Examination of Candida albicans strains from South Africa for the production of gliotoxin and other cytotoxic secondary metabolites

摘要

Candida species cause superficial mycosis and more serious systemic infections. The virulence factors of Candida are their adherence and hyphae formation ability and the production of hydrolytic enzymes. In addition, they produce secondary metabolites which are also implicated in the pathogenesis. Literature on the production of gliotoxin, one of the metabolites by Candida spp. is controversial. The aim of this study was to examine production of gliotoxin and related secondary metabolites by C. albicans strains isolated from the oral cavities of patients with oral infections. Seventeen strains of Candida albicans were obtained and were grown in Eagle’s minimal essential medium supplemented with 10% glucose and 5% foetal bovine serum for 10 and 30 days. Extraction of culture fluids and biomass was done using dichloromethane and examined using a two dimensional thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) with time of flight mass spectrometry (MS). Fifteen strains of C. albicans (88%) produced secondary metabolites with a molecular weight of 452 which was nearest to that of gliotoxin standard with a molecular weight of 326. Three major metabolites were isolated and identified. They were eburicol produced by 10 strains, Tryptophol produced by 10 strains and dehydro eburical produced by 12 strains of C. albicans. In conclusion, the strains of C. albicans isolated from the patients with oral infections did not produce gliotoxin. However, they produced tryptophol which is known to be produced by C. albicans, and they also produced eburicol and dehydro eburical which are intermediate compounds in the metabolic pathways to ergosterol. Further research is required to establish their role in the pathogenesis of this organism.