Kadsuphilols A−H, Oxygenated Lignans from Kadsura philippinensis

Eight new oxygenated lignans, kadsuphilols A−H (1−8), were isolated from the leaves and stems of Kadsura philippinensis. Four of the isolated lignans (1−4) possess the normal C18-dibenzocyclooctadiene skeleton, while the other four lignans (5−8) are C19-homolignans possessing a substituted cyclohexadienone ring with a spiro-benzofuranoid moiety. The structures of the isolated metabolites were elucidated through spectroscopic analyses, including 2D NMR experiments. Compounds 1 and 4 are the first report of an R-biphenyl configuration with a β-oxygenated substituent at the C-9 position. The in vitro radical-scavenging activities of these compounds using DPPH were tested and evaluated. Compound 3 exhibited more potent activity than vitamins C and E.