Anti-inflammatory, Radical-Scavenging, and Chelating Activities of Nor-triterpenes from Galphimia spp. (Malpighiaceae)

Abstract

Abstract Anti-inflammatory and radical-scavenging activities of the methanolic extract from the leaves of Galphimia spp. collected in Morelos, Mexico, and isolated galphimidin (1) and galphimidin B (2), were evaluated. Nor-triterpenes 1 and 2 displayed anti-inflammatory activity inhibiting the nitric oxide production by the LPS-induced RAW 264.7 cell model, with IC50 values of 22.62 and 20.19 µg/mL, respectively, which were higher than the crude extract with an IC50 of 42.92 µg/mL. Furthermore, the TPA (12-O-tetradecanoylphorbol-13-acetate)-induced ear edema in mice assay displayed results of EC50 of 2.03 mg/ear to the methanolic extract, 1.91 mg/ear to 1, and 1.42 mg/ear to 2. Docking analysis of 1 and 2 at the iNOS active site indicated the negative influence of water molecules by mediating the ligand-protein interaction through hydrogen bonds interactions that increase the energy expenditure. These results explain the observed anti-inflammatory action of 1 and 2 by iNOS inhibition, which is better modulated in silico by the absence of water in the active site. The methanolic extract showed a low radical-scavenging activity inhibiting free radicals DPPH• with values of 57.33% compared to isoquercetin and rutin as positive controls. Nevertheless, the crude extract displayed high activity inhibiting ABTS•+ free radicals at 83.31% that was in accordance with high reducing potential of total polyphenols by Folin-Ciocalteu method with value of 3591.11 mg of gallic acid (GAE)/g of biomass. Compounds 1 and 2 did not present radical-scavenging activities but showed metal-chelating activity of 27.62% and 30.54%, which were higher values than EDTA as positive control.