versicolorin-a and norsolorinic-acid

Aflatoxin B2 is a secondary metabolite produced by the ubiquitous molds Aspergillus flavus and Aspergillus parasiticus. The toxin was first characterized in 1963 as the etiological agent responsible for the infamous "Turkey X' disease. Since that time, much information on its chemistry, toxicity and biological activity has accumulated. A significant amount of work has been done to elucidate its biosynthesis. Evidence indicates the polyketide route as its point of origin. The steps involved in the polyketide pathway, the six identified intermediated compounds, and the experimental techniques and analytical instrumentation used to procure information on aflatoxin biogenesis are included in this review.

Topics: Acetates; Aflatoxin B1; Aflatoxins; Anthraquinones; Aspergillus; Aspergillus flavus; Chemical Phenomena; Chemistry; Sterigmatocystin

Kinetic pulse-labeling of aflatoxin pathway compounds was carried out in Aspergillus parasiticus, beginning with radioactive acetate. Norsolorinic acid, averufin, versicolorin A, and sterigmatocystin (all known as compounds which can be incorporated into the aflatoxin molecule) were radiotraced to follow their order of appearance. Aflatoxin species B1, B2, G1, and G2 were included. Norsolorinic acid and averufin appeared as early transient intermediates followed in order by versicolorin A, aflatoxins, and sterigmatocystin. To date, a mutually confirming array of results has been obtained with established precursors in wild-type strains of A. parasiticus and A. versicolor (as well as with an aflatoxin pathway mutant of A. parasiticus), which together establish a practical methodology for recognition of new pathway intermediates. The kinetic of pulse-labeling for sterigmatocystin in relation to aflatoxins suggests that duel branchlets may exist to flatoxins; i.e., sterigmatocystin may not be an obligatory aflatoxin precursor.

Topics: Aflatoxin B1; Aflatoxins; Anthraquinones; Aspergillus; Kinetics; Sterigmatocystin