Antioxidant properties of aqueous and ethyl acetate extracts of some plants used as herbal tea in Tanzania

Abstract

Okumu Ochanga, Mhuji Kilonzo

Objectives: The purpose of this study was to evaluate antioxidant activity of Rhus vulgaris, Sphaeranthus bullatus, Osyris lanceolata, Ocimum gratissimum, Cymbopogon citratus, Acacia nilotica, and Tylosema fassoglensis plants that have been used as herbal teas in Tanzania for treatment of various ailments including bacterial and fungal infections. Methods: Antioxidant activity of the aqueous (AQ) and ethyl acetate (ETA) plant extracts was assessed based on radical scavenging activity of the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) on January 2017. Briefly, DPPH (0.2 mm) was obtained by dissolving 3.94 mg of DPPH in 50 ml of pure methanol. The stock solutions of the extracts were prepared in methanol. Serial dilution using 96 well plates was employed to determine radical scavenging activities of different concentrations. Results: All plants demonstrated free radical scavenging activity ranging from 5.36% to 87.75% in different concentrations with the highest activity of 87.75% observed in S. bullatus aqueous extracts in its 500 mg/ml at 60 minutes and the lowest scavenging activity of 5.36% demonstrated by T. fassoglensis leaves ethyl acetate extracts in its 3.906 mg/ml. Scavenging activity was observed to change with polarity and time of reaction. Eighty five percent of AQ extracts exhibited the scavenging activity ranging from 80% to 87% at the concentration of 500 mg/ml compared to 39.3% that exhibited by ETA extracts at the same concentration. Total phenolic contents ranged from 57.7 ± 0.8 to 98.02 ± 1.1 mg gallic acid equivalent (GAE)/g dry weight. Conclusion: The use of herbal tea from S. bullatus, O. lanceolata, T. fassoglensis, A. nilotica, R. vulgaris, C. citratus, and O. gratissimum has potential antioxidant benefits to human health, so it should be used to prepare herbal tea for management of diseases.