STABILITY AND EFFICACY OF ANTI-DERMATOPHYTE CREAMS FORMULATED FROM SELECTED NIGERIAN MEDICINAL PLANTS

Abstract

Dermatophytosis is a fungal infection caused by dermatophytes which invade the keratinised tissue of humans or animals. Reported cases of skin irritation and increased epidermal thickness associated with some existing antifungal drugs necessitate the search for more efficient alternatives to treat the infections. Herbal alternatives are currently being explored but their stability and efficacy have not been fully reported. The aim of this work was to evaluate the physicochemical properties, stabilities and efficacies of formulated medicinal herbal anti-dermatophyte creams. The medicinal plants Cassia alata Linn, Cassia occidentalis Linn, Mitracarpus villosus Sw. Dc, Kigelia africana Jacq. and Acalypha wilkesiana Linn. were authenticated at the Herbarium of Nigeria Natural Medicine Development Agency, Lagos. The crude extracts were obtained with water, ethanol and petroleum ether separately using soxhlet extraction. Phytochemical analyses of the extracts were carried out by standard methods. Agar disc diffusion method was used to determine their antifungal activities against clinical isolates of Microsporum audounii, Epidermophyton floccosum, Trichophyton mentagrophytes and Malassezia furfur, all implicated in dermatophytic infections. Four cream formulations from triethanolamine, water, cetyl alcohol, steric acid and paraffin oil were subjected to colour, pH, spread of emulsion, rubbing-in effect and stability to centrifugation tests. The best formulation upon the determination of these characteristics was used as the cream base for anti-dermatophyte creams production. The formulated creams containing 0.5, 1.0, and 2.0% of the extracts were subjected to temperature stability test (-10, 4, 30, 37 and 45oC) using standard methods. Changes in fungal morphology, skin irritability and efficacy tests using six groups of 5 Wistar rats were carried out and the effectiveness of the extracts in the formulated creams was determined by comparing with 1% clotrimazole cream as reference drug. Data were analysed using ANOVA at α 0.05. Alkaloids content was highest in C. alata (4.2%) and lowest in A. wilkesiana (0.6%). The saponins (2.1%) and flavonoids (1.6%) contents were highest in A. wilkesiana while the lowest was in M.villosus (0.9%) and (0.06%), respectively. The C. alata contained highest tannin (2.4%) while M.villosus the lowest (0.04%). Ethanol extracts of the plants showed the best anti-dermatophytic activities (9-19 mm zones of inhibition) at 10000 µg/mL. The formulated cream base was white with pH 6.9, very high spreadability of emulsion, high rubbing-in effect, and stable at 4,000 rpm for 30 minutes. The formulated creams were stable to freeze-thaw test at -10 and 45oC, with pH range of 6.8 -7.3. There was no change in colour or odour with the exception of C. occidentalis extract cream. The skin sensitivity test indicated no irritation. Skin biopsy efficacy test showed that the cream containing 2% K. africana extract significantly exhibited the best mycological inhibitory activity compared to 1% Clotrimazole in terms of changes in fungal morphology. The formulation prevented dekeratinization from 55.4±0.6 to 32.4±0.2µm of the hair follicle and also reduced the epidermal thickness from 90.3±0.2 to 51.4±0.4µm to achieve 71.9 and 75.7% efficacy, respectively. The plant-based creams were stable and effective against dermatophytes. The clinical studies for their suitability for human use can be carried out.