Determination of the positional-species composition of plant reserve triacylglycerols by partial chemical deacylation

To determine the positional-species composition (PSC) of the sunflower oil triacylglycerols (TAGs), these TAGs were separated in a native state by pre parative TLC on alumina and subjected to a partial chemical deacylation wit h the Grignard reagent under anhydrous conditions. The rac-1,2-diacylglycer ols (DAGs) formed in this reaction were identified by comparing their TLC m obilities with the respective standard separated from the products of enzym atic hydrolysis of lecithin. Subsequently, the DAGs as their borate complex es were isolated from the reaction mixture by preparative TLC on silica gel . The quantitative fatty acid composition of both the DAGs and the initial TAGs was determined by capillary GLC. The PSC of TAGs calculated from the d ata obtained using a computer program was consistent with the data on sunfl ower TAG composition reported by other researchers using an independent met hod. Thus, the technique developed here makes it possible to obtain reliabl e data on the concentration of all TAG positional species in the plant tiss ue.