Anti-Dermatophytic Potential of Formulated Extract of Cola nitida (Vent.) Schott& Endl. (Stem Bark)

Abstract

The antifungal activities of stem bark ethanolic extract of Cola nitida [Vent.) Schott & Endl. against fungi associated with dermatophytes was determined in vitro by agar cup diffusion, agar dilution technique, and time kill assay. The result showed that the extract at concentrations ranging between 6 mg/mL to 0.5 mg/mL produced zone of inhibition between 10 ± 0.1 and 25 ± 0.2 mm against the test fungi. The MIC and MFC of the extract ranged from 22.5 to 3120 µg/mL and 45 to 3120 µg/mL respectively. The MICs for Trichophyton rubrum and T. tonsurans were less than 100 µg/mL and the mechanism of antibiosis indicated that the formulated ethanolic extract was highly fungicidal. Since lower MIC and MFC indicates higher efficacy, the MIC/MFC in this study are within the range of ≤ 100 and ≥ 1000 µg/mL. The highest MIC in this study is 3120 µg/mL and active extract are those having MIC values ≤ 8000 µg/mL. The MIC index values, being less than or equal to 2, indicated the fungicidal attribute of the formulated ethanolic extract and suggested that fungicidal effects be expected on all the tested dermatophytes. In the time kill assay, the percentage log reduction of the viable cell count ranged between 0.35 Log10 cfu/mL at 2 hr to 0.96 Log10 cfu/mL at 4 hr for T. tonsurans while it ranged between 0.29 Log10 cfu/mL at 2 hr to 0.85 Log10 cfu/ml. The results showed that the extract exhibited a broad spectrum antifungal activity and justifies the use of Cola nitida in folkloric medicine for the treatment of various skin diseases in Nigeria.