Mutagenicity of commercial Monascus fermentation products and the role of citrinin contamination

Abstract

Pigments produced as secondary metabolites by various isolates of moulds belonging to the genus Monascus have been used traditionally as colorants in Oriental food. Modern food industry has rediscovered these moulds as promising source for natural colorants. However, recent studies evidence that one of the secondary metabolites produced by Monascus is identical in structure to the mycotoxin citrinin. Thus, a sensitive HPLC method was developed to analyse these food colorants for contamination with citrinin. The mycotoxin could be detected in all the commercial Monascus samples at concentrations varying between 0.2 to 17.1 μg/g. In addition, the mutagenicity of commercial Monascus samples applying Salmonella-microsome assay and Salmonella-hepatocyte-assay was investigated and compared to the results obtained with citrinin. Citrinin and two Monascus extracts induced a positive dose depending mutagenic response in the Salmonella-hepatocyte-assay applying strain TA-98. However, no mutagenicity could be detected in the Salmonella-microsome assay, neither with nor without S9-mix, for citrinin and Monascus extracts, applying TA-98, TA-100, TA-1535, TA-1538 and TA-97. These findings provide further evidence that citrinin requires complex cellular biotransformation to exert mutagenicity.