Antioxidant Activity of Partially Purified Fractions of Daniellia oliveri (Rolfe) Hutch and Dalziellii Stem Bark Ethanolic Extract

Ojochenemi Ejeh Yakubu, Sunday Ene-Ojo Atawodi and Kayode Adebisi Arowora

Background and Objective: Oxidative stress has been an underline cause of many disease conditions which come into play using different mechanistic steps. Antioxidants and other natural mechanisms have been put in place to mitigate the initiation and/or propagation of these mechanisms and further translation to their effects. This study was designed for in vitro assessment of antioxidant claims of the plant and to identify the specific fraction responsible for the acclaimed effects using different methods. Materials and Methods: Fractionation was achieved by column chromatography using solvents of different polarities to obtain fourteen fractions, following which Total Antioxidant Capacity (TAC), Total Flavonoid Contents (TFC), Total Phenolic Content (TPC), β-carotene bleaching inhibition assay, anti-lipid peroxidation inhibition assay and metal-chelating inhibition assay were conducted. Results: Antioxidant activities of fractions expressed in mg mL^–1 of Trolox Equivalent (TE). Values ranged from 0.03-0.13 mg mL^–1. The total flavonoid concentration varied from 15.71-29.20 mg mL^–1 expressed as quercetin equivalent. The β-carotene bleaching inhibition assay varied from 21.20-89.60 μg mL^–1, while anti-lipid peroxidation inhibition assay and metal-chelating assay results varied from 13.98-41.63 nmol mL^–1 and 382.53-412.27 g mL^–1, respectively. Linear correlation analysis between the parameters revealed a weak positive relationship. Conclusion: Based on the results, it is concluded that fractions of ethanolic extract of D. oliveri stem bark, particularly fractions 11 and 12, possess potent antioxidant activity irrespective of parameters used, suggesting that this extract contains substances that could act through synergistic action related to, but not limited to direct free radical scavenging, chelation of transition metals and direct inhibition of lipid peroxidation.

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