THERMAL-DESTRUCTION OF FOLACIN - EFFECT OF PH AND BUFFER IONS

Thermal stability of four folacin derivatives at 100°C was determined as a function of pH and buffer ions. The degradation reaction at 100° C for all the folate forms studied followed first order kinetics. Under identical heating conditions, folic acid (PteGlu) and 5‐for‐myltetrahydrofolic acid (5‐CHOH4 PteGlu) were quite stable whereas 5‐methyltetrahydrofolic acid (5‐CH3 H4 PteGlu) and tetrahydrofolic acid (H4 PteGlu) were very labile. Both PteGlu and 5‐CHOH4 PteGlu were stable up to 10 hr of heating in pH 4–12, but unstable in more acidic conditions. 5‐CH3 H4 PteGlu showed greatest stability at pH 7. The rate constant for 5‐CH3 H4 PteGlu destruction is directly proportional to hydrogen ion concentration between pH 2.6 and 7.0 and inversely proportional to hydrogen ion concentration between pH 7–12. The stability of H4 PteGlu at 100°C was found to decrease linearly with the hydrogen ion concentration in the pH range 4–12. Universal buffer was found to cause higher thermal destruction rate only for 5‐CH3 H4 PteGlu and H4 PteGlu than the other buffers tested. Copyright © 1979, Wiley Blackwell. All rights reserved