INHIBITION OF AFLATOXIN PRODUCTION BY ASPERGILLUS-FLAVUS WITH PENTACHLOROBENZYL ALCOHOL, PHTHALIDE, AND PYROQUILON

Two isolates of Aspergillus flavus were grown in shake cultures for 4 days at 30 degrees C with 0 to 8 mu g/ml of 2,3,4,5,6-pentachlorobenzy l alcohol (PCBA) or phthalide and 0 to 30 mu g/ml of pyroquilon. The t hree compounds significantly inhibited the accumulation of aflatoxins B-1, B-2, and B-2a in cultures of both isolates. The effect of PCBA wa s most pronounced, followed by phthalide and then pyroquilon. With iso late SRRC-2089, the control contained 365 +/- 45 mu g of aflatoxin B-1 per gram mycelial dry weight, while in cultures treated with 8 mu g/m l PCBA, phthalide or pyroquilon, aflatoxin B-1 levels decreased by 98, 86, and 48%, respectively. At the 8 mu g/ml level, phthalide and pyro quilon did not significantly inhibit fungal growth with SRRC-2089, but PCBA caused a decrease of 12% in mycelial dry weight. Precursor feedi ng studies with [C-14]norsolorinic acid demonstrated that the enzymes converting norsolorinic acid and later precursors to aflatoxins were n ot inhibited by these compounds. Thus, inhibition of aflatoxin synthes is by PCBA, phthalide, and pyroquilon seems to be earlier in the biosy nthetic pathway before the synthesis of norsolorinic acid. (C) 1995 Ac ademic Press, Inc.