxena 2023), with globulins (54–60%) and albumins (10–15%) representing the predominant fractions in pigeon pea seeds (Olagunju and Omoba 2021).

Amino Acid Profile

Amino acid profiles serve as crucial indicators of protein nutritional quality in food, providing essential information about the presence of both essential and nonessential amino acids (Keskin et al. 2022). Notably, the amino acid composition of pigeon pea protein closely resembles that of soybean (Adenekan et al. 2018). Pigeon pea stands out as a rich source of various amino acids, including aspartic acid, lysine, leucine, arginine, and glutamic acid (Akande et al. 2010; Bamidele and Akanbi 2015; Oshodi, Olaofe, and Hall 1993; Solomon, Okomoda, and Oda 2017; Yang et al. 2020).

Moreover, pigeon peas contain sulfur-containing amino acids, methionine, and cystine, which are typically scarce in major legumes but are present in notable quantities in pigeon peas (Longvah et al. 2017). Approximately 43.61% of the total amino acids in pigeon peas is essential amino acids. Furthermore, linoleic acid and palmitic acid emerge as the predominant fatty acids in pigeon peas, comprising 54.8% and 21.4% of the total fatty acid content, respectively (Locali-Pereira et al. 2023). Table 2 provides a comprehensive amino acid profile of pigeon peas, highlighting the presence of essential amino acids essential for human nutrition.

TABLE 2 Amino acid profile of pigeon pea (mg/100 g).

Amino acid	Oshodi, Olaofe, and Hall (1993)	Yang et al. (2020)	USDA (2022)
Argininea	3230	279.9	1300
Histidinea	3410	361.7	774
Isoleucinea	4130	392.0	785
Leucinea	8570	679.7	1550
Lysinea	5860	740.8	1520
Methioninea	320	70.6	243
Phenylalaninea	9710	354.7	1860
Threoninea	2640	136.2	767
Valinea	5730	671.4	937
Alanine	6280	1547.8	972
Aspartic acid	990	126.4	2150
Cystine	—	—	250
Glutamic acid	1970	648.3	5030
Glycine	3950	160.7	802
Proline	5410	72.1	955
Serine	4770	220.0	1030
Tryptophan	—	9.5	212
Tyrosine	440	136.2	538

^aEssential amino acid.

Dietary Fiber

Dietary fiber is a type of carbohydrate that is resistant to digestion and absorption in the human small intestine, with complete fermentation in the large intestine (Soliman 2019). Soluble and insoluble fibers are the two rudimentary classifications of fiber. Cellulose, hemicellulose, and lignin are insoluble fibers, whereas pectin, gum, and mucilage are soluble fibers (Dhingra et al. 2012). The fiber of pigeon peas ranged from 1.988% to 7.22% (Akande et al. 2010; Fasoyiro et al. 2006). High–dietary-fiber diets have numerous health benefits, including avoiding or treating diseases such as constipation, obesity, diabetes, cardiovascular disease, piles, and some cancers (Soliman 2019). Besides, according to Maphosa and Jideani (2017), dietary fiber derived from legumes is used in the bakery, meat, extruded products, and beverage industries as stabilizers, texturizers, fortifiers, and fat substitutes.

Lipids

Like other legumes, pigeon peas are devoid of cholesterol and typically exhibit low-fat content (Karri and Nalluri 2017). Studies have reported varying fat content, ranging from 0.6% to 3.8% (Faris and Singh 1990), and more specifically, Anjulo, Doda, and Kanido (2020) found fat content ranging from 0.993% to 1.75%. Notably, pigeon pea seeds are characterized by their low-fat content, with palmitic and linoleic acids being the primary saturated and polyunsaturated fatty acids, respectively (Abebe 2022; Ade-Omowaye, Tucker, and Smetanska 2015). This low-fat content confers several health benefits, including a reduction in heart problems and cholesterol levels in the blood (Hessium et al. 2009). Furthermore, as highlighted by Affrifah, Uebersax, and Amin (2023), the low-fat content of legumes makes them appealing and healthy ingredients for various food applications.

Ash

The ash content reported in pigeon pea seeds varies, ranging from 3.75% to 5.31%, as documented by multiple studies (Amarteifio et al. 2002; Anjulo, Doda, and Kanido 2020; James et al. 2020; Kachare et al. 2019; Olalekan and Bosede 2010). Ash content serves as a measure of the total mineral content in food and is indicative of its overall mineral quality (Orekoya et al. 2021).

Carbohydrates

Carbohydrates serve as a primary source of dietary energy, constituting 40%–80% of total energy intake (FAO 1998). Pigeon pea emerges as a noteworthy source of carbohydrates, containing approximately 57.3%–58.7% (Jeevarathinam and Chelladurai 2020). Within pigeon peas, major carbohydrates include sugar, starch, and dietary fiber (Abebe 2022). Sekhon et al. (2017) reported varying levels of total soluble sugar in pigeon peas, ranging from 33.23 to 60.80 mg/g, while wild pigeon pea species exhibited soluble sugar levels between 38.10 and 40.54 mg/g. Additionally, Sharma, Agarwal, and Verma (2011) noted a soluble sugar content of 31 mg/g in dried pigeon pea. The starch content of pigeon peas was found to range from 41% to 53% (Sharma, Agarwal, and Verma 2011), with starch being recognized as the most important carbohydrate in the human diet (Miano et al. 2020). Furthermore, pigeon pea boasts a low glycemic index (Uchegbu and Ishiwu 2015), which has been associated with significant reductions in blood glucose levels (Panlasigui, Panlilio, and Madrid 1995).

Vitamins

Pigeon pea holds promise as a significant source of water-soluble vitamins such as thiamin, ascorbic acid, riboflavin, and niacin (Adepoju, Dudulewa, and Bamigboye 2019; Bamidele and Akanbi 2015; Kunyanga, Imungi, and Vellingiri 2013). Notably, it is abundant in vitamin A and contains higher levels of vitamin C compared to ordinary peas and beans (Odeny 2007; Saxena, Kumar, and Gowda 2010). Vitamins play a crucial role in maintaining optimal mental and physical health and in preventing birth defects in newborns (WHO/FAO 2004). Additionally, they collaborate with enzymes involved in metabolic pathways, facilitating the production of essential nutrients such as energy, carbohydrates, proteins, and fats (Huskisson, Maggini, and Ruf 2007). Furthermore, vitamins contribute to the maintenance of nervous system functions (Dai and Koh 2015). The vitamin of pigeon peas is detailed in Table 3.

TABLE 3 Vitamin content of pigeon pea (mg/100 g).

Vitamins	Kunyanga, Imungi, and Vellingiri (2013)	Adepoju, Dudulewa, and Bamigboye (2019)	Bamidele and Akanbi (2015)
Carotene	23.31	0.05	469.6
Thiamine	0.25	0.72	0.30
Riboflavin	0.09	0.14	0.31
Niacin	2.3	2.9	3.2
Ascorbic acid	1.7	4.8	25
Folic acid	—	100 μg/100 g	—

Minerals

Pigeon pea serves as a notable source of essential minerals including potassium, magnesium, sulfur, calcium, iron, and phosphorus (Adepoju, Dudulewa, and Bamigboye 2019; Amarteifio et al. 2002; Kunyanga, Imungi, and Vellingiri 2013). Legumes, including pigeon peas, are recognized for their low sodium content, which is integral to human health (Maphosa and Jideani 2017). The elevated potassium levels found in pigeon peas may prove beneficial for individuals taking diuretics to manage blood pressure or experiencing excessive potassium secretion (A'yuni et al. 2021). Iron is crucial for erythrocyte formation across all organs, including the brain, and vital for hemoglobin synthesis in fetuses and growing children is abundant in pigeon peas (Georgieff, Krebs, and Cusick 2019). Additionally, pigeon peas contain zinc, which is essential for maintaining the body's immune system (Cabrera 2015). Calcium, another vital mineral present in pigeon peas, enhances bone strength, supports dental health, aids muscle function, regulates blood clotting, facilitates nerve transmission and promotes the activity of digestive enzymes (Gupta and Nagar 2014; Soetan, Olaiya, and Oyewole 2010). Table 4 outlines the mineral content of pigeon peas per 100 g, comparing the data with information provided by the USDA (2022).

TABLE 4 Mineral content of raw pigeon pea (mg/100 g).

Minerals	Kunyanga, Imungi, and Vellingiri (2013)	Amarteifio et al. (2002)	USDA (2022)
Calcium	80.5	120–167	130
Potassium	—	163–293	1392
Magnesium	100.8	113–127	183
Copper	—	56	0.13
Iron	5.6	2.5–4.7	5.23
Zinc	2.7	7.2–8.2	2.76
Sodium	0.33	11.3–12.0	17
Phosphorous	334	—	367

Bioactive Compounds

Bioactive compounds, which are usually found in small quantities compared to macronutrients, play a crucial role in various food items (Singh et al. 2017). In pigeon pea, the main bioactive compounds identified so far are broadly classified into the flavonoids, phenolics, and stilbenes groups (Gargi et al. 2022). The high-performance liquid chromatography (HPLC) analysis of ethanol leaves extract revealed seven flavonoids including pinostrobin, orientin, naringenin, apigenin, apigenin-6,8-di-C-α-L-arabinopyranoside and pinostrobin chalcone, and two stilbenes, namely, pinostrobin, orientin, naringenin, apigenin, and pinostrobin chalcone (Wei et al. 2013).

Pal et al. (2011) found that the ethanol extract of pigeon pea leaves contains cajaninstilbene acid, pinostrobin, vitexin, and orientin, which exhibit antioxidant activities. The conducted by Orni et al. (2018) showed that pigeon pea roots contain bioactive compounds such as genistein, genistin, hexadecanoic acid, α-amyrin, β-sitosterol, longistylin A, longistylin C, cajanuslactone, coumarin, cajaninstilbene, pinostrobin, vitexin, and orientin, which have health benefits. Some protein fractions derived from leaves also demonstrated hepato-protective effects (Ahsan and Islam 2009). The roots pigeon peas were found to contain the isoflavonoids genistein and genistin, which exhibited antioxidant properties (Zhang et al. 2010). Wu et al. (2009) reported that the presence of phenolics (flavonoids and tannins) in aerial plants contributes to their anthelmintic activity. The bioactive compounds of various parts of pigeon pea are summarized in Table 5.

TABLE 5 The bioactive compounds of various parts of pigeon pea.

Bioactive compound	Parts used	Extract	References
Cajanuslactone	Leaves	Chloroform	Pal et al. (2011)
Cajanin, longistylin C, longistylin A, betulinic acid, pinostrobin, cajaninstilbene acid, orientin, vitexin	Leaves	Ethanol	Pal et al. (2011)
Protein fraction Cl-1	Leaves	Methanol	Ahsan and Islam (2009)
Genistein, genistin	Root	Ethanol:water	Zhang et al. (2010)
Cajanol (isoflavonoids)	Root	Ethanol	Pal et al. (2011)
Phenolics (flavonoids, tannins)	Aerial plants	Hydroalcoholic	Wu et al. (2009)
Cajaninstilbene acid, vitexin, orientin, pinostrobin	Leaves	Ethanol	Orni et al. (2018)
Luteolin, apigenin, quercitin, isorhamnetin, cajaninstilbene acid, pinostrobin, cajanin, longistylin A, longistylin C	Leaves	—	Orni et al. (2018)
Hordenine, juliflorine, betulinic acid, stigmasterol, beta-sitosterol	Leaves	—	Orni et al. (2018)

It has been reported that phenolic compounds exhibit strong antioxidant activity. A study conducted by Al-Saeedi and Hossain (2015) revealed that pigeon pea seed extracts are rich in total phenols, flavonoids, and antioxidants. According to Al-Saeedi and Hossain (2015), pigeon pea seeds have a total phenolic content of 74 mg GAE/g and a flavonoid content of 1.14 mg QE/g. Yang et al. (2020) found that pigeon pea seeds contain 23.15 mg GAE/g DW of total phenolic content and 15.13 mg QUE/g DW of total flavonoid content. On the other hand, Rani et al. (2014) reported lower total phenolic and flavonoid content in pigeon peas. Sharma, Singh, and Singh (2019) reported 21.57% free radical scavenging and 89.33 μg AAE/g of ferric-reducing antioxidant power.

Health Benefits of Pigeon Pea

Pigeon peas have a rich history of medicinal use dating back to prehistoric times in regions such as Asia, Egypt, and Africa (Upadhyaya et al. 2011). Traditional Chinese medicine utilizes pigeon peas to staunch bleeding, alleviate pain, and combat intestinal worms (Wu et al. 2009). In Oman, pigeon peas are commonly employed to address various chronic ailments (Al-Saeedi and Hossain 2015). In India, the leaves of pigeon pea find application in the treatment of ulcers, wounds, stomach tumors, and diabetes (Saxena, Kumar, and Gowda 2010; Tiwari et al. 2013). Moreover, pigeon peas have been utilized as an antipyretic and to alleviate menstrual discomfort, while in South America, they are employed in the treatment of dysentery (Zhang et al. 2013). In Africa, pigeon pea seeds are utilized in the treatment of hepatitis and measles (Saxena, Kumar, and Gowda 2010), and in Nigeria, pigeon pea leaves have been traditionally used to combat malaria (Ajaiyeoba et al. 2013).

In Argentina, pigeon pea leaves are utilized in infusions to treat bronchitis, genital infections, and skin infections (Kong et al. 2011). Similarly, in Bangladesh, both the leaves and seeds of pigeon peas are employed in the management of diabetes (Hasan, VajihaAafrin, and Antony 2015). The therapeutic efficacy of pigeon peas can be attributed to the presence of phenolic compounds, which exhibit multifunctional bioactivities with antiviral, anti-inflammatory, antioxidant, hypocholesterolemic, and hypoglycemic effects (Yang et al. 2020). According to Dinore and Farooqui (2022), pigeon pea leaves are rich in flavonoids, terpenoids, essential oils, and coumarin, underscoring their traditional medicinal significance. Pigeon pea leaf extracts hold potential as natural antioxidants and could find applications in both medicine and the health food industry (Wu et al. 2009).

A study by Yilwa et al. (2023) revealed the presence of various bioactive compounds in dried pigeon pea extracts, including alkaloids, flavonoids, terpenoids, steroids, phytosteroids, saponins, tannins, phenolanthraquinone quinones, xanthoproteins, and phlobatanin. Among these, phenolic compounds such as apigenin, orientin, biocanin A, vitexin, genistein, isovitexin, genistin, luteolin, isorhamnetin, and cajanin stilbene acid have been associated with a wide range of biological properties. These include antioxidant, antitumor, anti-inflammatory, antibacterial, antiviral, antiplasmodial, hypoglycemic, hypocholesterolemic, anticancer, and hepatoprotective activities. These phenolic compounds are recognized as primary phytochemicals contributing significantly to the medicinal properties of pigeon pea, as supported by various studies (Aja et al. 2015; Dai et al. 2013; Nix, Paull, and Colgrave 2015; Orni et al. 2018; Rinthong and Maneechai 2018; Tungmunnithum et al. 2021). The leaves, seeds, and roots of pigeon pea are used for a range of medicinal benefits (Table 6).

TABLE 6 Health benefits of different parts of pigeon pea.

Physiological activity	Results	References
Hypocholesterolemic effect	The extract from pigeon pea leaves has significant amounts of flavonoids, stilbenes, terpenoids, glycosides, and alkaloids, which are important for lowering blood cholesterol levels.	Aja et al. (2015)
Antimicrobial effect	The cajanol (isoflavone) produced by pigeon peas was found to be the first antifungal compound when tested against various fungal pathogens.	Nix, Paull, and Colgrave (2015)
Hypoglycemic activity	Pigeon pea is a very effective hypoglycemic healing plant, treating diabetes and its complications with varying degrees of hypoglycemic activity.	Hosseinpour-Niazi et al. (2015)
Hepatoprotective effect	The protein extracts from the pigeon pea can work against liver inflammation, and reduce liver damage and disease development, and its complications.	Rizk et al. (2016)
Cancer prevention	The presence of cajanol (isoflavone) in pigeon pea roots was proven to have anticancer and can be used to treat breast and lung cancer cells.	Luo et al. (2010)
Anti-inflammatory effect	The presence of cajaninstilbene acid in pigeon pea leaves and its derivatives was found to serve as a valuable anti-inflammatory.	Huang et al. (2016)
Ant-hyperglycemic activity	The consumption of germinated pigeon peas is found to control hyperglycemia.	Uchegbu and Ishiwu (2016)
Antidyslipidemic activity	Some statistical results revealed that pigeon pea has significant amounts of antidyslipidemic activity in the body.	Dai et al. (2013)

Food Application of Pigeon Peas

Pigeon pea demonstrates remarkable versatility, finding application across a spectrum of functions including food, feed, fodder, forage, and medicinal purposes (Abebe 2022; Sharma, Agarwal, and Verma 2011). It can be consumed in various forms, offering diverse culinary experiences. These include whole seeds, boiled seeds, roasted seeds, canned seeds, cream seeds, sprouted seeds, and dhal (split seeds without the seed coat). To prepare dry pigeon pea seeds for consumption, they are typically soaked overnight to soften before being carefully cooked with a touch of salt and an aromatic blend of spices. Whole seeds are commonly cooked and then sautéed with flavorful spices before being served alongside grains. Germinated seeds can be enjoyed either raw or cooked (Nwosu et al. 2013). Pigeon pea-based foods encompass a range of options, including vegetative pigeon pea seeds, whole dry seeds, and dehulled split cotyledons (Figure 1).

FIGURE 1. (A) Pigeon pea crop, (B) vegetative pigeon pea, (C) whole dry seed, and (D) dehulled split cotyledons of pigeon pea seeds.

The functional properties of pigeon pea flour, including its thickening ability, water-holding capacity, gelation capacity, emulsification capacity, and foaming capacity, render it an exceptional ingredient for various food formulations (Olalekan and Bosede 2010). Additionally, it serves as a viable gluten-free cereal replacement. Incorporating protein-rich pigeon peas into cereals has been identified as an effective strategy to combat protein-calorie malnutrition in developing countries (Karri and Nalluri 2017). Pigeon peas can be utilized to prepare a diverse range of food items, including bread, tempeh, fresh sprouts, ketchup, biscuits, noodles, snacks, and various extruded food products (Jeevarathinam and Chelladurai 2020). Several researchers advocate for the use of legume flour as a protein source in bakery products (Eneche 1999). Notably, pigeon pea flour is suitable for applications in food products such as cookies, bread, and chapatis due to its high protein, iron, and phosphorus content (Sachanarula, Chantarasinlapin, and Adisakwattana 2022; Yadav, Yadav, and Kumar 2011). Consequently, it has been recommended for inclusion in school feeding programs and for vulnerable populations in developing nations. Rampersad, Badrie, and Comissiong (2003) reported that blending pigeon pea flour with cassava flour yields suitable extruded food products.

Gomezulu and Mongi (2022) highlighted that pigeon pea protein isolate enhances the physical properties of beef sausages, leading to greater consumer preference compared to sausages prepared using chemical phosphate binders. They proposed its use as a substitute for chemical binders in sausage making. Similarly, Torres et al. (2007) found that germinated pigeon pea flour significantly enhances the nutritional value of pasta without compromising its sensory properties. Ohizua et al. (2017) investigated the quality attributes of composite flour comprising unripe cooking bananas, pigeon pea, and sweet potato. They concluded that blended flour is a rich source of protein, fiber, and carotenoids, suitable for preparing complementary foods and serving as a wheat substitute in pasta, puddings, and biscuit production. Furthermore, Gbenga-Fabusiwa et al. (2019) demonstrated that composite biscuits made from pigeon pea and wheat flour could offer a low-cost, nutritious, and safe dietary option for individuals with diabetes. Furthermore, Table 7 outlines the various applications of pigeon pea flour in the development of different food products.

TABLE 7 Pigeon pea flour-based food products.

Foods	Application	Results	Reference
Pasta	Addition of 5%, 8%, and 10% germinated pigeon peas to semolina	Blending 10% pigeon pea with semolina increased fat, protein, dietary fiber, minerals, and vitamin contents affecting the sensory properties than pasta made from 100% semolina	Torres et al. (2007)
Noodles	Noodles made from 40 g of pigeon pea starch plus 60 g of rice starch per 100 g of total starch, 50 g of pigeon pea starch plus 50 g of rice starch per 100 g of total starch, and 70 g of pigeon pea starch plus 30 g of rice starch per 100 g of total starch were used to create the noodles	Decreased cooking time, cooking loss as well as cooked weight of cookies Increased transparency, slipperiness, and overall acceptability The blending of rice starch with 70 g of pigeon pea starch produces noodles with superior quality	Yadav, Yadav, and Kumar (2011)
Biscuits	Addition of 25%, 35%, or 50% pigeon flour to millet flour	Increased protein and energy Blending the recipe with 35% pigeon pea flour with millet flour shows good flavor, texture, and overall acceptability	Eneche (1999)
Baked snacks	Addition of 5%, 10%, and 15% pigeon pea flour to cassava flour	Increased protein content Contain a suitable crisp and texture	Rampersad, Badrie, and Comissiong (2003)
Composite flour	Composite flour unripe cooking banana, pigeon pea, and sweet potato	Increased protein, fiber, and carotenoids	Ohizua et al. (2017)

Conclusion and Future Prospects

Investigating the nutritional composition, bioactive compounds, food uses, and health properties of pigeon peas have been the subject of several studies. This review aims to provide up-to-date information on the nutritional composition, bioactive compounds, food applications, and health benefits of pigeon peas. Pigeon pea has an interesting nutritional profile in macronutrients and micronutrients, but also in antinutrients. High-quality protein, significant amounts of essential amino acids and dietary minerals, and low levels of saturated fat, cholesterol, and sodium make it a suitable and healthy alternative to meat.

Pigeon peas serve a multitude of purposes, including food, forage, firewood, fence material, and soil fertility improvement. They are consumed in various forms: as whole seeds, split seeds (known as dhal), as a vegetable using green seeds, and as fresh pods. Dry pigeon pea seeds can be ground into flour to produce a range of food products such as bread, noodles, snacks, biscuits, and pasta. The different anatomical parts of pigeon peas, including green leaves, roots, seeds, and pods, are rich sources of bioactive compounds with diverse beneficial properties, including anti-inflammatory, antibacterial, antioxidant, antidiabetic, and anticarcinogenic effects. Despite the already reported good nutritional and health properties of pigeon peas, further study in the area of pigeon pea-based functional food products development is recommended along with raising consumer awareness about its nutritional advantage and therapeutic properties.

Author Contributions

Abdulmajid Haji: conceptualization, data curation, writing–original draft, writing–review and editing (equal). Tilahun A. Teka: conceptualization, writing–original draft, writing–review and editing (equal). Tizazu Yirga Bereka: conceptualization, writing–original draft, writing–review and editing (equal). Kumsa Negasa Andersa: writing–original draft, writing–review and editing (equal). Kasahun Desalegn Nekera: writing–original draft, writing–review and editing (equal). Gemechu Geleta Abdi: writing–original draft, writing–review and editing (equal). Alemu Lema Abelti: writing–original draft, writing–review and editing (equal). Markos Makiso Urugo: writing–original draft, writing–review and editing (equal).

Acknowledgments

We are grateful to God for blessing us with good health to be able to write this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author.