Two acylated flavonoid glycosides from Stachys bombycina, and their free radical scavenging activity

Preparative reversed-phase HPLC analysis of the methanol extract of the aerial parts of Stachys bombycina (Lamiaceae) afforded two acylated flavonoids glycosides, chrysoeriol 7-O-[6-O-acetyl-β-D-allopyranosyl]-(1 → 2)-β-D-glucopyranoside (1) and apigenin 7-O-β-D-(6-p-coumaroyl)-glucopyranoside (2), the former being a new natural product. The structures of these compounds were elucidated unambiguously by UV spectroscopic analyses using shift reagents, ESIMS, and 1D and 2D NMR spectroscopic techniques. The free radical scavenging activity of 1 and 2 compounds were assessed by DPPH assay, and the RC50 values were 1.25 × 10-2 and 7.69 × 10-4 mg/mL, respectively.