Benzophenones from Hypericum carinatum.

Two new benzophenones were isolated from the leaves of Hypericum carinatum. Their structures were established on the basis of 2D NMR spectroscopic analyses and mass spectrometry as cariphenone A (6-benzoyl-5,7-dihydroxy-2,2,8-trimethyl-2H-chromene) (1) and cariphenone B (8-benzoyl-5,7-dihydroxy-2,2,6-trimethyl-2H-chromene) (2). Five known compounds, the phloroglucinol derivative uliginosin B (3), 1-eicosanol, sitosterol, stigmasterol, and campesterol, were also characterized. Compounds 1-3 were evaluated for their total antioxidant capacity through a total radical-trapping parameter assay. Only compound 1 showed moderate antioxidant activity, exhibiting inhibition of chemiluminescence similar to that of quercetin at the same concentration.