Chemical Structures of Major Aflatoxins: B₁, B₂, G₁, and G₂

Figure 1 illustrates the chemical structures of the four major naturally occurring aflatoxins: B₁, B₂, G₁, and G₂. These toxic secondary metabolites are produced by Aspergillus flavus and Aspergillus parasiticus. The aflatoxins are classified into B and G types based on their fluorescence under UV light—blue (B) or green (G). Structurally, all four molecules share a coumarin nucleus fused with a bifuran ring. Aflatoxins B₁ and G₁ have a double bond in the terminal furan ring, whereas B₂ and G₂ lack this feature, resulting in differences in their toxicological potency. The methoxy (-OCH₃) and lactone groups are also notable structural features contributing to their high reactivity and biological activity.