Polyprenylated benzoylphloroglucinol-type derivatives including novel cage compounds from Hypericum erectum.

Hyperici erecti herba (Hypericum erectum THUNB.) showed a suppressive effect on generation of isovaleric acid by Corynebacterium xerosis. An ethyl acetate (AcOEt) soluble fraction of methanol extract of H. erectum showed the activity. The AcOEt fraction was separated by various successive choromatographical methods to give seven new compounds 1-7 along with some known compounds. The structures of the new compounds were elucidated to be polyprenylated benzoylphloroglucinol derivatives by means of HR-MS and NMR spectra including 2D-NMR. Some of these compounds had novel cage structures having benzoyltricyclo[3,3,1,1(3,7)]decane and benzoyltricyclo[4,3,1,1(3,8)]undecane skeletons arising from a polyprenylated phloroglucinol precursor by a transannular cyclization reaction. The isolated compounds were tested for suppressive activity, but they showed only weak activity.