Aflatoxins M 1 and M 2 : Preparation and purification

A crude product containing aflatoxins M 1 and M 2 , as well as large quantities of aflatoxins B 1 and B 2 , obtained by fermentation of rice with Aspergillus flavus NRRL 3251 was chromatographed on a silicic acid column. Almost all the B 1 and B 2 were separated from M 1 and M 2 . Aflatoxins M 1 and M 2 were eluted together with ethanol‐chloroform (5∶95 v/v). The combined M 1 and M 2 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 B 1 and B 2 and eluted with ethanol‐chloroform (1.5∶98.5 v/v) to obtain aflatoxin M 1 and mixtures of M 1 and M 2 . Rechromatography of M 1 on another silica gel column gave pure M 1 which was crystallized from acetonitrile. Aflatoxin M 2 was prepared by hydrogenation of M 1 and crystallized from acetonitrile.