Comparative oral toxicity of coenzyme Q10 and its (2Z)-isomer in rats: single and four-week repeated dose toxicity studies.

It has been reported that coenzyme Q10 (CoQ10) functions as an electron transfer carrier in mitochondria, and can produce an improvement in heart diseases such as congestive heart failure. Its (2Z)-isomer contains a cis-double bond at the 2-position of the decaprenyl side chain. As the original organic industrial synthesis of CoQ10 resulted in a product that contained a small amount of this isomer, the efficacy and safety of CoQ10 was determined using CoQ10 containing this isomer; however, no toxicity data have been reported for the (2Z)-isomer itself. Thus, we conducted single (2,000 mg/kg) and 4-wk repeated (1,000 mg/kg) oral dose toxicity studies in rats to compare the toxicological profiles of CoQ10 and its (2Z)-isomer. The two compounds displayed similar toxicological profiles, and it was concluded that neither CoQ10 nor its (2Z)-isomer produce toxic effects in rats in single or repeated doses.