Pimenta pseudocaryophyllus inhibits virulence factors and promotes metabolic changes in candida yeast

Abstract

Introduction: This is the fi rst study to examine the in vitro susceptibility and the expression of virulence factors in Candida species in the presence of Pimenta pseudocaryophyllus (Gomes) L.R. Landrum (Myrtaceae), a Brazilian plant known as pau-cravo. Additionally, the mechanisms of action of the crude ethanol extract and the ethyl acetate and aqueous fractions of this plant were investigated. Methods: The in vitro susceptibility of Candida was tested using the broth microdilution method, whereas an XTT reduction assay was used for biofi lms. Adherence was determined by counting the number of yeast cells that adhered to 100 oral epithelial cells, and hyphal formation was verifi ed in the hyphal induction medium M199. Flow cytometry with propidium iodide and FUN-1 was performed to assess the mechanism of action. Results: The results revealed that the crude ethanol extract and the ethyl acetate and aqueous fractions of P. pseudocaryophyllus inhibited the growth of Candida isolates at a minimal inhibitory concentration (MIC) ranging from 64 to 256µg/mL, whereas the 50% sessile minimal inhibitory concentration (SMIC50) ranged from 512 to >1,024µg/mL. Adherence and hyphal formation were signifi cantly reduced in the presence of the crude ethanol extract and both fractions. Although cell membrane injury was detected, the predominant mechanism of action appeared to be the alteration of yeast metabolism, as demonstrated by fl ow cytometry. Conclusions: Our results indicated that antifungal activity reduced the expression of virulence factors in yeast via the alteration of yeast metabolism, suggesting that the crude extract of P. pseudocaryophyllus and its fractions may contain novel antifungal agents.