Thioctic Acid in Milk

Thioctic add (a-lipoic acid) was isolated from milk and found to be associated with the fat globule membrane. The isolation procedure was as follows: Sweet cream buttermilk was hydrolyzed by refluxing for 3 hr with 6,0 ~ I{C1. A benzene extract of the hydrolysate was extracted with 5% NaHCO~ which, in turn, was acidified to pH less than 1 with 6.0 x J{CI. The acidified solution was extracted with ethyl ether, and the extract evaporated to dryness and stored under nitrogen --10 C. Identification of thioctic acid was accomplished by UV absorption spectra, thin-layer and gasliquid chromatography techniques.