Cyclic fatty esters: synthesis, characterization, and lipolysis of isomeric triglycerides of 9-(6-propyl-3-cyclohexenyl)-(Z)8-nonenoic acid.

Triglycerides of a model cyclic fatty acid (CFA) 9-(6-propyl-3-cyclohexenyl)-(Z)8-nonenoic acid (Ia) were synthesized for biological and toxicity evaluations. The monoacid triglyceride II (CyCyCy) was interesterified with triolein (OOO) to obtain mixtures of diacid triglycerides: III (OOCy), IV (OCyO), V (OCyCy), and VI (CyOCy). The interesterification mixtures were separated by preparative HPLC into two 'critical pairs' of isomeric triglycerides. Triglycerides III-VI were synthesized and a 13C-NMR method was developed to estimate 'critical pairs'. CFA-triglycerides were characterized by IR, NMR, HPLC and capillary GLC, and their relative rates of hydrolysis by lipase were compared. Although tricyclin (II) was completely resistant to lipolysis, triglycerides III and VI hydrolyzed significantly slower than triolein, and the 'critical pairs' hydrolyzed as readily as triolein. Therefore, partial CFA-triglycerides formed in heat-abused fats can undergo lipolysis and likely be absorbed like normal dietary fats.