Akhtar M J, Khan M A, Ahmad I
Department of Chemistry, University of Karachi, Pakistan.
J Pharm Biomed Anal. 1999 Mar;19(3-4):269-75. doi: 10.1016/s0731-7085(98)00038-7.
A study of the photodegradation of folic acid by ultraviolet radiation in aqueous solution has been made. Folic acid is photolysed by an apparent first-order kinetics and the log k-pH profile shows a gradual decrease in rate in the pH range 2.0-10.0. The profile indicates the appearance of three steps which reflect the participation of different ionic species of folic acid (pKa(1) 2.3, pKa(2) 8.3) in the photolysis reaction. The rate of photodegradation varies from 0.1550 x 10(-3) min(-1) (pH 10.0) to 5.04 x 10(-3) min(-1) (pH 2.5) in the pH range studied. The photolysis of folic acid shows that it is degraded to pterine-6-carboxylic acid and p-amino-benzoyl-L-glutamic acid. A maximum yield of these products is obtained at 3-8 h, depending upon the pH. An HPLC method has been used for the assay of folic acid and its degradation products.
对叶酸在水溶液中受紫外线辐射的光降解进行了研究。叶酸按表观一级动力学进行光解，log k-pH曲线表明在pH值2.0 - 10.0范围内反应速率逐渐降低。该曲线显示出三个阶段，反映了叶酸不同离子形式（pKa(1) 2.3，pKa(2) 8.3）参与光解反应。在所研究的pH范围内，光降解速率从0.1550×10⁻³ min⁻¹（pH 10.0）变化到5.04×10⁻³ min⁻¹（pH 2.5）。叶酸的光解表明它降解为蝶呤 - 6 - 羧酸和对氨基苯甲酰 - L - 谷氨酸。根据pH值不同，在3 - 8小时可获得这些产物的最大产量。已采用高效液相色谱法测定叶酸及其降解产物。
