Evaluation of Nitrite Radical Scavenging Properties of Selected Zimbabwean Plant Extracts and Their Phytoconstituents

Oxidative stress resulting from accumulation of reactive oxygen species has been associated with disease. The search for natural antioxidants of plant origin is necessitated by the side effects associated with synthetic antioxidants currently available. The objective of the study was to determine the antioxidant activity of Combretum zeyheri, Combretum platypetalum, and Parinari curatellifolia extracts by determining nitrite radical scavenging ability. The nitrite radical scavenging assay was used to evaluate the antioxidant potential of the extracts. The total flavonoid content of P. curatellifolia methanol extract was determined by the aluminium calorimetric method. The aqueous and ethanolic leaf extracts of C. zeyheri, C. platypetalum, and P. curatellifolia extracts exhibited nitrite radical scavenging activity. The results show the scavenging activity in the order of potency: P. curatellifolia > C. platypetalum > C. zeyheri with concentration values of 103 µg/mL, 158 µg/mL, and 188 µg/mL for the ethanol extracts and 92.5 µg/mL, 97.5 µg/mL, and 198 µg/mL for the water extracts, respectively. P. curatellifolia ethanol extract was the most potent and the total flavonoid content was estimated to be 0.4 ± 0.05 mg/g quercetin and could account for the activity. Thus, our findings provide evidence that C. zeyheri, C. platypetalum, and P. curatellifolia leaf extracts could be potential sources of natural antioxidants