Bioconversion of steroid glycosides by Nocardia restricta.

The bioconversion of steroid alkaloid tomatine by Nocardia restricta yields the conjugate with lactic acid. We studied the bioconversion of some steroid glycosides without a nitrogen atom in the molecule to determine the effect of the nitrogen atom. The glycosides were of three different types: sterol glycosides, bufadienolide rhamnoside and steroid saponine. The results of bioconversions showed that Nocardia restricta converts steroid glycosides differently according to the sugar bound to the steroid aglycone. It can be concluded that in the absence of a nitrogen atom in the steroid molecule no conjugation with lactic acid by Nocardia restricta occurs.