Discovery of structurally important cycloartane-type triterpenes from Dysoxylum binectariferum leaves and their anti-inflammatory activity

Seven undescribed cycloartane-type triterpenes (4–10) were isolated from the leaves of Dysoxylum binectariferum. The chemical structures and relative stereochemistry of all cycloartane triterpenes were determined by analysis of 1D and 2D NMR and ESI-HRMS spectroscopic data. Compound 4 was found to be a diastereoisomer of the previously discovered compound 2 (beddomeilactol). The compound 5 was identified as the methyl ester of compound 1 (beddomeilactone). The compounds 6 and 7 were found to be diastereoisomers with only a stereochemical change at C-4 and their absolute stereochemistry established by X-ray analysis. Compounds 6–8 and 10 were identified as 3,4-seco-cycloartane type triterpenes, while compound 9 was elucidated as nor-3,4-seco-cycloartane triterpene. Nitric oxide (NO) inhibition was used to assess the anti-inflammatory effects of all newly isolated natural products in LPS-induced RAW 264.7 cell line. It was found that compounds 1, 2, 6 and 8 showed good IC₅₀ values of 14.98 ± 4.06, 38.50 ± 2.88, 36.95 ± 3.24, and 35.37 ± 4.51 µM respectively for NO production inhibition and were non-toxic to RAW 264.7 macrophages.