Inhibition of the development of pathogenic fungi by extracts of some marine algae from the red sea of Jeddah, Saudi Arabia
In this study, the predominant marine algae were collected from three different sites in the coastal area of Al-Kumrah at south of the Red sea of Jeddah, during summer and autumn 2009. The different marine algae belonged to Chlorophyta (Enteromorpha prolifera and Ulva reticulata), Phaeophyta (Cystoseira myrica, Padina pavonica, Sargassum portieriatum and Turbinaria triquetra) and Rhodophyta (Gracilaria multipartita). Algal extraction was achieved successively by using petroleum ether, diethyl ether, ethyl acetate and methanol. The algae extracts were tested in vitro for antifungal activity against Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger and the yeast Candida albicans, by using agar-well diffusion method. The crude extracts of the tested algae revealed differences in their bioactivities. The maximum growth inhibition for fungi was recorded in ethyl acetate extract of T. triquetra against C. albicans (30 mm), methanol extract of E. prolifera (29 mm) and ethyl acetate extract of Padina pavonica (28 mm) against A. fumigatus. The results clarified that Chlorophyta and Phaeophyta exhibited the highest biological activity against the tested fungi, whereas the lowest was achieved in Rhodophyta. The minimal inhibitory concentrations (MICs) of the crude extracts of the tested algae ranged from 0.5 to 3.0 μg/ml. The results confirmed the potential of seaweed extracts as a natural source of antimicrobial compounds. The antifungal activity of different extracts of marine algae which belongs to Chlorophyta, Phaeophyta and Rhodophyta were examined against A. flavus, A. fumigatus, A. niger and the yeast C. albicans. The algae belonging to Chlorophyta and Phaeophyta exhibited the highest inhibitory effect against the test pathogenic fungi. The different extracts showed different activities against fungi. The antimicrobial activity depended on both algal species and the efficiency of solvents in the extraction of bioactive substances.
Keywords: Green algae, brown algae, red algae, solvent extracts, antifungal activity, minimal inhibitory concentrations (MICs)