In vitro antioxidant capacity and free radical scavenging evaluation of active metabolite constituents of Newbouldia laevis ethanolic leaf extract

Abstract

Background: The aim of the present study was to evaluate the in vitro antioxidant and free radical scavenging capacity of bioactive metabolites present in Newbouldia laevis leaf extract. Results: Chromatographic and spectrophotometric methods were used in the study and modified where necessary in the study. Bioactivity of the extract was determined at 10 μg/ml, 50 μg/ml, 100 μg/ml, 200 μg/ml and 400 μg/ml concentrations expressed in % inhibition. The yield of the ethanolic leaf extract of N.laevis was 30.3 g (9.93%). Evaluation of bioactive metabolic constituents gave high levels of ascorbic acid (515.53 ± 12 IU/100 g [25.7 mg/100 g]), vitamin E (26.46 ± 1.08 IU/100 g), saponins (6.2 ± 0.10), alkaloids (2.20 ± 0.03), cardiac glycosides(1.48 ± 0.22), amino acids and steroids (8.01 ± 0.04) measured in mg/100 g dry weight; moderate levels of vitamin A (188.28 ± 6.19 IU/100 g), tannins (0.09 ± 0.30), terpenoids (3.42 ± 0.67); low level of flavonoids (1.01 ± 0.34 mg/100 g) and absence of cyanogenic glycosides, carboxylic acids and aldehydes/ketones. The extracts percentage inhibition of DPPH, hydroxyl radical (OH.), superoxide anion (O.- 2), iron chelating, nitric oxide radical (NO), peroxynitrite (ONOO−), singlet oxygen ( 1 O 2), hypochlorous acid (HOCl), lipid peroxidation (LPO) and FRAP showed a concentration-dependent antioxidant activity with no significant difference with the controls. Though, IC 50 of the extract showed significant difference only in singlet oxygen ( 1 O 2) and iron chelating activity when compared with the controls. Conclusions: The extract is a potential source of antioxidants/free radical scavengers having important metabolites which maybe linked to its ethno-medicinal use.