Evaluation of the antifungal activity and mode of action of Lafoensia pacari A. St.-Hil., Lythraceae, stem-bark extracts, fractions and ellagic acid

Stem-bark extracts, fractions and the isolated constituent, ellagic acid of Lafoensia pacari St. Hil. (Lythraceae) were in vitro assayed for antifungal activity against a panel of yeasts, hialohyphomycetes as well as dermatophytes with the microbroth dilution method. The EtOH extract and its fractions and ellagic acid exhibited activity against Candida spp and Saccharomyces cerevisiae with MIC values between 250-1000 µg/mL, but they showed no action against filamentous fungi and dermatophytes (MIC>1000 µg/mL). Active extracts were evaluated in Neurospora crassa hyphal growth inhibition and sorbitol assays and then the effect of ergosterol on the MIC of ellagic acid was studied. The active extracts and its fractions and ellagic acid showed a blotchy zone around the paper disk and induced malformations of the hypha. Besides, MIC of the ellagic acid against the Saccharomyces cerevisiae was raised from 62 to 250 µg/mL in the presence of sorbitol 0.8 M, suggesting that the ellagic acid would probably exert its action on fungal cell wall. These results indicate that ellagic acid might be the main active antifungal compound of Lafoensia pacari and further suggest that the mode of antifungal action of these extracts and ellagic acid could be associated with the inhibition of fungal cell wall.