Kinetic and mechanistic investigations on reductions of aflatoxins by lactic acid.
The kinetics of reduction of AFB(1) to AFB(2) and AFG(1) to AFG(2) by lactic acid has been investigated in dilute aqueous acidic solutions (pH 3.35-4.50) as a function of the concentrations of lactic acid, AFB(1), AFG(1) and hydrogen ion at 37 degrees C. The rate of the reaction was found to be first order with respect to the concentrations of lactic acid and aflatoxins and independent on hydrogen ion concentration. The experimental results are interpreted in terms of mechanisms involving an initial formation of transient oxonium intermediate, which tends to polarize the olefinic (C=C) carbon, which in turn causes the hydride abstraction from alpha-carbon atom of lactic acid in rate determining step. The proposed mechanisms involve an overall transfer of two protons and two electrons from lactic acid to AFB(1) and AFG(1) to give the corresponding reduced less toxic products AFB(2) and AFG(2) and the oxidised product pyruvic acid.
Shukla
Ram S
RS
Silicates and Catalysis Division, Central Salt and Marine Chemicals Research Institute, Bhavnagar, India.
Verma
Ramtej J
RJ
Mehta
Daxa N
DN
D000348:Aflatoxins / Q000737:chemistry*; D001230:Aspergillus / Q000737:chemistry / Q000378:metabolism; D002273:Carcinogens / Q000737:chemistry*; D002855:Chromatography, Thin Layer; D016166:Free Radical Scavengers; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry*; D010084:Oxidation-Reduction; D019289:Pyruvic Acid / Q000737:chemistry
D000348:Aflatoxins; D002273:Carcinogens; D016166:Free Radical Scavengers; D019344:Lactic Acid; D019289:Pyruvic Acid