Toxicity and Antibiotic Activity of Kojic Acid Produced by Aspergillus luteo-virescens.

In a systematic investigation for new antibiotics it was observed by one of us (A. K.) that the crude culture filtrate of Aspergillus luteo-virescens was found to be antagonistic to gram-positive and gram-negative bacteria. In the chemical studies conducted by two of us (W. K., R. K.) it was noted that an antibiotic substance crystallized out in large amounts from this crude culture upon standing in the refrigerator, sometimes even at room temperature. The recrystallized material had a melting point of 152 C and gave a deep red color with FeCl3. It was suggested by Dr. Charles Thom that this material resembled kojic acid, 5-hydroxy-2-hydroxymethyl-8-pyrone, C6H604, isolated some thirty years ago (Saito, 1907; Yabuta, 1912, 1916). Subsequent study confirmed this identification. Kojic acid is a weak bacterial antagonist, its range of activity being in a dilution of 1:1,000 to 2,000 against the common test bacteria.