HPLC-PDA analysis and antioxidant activity of Algerian Lycium leaves

Abstract

Lycium is a genus of flowering plants in the nightshade family, Solanaceae. This study aims at investigating the chemical composition and the antioxidant activity of Lycium halimifolium Mill leaves. A fractionation of its crude hydro-methanolic extract was carried out using organic solvents. The characterization of chemical compounds was carried out by HPLC-PDA, and the antioxidant activity of different fractions was evaluated by two methods; DPPH and FRAP. The obtained results show that the two fractions; ethyl acetate (ACT) and n-butanol (BUT); of the leaves of L. halimifolium Mill exhibited considerable contents of polyphenols estimated at 21.66± 0.22, 42.21 ± 0.32 μg GAE/ mg DW, respectively. Whereas, those of flavonoids also showed interesting values estimated at 29.7 ± 0.03 for ACT and 20.3 ± 0.05 μg QE / mg DW for BUT. On the other hand, low levels of tannins were obtained and equal to 7.35 ± 0.02 (ACT) and 8.12 ± 0.36 μg CE / mg DW (BUT). The evaluation of the two fractions’ antioxidant activity showed that the BUT fraction (IC50= 56.142 ± 0.54 μg/ml) was more active than the ACT fraction (IC50= 303.04 ±1.35μg/ml). The chromatographic identification of ACT fraction made it possible to characterize a flavonoid (rutin) with a rate equal to 9.95% and a phenolic acid: protocatechic acid with 3.45%. While the BUT fraction contains the phenolic acid: the Protocatechic acid estimated at 19.11%. Protocatechic acid was reported to have been identified for the first time in this work in the leaves of L. halimifolium Mill.