Evaluation of antioxidant activity and identification of major polyphenolic constituents of Ebenus cretica L. [Thesis (M.Sc.)]

Phytochemical analyses of wild-growing plants could lead to the isolation and identification of secondary metabolites with significant biological activity. Many such plants used in traditional medicine and nutrition have already been explored. Recently there is a growing interest for unexplored wild-growing plants as potential inexpensive and renewable sources of added value natural products. The purpose of this study was to perform an assessment of the phytochemical composition and exploitation potential of the plant Ebenus cretica and to evaluate the antioxidant activity of its extracts (fractions) as well as to isolate and characterise polyphenolic metabolites using LC-DAD-MS (ESI+) and NMR methods. Aerial parts of the plant were extracted with solvents of increasing polarity and the resulting fractions were studied for their polyphenolic content and antioxidant potential. The total phenolic content of the fractions was determined using the Folin-Ciocalteu method and ranged between 108 and 428 mg of GAE/g dry extract. The antioxidant activity was evaluated using the DPPH and the Co(II)-EDTA-induced luminol chemiluminescence assay. The ethyl acetate fraction displayed the highest antioxidant activity in both assays. The chemical profile of the plant was evaluated by LC-DAD-MS (ESI+) and a significant number of compounds were identified. Results showed that E. cretica L. is rich in flavonoids, especially rutin (quercetin-3-O-rutinoside), isoflavones, as well as luteolin and quercetin derivatives. Furthermore, two metabolites (rutin and ombuine 3-O-rutinoside) were isolated for the first time from E. cretica and their structures were unambiguously identified by NMR spectroscopy.