Antifungal properties of Singapore gorgonians: a preliminary study

Gorgonians possess a huge array of secondary metabolites for various functions, many of which are not known. One of these functions is antifungal. This study investigates if gorgonians from reefs in Singapore can defend themselves against the settlement and invasion of fungi. Crude extracts from 10 species of gorgonians from three families, Ellisellidae, Subergorgiidae and Plexauridae, were screened against nine species of deuteromycetous fungi previously isolated from gorgonians. Minimum Inhibitory Concentration (MIC) experiments were carried out in 96-microwell plates using extract concentrations ranging from 1.5 to 24.0 mg/ml. Extracts from Euplexaura cf. pinnata, Echinogorgia sp. C, Junceella cf. gemmacea, Subergorgia suberosa, Ctenocella cf. umbraculum and Junceella sp. A were found to possess inhibitory effects on fungi. MICs range from 1.5 to 18.0 mg/ml. Results showed that most of the antifungal activities were exhibited by Euplexaura cf. pinnata and Echinogorgia sp. C from the family Plexauridae. However, for most gorgonian species, the concentrations required to inhibit fungal growth are much higher than the natural concentrations of extracts found in gorgonian tissues. Only the extracts of Echinogorgia sp. C, C. cf. umbraculum and S. suberosa were found to inhibit fungal growth of a few fungal species at a concentration lower than that of its natural concentration.