THIOCTIC ACID, (-)- is less biologically potent enantiomer of thioctic acid than (+)-enantiomer. Dihydrolipoamide dehydrogenase from human renal carcinoma does not accept the S-enantiomer as a substrate in comparison to R-enantiomer but S-enantiomer is an inhibitor of the overall reaction of the bovine pyruvate dehydrogenase complex. Chronic parenteral treatment with the antioxidant alpha-lipoic acid enhances insulin-stimulated glucose transport and non-oxidative and oxidative glucose metabolism in insulin-resistant rat skeletal muscle, with the R-(+) enantiomer being much more effective than the S-(-) enantiomer. The racemate of lipoic acid at high dosage reduced the life span significantly of immunosuppressed mice but the S(-)-enantiomer of lipoic acid increased the 50% survival rate. The thioctic acid, (-)- was shown to be toxic when administered to thiamine-deficient rats.

9β,10α,17α-pregna-4,6-diene-3,20-dione ((8S,9R,10S,13S,14S,17R)-17-Acetyl-10,13-dimethyl-8,9,10,11,12,13,14,15,16,17-decahydro-1H-cyclopenta[a]phenanthren-3(2H)-one) is an isomer of Dydrogesterone, a synthetic progestin largely used in hormone therapy, on the central nervous system by studying two markers of the neuroendocrine function. 9β,10α,17α-pregna-4,6-diene-3,20-dione is one of major impurities of dydrogesterone. The physiological and toxicological properties of this compound have not been evaluated in humans.