In vitro and ex vivo antibiofilm activity of riparin 1, and its nor and dinor homologs, against dermatophytes.

Dermatophytosis is one of the most frequent superficial mycoses in the world. They are mainly caused by the dermatophytes Trichophyton rubrum and Microsporum canis . Biofilm production is an essential factor in the pathogenesis of dermatophytes; it confers drug resistance and significantly impairs antifungal effectiveness. Therefore, we evaluated the antibiofilm activity of an alkamide-type alkaloid called riparin 1 (RIP1) against clinically relevant dermatophytes. We also produced synthetic nor (NOR1) and dinor (DINOR1) homologs for pharmacological evaluation, with a 61-70% yield. We used in vitro (96-well polystyrene plates) and ex vivo (hair fragments) models to verify the effects of these compounds on the formation and viability of biofilms. RIP1 and NOR1 showed antifungal activity against strains of T. rubrum and M. canis , but DINOR1 showed no significant antifungal activity against the dermatophytes. Furthermore, RIP1 and NOR1 significantly reduced the viability of biofilms in vitro and ex vivo ( P < 0.05). RIP1 was more potent than NOR1, possibly due to the distance between the p -methoxyphenyl and the phenylamide moieties in these compounds. Due to the significant antifungal and antibiofilm activities observed for RIP1 and NOR1, we suggest that they could be useful in the treatment of dermatophytosis.