The above
obtained residual sample was subjected to repeated
preparative thin layer chromatography using different
solvent systems, e.g solvent system 1. Methanol (5%):
benzene (95%) and solvent system 2. Chloroform (60%):
benzene (30%): acetic acid (10%). Three homogeneous
spots were collected in solvent system 2, having Rf values
of 0.87, 0.79 and 0.75 respectively