Aflatoxin biosynthetic pathway extrolites in airborneAspergilli seriesVersicolores

Abstract

TheAspergilli of the seriesVersicolores include several airborne species to which we are exposed daily. Most of them synthesise sterigmatocystin, a mycotoxin precursor of aflatoxins recognised as potentially carcinogenic for humans (group 2B) by the International Agency for Research on Cancer. Our objective was to study the potential role of these moulds in the synthesis of extrolites of the aflatoxin biosynthetic pathway. A total of 124 isolates belonging to the eight species of the seriesVersicolores collected in French bioaerosols were studied:Aspergillus amoenus (n=1),Aspergillus creber (n=45),Aspergillus fructus (n=2),Aspergillus jensenii (n=39),Aspergillus protuberus (n=6),Aspergillus puulaauensis (n=5),Aspergillus sydowii (n=14) andAspergillus tabacinus (n=2). All these isolates and a reference strain of each species were extracted using ethyl acetate acidified with 1% (v/v) acetic acid. In each extract, we screened for the following extrolites of the aflatoxin biosynthetic pathway by UPLC-HRMS: norsolorinic acid, versicolorin A, 6-demethylsterigmatocystin, sterigmatocystin, 8-O-methylsterigmatocystin, 5-methoxysterigmatocystin and aflatoxins B1, B2, G1 and G2. All extrolites, except aflatoxins, were found variably among species. Sterigmatocystin was found in extracts of all eightVersicolores species, including A.sydowii andA. tabacinus whose ability to synthesise sterigmatocystin was questioned or unknown, respectively.