Polyprenylated phloroglucinols from hypericum maculatum

Abstract

A detailed phytochemical investigation of the dichloromethane extract of the aerial parts of Hypericum maculatum Crantz. led to the isolation of four new (2-5) and six known (1a/b, 6-10) polyprenylated phloroglucinol derivatives. The new compounds were identified by means of spectral methods (MS, NMR, IR, UV) as (E)-4-(3,7-dimethylocta-2,6-dien-1-yl)-5-hydroxy-2-(3-methylbut-2-en-1-yl)-3,6-dioxocyclohexa-1,4-dien-1-yl isobutyrate (2), (E)-2-(3,7-dimethylocta-2,6-dien-1-yl)-5-hydroxy-4-(3-methylbut-2-en-1-yl)-3,6-dioxocyclohexa-1,4-dien-1-yl isobutyrate (3), (E)-4-(3,7-dimethylocta-2,6-dien-1-yl)-5-hydroxy-2-(3-methylbut-2-en-1-yl)-3,6-dioxocyclohexa-1,4-dien-1-yl 2-methylbutanoate (4) and (E)-2-(3,7-dimethylocta-2,6-dien-1-yl)-5-hydroxy-4-(3-methylbut-2-en-1-yl)-3,6-dioxocyclohexa-1,4-dien-1-yl 2-methylbutanoate (5). The known compounds have been identified as hyperpolyphyllirin/hyperibine J (1a/b), erectquione A (6), (E)-1-(3-(3,7-dimethylocta-2,6-dien-1-yl)-2,4,6-trihydroxyphenyl)-2-methylpropan-1-one (7), (E)-1-(3-(3,7-dimethylocta-2,6-dien-1-yl)-2,4,6-trihydroxyphenyl)-2-methylbutan-1-one (8), 1-(5,7-dihydroxy-2-methyl-2-(4-methylpent-3-en-1-yl)chroman-8-yl)-2-methylpropan-1-one (9) and 1-(6,8-dihydroxy-1,1,4a-trimethyl-2,3,4,4a,9,9a-hexahydro-1H-xanthen-5-yl)-2-methylpropan-1-one (10). The stereochemistry of 1a is described for the first time. The cytotoxicity of 1-6 on SKW-3, BV-173 and K-562 tumor cell lines was determined using MTT based assays.