Krishnolides A-D: New 2-Ketokhayanolides from the Krishna Mangrove, Xylocarpus moluccensis.

Four new khayanolide-type limonoids with a 2-carbonyl group, named krishnolides A-D (-), were isolated from the seeds of an Indian mangrove, , collected in the mangrove swamp of Krishna estuary, Andhra Pradesh. The relative and absolute configurations of these compounds were established by HR-ESIMS, extensive NMR investigations, single-crystal X-ray diffraction analysis with CuKα radiation, and experimental electronic circular dichroism (ECD) spectra. Krishnolides A-D are unusual khayanolides containing two large ester substituents of five or four carbon atoms at the C-3 and C-30 positions, respectively. Krishnolide A, containing an 8,14-epoxy group, exhibited moderate anti-Human Immunodeficiency Virus (HIV) activity with an IC value of 17.45 ± 1.65 μM and a CC value of 78.45 ± 1.69 μM, respectively. This is not only the first report of natural khayanolides from Indian mangroves of the genus , but also the first report of the anti-HIV activity of khayanolide.