Assay of Folic Acid Activity
The microbiological methods of assay are preferred, since they are more practical than rat or chick assay procedures from the standpoint of time and cost. Even at this time the assay methods are not adequate, especially for differentiating the various active molecules. Lactobacillus casei (acid production) and Streptococcus faecalis (growth) have been employed for total activity toward these organisms. The Association of Official Agricultural Chemists adopted revised procedures in 1958. One of the problems involves hydrolysis of the bound forms of the vitamin in foods. Newer enzymatic procedures for hydrolysis offer promise.
Blood serum folic acid may be determined by the method of Herbert, and the results of this determination gives an indication of the state of folic acid nutrition of an individual. Chemical methods are developing around the fluorescence character of folic acid compounds. Duggan and co-workers surveyed the potential applicability of such methods for the determination of many biological compounds and list the wavelength of maximum activation and of maximum fluorescence for a variety of molecules including folic acid and folinic acid CF).
