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Received: 24 March 2016
Received in revised form: 28 June 2016
Accepted: 1 July 2016
Keywords
Tea
Cyclodextrin
Antioxidants
Thermal analysis
Abstract
Sideritis spp. (also known as Mountain tea), is a very common herb in Mediterranean basin, rich in bioactive polyphenolic ingredients. In this study, extraction from Sideritis scardica (SS) and concomitant inclusion complex formation of polyphenols in aqueous solutions of cyclodextrins (CDs) was investigated, by estimating the total phenolic content (TPC) and the antioxidant capacity of the extracts. Our results showed that the utilization of cyclodextrins boost the extraction yield of polyphenols. Both TPC and antioxidant capacity of SS aqueous extracts, containing CDs, presented greater values compared to pure SS aqueous extracts. Furthermore, the implementation of differential scanning calorimetry (DSC), conducted under inert and oxidative conditions, suggested the potential formation of inclusion complexes. The green extraction of Sideritis using cyclodextrins could pave the road for herb's more effective extraction and use in food and nutraceutical industry.
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Introduction
Cyclodextrins (CD) (cyclic glucose oligomers having six, seven or eight glucose units, linked by 1,4-a-glucosidic bonds and called respectively a-, ß- and y-cydodextrin) are formed by the enzymatic modification of starch. ß-cyclodextrin (ß-CD) is one of the most commonly used cyclodextrins due to its low cost production and the non-toxic character (Kurkov and Loftsson, 2013). As cyclodextrins are derived from starch, they are generally regarded as essentially non-toxic materials. However, ß-cyclodextrin can form insoluble complexes with cholesterol that disrupt the function of the kidneys so it should not be used in parenteral applications and its oral use should be limited to a daily maximum of 5 mg/kg. Both a-cyclodextrin, y-cyclodextrin and hydroxylpropyl-ß-cyclodextrin are suitable for oral applications. The acceptable daily intakes (ADIs) are given as "non-specified" by JECFA (Joint FAO/ WHO Expert Committee on Food Additives) for a-cyclodextrin and y-cyclodextrin (Astray et al., 2009). Oral bioavailability is very low and ß-CD is mainly metabolized by gut microbiota (Kurkov and Loftsson, 2013). 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD) is a ß-CD derivative, which presents enhanced water solubility and lower toxicity (Hsu et al, 2013).
ß-CD and HP-ß-CD can form inclusion complexes with a variety of bioactive molecules. In particular, CDs are shaped like a truncated cone and their central cavity is rather lipophilic, while their...