- Identification of 9,13-dicis-retinoic acid as a major plasma metabolite of 9-cis-retinoic acid and limited transfer of 9-cis-retinoic acid and 9,13-dicis-retinoic acid to the mouse and rat embryos. Tzimas, G., Sass, J.O., Wittfoht, W., Elmazar, M.M., Ehlers, K., Nau, H. Drug Metab. Dispos. (1994)