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Ten new limonoids, named xylomolins O-X, were isolated from seeds of the mangrove Xylocarpus moluccensis, collected in the mangrove swamp of Trang Province, Thailand. Their structures were elucidated on the basis of comprehensive spectroscopic data analysis. The absolute configurations of five compounds (1, 3, 8-10) were unequivocally determined by single-crystal X-ray diffraction analyses, conducted with Cu Kα radiation. Xylomolins OU (1-7) are structurally intriguing mexicanolides, and xylomolin V (8) is a derivative of azadirone. Xylomolin W (9) is the first phragmalin 1,8,9-orthoester with report on X-ray crystallography from the genus Xylocarpus. In addition, xylomolin X (10) is the fifth member of the khayalactone class of limonoids with a hexahydro-2H-2,5-propanocyclopenta[b]furan motif. Compounds 1-10 inhibited NO production in LPS-activated RAW 264.7 macrophages in the range of 10.45-95.47% at the concentration of 100.0 μM. Xylomolin X (10) and xylomolin V (8), exhibited the most potent activity with IC 50 values of 9.90 ± 1.84 μM and 14.66 ± 2.33 μM, respectively., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2023. Published by Elsevier B.V.)