Nitric oxide production inhibitors from Vietnamese Scutellaria indica: An in vitro and in silico study

Seven metabolites (1–7) were isolated from the Vietnamese Scutellaria indica, guided by anti-inflammatory activity. The identified compounds comprise scrocaffeside A (1), naringenin-7-O-glucoside (2), darendoside B (3), decaffeoylverbascoside (4), plantainoside C (5), acteoside (6), and isoacteoside (7). This is the first time the compounds 1–3 and 5 were isolated from the entire Scutellaria indica. Compounds 1–7 tested for their anti-inflammatory potential by inhibiting nitric oxide (NO) production. Compound 1 showed the most activity (IC50 = 31.4 μM), followed by compounds 2, 4, 6, and 7 exhibited IC50 values of 41.2, 87.4, 52.2, and 44.6 μM, respectively. However, compounds 3 and 5 were inactive (IC50 > 100 μM). Molecular docking was applied to study the affinity and interactions between compound 1 and inflammatory-caused proteins based on the in vitro results. Compound 1 generated the lowest binding free energy with the cyclooxygenase-2 (COX-2) target, which was −9.8 kcal/mol, followed by inducible nitric oxide synthase (iNOS, –8.4 kcal/mol), and interleukin-8 (IL-8, –7.6 kcal/mol). The results indicate that compound 1 derived from S. indica has the potential to be further explored and developed as an inflammatory inhibitor.