Nitric oxide inhibitory flavonoids from traditional Chinese medicine formula Baoyuan Decoction

Three new flavonoid glycosides, (3R)-(+)-isomucronulatol-2'-O-β-D-glucopyranoside (1), (3R)-(-)-isomucronulatol-7-O-β-D-apiofuranosyl(1→2)-β-D-glucopyranoside (2), and (2S)-(-)-7,8-dihydroxylflavanone-4'-O-β-D-apiofuranosyl(1→2)-β-D-glucopyranoside (3), along with eight flavanones (4, 8, 10, 12, 15, 16, 21, and 24), four isoflavones (5, 11, 13, and 23), four chalcones (6, 14, 17, and 18), two isoflavans (19-20), one flavone (7), one flavonol (9), and one dihydrochalcone (22) were isolated from Baoyuan Decoction (BYD), a traditional Chinese medicine formula. The structures of the new compounds were established by detailed analysis of NMR and HRESIMS spectroscopic data, and their absolute configurations were determined by electronic circular dichroism (ECD) data. The inhibitory effects of the isolates were evaluated on nitric oxide production in lipopolysaccharide activated RAW 264.7 macrophage cells. Compounds 6, 9, and 10 showed the significant inhibitory activities, with IC50 values of 1.4, 13.8, and 9.3 μM, respectively, comparable to or even better than the positive control, quercetin (IC50, 16.5 μM). The assignment of these isolated flavonoids was achieved using UPLC-Q-trap-MS, and the results suggested that they were originated from Astragalus membranaceus and Glycyrrhiza uralensis.