CYCLOPROPANE FATTY ACID METABOLISM: PHYSICAL AND CHEMICAL IDENTIFICATION OF PROPANE RING METABOLIC PRODUCTS IN THE ADIPOSE TISSUE.

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AbstractTwelve male weanling rats were distributed equally into 3 groups and placed on fat‐free diets. The diets of groups 1 and 2 were supplemented with 0.54% of recemic methylcis‐9,10‐methylene octadecanoate (CMO) and racemic methyltrans‐9,10‐methylene octadecanoate (TMO), respectively. Group 3 served as a control. Gas liquid chromatography (GLC) analyses of the adipose tissue methyl esters indicated at the level fed, that cyclopropane fatty acids do not affect normal fatty acid metabolism as has been shown for cyclopropene fatty acids. GLC analyses of groups 1 and 2 revealed the presence of a different unidentified fatty acid for each of the acids fed in addition to the CMO and TMO acids themselves. Each of the unidentified acids and the CMO and TMO acids were isolated and purified by preparative GLC. The absolute identity of the CMO and TMO acids fed and isolated from body fat was established by IR, NMR, and mass spectra. The biodegradation products of the CMO and TMO esters were shown to becis‐ andtrans‐3,4‐methylene dodecanoic acid, respectively. Unequivocal proof of structure was established through synthesis followed by comparison of IR, NMR, and mass spectra and melting points, GLC retention times, and elemental analyses with those obtained for the degradation products. Neither member of the racemic mixtures of either thecis or thetrans cyclopropane acids was preferentially utilized by the rat as shown by the lack of octical activity in the degradation products and the CMO and TMO acids isolated from the body fat. The accumulations of the 3,4‐methylene dodecanoic acids in the adipose tissue of the rats fed CMO and TMO cyclopropane fatty acids suggest the inability of the beta oxidation enzyme system to proceed past the cyclopropane ring in a fatty acid chain. The synthesis ofcis‐ andtrans‐3‐dodecenoic acids, intermediates in the synthesis of the 3,4‐methylene dodecanoic acids, and the geometrical cyclopropane isomers are discussed.