Phenolic contents, antioxidant activity and spectroscopic characteristics of <em>Pterocarpus angolensis </em>DC. stem bark fractions

Abstract

Oxidative stress has been implicated in the damage of biological molecules resulting in aging and diseases such as Alzheimer, cancer, diabetes, cardiovascular disorders. The study aimed at determining the phenolic contents and antioxidant activities of <em>Pterocarpus angolensis</em> crude extract and fractions. The crude extract and fractions of <em>P. angolensis </em>were evaluated for their phenolic contents using Follin-Ciocalteu reagent. The antioxidant activities were evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and reducing power assays. Ultraviolet-Visible and Fourier transform infrared spectroscopy were used to assess the spectroscopic characteristics. We obtained 7 fractions from the crude extracts after column chromatography on silica gel 60. The results showed that fraction two (PaF2a) displayed the highest DPPH radical scavenging activity (18.7 &micro;g/ml) but had the lowest phenolic content while fraction three (PaF2b) exhibited the highest reducing power activity (44.28 &micro;g/ml) with high phenolic content. Spectroscopic details showed that PaF2a had maximum absorbance at 287.1 nm while PaF2b displayed maximum absorbance at 288.2 nm. The infra-red spectroscopy presented four main characteristic fingerprinting at 1606, 1518, 1444 and 1064 cm^-1as fingerprints for <em>P. angolensis</em>. There was a difference in the wave number at C==C and C-O vibrations between PaF2a and PaF2b. In conclusion, this study has shown that PaF2a and PaF2b are the antioxidant rich fractions of <em>P. angolensis</em> stem bark and exhibited different spectroscopic characteristics.