Enzymatic synthesis of vitexin glycosides and their activity

Vitexin is an active component of many traditional chinese medicines, and is found in various plants. The low solubility of vitexin limits its pharmaceutical usage. In this study, solvent-stable β-fructosidase was used to glycosylate vitexin in organic solvents. The β-fructosidase showed high activity and stability in 30-80% (v/v) ethyl acetate with 90-99% yields of vitexin glycosides. Highly efficient synthesis of β-d-fructofuranosyl-(2→6)-vitexin (1.04 g L^-1) and β-d-difructofuranosyl-(2→6)-vitexin (0.45 g L^-1) was attained in 50% (v/v) ethyl acetate solvent system from 1.5 g L^-1 vitexin. Two novel vitexin glycosides showed higher anti-tumor activities compared to that of vitexin by employing a human breast cancer cytotoxicity assay.