Antifungal activity in Juglans nigra green husks

Juglans spp. (Juglandaceae) are known to be used in folk medicine to treat a wide range of health disorders. In this work, the activity against yeasts and dermatophyte strains was assessed from fresh green husks of J. nigra. The material was extracted with 70% aqueous ethanol using an Ultra-Turrax homogeniser. Subsequently, volatile (VF) and no volatile (NVF) fractions were obtained by extract distillation under vacuum and evaluated for their antifungal activity. Six yeasts (five Candida spp. and Cryptococcus neoformans) and seven dermatophytes (four Trichophyton spp., two Microsporum spp. and Epidermophyton floccosum) were assayed by broth macrodilution methods [1] to determine minimum inhibitory concentrations (MIC), and for a reference antifungal compound (fluconazole). Minimum lethal concentration (MLC) was also evaluated. Phenolic profiles of the fractions were established by HPLC-PDA-ESI/tandem MS. MICs between 48–768 µg/mL and 192–768 µg/mL were obtained against yeasts and dermatophytes, respectively, for NVF. The VF, the most active fraction, showed MICs between 23.8–95.3 µg/mL and 23.8–47.6 µg/mL for yeasts and dermatophytes, respectively. An important activity was verified from VF, the MLC values being lower than those of fluconazole for eight fungi: Candida albicans, C. tropicalis, C. krusei, Cryptococcus neoformans, Trichophyton rubrum, T. mentagrophytes, Microsporum canis and M. gypseum. Chromatographic profile of Juglans nigra VF showed that naphthoquinones are the main phenolic compounds. These results suggest that this fraction can constitute an alternative for the treatment of Candida krusei, a recurrent strain of vulvovaginal candidosis and dermatophytes of nails and skin.

Acknowledgements: FCT and POCTI/FEDER for financial support and LEM/UC integrated in RNEM of Portugal for the HPLC/MS analyses.

References: 1. Clinical and Laboratory Standards Institute (CLSI) (2008). Wayne, Pa, USA.