Isohematinic acid

Isohematinic acid, an antibiotic newly isolated from the culture broth of Actinoplanes philippinensis SANK 61681, was assessed for its ability to enhance nonspecific resistance to bacterial infections against Escherichia coli and Pseudomonas aeruginosa in mice. This agent, as well as BM 12,531 (Azimexon), was found to prolong the survival of normal mice infected with E. coli and also of compromised mice infected with either E. coli or P. aeruginosa, whose defense system had been deteriorated by treatment with carboquone, an alkylating agent. Like BM 12,531, isohematinic acid administered to normal mice significantly increased the nitroblue tetrazolium reducing potency of polymorphonuclear leucocytes (PMN), indicating that the microbicidal activity of PMN was enhanced by these agents. In addition, in the compromised mice these agents were able to restore the number of peripheral blood leucocytes, which had been reduced to about 30% of the normal level by carboquone. These results suggest that isohematinic acid, like BM 12,531, enhances nonspecific resistance to these bacterial infections by stimulating the microbicidal activity of PMN and inducing leucocytosis.

Physico-chemical characterization of isohematinic acid revealed that this antibiotic has a succinimide nucleus. From elemental analysis, the molecular formula of isohematinic acid was determined to be C8H9NO4. Isohematinic acid showed weak antimicrobial activities against anaerobic bacteria, such as Bacteroides fragilis and Propionibacterium acnes.

New antibiotic, isohematinic acid, was found in the culture broth of an actinomycete strain SANK 61681, which was identified as a strain of Actinoplanes philippinesis. Fermentation of isohematinic acid was performed by conventional submerged culture in a 600-liter fermentor. Isolation of isohematinic acid was performed by adsorption of the antibiotic from the culture filtrate on a column of Diaion HP-20 followed by elution with aqueous acetone and extraction with ethyl acetate. Isohematinic acid was finally crystallized from hot methanol.