New Bioflavonoids from Solanum nigrum L. by Anticholinesterase and Anti-tyrosinase Activities-guided Fractionation

Two new biflavonoids, (8-hydroxy-3'-beta-D-galactosyl-isoflavone)-2'-8'''-(4'''-hydroxy-flavone)biflavone (2); 2', 3', 5-trihydroxy-5 ''-methoxy-3 ''-O-a-glucosyl-3-4'''-O-biflavone (3) and along with apigenin (1) and quercetin-3-O-beta-glucoside (4) were isolated by activity guided fractionation from the whole plant of Solanum nigrum L.. The structures were established on the basis of UV, IR, 1D, 2D NMR and HRESI-MS spectroscopic methods. The anticholinesterase activity was performed against acetylcholinesterase and butyrylcholinesterase - the chief enzymes of Alzheimers' disease - using the Ellman method. The tyrosinase inhibitory activity was performed according to L-DOPA method. Since the ethyl acetate (IC50: 90.6+/-0.3 mu g/mL) and n-butanol (IC50: 140.6+/-1.7 mu g/mL) extracts exhibited good butyrylcholinesterase inhibitory activity, both were fractionated and the active fractions were used for isolation of the compounds. These both extracts were also exhibited better tyrosinase inhibitory activity (IC50: 76.0+/-0.6, and 156.8+/-1.9 mu g/mL, respectively). Tested enzyme inhibitory activities of S. nigrum were presented in this study for the first time.