Screening of Chinese herbal drug extracts for inhibitory activity on nitric oxide production and identification of an active compound of Zanthoxylum bungeanum

Sixty-eight water and methanol extracts from 34 Chinese herbal drugs, most of which are used for inflammatory diseases, were screened for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated J774.1 macrophages and in LPS/interferon (IFN)-γ-stimulated mouse peritoneal exudate macrophages. Among the extracts, methanol extracts of Myristica fragrans, Plantago asiatica, Rubia cordifolia, and Zanthoxylum bungeanum showed significant inhibition in J774.1 macrophages, while in mouse peritoneal exudate macrophages, water extracts of Ru. cordifolia and Scutellaria baicalensis and methanol extracts of Angelica megaphylla, My. fragrans, and Z. bungeanum inhibited the NO production. Among them, inhibition of water extract of Sc. baicalensis was found to be mainly due to direct scavenging of NO radicals, through an examination of its scavenging activity on PAPA NONOate-generated NO radicals, while water extract of Ru. cordifolia and methanol extracts of An. megaphylla, My. fragrans, P. asiatica, and Z. bungeanum showed inhibition on iNOS mRNA expression. At last, an inhibitory compound on iNOS mRNA expression was isolated from a methanol extract of Z. bungeanum and identified as 4-O-β-D-glucopyranosyldihydroferulic acid by NMR spectral analyses and chemical synthesis.