Quinolone alkaloids with nitric oxide production inhibitory activity from Orixa japonica.

Four new quinolone alkaloids, orixalone A (1), B (2), C (3), and D (4), together with 12 known compounds were isolated from the stems of Orixa japonica. Orixalone A (1) inhibited nitric oxide production in murine macrophage-like RAW 264.7 cells stimulated with interferon-gamma and lipopolysaccharide.