Abstract
Aflatoxins are a family of toxic secondary metabolites produced by certain strains of the common molds Aspergillus flavus and A. parasiticus. The general biosynthetic pathway of aflatoxin appears to be as follows: acetate/malonate norsolorinic acid → averantin → averufin → versiconal hemiacetal acetate → versicolorin A → sterigmatocystin → aflatoxins. Within the context of this general pathway, some mechanistic details concerning formation and subsequent conversion of these individual metabolites have been provided by NMR studies-in particular, 13C-NMR. The chapter focuses on the studies that have provided information concerning bonds broken and formed during the biosynthetic process. The preliminary data on toxicity and mutagenicity indicate that the evolution of the aflatoxin pathway may be a response to selective pressures from mycophagous species in nature. Because of the abundant biosynthetic data and the availability of blocked mutants, this system may be uniquely suited among micrcbial secondary pathways for testing this ecological hypothesis.