Isolation, structure elucidation, and biological activity of flavone 6-C-glycosides from Allaria petiolata

Preparative reversed-phase HPLC analysis of a methanol extract of the seeds of Alliaria petiolata afforded four flavone 6-C-glycosides: isoorientin, swertiajaponin, swertisin and isoscopatin-2"-beta-D-glucopyranoside. The molecular structures were elucidated by UV, ESIMS and comprehensive 1D (H-1 and C-13) and 2D (gradient multiple quantum filtered H-1-H-1 COSY, H-1-C-13 HSQC and H-1-C-13 HMBC) NMR analyses. The antibacterial and free radical scavenging activity, and general toxicity of these compounds were assessed. While none of these glycosides showed any significant antibacterial activities at test concentrations, all these compounds showed prominent free radical scavenging activity (IC50 values: 1.25 x 10(-2) to 7.69 x 10(-3) mg/mL) in DPPH assay. In the brine shrimp lethality assay very low levels of general toxicity (LD50 > 1.00 mg/mL) were displayed.