In vitro antioxidant and antifungal activities of Rhizophora racemosa G.F.W. Mey. stem bark extracts

Abstract

Rhizophora racemosa is used traditionally in Nigeria to treat human microbial infections. In this study, the dichloromethane (DCM), ethylacetate (EAC) and ethanol (ETH) stem bark extracts of Rhizophora racemosa were evaluated for their antioxidant and antifungal activities. Antioxidant activity was evaluated by measuring their DPPH and ABTS radical scavenging activities, H2O2 scavenging activity, reducing power and metal chelating activity. The antifungal activity against Trichophyton mentagrophyte, Microsporum canis, Trichophyton rubrum and Epidermophyton floccosum was evaluated by the agar well diffusion and microdilution assays. In the antioxidant assay, ETH extract exhibited a higher radical scavenging activity (DPPH and ABTS), H2O2 scavenging activity and reducing power than EAC extract, while the EAC extract demonstrated a greater metal chelating ability than the other extracts. In the antifungal test, EAC and ETH extracts demonstrated inhibitory effects (MIC = 250–440 µg/mL and 180–300 µg/mL, respectively) with the ETH extract being the most effective against the test etiological agents. Rhizophora racemosa stem bark may serve as potential sources of new antioxidant and antifungal compounds.