Nitric Oxide Inhibitory Constituents from the Fruits of Amomum tsao-ko

ABSTRACT

Bioactivity-guided fractionation of MeOH extract of the dried fruits of Amomum tsao-ko led to isolation of nine compounds (1 – 9). Their structures were elucidated by spectroscopic methods including extensive 1D and 2D-NMR, as alpinetin (1), naringenin-5-O-methyl ether (2), naringenin (3), hesperetin (4), 2′,4′,6′-trihydroxy-4-methoxy chalcone (5), tsaokoin (6), boesenbergin B (7), 4-hydroxyboesenbergin B (8), and tsaokoarylone (9). Of these, compound 8 was isolated from a natural source for the first time, which was previously reported as a synthetic product. The isolated compounds (1 – 9) were tested for their inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages. Among them, three chalcone derivatives (compounds 5, 7, and 8) and a diarylheptanoid (compound 9) exhibited significant inhibitory activity on the NO production with IC₅₀ values ranging from 10.9 to 22.5 µM.