Natural and in vitro coproduction of cyclopiazonic acid and aflatoxins

Eighty samples of animal feeds of different origins were screened for the natural co-occurrence of cyclopiazonic acid (CPA) and aflatoxins in Portugal. Forty-five strains of Aspergillus flavus were collected from those samples and studied for their ability to produce these mycotoxins, in vitro. CPA was detected by thin-layer chromatography using Erhlich's reagent for confirmation. Aflatoxins were determined by high-pressure liquid chromatography with postcolumn iodination. Only 5 of the 80 samples (6.2%) were naturally contaminated with cyclopiazonic acid (0.16 mg/kg) and 36 (45.0%) with aflatoxin B1 (AFB1) (from 0.001 to 0.016 mg/kg). An in vitro study of the 45 strains of A. flavus was performed in cracked corn at 25 degrees C (water activity, a(w) = 0.96), incubated for 21 days to CPA production. For in vitro production of aflatoxins, the same substrate was incubated at 28 degrees C for 14 days. Nineteen of the strains (42.2%) produced CPA (ranging from 0.5 to 1.45 mg of CPA/kg) and 23 of them (51.1%) produced AFB1 (from 0.001 to 0.844 mg/kg). Only 10 isolates (22.2%) produced both CPA and AFB1 (0.05 to 0.10 mg/kg and 0.001 to 0.230 mg/kg, respectively). Thirteen strains did not produce either CPA nor AFB1.