Aspergillus parasiticus accumulates averufin and versicolorin A in the presence of bicarbonate

Sodium bicarbonate has previously been shown to inhibit aflatoxin production by Aspergillus parasiticus . The abnormal pigmentation of colonies grown in the presence of bicarbonate suggested that intermediates of the aflatoxin biosynthetic pathway were accumulating. Aspergillus parasiticus NRRL 2999 cultures grown in the presence of sodium bicarbonate were extracted with acetone and chloroform. Thin layer chromatograms of these extracts were compared to the thin layer chromatograms of extracts from mutant strains which accumulate norsolorinic acid, averufin, and versicolorin A. Development by four separate solvent systems suggested that averufin and versicolorin A accumulated in the bicarbonate-grown wild type cultures. The identity of these intermediates was confirmed by desorption chemical ionization mass spectrometry which showed M+1 peaks of 369 and 339 where M is the molecular weight of averufin and versicolorin, respectively.