Resumo

ANGULO-ESCALANTE, Miguel Ángel et al. Extracts of Swietenia humilis Zucc. Seed with Antifungal Activity in Rhizopus stolonifer (Ehrenb.:Fr.) Vuill. Rev. mex. fitopatol [online]. 2009, vol.27, n.2, pp.84-92. ISSN 2007-8080.

The present study is aimed to evaluate the antifungal effect of extracts obtained from seeds of Swietenia humilis, a tree of the meliaceae family rich in secondary metabolites with in vitro antifungal activity for the control of Rhizopus stolonifer. Extracts were obtained from the seeds using dichloromethane, methanol and hydro-alcoholic, and incorporated individually on a medium of potato-dextrose-agar (PDA) at 1, 2.5, 5 and 7.5% concentrations. The effect was determined on the mycelia growth inhibition, sporulation, and alteration of the Rhizopus stolonifer vegetative and germinative structures. R. stolonifer is a causal agent of vegetables soft rot. The mycelia growth inhibition induced by the methanol extract, was directly proportional to the concentration at 7.5%, and inhibited the mycelia growth about 70.3%. The hydro-alcoholic and dichloromethane extracts did not significantly affect this parameter. Applications over 5% of methanol extract did not allow fungi spore formation, whereas the hydro-alcoholic and dichloromethane about extracts inhibited 85.8 and 97.7% respectively at a concentration of 7.5%. The methanol extract decreased size and changed color of the fungi sporangium. The sporangium diameter in the control was 275 μM and 110 μM exposed with the methanol extract at 2.5%. Furthermore, zygospores formation was induced by this extract at 5%, as a result of a reproduction mechanism in adverse conditions that do not allow an asexual reproduction. The effect of the methanol extract in mycelia growth inhibition, sporulation, and alteration of the germination structures observed in this study can be attributed to the presence of compounds related with terpenoids. Their presence was demonstrated with characterization reactions and thin layer chromatography. Therefore, Swietenia humilis can be a source of secondary metabolites for new fungicides development.

Palavras-chave : Sporulation; mycelia growth; methanol extract.