4-Methylthiazole-5-Acetic Acid — A Urinary Metabolite of Thiamine

Abstract

A compound identified as 4-methylthiazole-5-acetic acid (TAA) has been isolated from the urine of rats receiving injections of either ¹⁴2C-thiazole-labeled thiamine or ¹⁴2C-thiazole-labeled oxythiamine. Rats injected daily for 8 to 20 weeks with 40 µg of ¹⁴C-thiamine excreted 9.5% of their daily dose as TAA. Rats injected daily with 80 µg of ¹⁴C-oxythiamine excreted 12.1% of their daily dose as TAA. Rats injected with 80 µg oxythiamine + 40 µg ¹⁴C-thiamine excreted only 3.9% of their daily intake as TAA suggesting that oxythiamine inhibits this pathway of thiamine degradation.