Antimycotic activity of eugenol against selected water molds.
This study was conducted to investigate the antimycotic activities of eugenol (4-allyl-2-methoxyphenol, 99.9%), a major essential oil of clove, against some fish pathogenic species of Saprolegniaceae, as well as to determine the toxicity of eugenol to selected cultured fish. Two eugenol solutions were used in this study: (1) 10% v/v solution in dimethyl sulfoxide (DMSO) and (2) FA 100, which contains 10% v/v eugenol. The fungal species investigated were Saprolegnia parasitica, S. diclina, S. ferax, S. salmonis, Achlya klebsiana and Aphanomyces piscicida. The minimum inhibitory concentrations (MICs) of eugenol in DMSO against Saprolegnia spp., A. klebsiana and A. piscicida were 500, 250 and 125 µg/ml, respectively. The fungicidal concentrations (for complete killing) were 1000, 500 and 250 µg/ml, respectively. In contrast, the MICs of FA 100 against S. parasitica, other Saprolegnia spp., A. klebsiana and A. piscicida were 250, 125, 250 and 63 µg/ml, respectively, and the fungicidal concentrations were 1000, 1000, 1000 and 63 µg/ml, respectively. Zoospores of the Saprolegnia spp. tested and of A. klebsiana could not germinate in the presence of a concentration of 250 µg/ml of either eugenol solution, while those of A. piscicida were killed by a concentration of 125 µg/ml of either eugenol solution. Eugenol was highly toxic to salmonids but less toxic to cyprinids.