CHEMILUMINESCENCE IS A RAPID AND SENSITIVE METHOD TO ASSESS PHOSPHATIDYLCHOLINE OXIDATION

The aim of this work was to test the suitability of chemiluminescence (CL) and isothermal microcalorimetry as simple, sensitive, and direct methods for the estimation of oxidation status of phosphatidylcholine in raw material and in lipid-based formulations. Such methods would av oid extensive sample preparation, allowing their use during early deve lopment work. Soya phosphatidylcholine (S-PC) was dissolved in medium- chain monoacylglycerol (MCM) and stored at 40 degrees C in air and und er nitrogen. Oxidative status was measured at different times by thiob arbituric acid value, iodometry, UV spectroscopy, high performance liq uid chromatography (HPLC)-evaporative light scattering (ELS)-UV detect ion, isothermal microcalorimetry, and direct chemiluminescence. Oxidat ion parameters were analyzed in terms of the mechanism of oxidation. D ata from the various methods were also found to be well correlated wit h that obtained from direct CL measurements. Induction times of about 21 days were found for a 50/50 w/w S-PC/MCM sample stored in air. MCM was found to have a protective effect on S-PC. Results indicate that b oth isothermal microcalorimetry and direct CL techniques can be used f or estimation of the oxidation levels in phosphatidylcholines and shou ld be applicable to phospholipids in general. MCM is a novel solvent f or this purpose. CL measurements have the additional advantages of bei ng rapid and convenient. Specifics of method development have been dis cussed.