FORMULATION AND ANTIMICROBIAL EVALUATION OF A NIOSOMAL GEL INCORPORATING KIGELIA AFRICANA EXTRACT

Abstract

Topical delivery of herbal antimicrobials is often limited by poor stability and skin penetration of the free extract. This study aimed to develop and evaluate a niosomal gel loaded with the methanolic extract of Kigelia africana for topical antimicrobial application. Niosomes were prepared by the thin-film hydration (hand-shaking) technique using Span 60 and cholesterol in five surfactant-to-cholesterol ratios (F1–F5) and were characterized for particle size, polydispersity index (PDI), zeta potential, entrapment efficiency and surface morphology. The optimized niosomal dispersion was incorporated into a Carbopol 934 gel base and evaluated for appearance, pH, viscosity, spreadability, drug content, in-vitro drug release, and antimicrobial activity against Escherichia coli by the agar well diffusion method. Formulation F2 (Span 60: cholesterol, 150:100 mg) was identified as optimal, exhibiting the smallest particle size (128.42 nm), lowest PDI (0.241), highest negative zeta potential (−30.6 mV) and greatest entrapment efficiency (89.18 ± 0.51%) among the five formulations tested. Scanning electron microscopy confirmed spherical, smooth, uniformly distributed vesicles. The corresponding niosomal gel was brown, smooth and homogeneous, with a pH of 6.7 ± 0.03, viscosity of 5989 ± 0.54 cps, spreadability of 10.59 ± 0.12 g·cm/s and drug content of 97.82 ± 0.41%, and it exhibited sustained drug release reaching 92.7 ± 0.39% at 12 h. In the agar well diffusion assay, the niosomal gel produced a larger zone of inhibition against E. coli (13 ± 0.4 mm) than the pure extract (9.0 ± 0.3 mm), approaching the activity of standard ciprofloxacin (18 ± 0.2 mm, 10 μg/mL). These findings demonstrate that niosomal encapsulation markedly enhances the physicochemical performance and antimicrobial efficacy of Kigelia africana extract, supporting the developed gel as a promising, stable, natural alternative for the topical management of microbial skin infections.