Phytochemistry and antioxidant assays of <i>Entandrophragma angolense</i> (Welw.) C.DC. (meliaceae) using DPPH and nitric oxide free radical scavenging methods

Abstract

Background: Medicinal plants have always been a veritable source of bioactive compounds and also serve as ‘lead molecules’ and templates for the design of medicinally useful synthetic molecules. Entandrophragma angolense Meliaceae, chemically characterized by synthesis of modified triterpenes known as limonoids which are powerful antioxidants and may help to prevent certain cancers and cardiovascular disease.

Objectives: To carry out phytochemical screening of the methanol bark and leaf extracts of Entandrophragma angolense, evaluate and compare the antioxidant activity of the methanol bark and leaf extracts of Entandrophragma angolense.

Method: The different phytochemicals in E. angolense were screened for using standard methods. The antioxidant activity of the plant was accessed using two DPPH free radical scavenging and Nitric oxide scavenging activities.

Result: The presence of alkaloids, flavonoids, condensed and hydrolysable tannins, saponins, steroidal nucleus, anthraquinones and reducing sugars in the methanolic bark extract were confirmed, with similar result for the methanolic leaf extract, except for the absence of alkaloids, anthraquinone and reducing sugars. The antioxidant assays indicated that both extracts from the two morphological plant parts showed considerable antioxidant activities (bark IC₅₀ 0.45, leaf IC₅₀ 0.41 for DPPH assay and bark IC₅₀ 0.42, leaf IC₅₀ 0.38 μg/ml for Nitric oxide assay) when compared with the standards (Ascorbic acid IC₅₀ 0.40 and IC₅₀ 0.40 μg/ml for DPPH and Nitric oxide assay, respectively, and Gallic acid, IC₅₀ 0.25 and IC₅₀ 0.35 μg/ml for DPPH and Nitric oxide assay, respectively).

Conclusion: E. angolense could be a potential source of natural antioxidant that could have greater importance as therapeutic agent in preventing or slowing accumulation of lipid peroxidation, and thereby oxidative stress related degenerative diseases.

Keywords: Phytochemical screening, Entandrophragma angolense, Antioxidant, DPPH, Nitric oxide