Detection and microbiologic assays of antimetabolites

The biochemical considerations applicable in the detection of new antimetabolites are very similar to those used in developing microbiologic assays for these drugs. An in vitro system for detection of antimetabolites was developed based on different sensitivities to such drugs of bacteria cultivated in complex versus completely synthetic media. A number of new antimetabolites of amino acids, vitamins, and purines or pyrimidines were isolated and microbiologic assays for these drugs were developed. As an example of the technology utilized and possibilities available, an assay for cytosine arabinoside was described. It can detect 0.5-microgram/ml concentrations of this drug even in the presence of other antitumor or antibacterial antibiotics.