Chemical constituents with antioxidant activity from the branches and leaves of Hultholia mimosoides

Four undescribed homoisoflavanoids ( 1 - 4 ), one homoflavonoid ( 5 ), ten dibenzoxocin derivatives ( 6a - 10a and 6b - 10b ), one dibenzoxocin-derived phenolic compound ( 11 ), one diterpenoid ( 13 ), three aliphatic dicarboxylic acid derivatives ( 14 - 16 ), together with the known diterpenoid 12- O -ethylneocaesalpin B ( 12 ) were obtained from the branches and leaves of Hultholia mimosoides . Their structures were elucidated by extensive spectroscopic techniques. Notably, each of the dibenzoxocins 6 - 10 existed as a pair of interconvertible atropisomers and the conformation for these compounds was clarified by NMR and ECD analyses. Protosappanin F ( 11 ) was a previously undescribed dibenzoxocin-derived compound in which one of the benzene rings was hydrogenated to a polyoxygenated cyclohexane ring and an ether linkage was established between C-6 and C -12a. The isolated polyphenols were tested for induction of quinone reductase and compounds 3 and 8 showed potent QR-inducing activity in Hepa-1c1c7 cells.