Undescribed C-Glycosylflavones from Corn Silk and Potential Anti-inflammatory Activity Evaluation of Isolates

Abstract

Phytochemical investigation of corn silk resulted in isolation and characterization of four flavone C-glycosides, chrysoeriol 6-C-β-oliopyranosyl-7-O-β-D-glucopyranoside (1), 3′-methoxycassiaoccidentalin A (2), chrysoeriol 6-C-β-boivinopyranosyl-7-O-β-D-glucopyranoside (3), and ax-4"-OH-3′-methoxymaysin (4), a triterpenoid, friedelin (5), two sterols, (22E)-5,8-epidioxyergosta-6,22-dien-3β-ol (6) and 6β-hydroxystigmasta-4,22-diene-3-one (7), and a mixture of β-sitosterol and stigmasterol. Compounds 1 and 2 were previously undescribed. Structure elucidation of the isolated compounds was attained using spectral data including 1D and 2D NMR and HRESIMS. Compounds 1, 2, 5, and 6 inhibited iNOS activity in LPS-induced macrophages and decreased nitrite levels by 68.64+4.46, 65.67 + 6.47, 88.50 + 0.50, and 94.00 + 4.00 %, respectively, at 50 µM. Compound 5 also showed inhibition of NF-κB (51.00+1.50 %). Compounds 1 and 2 induced NAG-1 activity in chondrocytes by 1.80 + 0.05 and 2.00 + 0.13 fold, respectively. The extract of corn silk, however, did not exhibit inhibition of iNOS or NF-κB but induced NAG-1 by 1.80+ 0.51 fold.