Aflatoxins M₁ and M₂: Preparation and purification

Abstract

A crude product containing aflatoxins M₁ and M₂, as well as large quantities of aflatoxins B₁ and B₂, obtained by fermentation of rice withAspergillus flavus NRRL 3251 was chromatographed on a silicic acid column. Almost all the B₁ and B₂ were separated from M₁ and M₂. Aflatoxins M₁ and M₂ were eluted together with ethanol-chloroform (5∶95 v/v). The combined M₁ and M₂ fraction was placed on a Merck silica gel (0.05–0.2 mm) column to be washed with hexane-chloroform (1∶1 v/v) and chloroform to remove traces of B₁ and B₂ and eluted with ethanol-chloroform (1.5∶98.5 v/v) to obtain aflatoxin M₁ and mixtures of M₁ and M₂. Rechromatography of M₁ on another silica gel column gave pure M₁ which was crystallized from acetonitrile. Aflatoxin M₂ was prepared by hydrogenation of M₁ and crystallized from acetonitrile.