The Reduction of Folate by Borohydride^*

Oxidative degradation of dihydrofolate and tetrahydrofolate

“…DEU-cellulose (Schleicher and Schuell, type 20) was prepared as described previously (13). Columns (2 cm x 14 m) were routinely eluted using 408 ml of 0.13 M ammonium acetate in the mixing flask and 433 rnl of 2.0 M ammonium acetate in the reservoir, although the concentrations of solutions used for elution were often varied to effect certain separations (any change in concentration is noted with the individual experiment).…”

“…We chose column chromatography (primarily using DEAE-cellulose) as a method for examining the products of degradation of tetrahydrofolate or dihydrofolate because it is a convenient means of both separating and estimating quantitatively many of the suspected breakdown products (13,16), Since oxidation of tetrahydrofolate produced a mixture of many products, including 7,8-dihydrofolate, we first examined the degradation of dihydrofolate. Products occurred in three peaks: peak l centered at 45 mi, peak 2 at 110 ml, and peak 3 at 285 ml.…”

“…In addition, if oxidation was incomplete, some dihydrofolate could be seen at its elution volume of about-365 ml, and ferrocyanide was eluted from about 180 to 210 ml. Beak 3 was identified as folate by its elution position (13) and its ultraviolet absorption spectra in acidic, neutral, and basic solution.…”

Resistance of 5,10-methenyltetrahydrofolate to ultraviolet radiation

“…Folic acid was reduced with sodium borohydride, and the resulting THFA was formylated with formic acid according to the method described in [20], modified by us. Aqueous sodium borohydride solution was added dropwise to the FA solution (its pH being maintained within 8.5-9.0 and the temperature below 10°C ) with argon bubbling.…”

Chemical Changes of Vitamins during Food Processing

“…In the presence of molecular oxygen or other oxidants, 5-methyl-THF, which is the principal naturally occurring form of folacin in many foods, undergoes partial oxidation to form 5-methyl-5,6-dihydrofolic acid (5-methyl-DHF; Fig. 17.5B) (Larrabee et al 1961(Larrabee et al , 1963Scrimgeour and Vitols 1966;Gupta and Huennekens 1970;Blair et al 1975). 5-Methyl-DHF has been shown to exhibit folacin activity similar to that of folie acid (Gregory et al 1984B), although it is highly susceptible to cleavage of the C-9-N-10 bond in strongly acidic media (Maruyama et al 1978; Lewis and Rowe 1979).…”