Characterization and biological activity of the main flavonoids from Swiss Chard (Beta vulgaris subspecies cycla)

The molecular components of a phenolic fraction (P2), obtained from liquid chromatography of a Swiss Chard (Beta vulgaris subsp. cycla) extract, were identified using HPLC-ESI-MS/MS. The primary P2 components were: vitexin-2″O-rhamnoside, its demethylated form 2″-xylosylvitexin, isorhamnetin 3-gentiobioside, and rutin. P2 “in toto” and the single components were characterized for antioxidant capacity, antimitotic activity on MCF-7 human breast cancer cells and for toxicity to human lymphocytes and macrophages. P2 inhibited MCF-7 cell proliferation (IC50 value=9 μg/ml) without inducing apoptosis, showed no toxicity to human lymphocytes and slight toxicity to macrophages. Vitexin-2″O-rhamnoside strongly inhibited DNA synthesis in MCF-7 cells, whereas 2″-xylosylvitexin and isorhamnetin 3-gentiobioside were activators; combinations of activators and inhibitors maintained the over-all inhibitory effect.