Abstract
Chemical investigation of the aerial parts of Oncocalyx glabratus resulted in the isolation of three new flavan derivatives, 5,3', 4'-trihydroxyflavan 7-O-gallate (1), 5,4'-dihydroxyflavan 7-3'-O-digallate (2) and 5,3'-dihydroxyflavan 7-4'-O-digallate (3), named oncoglabrinol A, B and C, respectively, together with four known flavonols, (+)-catechin (4), (+)-catechin-7-O-gallate (5), catechin-7-4'-O-digallate (6A) and catechin-7-3'-Odigallate (6B). The structures of the compounds were established by 1D, 2D NMR and ESI-HRMS spectral analyses. The biological activity of the compounds was tested through a series of in vitro assays designed for determining cytotoxicity, antiviral activity against hepatitis B virus, and antidiabetic activity. All compounds were found non-toxic and showed moderate anti-HBV activity. Compounds 3 and 6 showed dual PPAR agonistic activity while others were not effective.