Bioassay-Guided Investigation of the Tanzanian Plant <i>Pyrenacantha kaurabassana</i> 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-12<i>H</i>-benzo­[<i>b</i>]­xanthene-4-carboxylic acid (<b>1</b>) and 6,7-dihydroxy-10,11-dimethoxy-9-(7-methoxy-3-methyl-1-oxoisochroman-5-yl)-2-methyl-12-oxo-12<i>H</i>-benzo­[<i>b</i>]­xanthene-4-carboxylic acid (<b>2</b>), and a new hexadecahydrochrysen-3-ol (<b>3</b>) were isolated from the tubers of <i>Pyrenacantha kaurabassana</i>. Compounds <b>1</b> and <b>2</b> 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