Antimicrobial agents from higher plants: Activity and structural revision of flemiflavanone-D from Flemingia stricta

Flemiflavanone-D from Flemingia stricta is active in vitro against Staphylococcus aureus and Mycobacterium smegmatis. Reexamination and interpretation of its spectral properties required revision of its molecular formula to C₂₅H₂₈O₆ and its structure to 2S-5,7,4′-trihydroxy-6-γ,γ-dimethylallyl-3′-γ,γ-dimethylallyl-oxidoflavan-4-one. The new structure was confirmed when reaction with chlorotrimethylsilane sodium iodide in acetonitrile deoxygenated and cyclized flemiflavanone-D to the known dicycloeuchrestaflavanone A. The absolute stereochemistry of flemiflavanone-D was established to be 2S by circular dichroism measurements.     

A naphthalene glucoside lactone from Rhamnus wightii

A new naphthalene glucoside lactone was isolated from the acetone extract of the stem bark of Rhamnus wightii. Cynodontin, chrysophanol, physcion, musizin, lupeol, sitosterol, 7-hydroxy-5-methoxyphthalide, emodin, sitosterol glycoside, β-sorigenin are the known compounds; β-sorigenin may be an artifact of its glucoside. The co-occurrence of two lactone ring compounds, 7-hydroxy-5-methoxyphthalide and the naphthalide glucoside is the significant feature of this plant.