Spectroscopic changes in fatty acids

Abstract

Catalytic reduction of tung oil shifted the absorption maximum of the mixed acids from 270 to 230 m[mu], i.e., the same change which occurs in vivo when tung oil is fed to a hen or rat. Absorption at 270 m[mu] is evidently caused by 3 conjugated unsaturated linkages, that at 230 m[mu] by 2 such linkages. Prolonged refluxing of polyethylenic acids with KOH produces a re-orientation of the unsaturated linkages from unconjugated to conjugated positions. When large amts. of "pro-absorptive" polyethylenic acids are included in the diet of the rat they are stored in the fat deposits unchanged. The predominance of absorptive acids found in the fats of some mammals, e.g., the cow, cannot therefore be made the basis of a general rule. The absorption of the acids from rats receiving an almost saturated fat (coconut oil) suggests however that when the intake of polyethylenic acids is low they are largely converted to the absorptive form. Polyethylenic acids from dried grass were found in the "pro-absorptive" form. "Absorptive" acids present in the fats of herbivorous animals such as the cow must be converted in the animal.