New nitric oxide production inhibitors from Syzygium bullockii.

Three undescribed triterpene glycosides syzybullosides A-C (1–3) along with fourteen known compounds were isolated from the leaves of Syzygium bullockii (Hance) Merr.& L.M. Perry, including six triterpene glycosides (1–6), four phenolics (7–9, 17), four megastigmanes (10–13), and three flavonoids (14–16). The structures of 1–17 were elucidated by extensive spectroscopic analysis, including IR, HR-ESI–MS, 1D and 2D NMR spectra. Compounds 1–10 and 12–17 inhibited nitric oxide (NO) production in lipopolysaccharide activated RAW264.7 cells with IC₅₀ values ranging from 1.30 to 13.70 µM, lower than that of the positive control compound, L-NMMA (IC₅₀ = 33.8 µM). [ABSTRACT FROM AUTHOR]