Nitric Oxide Inhibitors from the Stem Bark of Biancaea decapetala: An In Vitro and In Silico Study

This study presents the anti-inflammatory potential of compounds isolated from the stem bark of Biancaea decapetala (Roth) O.Deg., Fabaceae. Sixteen compounds were isolated through anti-inflammatory activity-guided fractionation, with structures elucidated mainly through NMR techniques. Notably, compounds 4,4′-dihydroxy-2-methoxystilbene, dihydrodehydrodiconiferyl alcohol, isolariciresinol, sappanchalcone-3′-methylether, and nocomtol were identified in this plant for the first time. The in vitro anti-inflammatory activity of all isolated compounds was assessed against lipopolysaccharide (LPS)-induced nitric oxide production in macrophage RAW264.7 cells. Compounds 3-deoxysappanchalcone and sappanchalcone-3′-methylether exhibited the most potent inhibitory activity with IC₅₀ values of 9.82 and 10.89 μM, respectively. Compounds isoliquiritigenin-4-methylether, intricatin, 4,4′-dihydroxy-2-methoxystilbene, dihydrodehydrodiconiferyl alcohol, isolariciresinol, isoliquiritigenin, protocatechuic acid, and nocomtol demonstrated moderate inhibitory effects with IC₅₀ values ranging from 42.51 to 86.13 μM. Conversely, compounds threo-7-methoxysyringylglycerol, 3-deoxysappanchalcone, 16-hydroxy-8(17),13-labdadien-15,16-olid-19-oic acid, vomifoliol, 15-dihydroxylabda8(17),13E-dien-19-oic acid, and taxiresinol, were inactive. In silico docking simulations further supported the experimental findings, indicating a high correlation between docking score and the number of interactions. These results underscore the potential of active constituents from B. decapetala for further exploration in the development of anti-inflammatory agents.