Evaluation of the anti-radical activity of methanolic and aqueous extracts of stem, stem bark and leaves of Waltheria indica by scavenging the free radical cation ABTS

Abstract

Background: Waltheria indica is an antioxidant rich flowering plant species in its various parts and usually used in sub-Saharan Africa’s traditional medicine. The aim of this work was to evaluate the anti-radical activity of different concentrations of aqueous and methanolic extracts of stem, stem bark and leaves of Waltheria indica, in order to determine the most antioxidant organ of the plant on the one hand and the type of extraction allowing to collect the maximum of bioactive compound on the other hand. Methods: The method used is based on the measurement of the free radicals of the radical cation of 2,2'-azinobis [3-ethylbenzothiazoline-6-sulfonic acid] (ABTS•+) compared to that of a reference antioxidant, the gallic acid. Results and Discussion: With the methanolic extraction, the results obtained showed that the stem bark was the most active organ followed by the stem and then the leaves. The IC50 obtained were: for the stem bark (IC50 = 4.3 µg.mL-1); for the stem (IC50 = 6 µg.mL-1); and the leaf (IC50 = 37.5 µg.mL-1). Gallic acid, the referenced antioxidant, showed an IC50 of 0.41 µg.mL-1. Regarding the extraction method, aqueous extraction had a higher yield (IC50 of stem aqueous extract = 2.5 µg.mL-1) compare to methanolic extraction (IC50 of stem methanolic extract = 6 µg.mL-1). Conclusion: Aqueous extraction showed a better yield than methanolic extraction. The various organs of Waltheria indica, particularly the stem bark, can provide natural antioxidants that can be used in preventive medicine.