Antifungal activity of Erigeron floribundus ( Asteraceae ) from Côte d ’ Ivoire , West Africa

Purpose: Erigeron floribundus is a reputed medicinal plant used in Côte d’Ivoire, West Africa for the treatment of skin disorders. The aim of this study was to evaluate the antifungal activity of this plant against fungi from human origin. Method: Dichloromethane, methanol 80% and aqueous extracts from the leaves with stem were tested for their antifungal activity against 7 strains of dermatophytes (Epidermophyton floccosum, Microsporum canis, M. gypseum, M. langeronii, Trichophyton mentagrophytes, T. rubrum, T. soudanense) and one strain of the filamentous fungus, Scopulariopsis brevicaulis. The assays were performed using the agar dilution method at serial concentrations ranging from 2 to 0.06 mg/ml. Result: Only the dichloromethane extract exhibited an activity against Microsporum canis and a broad spectrum of good antifungal activity against all the remaining fungi tested. Conclusion: To the best our knowledge, this is the first report of the antifungal activity of Erigeron floribundus against a wide range of dermatophytes, including Microsporum langeronii and Trichophyton soudanense, the most frequent dermatophytes in Côte d’Ivoire. E. floribundus might be potential sources for improved traditional medicines or new antidermatophyte agents for the treatment of dermatomycoses.


INTRODUCTION
Dermatophytes are fungi that can cause infections of the skin, hair, and nails due to their ability to utilize keratin.The organisms are transmitted by either direct contact with infected host (human or animal) or by direct or indirect contact with infected exfoliated skin or hair.The most common clinical manifestations are beard, glabous skin, scalp, groin, hand, feet, and nails.These infections, which constitute the most frequent fungal diseases in human Despite the existence of antifungal agents effective on dermatophytes, there is a need to search for alternatives.The relative high cost and constraints due to the length of the modern treatment curb the control of the dermatomycoses in developing countries like Côte d'Ivoire.Patients, in particular, the resource-poor people from remote areas still use traditional medicine for the treatment of various diseases from microbial and non microbial origin 6,7 10,11 was adopted to name the species.

Preparation of plant extracts
Powdered portions of the plant material (100 g) were successively extracted with five times their weight of water, dichloromethane and methanol (80%) at room temperature for 15 h.The filtrates were evaporated on a rotary evaporator (40 °C) to yield the crude extracts.For the aqueous extracts, 10 g of powder in 250 ml distilled water were boiled during 15 min.Each of the extracts was lyophilized and weighed.The yield was 4.20, 15.05 and 1.86 %, respectively, for the dichloromethane, methanol and aqueous extracts.

Fungi cultures
The antifungal activity of E. floribundus was evaluated against 8 strains of fungi, provided by the Medical Analysis Laboratory of Marseille (France).Seven of the strains were clinical isolates of the following dermatophyte species: Epidermophyton floccosum, Microsporum canis, M. gypseum, M. langeronii, Trichophyton mentagrophytes, T. rubrum and T. soudanense.One strain (Scopulariopsis brevicaulis) was an environmental filamentous fungus.

Antifungal assay
The antifungal activity was assessed according to the agar dilution method 12 on Sabouraud agar (Difco).Plant extracts were dissolved in dimethylsulfoxide and diluted to give serial twofold dilutions that were incorporated into growth medium.The resulting concentrations ranged from 2 to 0.06 mg/ml.Sabouraud agar plates were inoculated with 0.2 ml of a particular dermatophyte or fungi strain.The plates were incubated in duplicate over a period of 15 days at 30 °C.The minimal inhibitory concentration (MIC), defined as the lowest concentration that produced no visible fungal growth after the incubation time, was recorded.

RESULTS
The antifungal activity of dichloromethane, methanol (80 %) and aqueous extracts obtained from Erigeron floribundus revealed that only the dichloromethane extract showed a good antifungal activity against the dermatophytes and filamentous fungus used (Table 1).The MIC values were 0.25 mg/ml against the strains of Epidermophyton floccosum, Microsporum gypseum, M. langeronii, T. rubrum, T. sudanense and S. brevicaulis.The extract was effective on Trichophyton mentagrophytes with MIC value of 0.5 mg/ml and exhibited a moderate activity against Microsporum canis, with MIC value of 1 mg/ml.No antifungal activity was observed for both methanol and aqueous extracts.

DISCUSSION
In the present study, Erigeron floribundus was investigated for its antifungal activity against dermatophytes and filamentous fungus.E. floribundus is a medicinal plant commonly used in traditional medicine in Côte d'Ivoire as well as in other African countries to cure skin infections.The result indicated that the dichloromenthane extract was the most effective on clinical isolates of dermatophytes.This crude extract exhibited a broad spectrum antifungal activity with MIC values ranging between 1 and 0.25 mg/ml against Microsporum canis, M. gypseum, M. langeronii, Trichophyton mentagrophytes, T. rubrum, T. soudanense, Epidermophyton floccosum and Scopulariopsis brevicaulis.To the best of our knowledge, this is the first time the antifungal activity of E. floribundus has been reported against M. langeronii and T. soudanense, the most frequent dermatophytes causing dermatomycoses in Côte d'Ivoire.In a previous screening of 100 plants from Rwanda 13 and 228 from Uganda 14 for their antimicrobial activity, the ethanol (80%) extract of E. floribundus was shown to display antifungal activity against Microsporum canis and Trichophyton mentagrophytes with a MIC of 500 mg/ml.Both methanol and aqueous extracts of E. floribundus did not exert antifungal activity against the fungi tested.Previous antifungal screening carried out by Tra Bi et al. 15 on several ivorian medicinal plants indicated that the same dichloromethane extract tested here was active on yeast while the methanol extract was not effective.This observation may be attributed to the nature of the biological active compounds.The antifungal activity observed for the dichloromethane extract suggests that the active metabolites of Erigeron floribundus are mostly lypophilic (dichoromethane).E. floribundus from Cameroon was chemically screened and yielded saponins, flavonoïds, tannins, phenols, alkaloids and essential oils 16 .Among these compounds, the essential oils and flavonoids can be incriminated in the antifungal activity of E. floribundus.Some of these groups of compounds are lipophilic due to the presence of a prenyl chain.Therefore these components can be extracted by non polar solvents such as dichloromethane.The prenylated groups render the actives molecules more lipophilic inducing antimicrobial activity within interactions with cell membranes.This may probably explain the lack of activity observed with the polar (ethanol, methanol and water) extracts.However, there is a need to test the saponins, flavonoïds, tannins, phenols, alkaloids from E. floribundus for their antidermatophyte activity.A study is underway in order to identify the precise actives principles and understand the mode of action of E. floribundus.

1 , 4 .
are widespread in tropical countries.Dermatomycoses due to Epidermophyton floccosum, Microsporum gypseum, Trichophyton mentagrophytes and T. rubrum are commonly worldwide.Dermatoses caused by Trichophyton soudanense are limited to Africa.For instance, tinea capitis are endemic problem in Africa where they constitute a serious public health problem, particularly in children 2 and immunodeficient patients 3,In Côte d'Ivoire, the most frequent etiologic agents in school children are Microsporum langeronii and Trichophyton soudanense that infect scalp and hair 5 .
Our results offer a scientific basis for the use of Erigeron floribundus in traditional medicine in Côte d'Ivoire for treatment of skin disorders.The dichloromethane extract of this plant showed promising antifungal activity against dermatophytes, some of which are the most frequent species implicated in dermatomycoses in Côte d'Ivoire.This plant may also find application in veterinary medicine as some of the tested dermatophytes like Microsporum canis and Trichophyton mentagrophytes are zoophilic 17 .