August 26/Food & Farm Week -- According to a study from Tianjin, People's Republic of China, "Three polysaccharide-rich fractions named GTPS, OTPS, and BTPS were isolated from green tea, oolong tea, and black tea, respectively. Chemical characteristics, glycosidase inhibitory effects, and antioxidant properties of the three fractions were compared."

"Monosaccharides of GTPS were composed of D-rhamnose, L-arabinose, D-xylose, D-mannose, D-galactose and D-glucose, but there were no xylose and mannose detected in OTPS and BTPS. The molecular weight distributions were decreased from 9.2 to 251.5 KDa to 3.8 to 32.7 KDa with the fermentation of the tea from green tea to black tea.

"BTPS showed the highest alpha-glucosidase inhibitory activity, antioxidant activities on hydroxyl radicals and DPPH radicals. The differences in antioxidant activities and glycosidase inhibitory properties among the three polysaccharide-rich fractions appeared to be related to differences in monosaccharide composition and molecular weight distribution of the polysaccharide. Diabetes mellitus (DM) is one of the primary threats to human health due to its increasing prevalence, chronic course and disabling complications. Control of postprandial hyperglycemia and inhibition of oxidative stress are suggested to be important in the treatment of diabetes. Many efforts had been made to search for effective and safe alpha-glucosidase inhibitors and antioxidants from natural materials to develop a physiological functional food or lead compounds for curing diabetes. Coarse tea was used to cure diabetics in people in China and Japan. The hypoglycemic activity increased with the contents of polysaccharide in coarse tea. Many studies have focused on the hypoglycemic activities of tea polysaccharides, but little is known about the glycosidase inhibitory effects of tea polysaccharide," wrote H.X. Chen and colleagues, Tianjin University.

The researchers concluded, "The aim of this study was to find a tea polysaccharide with the best potential for exploitation in curing diabetes."

Chen and colleagues published their study in the Journal of Food Science ("Physicochemical Properties and Antioxidant Capacity of 3 Polysaccharides from Green Tea, Oolong Tea and Black Tea." Journal of Food Science, 2009;74(6):C469-C474).

For more information, contact H.X. Chen, Tianjin University, School Pharmaceutical Science & Technology, Tianjin Key Laboratory Modern Drug Delivery & High Effic, Tianjin 300072, People's Republic of China.

From the August 31, 2009, Prepared Foods E-dition