Dehydrozingerone enhances the fungicidal activity of glabridin against Saccharomyces cerevisiae and Candida albicans

Drug resistance commonly occurs when treating immunocompromized patients with fungal infections. Dehydrozingerone-a phenolic compound isolated from the rhizome of Zingiber officinale-inhibits drug efflux in Saccharomyces cerevisiae by overexpression of the ATP-binding cassette (ABC) transporter Pdr5p. We aimed to investigate whether dehydrozingerone enhances the antifungal activity of glabridin-an isoflavan isolated from the roots of Glycyrrhiza glabra L.-by attenuating multidrug resistance through the intrinsic expression system of multidrug-efflux-related genes in a wild-type strain of the model yeast. The antifungal activity of 50 mu mol l(-1) glabridin alone was weak and temporary against S. cerevisiae; however, cell viability was significantly inhibited when the cells were co-treated with glabridin and dehydrozingerone. This enhancement was also observed in human pathogenic Candida albicans. Glabridin efflux did not depend on a particular drug efflux pump; instead, the transcription factors PDR1 and PDR3-regulating the transcription of multiple genes encoding drug efflux pumps-were involved in the antifungal activity and efflux of glabridin. qRT-PCR analysis revealed that dehydrozingerone reduced glabridin-induced overexpression of the ABC transporter-related genes PDR1, PDR3, and PDR5 to the levels observed in untreated cells. Our findings indicated that dehydrozingerone potentiates the efficacy of plant-derived antifungals through its effects on ABC transporters.