New pyranonaphthoquinone and pyranonaphthohydroquinone from the roots of Pentas longiflora.

Several quinone type compounds were isolated from the hexane, dichloromethane, and ethyl acetate extracts of the roots of Pentas longiflora. The hexane extract afforded two new compounds, [(3alpha,3'alpha,4beta,4'beta)-3,3']-dimethoxy-cis-[4,4'-bis(3,4,5,10-tetrahydro-1H-naphtho[2,3-c]pyran)]-5,5',10,10'-tetraone (1) and cis-3,4-dihydroxy-3,4-dihydromollugin (2), together with six known compounds, namely, pentalongin, mollugin, trans-3,4-dihydroxy-3,4-dihydromollugin, methyl-2,3-epoxy-3-prenyl-1,4-naphthoquinone-2-carboxylate, tectoquinone, and 3-hydroxymollugin. From the dichloromethane extract were isolated the three known compounds 3-methoxymollugin, methyl-3-prenyl-1,4-naphthoquinone-2-carboxylate, and scopoletin, while the ethyl acetate extract afforded the known 2-methoxy-3-methylanthraquinone.

A benzochromene from the roots of Pentas bussei.

A new homoprenylated benzochromene, methyl-5,10-dihydroxy-7-methoxy-3-methyl-3-[4-methyl-3-pentenyl]-3H-benzo[f]chromene-9-carboxylate (1), was isolated from the roots of Pentas bussei, collected from Kenya. The structure of this new compound was determined by spectroscopic data interpretation.