Abstract
The structure and hypoglycemic activity of tea polysaccharides has been extensively studied, while there are few reports on the characterization and hypoglycemic activity of dark tea polysaccharides. The crude dark tea polysaccharide (CDTPS) was optimally extracted from Fuzhuan dark tea. Six polysaccharide fractions (namely DTPS-1, DTPS-2, DTPS-3, DTPS-4, DTPS-5, and DTPS-6) were isolated from CDTPS, and their physicochemical, structural, and biological properties were compared and analyzed. The results revealed that the compositions, structural characteristics, and biological properties of the six DTPSs were different. Therein, DTPS-4 and DTPS-6 had looser morphology, faster solubility, and a more stable structure. Additionally, DTPS-4 had the optimum in vitro antioxidant capabilities, and DTPS-6 had the strongest in vitro hypoglycemic capabilities. In addition, a correlation analysis revealed that the molecular weight and uronic acid content were significantly related to their antioxidant and hypoglycemic activities. Our results indicated that DTPS-4 and DTPS-6 could be further developed into functional foods or additives, respectively.
Highlights
Tea is the second-largest consumed beverage in the world after water, with a long history
According to the optimal conditions obtained by the analysis and design, the crude dark tea polysaccharide (CDTPS) yield was obtained 8 of (6.067 ± 0.06%) by repeating three times, which was consistent with the predicted value, confirming the reliability of the response surface model
The extraction process of CDTPS was optimized, and the extraction yield, chemical composition, and structural and biological properties of the six DTPSs obtained from CDTPS were compared
Summary
Tea is the second-largest consumed beverage in the world after water, with a long history. Many in vivo experiments have shown that tea polysaccharides could reduce blood glucose by enhancing antioxidant capacity [3,16]. Studies have indicated that Fuzhuan DTPSs had a good capability to scavenge a variety of free radicals [17]. Qingzhuan DTPSs have been reported to possess good free radical scavenging and absorption capacities and ferric reducing activity [18]. These all reveal that DTPS can play a role in decreasing blood glucose via a variety of mechanisms and is expected to be further developed as a potential candidate substance for preventing and alleviating diabetes
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