Bioassay-guided investigation of the Tanzanian plant Pyrenacantha kaurabassana for potential anti-HIV-active compounds.

Two new anti-HIV xanthones, 6,7,11-trihydroxy-10-methoxy-9-(7-methoxy-3-methyl-1-oxoisochroman-5-yl)-2-methyl-12-oxo-12H-benzo[b]xanthene-4-carboxylic acid (1) and 6,7-dihydroxy-10,11-dimethoxy-9-(7-methoxy-3-methyl-1-oxoisochroman-5-yl)-2-methyl-12-oxo-12H-benzo[b]xanthene-4-carboxylic acid (2), and a new hexadecahydrochrysen-3-ol (3) were isolated from the tubers of Pyrenacantha kaurabassana. Compounds 1 and 2 showed moderate anti-HIV activity when tested in the deCIPhR assay on HIV virus type NL4-3, with IC50 values of 21 and 2 µg/mL, respectively.