Methyl jasmonate stimulates aflatoxin B1 biosynthesis by Aspergillus parasiticus

Aflatoxin B-1 (AFB(1)) is a highly toxic and carcinogenic metabolite produced by certain Aspergillus species on agricultural commodities. One factor promoting the production of aflatoxin is the presence of high levels of fatty acid hydroperoxides often found in plant material under stress. Jasmonic acid (JA) and its methyl ester (MeJA) are derived from linolenic acid, and their biosyntheses involve the production of lipid hydroperoxides. Exposure of aflatoxigenic mold to jasmonates is likely because the mold attacks plant material and possibly initiates the production of jasmonates. In this study the effect of MeJA on the growth of Aspergillus parasiticus and AFB(1) biosynthesis is reported. MeJA, at a final concentration of 10(-4) M in yeast extract sucrose medium, did not have any apparent effect on mycelial growth during the 16 days of observation but did increase significantly the levels of AFB(1) after the seventh day of growth. After the ninth day, AFB(1) production was decreased in contrast to the control cultures, where the production was constantly increasing. AFB(1) determination was performed by immunoaffinity and HPLC after derivatization to AFB(2a).