Isolation of benzoic and cinnamic acid derivatives from the grains of Sorghum bicolor and their inhibition of lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells

Two new caffeoylglycerols, (hwanggeumchal A-B, 9-10), together with eight known derivatives (1-8) were isolated from the grains of Sorghum bicolor (L.) Moench var. hwanggeumchal. Their chemical structures were established mainly by 1D and 2D NMR techniques and MS data analysis. Amongst those, methyl 3,4-dihydroxybenzoate (2), 3,4,5-trihydroxycinnamate (3), methyl 3,4-dihydroxycinnamate (5), caffeoylglycolic acid methyl ester (7) and 1-O-caffeoylglycerol (8) displayed potential inhibitory effects against LPS-induced NO production in macrophage RAW264.7 cells with IC50 values of 11.9, 2.9, 27.1, 29.0 and 18.5μM, respectively. Furthermore, these compounds dose-dependently reduced the LPS-induced iNOS expression. In addition, pre-incubation of cells with compounds 2, 3 and 5 significantly suppressed LPS-induced COX-2 protein expression. SAR investigation revealed that compounds with a methyl ester (COOCH3) group possessed stronger activity. Our obtained data suggest that S. bicolor and its caffeoylglyceride-enrich extracts may be applied as supplemental and/or functional foods having a beneficial effect against inflammation.