In vitro and in vivo antidermatophytic activity of the dichloromethane-methanol (1:1 v/v) extract from the stem bark of Polyscias fulva Hiern (Araliaceae)

Abstract

Background: During the last decades, the number of people suffering from dermatophytoses has seriously increased, mainly due to the development of resistant strains of microorganisms to a range of formally efficient antibiotics. Polyscias fulva, a medium size tree which grows in the West Region of Cameroon is traditionally used for local application against dermatoses and orally against venereal infections. The dichloromethane-methanol (1:1 v/v) extract from the stem bark of Polyscias fulva was evaluated for its in vitro and in vivo antifungal activities.

Methods: The plant extract was prepared by maceration of its stem bark powder in CH(2)Cl(2)-MeOH (1:1 v/v). The extract obtained was successively partitioned in hexane, ethyl acetate and n-butanol. Phytochemical screening was performed using standard methods. In vitro antidermatophytic activity was assayed by the well diffusion and broth microdilution methods. The degree of dermal irritation of the crude extract was determined in guinea pigs using the occluded dermal irritation test method. The in vivo antidermatophytic activity of the extract-oil formulation (1.25, 2.5 and 5% w/w concentrations) was evaluated using Trichophyton mentagrophytes-induced dermatophytosis in a guinea pigs model.

Results: Phytochemical screening indicated that, the crude extract, ethyl acetate, n-butanol and residue fractions contain in general saponins, tannins, alkaloids, anthraquinones and phenols while the hexane fraction contains only alkaloids. The ethyl-acetate, n-butanol and residue fractions displayed higher antifungal activities (MIC = 0.125-0.5 mg.mL(-1)) against eight dermatophytes as compared to the crude extract (MIC = 0.5-1 mg.mL(-1)). This latter appeared to have slight perceptible erythema effects on guinea pigs as the primary irritation index (PII) was calculated to be 0.54. In vivo, the antidermatophytic activities of the extract-oil formulations were dose-dependent. Griseofulvin-oil 5% at 0.01 g/kg and formulated extract-oil (5%) at 0.1 g/kg eradicated the microbial infection after thirteen and fourteen days of daily treatment respectively.

Conclusions: The results of preclinical in vitro and in vivo evaluations indicate that the extract-oil formulation at 5% may constitute an alternative means to alleviate fungal infections caused by dermatophytes.

Figure 1

Evolution of lesion scores during treatment of infected guinea pigs: females (1a) and males (1b). G: Griseofulvin-oil; KPOC: Palm Kernel oil control; NC: Negative control; SC: Simple control (Non infected or non treated).

Figure 2

Comparative illustration of the evolution of the infection during treatment of infected guinea pigs with P. fulva extract-oil. 1: Uninfected animal. 2: Infected untreated animal. 3: Infected animal treated with 0.1 g/kg of palm Kernel oil. 4: Infected animal treated with 0.01 g/kg of griseofulvin-oil at 5%. 5: Infected animal treated with 0.1 g/kg of extract-oil at 1.25%. 6: Infected animal treated with 0.1 g/kg of extract-oil at 2.5%. 7: Infected animal treated with 0.1 g/kg of extract-oil at 5%.

Figure 3

Evolution of the percent culture recovery during treatment of infected guinea pigs: females (3a) and males (3b). G: Griseofulvin-oil; KPOC: Palm Kernel oil control; NC: Negative control; SC: Simple control (Non infected or non treated).

Figure 4

Illustration of the irritant effect of Polyscias fulva extract moistened with distilled water.

Figure 5

Degree of irritation and it trends of change since opening of the patch 24 h after dermal application of 0.5 g of dichloromethane-methanol (1:1v/v) extract from the stem bark of Polyscias fulva.