ESTIMATION OF THE BIOLOGICAL POTENCY OF VARIOUS FORMS OF VITAMIN A

Abstract

The low biological potency of 9-cis and 9,13-di-cis vitamin A, heretofore measured by growth and liver storage assays, has been confirmed by vaginal smear assays. Appreciable quantities of these isomers in pharmaceuticals would lead to overestimation of biological potency by the U.S.P. XV or the antimony trichloride methods. In an extensive series of assays the U.S.P. method accurately estimated the biological potency of most oil-soluble, water-dispersed, and dry, stabilized samples of vitamin A. The antimony trichloride method did not accurately estimate biological potency but, for many samples, correction of these values in accordance with their maleic values was not justified. Water-dispersed and dry, stabilized samples of vitamin A were not better utilized than oil solutions of the vitamin.