Can heatstable antithiamin factors inactivate thiamin in vitro and/or in vivo?

Aqueous solutions of thiamin hydrochloride were incubated with catechol for 24 hr, pH 7.4 at 50 degrees C. Additional solutions of thiamin and catechol were incubated separately. After incubation the remaining thiamin was analyzed by the thiochrome procedure which showed that the thiamin in the thiamin-catechol mixture was reduced by 82.5-90% and the thiamin incubated alone by 18-20%. The solutions were fed to groups of rats after they had been on a thiamin free diet for 17 days. Body weight gains, erythrocyte transketolase (ETKA), thiamin pyrophosphate effect (TPPE) and liver and urine thiamin were measured. The results of these experiments showed that given the thiamin-catechol mixture (after incubation at pH 7.4, 50 degrees C for 24 hr) produced thiamin deficiency according to ETKA and TPPE values indicating that the thiamin was unavailable in vivo as well as in vitro. However, rats given thiamin and catechol separately (even after incubated each) no thiamin deficiency was observed.