| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4561899 | Food Research International | 2012 | 9 Pages |
Oolong tea (OT) is unique for its flavor and healthy effects. We have reported that the polypheonols of OT possessed antioxidant anticancer, and hypolipidemic effects. In addition, tea polysaccharides (TPS) have long been recognized to have antioxidant, immunomodulatory and antidiabetic properties. Since there are three typical kinds of OTs, e.g. Tieguanyin, Fenghuangdancong and Dahongpao with the lightest, intermediate and the highest degree of fermentation respectively, it is important for us to know whether fermentation degree affected the production and their bioactivities of tea polysaccharide. In the present study, three polysaccharides named TTPS, FTPS and DTPS were isolated from these three typical kinds of oolong teas in the above order respectively. Physicochemical characteristics, in vitro antioxidant activity and alpha-glucosidase inhibitory effect of TTPS, FTPS and DTPS were studied. Analysis of the chemical compositions (protein, rot neutral sugars and uronic acid) revealed that they all belonged to acid heteropolysaccharides bound with protein. The contents of protein and uronic acid but rot neutral sugars proportionally increased with degree of fermentation, highest in DTPS, which significantly correlated with their potencies in antioxidant and alpha-glucosidase inhibitory activities. Analysis of neutral sugar compositions showed that they all contained seven monosaccharides with different molar ratio. Measurements of their molecular weight by high performance gel permeation chromatography indicated that 92.9% of TTPS and 94.4% of DTPS had a peak of molecular weight of 0.82 × 106 and 2.64 × 106 respectively, but that of FTPS had 34.2% with 0.93 × 106 and 68.8% with 0.01 × 106 respectively. Fourier Transform IR spectra exhibited that they all had similar characteristic absorption bands of uronic acid, protein, polysaccharide and pyran-glycosides respectively. Furthermore, measurements of antioxidant activities by assays of DPPH, ABTS and ferric-reducing antioxidant power (FRAP) showed that DTPS was the most potent, FTPS the next and TTPS the least respectively. Similarly, DTPS possessed the strongest inhibitory potential against alpha-glucosidase activity, followed by FTPS and then TTPS. The potencies of the bioactivities of these three OTPS were apparently proportional to their contents of protein and uronic acid, suggesting that the higher degree of fermentation of oolong teas produced higher contents of protein-bound acid heteropolysaccharides accompanied with higher antioxidant and alpha-glucosidase inhibitory activities. Perhaps, DTPS had a potential to play a role in prevention of type 2 diabetes mellitus. Further studies to confirm this contention is in progression.
► Three polysaccharides were isolated from three typical kinds of oolong teas. ► DTPS was the most potent antioxidant activities. ► DTPS possessed the strongest inhibitory potential against alpha-glucosidase activity.
