Efficient method for screening and identification of radical scavengers in the leaves of Olea europaea L.

In this article, an efficient method was developed to screen, isolate and identify the major radical scavengers in the leaves of Olea europaea L. by DPPH-HPLC-DAD, HSCCC and NMR. The method of DPPH-HPLC-DAD was used to screen the major radical scavengers. It was found that three major constituents (A, B, C) in the extract of the leaves of O. europaea L. possessed potential antioxidant activities. In order to identify the chemical structures of those compounds, the HSCCC method with a two-phase solvent system composed of petroleum ether-ethyl acetate-water at an optimized volume ratio of 6:600:700 (v/v/v) together with column chromatography was developed to isolate and purify the active compounds. Pure compounds A (225 mg), B (10 mg) and C (12 mg) with purities 92.6, 95.1 and 96.4%, respectively, were obtained from the crude sample (500 mg). Their structures were identified as oleuropein (A), luteolin-7-O-glucoside (B) and verbascoside (C) by (1) H-NMR and (13) C-NMR.