ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF Sclerocarya birrea (A. Rich.) Hochst SEED AND LEAF EXTRACTS

Abstract

Marula (Sclerocarya birrea (A. Rich.)Hochst.)is often referred to as the “tree of life “since its leaves, stem barks, roots, and fruits are used as food and traditional medicine. The present study is undertaken to investigate antioxidant and antimicrobial activities of the aqueous and methanolic extracts of S. birrea leaf and seed extracts. Qualitative analysis of major secondary metabolites including alkaloids, flavonoids, saponins, steroids, tannins and terpenoids of the S. birrea crude extracts were carried out using standard methods. The antimicrobial experiment was arranged as three factor experiment with extracts: leaf and seed of S. birrea; water and methanol; two bacteria: E. coli and S. aureus, and two fungi: Aspergillus versicolor, and A. niger in three replications. A complete randomized design (CRD) was used to determine the antimicrobial activities using disc diffusion and broth dilution methods. The results of the phytochemical screening of leaf aqueous extract has revealed the presence of alkaloids, flavonoids, terpenoids, tannins, and steroids while alkaloids, saponins, flavonoids, terpenoids, tannins, and steroids were detected in methanolic leaf extract of S. birrea. The antioxidant activity of the S. birrea crude extract as measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH)method indicated the highest DPPH radical scavenging activity (39.25%), hydrogen peroxide scavenging activity (17.77%) in the aqueous seed extract. The highest concentration of the methanolic leaf extract (200mg/ml) presented the strongest antibacterial activity showing the maximum zone of inhibition (18.53mm) against S. aureus. On the other hand, the seed aqueous extract presented the weakest antibacterial activity with the lowest inhibition zone of 13.67mm against E. coli. The highest concentration of the extract revealed the highest antifungal activity (19.93mm) that was recorded for methanolic seed extract against A. versicolor. The methanolic extract from leaf presented the strongest antibacterial activity with a Minimum inhibitory concentration (MIC) of 3.13mg/ml and a corresponding Minimum Bactericidal Concentration (MBC) of 3.13mg/ml against S.aureus. The strongest antifungal activity with (MIC) of 6.25mg/ml and the corresponding Minimum Fungicidal Concentration (MFC) of 6.25mg/ml was recorded for methanolic extract of S. birreaagainst A. versicolor. Furthermore, S. aureus was the more susceptible to the antibacterial activity while A. versicolor was more susceptible to the antifungal activity of the S. birrea crude extracts