Submitted to: Review Article
Publication Type: Review article
Publication Acceptance Date: 6/25/2005
Publication Date: 7/1/2005
Citation: Lin, J.T. Identification of the molecular species of phosphatidyl cholines and phosphatidyl ethanolamines incorporating radiolabeled fatty acids in plant microsomes by hplc. Review Article. Interpretive Summary: This is a review of the author’s accomplishments in phophoslipids invited by the publisher. High-performance liquid chromatography (HPLC) can be used for the identification and quantification of the molecular species of lipid classes, phosphatidylcholines (PC) and phosphatidylethanolamines (PE). The molecular species of radiolabeled PC and PE incorporating various radiolabeled fatty acids in castor microsomes were identified by HPLC with a flow scintillation analyzer. The identification method in detail and the examples were described in detail in this review article. The method has been used to study the selectivity among various fatty acids in key enzyme steps of the biosynthesis of castor oil. The presence of a hydroxyl group on ricinoleate (12-hydroxyl, C18 long-chain fatty acid) underlies many industrial uses such as the manufacture of lithium grease, plastics, coatings and cosmetics. Castor oil contains 90% of its fatty acids (FA) as ricinoleate and is the only commercial source of ricinoleate. The key enzyme steps on the pathway can be the targets of the genetic engineering for the new oil seed plant to produce castor oil substitute.
Technical Abstract: Reversed-Phase C8 HPLC methods were developed for the separation of the molecular species of phosphatidylcholines (PC) and phosphatidylethanolamines (PE) using linear gradient of methanol-water containing ammonium hydroxide as silanol suppressor. The elution order of given PC and PE is inversely related to the polarity of its fatty acid constituents. For acyl chains with lower polarity, elution time increases as follows: ricinoleic acid < linolenic acid < myristic acid < palmitoleic acid < palmitelaidic acid < arachidonic acid < linoleic acid < palmitic acid < oleic acid < elaidic acid < petroselinic acid < hexadecyl ether < stearic acid < arachidic acid. The molecular species of PC and PE incorporating various [14C]fatty acids, stearate, oleate, linoleate, linolenate, ricinoleate, palmitate and laurate, in castor and soybean microsomes were identified by matching the HPLC retention times of the standards using an absorbance detector (205 nm) and of the [14C]phospholipids incorporating [14C]fatty acids using a flow scintillation analyzer. When the standards were not available the identification was made by the HPLC elution characteristics of these lipid classes. The [14C]fatty acids were predominately incorporated at the sn-2 position of both PC and PE. Many relative retention times (RRT) of the molecular species of PC and PE are reported.