Evaluation of nitric oxide inhibition effect in LPS-stimulated RAW 264.7 macrophages by phytochemical constituents from Mesua beccariana, Mesua congestiflora, and Mesua ferrea

This study was conducted to evaluate the anti-inflammatory properties of the secondary metabolites and extracts from Mesua species by using nitric oxide inhibition and protein denaturation assays. Our phytochemical investigations on three species of Mesua plants, Mesua beccariana, M. congestiflora, and M. ferrea have resulted in sixteen pure metabolites. The anti-inflammatory effects of the crude extracts, as well as the pure metabolites were evaluated against mouse leukemic monocyte RAW 264.7 macrophage cell line and protein denaturation assay. All the crude extracts exhibited concentration dependent inhibition of the anti-inflammatory activity against RAW 264.7 cells. The effects of the crude extracts on inhibition of egg albumin denaturation were also evaluated. The crude extracts of M. beccariana and M. congestiflora showed significant inhibition of protein denaturation as compared to the reference drug, diclofenac sodium. Among the pure constituents tested, three xanthones, macluraxanthone (7), alpha-mangostin (10) and mesuarianone diacetate B (13) possessed significant in-vitro anti-inflammatory properties against RAW 264.7 cells with IC50 values of less than 16.0 mu M. The structure-activity relationship study of these xanthone was predicted based on the anti-inflammatory effects. It is deduced that xanthone derivatives which have trihydroxylated prenylated, diprenylated and indirectly prenylated and acetylated substituent groups on the xanthone skeleton contributed remarkable anti-inflammatory activity.