Abstract
Twelve representative edible Chinese teas (Camellia sinensis L.) from six categories (dark tea, black tea, oolong tea, white tea, yellow tea, and green tea) were selected in this study. Tea polysaccharides (TPs) were extracted with hot water, and their structural properties and biological activities, mainly antioxidant and anti-diabetic activities, were systematically evaluated. Results revealed that the extraction yields of TPs ranged from 1.81% to 6.38%, and Pu-erh tea polysaccharides had the highest extraction yield (6.38 ± 0.28%). The chemical compositions, molecular weight, and compositional monosaccharides of TPs varied among the six categories of tea. It appeared that all TPs were protein-bound acid heteropolysaccharides, and all TPs exhibited obvious antioxidant and anti-diabetic (e.g., α-glucosidase inhibitory and antiglycation) activities. Particularly, Pu-erh tea polysaccharides also contained the highest total phenolic and protein contents, and also exhibited the best antioxidant and anti-diabetic activities. Moreover, for the structural-function relationship, the heat map analysis found that total phenolic and protein contents in TPs were positively correlated with their antioxidant and anti-diabetic activities, indicating that the presence of phenolic compounds and proteins in the TPs might be the main contributors to their bioactivities. The conclusion from this study can help understand the structural-function relationship of crude tea polysaccharides.
Highlights
Tea, the product made from the leaves of Camellia sinensis L., has become a very popular beverage around the world [1]
Different kinds of tea had great effects on the antioxidant activities of Tea polysaccharides (TPs), especially, the dark tea and black tea polysaccharides exhibit excellent antioxidant activities, which might be associated with the complex alterations in the chemical compositions of tea that occurred during different fermentation degrees, leading to changes in their biological characteristics
Results revealed that the main compositional monosaccharides of TPs were Man, Rha, GlcA, GalA, Glc, Gal, and Ara
Summary
The product made from the leaves of Camellia sinensis L., has become a very popular beverage around the world [1]. Recent studies report that drinking tea imparts various nutritional and health functions, such as antioxidation, immuno-regulation, anti-inflammation, anticancer, anti-obesity, anti-diabetes, cardiovascular protection, and hepatoprotection [5,6,7,8]. These health functions can be mainly attributed to various bioactive components in tea, such as polyphenols (e.g., catechins and flavonoids), polysaccharides, pigments, alkaloids (theobromine, caffeine, theophylline, etc.), free amino acids, saponins, and inorganic elements [9]. The results can be helpful for further application of tea polysaccharides in the development of functional food in the food industry
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