New benzylresorcinol and benzylstilbene derivatives from the fruits of orchid Galeola nudifolia Lour. with anti-neuroinflammatory activity.

Galeola nudifolia is a medicinal orchid recognized as a valuable source of structurally diverse natural products with potential therapeutic applications. Its chemical composition and biological activities remain largely unexplored, particularly with respect to anti-neuroinflammatory activity. Bioassay-guided investigation of the non-polar fractions of G. nudifolia fruits led to the isolation of six new compounds, including three benzylresorcinol (1-3) and three benzylstilbene (4-6) derivatives, together with thirteen known compounds (7-19). Their structures were elucidated through comprehensive spectroscopic analyses, including HR-ESIMS, 1D and 2D NMR experiments. The anti-neuroinflammatory activities of all isolated compounds were evaluated in LPS-stimulated BV-2 microglial cells by measuring nitric oxide (NO) production. Compounds 1-6 and 8-13 exhibited significant inhibitory effects on NO production, with IC50 values ranging from 6.59 to 15.79 µM. Notably, compounds 6 (IC50 = 7.77 µM), 10 (IC50 = 7.48 µM), 11 (IC50 = 8.62 µM), and 12 (IC50 = 6.59 µM) showed superior inhibitory potencies compared to the positive control (grossamide, IC50 = 9.23 µM). Immunofluorescence analyses showed that compound 12 reduced iNOS expression and NF-κB p65 nuclear translocation, whereas molecular docking provided qualitative predictions of possible interactions of compounds 6 and 10-12 with iNOS and the IκBα/NF-κB complex. These findings expand the known chemical diversity of G. nudifolia and identify its benzylstilbene derivatives as natural products with anti-neuroinflammatory activity.