Xylomexicanins E-H, new limonoids from Xylocarpus granatum

Four novel tetranortriterpenoids, xylomexicanins E H (1-4), were isolated from the seeds of the Chinese mangrove, Xylocarpus granatum. Among them, xylomexicanin E (1) represents the first example of limonoid with azaspiro skeleton between B (pyrrolidine) and C rings, whose biosynthetic pathways were proposed. The structures were elucidated on the basis of one- and two-dimensional NMR (including H-1, C-13 NMR, DEPT, H-1-H-1 COSY, HSQC, HMBC, and NOESY) and confirmed by high-resolution mass spectrometry. Compound 2, the second example of a limonoid with a C-9-C-30 linkage, showed moderate activity against the A549 and RERF cell line with IC50 value of 18.83 and 15.83 mu M, (C) 2014 Elsevier Ltd. All rights reserved.