Determination of molecular species of oil triacylglycerols by reversed‐phase and chiral‐phase high‐performance liquid chromatography

Abstract

A method is described for the determination of molecular species of oil triacylglycerols. The method is based on the analytical separation of the enantiomeric sn-l,2-and sn-2,3-diacylglycerols, derived from triacylglycerols, by high-performance liquid-chromatography (HPLC) on a chiral column containing N-(R)-l-(a-naphthyl)ethylaminocarbonyl-(S)-valine as stationary phase. Model triacylglycerol molecules comprising three known fatty acids were isolated from peanut oil and cottonseed oil by a combination of argentation-TLC and reversed-phase HPLC and submitted to partial chemical deacylation. The derived sn-l,2(2,3)-diacylglycerols were analyzed and fractionated as 3,5-dinitrophenyl urethane derivatives by reversed-phase HPLC according to chalnlength and unsaturation. From the sn-l,2(2,3)-diacylglycerol composition and the diacylglycerol sn-l,2-and sn-2,3-enantiomer composition, the individual molecular species of four peanut oil triacylglycerols and one cottonseed oil triacylglycerol were identified and quantitated. The method can be applied to triacylglycerols of any other oil or fat.In stereospecific analysis of oil triacylglycerols, representative diacylglycerols should be produced by enzymatic or chemical partial deacylation and studied for fatty acid distribution (1). In the previous methods, the enantiomeric sn-l,2(2,3)-diacylglycerols, isolated by preparative thinlayer chromatography (TLC), were transformed into phospholipid-like molecules. The two enantiomeric synthetic phospholipids were then differentiated by the stereospecific action of phospholipase A (2) or phospholipase C (3). The diacylglycerol enantiomers are preferentially separated by high-performance liquid chromatography (HPLC) either as diastereomers on a classical silica column (4,5), or more currently as 3,5-dinitrophenylurethane (DNPU) derivatives on a chiral column (6-8}.In a previous study (9), we submitted pure peanut oil triacylglycerols isolated by argentationTLC and reversedphase HPLC to partial chemical deacylation, and we fractionated the pure enantiomeric diacylglycerols as DNPU derivatives by reversed-phase HPLC. The diacylglycerol enantiomers were consecutively separated by chiral-phase HPLC (8).The present study reports the determination of molecular species of the major peanut oil diacid-and triacidtriacylglycerols from the data previously obtained. These results complete those of another study on triacylglycerol structure of an African peanut oil of the same origin (10).

Stereospecific Analysis of Fatty Acid Composition of Chufa (Cyperus esculentus L.) Tuber Oil

“…Oleic acid was also the main fatty acid in the sn-3 position followed by palmitic, stearic, linoleic, linolenic, and palmitoleic acid. This differed from others who reported that the fatty acids located at the sn-3 position was highly influenced by their respective concentration in the total fatty acids at the other positions [8,15,16]. Palmitic acid and stearic acid were distributed primarily in the sn-1 and sn-3 positions, while oleic acid and linoleic acid were found in greater amounts at the sn-2 position.…”

“…In most vegetable oils, unsaturated fatty acids occupy the sn-2 position and saturated fatty acids are located in the sn-1 and sn-3 positions. The preponderance of linoleic acid at the sn-2 position is well known in vegetable oils [5,8,16]. The distribution of fatty acids between sn-1 and sn-3 position was nearly symmetrical for palmitic acid, stearic acid, and oleic acid, which is in agreement with Brockerhoff and Yurkowski [8].…”

Positional Distribution of Fatty Acids in Perilla (Perilla frutescens L.) Oil

“…In most vegetable oils, unsaturated fatty acids occupy the sn-2 position, and saturated fatty acids are located more in the sn-1 and sn-3 positions. The preponderance of more unsaturated fatty acids at the sn-2 position is well known in vegetable oils [9,13,14]. The distribution of saturated fatty acids (palmitic and stearic acids) was more pronounced at sn-1 and 3 rather than at sn-2, which is in agreement with data reported earlier.…”

Stereospecific Positional Distribution of Fatty Acids of Camellia (Camellia japonica L.) Seed Oil

“…At sn ‐2 and 3 positions, however, the linoleic acid was present more than the stearic acid. It is well known that the unsaturated fatty acids occupy more at the sn ‐2 position in most vegetable oils, whereas the saturated fatty acids are located more at the sn ‐1 and sn ‐3 positions (Brockerhoff and Yurkowski 1966; Sempore and Bezard 1991). The preponderance of the unsaturated fatty acids, such as the oleic and linoleic acids (totally 96.4%) at the sn ‐2 position is clearly elucidated in the camellia oil.…”