Abstract
Although several methods for determination of alkenyl type glycerophospholipids (i.e., plasmalogens) have been reported so far, any methods were insufficient because of complicated procedure and from accurate and sensitive point of view. It was also impossible by the former methods to measure intact alkenyl type glycerophospholipids separating from other glycerophospholipids such as diacyl type glycerophospholipids. In the present study, for the purpose of developing highly sensitive and convenient determination of alkenyl type glycerophospholipids, we investigated HPLC method using radioactive iodine, based on the fact that triiodide (1-) ion (I3-) specifically reacts with vinyl ether bonds (-CH2-O-CH=CH-) of alkenyl type glycerophospholipids in methanol solution. A commercial radioactive iodine (125I-) could be safely (almost 100 % recovery) and efficiently (70-80%) converted to radioactive triiodide (1-) ion (125I3-), which is capable of binding to alkenyl type glycerophospholipids, by oxidizing 125I- with hydrogen peroxide (H2O2) in methanol under acid condition (pH 5.5-6.0) .I3- reacted with alkenyl type glycerophospholipids at the molar ratio of1 : 1, and one or two moles of vinyl ether bonds were involved in binding with iodine per one mole of iodine atom. We could detect alkenyl type glycerophospholipids at high sensitivity such that the lower detection limit of concentration is several ten pmol using 125I reagents (1.85 MBq/mL) prepared in this study.
