In Vitro Anti-Inflammatory Activity and Molecular Docking Analysis of Compounds Isolated from Beyeria viscosa

Inflammation contributes to the progression of numerous chronic diseases, and plants are a rich source of bioactive secondary metabolites. In this study, bioassay-guided isolation of the previously unexplored Australian native plant Beyeria viscosa (Labill.) Miq. yielded eleven known compounds (1-11). The chemical structures of these compounds were identified by detailed spectroscopic data analysis, and definitive structural confirmation was established using single-crystal X-ray crystallography for fritillebic acid (8) and herbacetin 3,7,8-trimethyl ether (5) for the first time. All compounds were first screened for nitric oxide (NO) inhibitory activity and cytotoxicity in lipopolysaccharide (LPS) and interferon (IFN)-γ-stimulated RAW 264.7 macrophages, and the active NO inhibitors were further assessed for tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) inhibition. Notably, compounds 5, 8, and 10 were evaluated for NO inhibitory activity for the first time, with compound 8 being the most potent (IC₅₀ = 8.8 ± 1.3 μM), compound 10 showing moderate potency (IC₅₀ = 12.2 ± 8.8 μM), and compound 5 being inactive. Among all tested compounds, fritillebic acid (8) emerged as the most active constituent, showing strong NO inhibition and moderate suppression of TNF-α and IL-6 production; therefore, it was further assessed in LPS-stimulated N-11 microglial cells, where it retained NO inhibitory activity (IC₅₀ = 12.3 ± 0.5 μM) with a favorable activity-cytotoxicity profile (LC₅₀ = 107.9 ± 1.9 μM). Consistent with the promising activity, molecular docking of compound 8 showed strong receptor-binding affinity with selected inflammation-related targets. Moreover, preliminary structure-activity relationship analysis of all isolated compounds suggested that substitution and oxygenation patterns may influence NO inhibitory potency. Overall, these findings identify fritillebic acid as the major anti-inflammatory lead from B. viscosa and highlight Australian native plants as a source of bioactive secondary metabolites.