THE THERMAL STABILITY OF FOLIC (PTEROYLGLUTAMIC) ACID

Abstract

The successful degradation and synthesis of the accessory food factor variously known as vitamin Be, L. casei factor, S. lactis R factor, folic acid and, finally, pteroylglutamic acid (Angier et al., 1946) has not only given rise to more exact work on the significance of this vitamin in anaemia of different kinds, hut has also enabled a more precise standardization of the microbiological assay of the factor to be made. Such assay, of course, involves the heat sterilization of the standard test solutions containing folic acid and, as little is known of the thermal stability of this vitamin, this study was undertaken. The first step was to establish the relation between pll and recovery ol" adiletl folic acid at temperatures of 100° and 121° C. (15 Ib. steam pressure), concurrently investigating the effect of various buffer solutions. The second step was to study the kinetics of the thermal destruction demonstrated. EXPERIMENTAL. MATERIALS. Folic acid 3torJ: solution.Synthetic pteroylglutamic acid ("Folvitc" ot Lederle Laljoratories) was used. 10 mg. were dissolved in distilled water by steaming and made up to 2 litres. Later a 50 p.c. water-alcohol mixture was used to dissolve Ihe "Folvite". 1 ml. ot atock solution contained 5jig. of *'Folvite". Buffer Solutions.(a) Sodium Acetate-Bydrochlori^; Acid. AIM sulution of sodium acetate was prepared in distilled water. For most experiments 10 ml. were diluted to about 40 ml. and the pH adjusted to the desired value with 6 N HCl. The volume was then miade up to 50 ml. In preparing larger volumes 50 ml. of acetate after pH adjustment were made up to 250 ml.(b) Sodium Phoaphatc-Cilric Acid. Solutions of 0*1 M citric acid and 0-2 M disodium hydrogen phosphate were prepared. Varying volumes of tho one were made up to 50 ml. with the other to yield the desired pH. Any final adjustment was made with 6 N HCl or 10 p.c. NaOH.(c) PhoNphate-Phthalatc. 10 ml. of a solution 0-5 M with respect to both potassium dihydrogen phosphate and potassium hydrogen phthalate were diluted to about 45 ml., the pH adjusted to the desired value with NnOII solution and the volume made up to 50 ml.(d) Glycine-Sadluvi Hydroxide. A solution of glycine (0-1 M) was prepared in 0-1 N NaCl solution and varying volumes as required were made up to 50 ml. with 0*1 N NaOH,

Thermal Destruction of Folacin: Effect of Ascorbic Acid, Oxygen and Temperature

“…PteGlu has been the most studied folate form in this regard. Dick et al (1948) undertook a study to determine the thermal stability of PteGlu. Their results showed that PteGlu is stable up to 1 hr when heated at 1OO'C in solutions with pH above 5.…”

Effect of Oxygen on Thermal Degradation of 5‐Methyl‐5,6,7,8‐Tetrahydrofolic Acid

“…Previous studies of thermal degradation of folic acid and its predominant naturally occurring form, 5-CH,-5,6,7,8-tetrahydrofolic acid (5-CH,-THF) have not produced consistent rate expressions or activation energies (Dick et al, 1948;Garret, 1966;Shah et al, 1976;Chen and Cooper, 1979;Ruddick et al, 1980). Reaction rate expressions have ranged from zero to first order in folic acid.…”

Folic Acid - The Occurrence and the Role in Human Nutrition

“…The compound is showing the optical rotation, and is dextrorotary (optical rotation angle of polarized light is equal to +20 o ). It has limited solubility in water, but is soluble in acidic and alkaline solutions and insoluble in organic solvents (Dick et al 1948, Lund 1994. Acidic conditions, light and high temperatures increase the susceptibility of folic acid to cleavage (Dick et al 1948).…”

“…It has limited solubility in water, but is soluble in acidic and alkaline solutions and insoluble in organic solvents (Dick et al 1948, Lund 1994. Acidic conditions, light and high temperatures increase the susceptibility of folic acid to cleavage (Dick et al 1948). There is great variability in the thermal stability of folates (Mnkeni & Beveridge 1982, Day & Gregory 1983.…”