Regiospecific analysis of triacylglycerols using allyl magnesium bromide

A method for the regiospecific analysis of triacylglycerols (TAG), using the Grignard reagent allyl magnesium bromide (AMB) to partially deacylate TAG, is described. 1,3‐Distearoyl‐2‐oleoyl‐glycerol (SOS) and 1,3‐didecanoyl‐2‐palmitoyl‐glycerol (CPC) were reacted with AMB. From the resulting mixture, the four different classes of partial acylglycerols and TAG were isolated, and the mole ratios between stearic acid and oleic acid, or decanoic acid and palmitic acid, respectively, were determined in each fraction. Different approaches of calculating the composition of the fatty acids in positionssn‐1(3) andsn‐2 of the original TAG were compared. For thesn‐2 position, the best estimate was the direct determination of the fatty acid composition of 2‐monoacylglycerol (MAG). Mole percentages of stearic acid and decanoic acid in thesn‐1(sn‐3) positions of SOS and CPC, respectively, were most accurately estimated from the fatty acid compositions of TAG and 2‐MAG according to the formula: 1.5×TAG−0.5×2‐MAG. Using AMB and the present method of calculation, the results obtained were more accurate and showed smaller standard derivations than those obtained using other common deacylating agents, such as ethyl magnesium bromide or pancreatic lipase.