Five new compounds, 10-oxomornigrol F (1), (7″R)-(-)-6-(7″-hydroxy-3″,8″-dimethyl-2″,8″-octadien-1″-yl)apigenin (2), ramumorin A (3), ramumorin B (4), and (4S,7S,8R)-trihydroxyoctadeca-5Z-enoic acid (5), together with 31 known compounds (6-36), were isolated from the twigs of Morus alba (Moraceae). The chemical structures of these compounds were established using spectroscopic analyses, 1D and 2D NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and Mosher's methods. The anti-inflammatory activities of the compounds were evaluated by investigating their ability to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production in macrophage RAW 264.7 cells. Compounds 1, 2, 13, 17, 19, 25-28, and 32 showed inhibitory effects with IC50 values ranging from 2.2 to 5.3μg/mL. Compounds 1, 2, 17, 25, and 32 reduced LPS-induced inducible nitric oxide synthase (iNOS) expression in a concentration-dependent manner. In addition, pretreating the cells with compound 1, 17, and 32 significantly suppressed LPS-induced expression of cyclooxygenase-2 (COX-2) protein.
Keywords: Anti-inflammatory activity; Flavonoid; Moraceae; Morus alba; NO inhibition.
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