An assessment of the role of intracellular reductive capacity in the biological clearance of triarylmethane dyes

J Hazard Mater. 2007 Oct 22;149(2):518-22. doi: 10.1016/j.jhazmat.2007.08.022. Epub 2007 Aug 12.


The second-order rate constants (at pH 7, 25 degrees C) for the reduction of three cationic triarylmethane dyes [pararosaniline (PR+), malachite green (MG+), methyl green (MeG+)] by NADH were 1.4 x 10(-2) to 6.7 x 10(-2)mM(-1)min(-1). Based on these values the intracellular nonenzymatic reduction of TAM+ to TAM-H by endogenous NADH was estimated to proceed with an average half-life of 30 min. Rapid and significant adduct formation was observed with the thiol, 3-mercaptopropionic acid (MPA), suggesting that the primary intracellular form of the dyes must be a thiol adduct and that the conversion to adduct form takes place within ms-s. These time frames, when compared to the min-h time frame for microbial clearance of triarylmethanes from culture media, suggest that transport must be the rate-limiting step in non-adsorptive (chemical) clearance of the dyes and that the presence of enzymes to complement the nonenzymatic reductive and adduct-forming activities cited serves a kinetically limited purpose. It appears that a superior catalytic scavenger will be one with a superior transport capacity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Coloring Agents / chemistry*
  • Hydrogen-Ion Concentration
  • Methane / chemistry*
  • Molecular Structure
  • NAD / chemistry
  • Oxidation-Reduction
  • Rosaniline Dyes / chemistry


  • Coloring Agents
  • Rosaniline Dyes
  • NAD
  • malachite green
  • Methane