NO inhibitory constituents from Glycosmis craibii var. glabra

Six novel compounds, comprising three quinolones (1a, 1b, and 2) and three flavanones (3–5), along with seven known analogs (6–13), were isolated from the 95% EtOH extract of the stems and leaves of Glycosmis craibii var. glabra. The structures of the new compounds were elucidated using HR-ESI-MS, UV, and 1D and 2D nuclear magnetic resonance (NMR) data analysis. The absolute configurations were determined through Mosher ester and electronic circular dichroism (ECD) spectral analysis. Compounds 2, 6, 9, and 10 demonstrated inhibition of nitric oxide (NO) production stimulated by lipopolysaccharide in BV-2 microglial cells, with IC₅₀ values ranging from 13.5 to 20.1 μmol·L⁻¹, comparable to the positive control, dexamethasone.