Limonoids from the seeds of Xylocarpus granatum and Xylocarpus moluccensis, Suratthani province

Abstract

The present study is to isolate and characterize the bioactive limonoids from the seeds of Xylocarpus granatum Koeing. and Xylocarpus moluccensis Roem. collected in Suratthani province. Chromatographic fractionation of EtOAc crude extract of X. granatum led to the isolation of ten known compounds, namely xyloccensin K (1), 6-acetoxycedrodorin (2), andirobin (3), methylangolensate (4), methyl-6-β-hydroxy angolensate (5), gedunin (6), 7-deacetylgedunin (7), kihadalactone A (8), toonaciliatavarin E (9) and protoxylocarpin G (10). Likewise, the isolation of EtOAc crude extract of X. moluccensis provided a new mexicanolide, named as thaimoluccensin D (14), and additional three known compounds including protoxylocarpin H (11), moluccensin I (12), 2-hydrofissinolide (13) and hispidone (15), other than compounds 3, 4, 6 and 7 also found in X. granatum. The structures of isolated compounds were established mainly by analysis of spectroscopic data and by comparison with data in the literature for known compounds. Furthermore, the complete assignments of NMR and the crystal structure of andirobin (3) obtained from both species were herein reported for the first time. Isolated compounds were further tested for their anti-inflammatory effects by monitoring the inhibition of nitric oxide (NO) production in activated macrophage RAW 264.7 cells. Only a gedunin type limonoid, 7-deacetylgedunin (7), showed the most potent activity with an IC₅₀ value of 4.75 µM.