Effect of riboflavon analogs on the growth of Tetrahymena pyriformis.

Several analogs of riboflavin differing with respect to the substituent at C7, C8 or C10 were examined for their ability to replace riboflavin and to act as riboflavin antagonists in inhibiting growth of Tetrahymena pyriformis. Generally, the analogs with altered substituents at C7 or C8 (the 8-ethyl, 7,8-diethyl, 7-chloro and 8-chloro analogs) supported some growth but inhibited riboflavin-supported growth. However, the 8-bromo analog had no biological activity. The 7-ethyl analog with a bis(2-hydroxyethyl)aminoethyl side chain was the most potent antagonist. These results were compared with those observed in Lactobacillus casei and the rat.