Stereospecific analysis of TAG from sunflower seed oil

• Published in: Journal of the American Oil Chemists' Society 2003-01, Vol.80 (1), p.5-8
• Main Authors: Boukhchina, Sadok, Gresti, Joseph, Kallel, Habib, Bézard, Jean
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Chiral‐phase HPLC; Fat industries; Food industries; Fundamental and applied biological sciences. Psychology; reversed‐phase HPLC; stereospecific analysis; sunflower seed oil; triacyl‐sn‐glycerols
• ISSN: 0003-021X; 1558-9331
• DOI: 10.1007/s11746-003-0641-0

Stereospecific analysis of TAG from a sunflower seed oil of Tunisian origin was performed. The TAG were first fractionated according to chain length and degree of unsaturation by RP‐HPLC. The four major diacid‐ and triacid‐TAG fractions were palmitoyldilinoleoyl‐glycerol, dioleoyllinoleoylglycerol, oleoyldilinoleoylglycerol, and palmitoyloleoyl‐linoleoyl‐glycerol, amounting to 7.2, 16.6, 29.5, and 12 mol%, respectively. The TAG of the four fractions were individually submitted to stereospecific analysis, using a Grignard‐based partial deacylation, separation of sn‐1,2(2,3)‐DAG from sn‐1,3‐DAG by boric acid‐impregnated silica gel TLC plates, conversion of the sn‐1,2(2,3)‐DAG to their 3,5‐dinitrophenylurethane (DNPU) derivatives, fractionation of DNPU derivatives by RP‐HPLC, resolution of the DNPU‐DAG by HPLC on a chiral column, transmethylation of each sn‐DNPU‐DAG fraction, and analysis of the resulting FAME by GC. The data obtained were used to determine the triacyl‐sn‐glycerol composition of the main TAG of the oil. Fifteen triacyl‐sn‐glycerols were identified and quantified, representing, along with the monoacid‐TAG, trilinoleoylglycerol and trioleoylglycerol, more than 90% of the total oil TAG. The two major triacyl‐sn‐glycerols were trilinoleoyl‐glycerol and 1‐linoleoyl‐2‐linoleoyl‐3‐oleoyl‐glycerol (18.6 and 18.5% of the total, respectively). Results clearly identified linoleic acid as the major FA at the sn‐2 position, whereas oleic and palmitic acids were the major FA at the sn‐3 position. The sn‐1 position was occupied to nearly the same extent by linoleic and oleic acids, and to a greater extent by palmitic acid, which was practically absent at the sn‐2 position.