Ten limonoids and three protolimonoids from the Thai mangrove Xylocarpus moluccensis

Ten new limonoids, named xylomolones E-N (1-10), and two new protolimonoids, named xylomolones O (11) and P (12), were isolated from seeds of the Thai mangrove Xylocarpus moluccensis, together with the known compound, hispidone acetonide (13). The structures of these compounds were established by extensive NMR spectroscopic data, single-crystal X-ray diffraction analysis, and comparison of experimental ECD spectra. The absolute configurations of xylomolones E (1) and L (8) were unambiguously determined by single-crystal X-ray diffraction analyses, conducted with Cu Kα radiation. Xylomolones E-L (1-8) are mexicanolide-type limonoids, among which xylomolones J (6) and K (7) contain a C₇/C₂₈δ-lactone ring, whereas xylomolones M (9) and N (10) are phragmalin-type limonoids. Xylomolones O (11) and P (12) are two new protolimonoids. In addition, the ¹H and ¹³C NMR spectroscopic data for hispidone acetonide (13) was first assigned completely. In bioassay, xylomolones F (2), M (9), and P (12) exhibited moderate inhibitory activity against the production of NO in LPS-induced RAW 264.7 cells with IC₅₀ values of 31.54 ± 7.27, 62.84 ± 17.62, and 22.7 ± 6.56 μM, respectively.