Stereospecific analysis of triacyl‐sn‐glycerolsvia resolution of diastereomeric diacylglycerol derivatives by high‐performance liquid chromatography on silica

Abstract

and bKarlshamns LipidTeknik, S-104 65 Stockholm, Sweden 695The compositions of positions sn-1, 2 and 3 of triacylglycerols can be determined by partial hydrolysis with ethyl magnesium bromide, derivatization of the total products with (S)-(-F)-l-(1-naphthyl)ethyl isocyanate and isolation of the diacyl-sn-glycerol urethane derivatives by chromatography on solid-phase extraction columns containing an octadecylsilyl phase. The diastereomeric sn-l,2and 2,3-diacylglycerol derivatives are separated by highperformance liquid chromatography on silica for determination of their fatty acids by gas chromatography. Each step in the process has been evaluated rigorously. The compositions of all three positions can be calculated with good accuracy from the analyses of these compounds and that of the total triacylglycerois. Although the 1,3-sndiacylglycerol derivatives can also be isolated easily, they do not give reliable results for the composition of position sn-2 because acyl migration occurs during their generation. The stereospecific analysis procedure has been applied to some plant and animal triacyl-sn-glycerols of commercial and scientific interest, containing predominantly C16 and C18 fatty acids, i.e. safflower, sunflower, olive and palm oils, tallow, egg and rat adipose tissue. The method is not at present suited to the analysis of more complex triacylglycerols, such as milk fat or fish oils, and problems associated with these are discussed.

Lipase-catalyzed interesterification of egg-yolk phosphatidylcholine and plant oils

“…Additionally, evening primrose oil and borage oil contain γ-linolenic acid (10.4 and 20.7%, respectively). A stereospecific analysis in edible plant oils showed that with some exceptions such as cocoa butter or peanut oil, unsaturated fatty acids are almost equally distributed in all positions of the glycerol skeleton (Brockerhoff and Yurkowski 1966;Christie et al, 1991).…”

Enzymatic Analysis of Positional Fatty Acid Distributions in Triacylglycerols by 1(3)-Selective Transesterification with <i>Candida antarctica</i> Lipase B: a Collaborative Study

“…Methanol, ethanol 99. 5 , potassium hydroxide, sodium methylate in methanol solution 28 , and other reagents were purchased from Kanto Chemical Co. Tokyo, Japan , Wako Pure Chemical Industries Osaka, Japan , and Nakalai Tesque Inc. Kyoto, Japan and were of analytical grades unless otherwise specified.…”

“…In addition to chemical 1,2 and NMR 3 methods, enzymatic methods to analyze the positional distributions of FAs in triacylglycerols TAGs have been developed since the 1960s 4 8 . These methods are based on selective hydrolysis of acyl groups at the 1 3 -position of TAGs using porcine pancreatic 4,5 or microbial lipases, such as Rhizopus oryzae lipase 6,7 . Although these methods have been applied to various vegetable and animal oils consisting mainly of C14-20 FAs, they are not suitable for TAGs containing short chain SC, C6 and polyunsaturated PU, C20 and 4 double bonds FAs.…”

Some recent advances in the chromatographic analysis of lipids

“…This type of separation served as the basis for a novel procedure for stereospecific analysis of triacylsn-glycerols from natural oils and fats, i.e. for determining the compositions of fatty acids esterified to each of positions sn-1, sn-2 and sn-3 [37,38]. Triacyl-sn-glycerols were subjected to partial hydrolysis with a Grignard reagent and the p roducts we re conve rted to the (S) -( + ) -1 -( 1 -n ap h t hy l ) e t hy l urethane derivatives.…”