Preparation of 14C-Labeled Aflatoxin B1

Abstract

Abstract A successful method to obtain 14C-labeled aflatoxin B1 from Aspergillus parasiticus ATCC 15517 was developed. The nitrogen-free resting culture contained mycelia from a 72 hr primary culture, 0.02M glucose, 0.005M (1 mCi/mmole) acetate-1-14C, salts, and trace metals. It was incubated 12 hr at 30°C. Aflatoxin B1-14C was isolated from chloroform extracts of the resting culture by column chromatography on silica gel H eluted under pressure with a continuous gradient of chloroform to chloroform-methanol (98+2). The ultraviolet spectrum of the 14C-labeled aflatoxin was examined. The ratios of the absorbances at 220/265 and 362/265 nm compared to established values and a reference standard were used as criteria of chemical purity. Label integrity was verified by chromatography, hydrogenation to the tetrahydrodeoxoaflatoxin B1, and conversion to the hemiacetal and the epimeric acetates. After purification, 1.37 mg 14C-labeled aflatoxin B1 of specific activity 744 μCi/mmole was obtained from 2 mCi acetate-1-14C of specific activity 1 mCi/mmole.