Chemical characterization of heteropolysaccharides from green and black teas (Camellia sinensis) and their anti-ulcer effect.

Abstract In order to obtain polysaccharides from green and black teas ( Camellia sinensis ), commercial leaves were submitted to infusion and then to alkaline extraction. The extracts were fractionated by freeze-thawing process, giving insoluble and soluble fractions. Complex arabinogalactan protein from the soluble fractions of both teas (GTPS and BTPS) were determined by methylation analysis and 1 H/ 13 C-HSQC spectroscopy, showing a main chain of (1 → 3)-β-Gal p , substituted at O -6 by (1 → 6)-linked β-Gal p with side chains of α-Ara f and terminal units of α-Ara f, α-Fuc p and α-Rha p . A highly branched heteroxylan from the insoluble fractions (GTPI and BTPI) showed in methylation analysis and 1 H/ 13 C-HSQC spectroscopy the main chain of (1 → 4)-β-Xyl p , substituted in O -3 by α-Ara f , β-Gal p and α-Glc p units. Evaluating their gastroprotective activity, the fractions containing the soluble heteropolysaccharides from green (GTPS) and black teas (BTPS) reduced the gastric lesions induced by ethanol. Furthermore, the fraction of insoluble heteropolysaccharides of green (GTPI) and black (BTPI) teas also protected the gastric mucosa. In addition, the maintenance of gastric mucus and reduced glutathione (GSH) levels was involved in the polysaccharides gastroprotection.