Chemical structure and serological activity of natural and synthetic cardiolipin and related compounds.

Since its first isolation from ox heart by Pangborn (1941), cardiolipin has found general application in the sero-diagnosis of syphilis. Mixtures of cardiolipin, lecithin, and cholesterol have replaced the former tissue extracts as antigens in flocculation and complement-fixation tests. International reference preparations of cardiolipin and of lecithin are being distributed under the supervision of WHO and analytical requirements for these substances have been published in the International Pharmacopoeia (1955). Occasionally, however, analytical data of serologically satisfactory batches are not within the required ranget. Inasmuch as natural compounds generally have a certain variation in composition, the use of synthetic products would be advantageous from the point of view of standardization. In the first part of this paper, literature regarding the chemical structure of cardiolipin and the serological activity of similar synthetic compounds is reviewed. It will be seen that investigations did not result in the preparation of an entirely satisfactory substitute for cardiolipin. Recently, de Haas and van Deenen (I 965a) succeeded in synthetizing a diphosphatidylglycerol. The serological activity of their product has been studied in our Institute and the results are reported in the second part of this paper.