Synthesis of a triglyceride containing a lactonizable hydroxy fatty acid and investigations into the behavior of this triglyceride and related lactones with application to the analysis of beef tallow

The presence of lactones in beef tallow and butter suggested a similarity between the two fats. Butter $\gamma$- and $\delta$-lactones are believed to be derived from precursor 4- and 5-hydroxy fatty acids, respectively. However, methodology was never adequately developed for the concurrent analysis of lactones and their precursor hydroxy fatty acids. This led to the current research objective to investigate the potential for concurrent analysis of lactones and precursor hydroxy fatty acids in beef tallow. A synthesis was developed for 2-(5-hydroxy)-dodecanoyl-1,3-dihexadecanoyl glycerol. This triglyceride proved extremely useful in evaluating methods for the analysis of triglycerides containing lactonizable hydroxy fatty acids. The approach chosen was preparation of 5-ketododecanoic acid as an intermediate in the synthetic scheme. The initial step in the developed methodology for analysis of lactones and hydroxy fatty acids was silica gel column chromatography to concentrate the polar fraction of beef tallow followed by a digitonin column which enabled the removal of cholesterol from the polar fraction. The hydroxy function was then derivatized to prevent spontaneous lactonization of hydroxy fatty acids. A number of methods were evaluated for the preparation of the methyl ether, trimethylsilyl and t-butyldimethylsilyl derivatives of the hydroxy function. Only the trimethylsilyl derivative proved successful due either to attack of the lactone function upon derivatization of the hydroxy group or formation of the lactone from the hydroxy triglyceride. Preparation of the fatty acid methyl esters was then required prior to gas chromatography/mass spectrometry. All attempts to prepare the methyl esters resulted in opening of the lactone such that the precursor hydroxy fatty acids and lactones would yield the same derivative. Methods evaluated included the official American Oil Chemists Society method (saponification followed by BF$\sb3$-MeOH), acid-catalyzed transesterification and base-catalyzed transesterification with potassium hydroxide and sodium methoxide. Derivatized 5-hydroxy methyl dodecanoate, tetradecanoate and hexadecanoate were identified in beef tallow. However, it is impossible to state whether the compounds were derived from precursor hydroxy fatty acids or $\delta$-lactones. The behavior of lactones and hydroxy fatty acids proved exceedingly complex due to interconversion of these compounds.U of I OnlyETDs are only available to UIUC Users without author permissio