Antifungal effects of hydrolysable tannins and related compounds on dermatophytes, mould fungi and yeasts

A series of hydrolysable tannins and related compounds was evaluated for an tifungal activities against filamentous fungi (Epidermophyton floccosum; Mi crosporum canis; Microsporum gypseum; Trichophyton mentagrophytes; Trichoph yton rubrum; Trichophyton tonsurans; Trichophyton terrestre; Penicillium it alicum; Aspergillus fumigatus; Mucor racemosus; Rhizopus nigricans) and opp ortunistic yeasts (Candida albicans; Candida glabrata; Candidata krusei; Cr yptococcus neoformans), using the agar dilution method. While all samples h ad no activity against the filamentous fungi in concentrations of 1.1-5.9 m u M (1000 mu g/ml), the phenolic compounds displayed significant potencies against all the opportunistic yeasts tested but C. albicans, with minimum i nhibitory concentrations ranging from 0.02 to 0.1 mu M (16-125 mu g/ml). Al though the presence of galloyl groups in flavonoids did not necessarily pro duce activity, this structural element, an HHDP moiety or its oxidatively m odified entity proved to be an important structural feature of hydrolysable tannins. Comparison of dilution methods provided strong evidence of depend ence of MIC values on the test method. Employing the microdilution broth me thod, the ellagitannin corilagin (MIC 0.8 nM) was found to be similarly pot entially active as amphotericin B (MIC 0.5 nM) and sertaconazole (MIC 0.9 n M) against Candida glabrata strains. The order of effectiveness observed be ing 64- and 4-8-fold increased for corilagin and the reference compounds re spectively! when compared with that of the agar dilution test.