Phytochemical Constituents and in vitro Antioxidant Capacity of Methanolic Leaf Extract of Oxytenanthera abyssinica (A. Rich Murno)

Abstract

Aims: The antioxidant and phytochemical properties of leaf extracts of the Nigerian Oxytenanthera abyssinica were evaluated at different concentrations using ascorbic acid standard. This preliminary study investigates the potentially bioactive components of the plant which may renew research into its medicinal value. Study Design: Cold extraction of the leaf parts followed by evaluation of phytochemicals and antioxidant capacity using chromatographic and spectrophotometric methods. Place and Duration of Study: Department of Biochemistry, College of Natural and Applied Sciences, Michael Okpara University of Agriculture P.M.B.7267 Umudike Abia State, Nigeria. Methodology: The antioxidant properties were determined using three assay models: the 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) colorimetric test and  a modified version of in vitro antioxidant TBARS after cold extraction maceration. The activity was determined at different concentrations (10μg/ml,50μg/ml,100μg/ml,200μg/ml and 400μg/ml) of the extract and expressed as % inhibition. phytochemicals were determined by standard detection and spectrophotometric methods. Results: The yield of the methanolic leaf extract of Oxytenanthera abyssinica was 3.92% w/w dry matter.  Steroids (steroid glycoside), alkaloids, saponins, tannins, cardiac glycosides, flavonoids, phlobatanins, anthroquinone and terpenes were detected while cyanogenic glycosides were absent. The quantitative analysis yielded (in mg/100g):  flavonoids (1.51±0.23), alkaloids (1.40±0.02), polyphenols (1.31±0.32), tannins (0.071±0.40) and saponins (1.2±0.10). Oxytenanthera abyssinica’s DPPH reduction was highest at 400μg/ml (82.10 ± 0.01%) with IC50 of 56.2μg/ml. The ferric reducing power of the extract at 400μg/ml was 61±1.52% (FRAP: 0.61) and the inhibition of lipid peroxidation measured as TBARS was 81.0 ±1.11%. Conclusion: There is an indication that Oxytenanthera abyssinica contains important phytochemicals and an antioxidant capacity comparable with standard antioxidant compounds that may be linked to its beneficial effects on health.