ISOLATION OF AN INHIBITOR OF ASPERGILLUS-PARASITICUS FROM WHITE POTATOES (SOLANUM-TUBEROSUM)

White potatoes did not support the growth of A. parasiticus NRRL 2999 unless they were heated to above 60.degree. C. The mold grew well on autoclaved potatoes and produced, on an average, 8 .mu.g/g total aflatoxins (mainly B1 and G1) at 27.degree. C and 95-97% relative humidity in 20 days. When soluble potato starch was substituted for sucrose in yeast extract-sucrose (YES) medium, the maximum growth of A. parasiticus was 80% of that observed in YES medium, but total aflatoxin production was only 0.5-1.0% of the production in YES medium. Chlorogenic acid and solanine, at levels normally found in the white potato, did not show appreciable fungitoxic activity towards A. parauticus in vitro. Caffeic acid partially inhibited the growth of A. parauticus and the production of aflatoxins at 0.01 M concentration in YES medium. A compound with high inhibitory activity towards A. parauticus was isolated from the potatoes. The compound is extractable with ethyl acetate. From its behavior on TLC systems, its UV spectrum and its reactions with chromagenic spray reagents, it is inferred that the compound is phenolic in nature. It appears to be a hydroxy-cinnamic acid derivative structurally similar to caffeic acid but lacking the o-dihydroxy structure of caffeic acid.