Acyl migration in 1,2-dipalmitoyl-sn-glycerol

The acyl migration of 1,2-dipalmitoyl-sn-glycerol (1,2-DPG) to 1,3-dipalmitoglycerol (1,3-DPG) in different states, neat, in the presence of egg yolk lecithin (sonicated and unsonicated) and on silica gel was studied. The isomerization was quantitated by scanning densitometry of charred TLC plates, at different temperatures and for varying periods of time. At equilibrium the amount of 1,3-DPG was found to be 56%. The rates of initial isomerization, and the time required to isomerize to half the equilibrium quantity (i.e., t _{1 2} eq. = 1,3-DPG 28%) under the above conditions was estimated. In the case of neat melt at 74°C and in an organic solvent the time required to t _{1 2} eq. is 18 h and a few days, respectively. However, at 62°C in the presence of a polar solvent (sodium phosphate buffer at pH 7.0) the t _{1 2} eq. is 1 - 2 h. On dry silica gel (TLC plate) at 24°C the t _{1 2} eq. is reached in less than 1 h.