Antioxidative Flavan-3-ol Dimers from the Leaves of Camellia Fangchengensis

Camellia fangchengensis Liang et Zhong, belonging to the genus Camellia sect. Thea (Theaceae), is an endemic tea species to the south and southwest areas of Guangxi province, People's Republic of China. Known as a wild tea plant, the leaves have been used for producing green tea or black tea by the local people of its growing area. HPLC and LC-MS analysis showed the leaves contain oligomeric catechins as major phenolic components. Further detailed phytochemical study led to the identification of five flavan-3-ol dimers (1-5) including two new ones, fangchengbisflavans A (1) and B (2) from the leaves of C. fangchengensis, together with six known monomers (6-11) and one glucoside (12), in addition to gallic acid (13). Their structures were determined by extensive spectroscopic analysis. Most of the isolates displayed significant antioxidant activities in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. The results suggested that the leaves of C. fangchengensis, rich in flavan-3-ol oligomers and monomers as potent antioxidants, could be a valuable plant resource for the production of tea and natural beverages.