Evaluation of the Inhibitory Effect of Marine Macroalgal Ulva lactuca Extracts on Oral Candida spp. Biofilms Formation

The increasing clinical and microbiological resistance of Candida species towards several commonly prescribed antifungal agents has stimulated the search for new active antifungal compounds from natural resources. The most important virulence factors of pathogenic Candida species are biofilm formation and hyphal development, making treatment very challenging due to the spread of resistant Candida isolates. This study was designed to explore the potential of different types of Ulva lactuca extracts on the growth of Candida spp < em>., and evaluate the morphological alterations and time-kill as well. Methanol was the best solvent for extracting bioactive components from the examined algae Ulva lactuca (Chlorophyta) exhibiting the highest antifungal effect, followed by ethanol and chloroform. The minimum inhibition concentration (MIC) of U. lactuca methanol extract (ULME) was 62.5mg/ ml, and the minimum fungicidal concentration (MFC) was 125mg/ ml against all the tested oral Candida spp. Different concentrations of ULME (1xMIC, 2xMIC and 4xMIC) influenced the micromorphology of the tested oral Candida spp. and had an impact on biofilm formation. In the time-kill curves, ULME showed a concentration-dependent fungicidal effect. The cytotoxicity results showed that ULME has no significant toxic effects against normal human lung fibroblast cells (MRC-5 cell line). Moreover, the major phytochemical compounds were fatty acids, identified and quantified by using Gas Chromatography-Mass Spectrometry (GC/MS). In conclusion, ULME may be an alternative to conventional antifungal drugs for the treatment of oral candidiasis.