Physicochemical characterization of puerh tea polysaccharides and their antioxidant and alpha-glycosidase inhibition

Puerh tea is one of the most popular (or healthiest) beverages in Southeast Asia, because of its higher antioxidant, hypolipidemic and antidiabetic effects. One of the important active ingredients, tea polysaccharides (TPS) has long been recognized to possess immune modulatory and antidiabetic effects. In the present work, polysaccharides were isolated from puerh tea (PTPS) with aging (mild fermentation) for 1 year (PTPS-1), 3 years (PTPS-3) and 5 years (PTPS-5), respectively. The results obtained indicated that all of these three kinds of PTPS are acid heteropolysaccharides bound with proteins, with differences in molecular weights and in monosaccharide compositions. The longer aging process not only produced a higher yield of PTPS but also had higher contents of proteins and uronic acids which proportionally correlated with their antioxidant and a-glycosidase inhibitory activities (PTPS-5 > PTPS-3 > PTPS-1). The anti-a-glycosidase activities of PTPS-5 and PTPS-3 were found to be three times more and equally potent than that of the antidiabetic drug acarbose. All of these findings firstly indicate that the aging process not only induced changes in chemical compositions and proteins conjugation in PTPS, but also markedly enhanced antioxidant and anti-alpha-glycosidase activities. PTPS-5 exhibited potential antidiabetic effect and merits further studies. (C) 2013 Elsevier Ltd. All rights reserved.