Res. Chem. Intermed.
, Vol. 28, No. 6, pp. 505–515 (2002)
Also available online - www.vsppub.com
Free radical reactions of pyridoxal (vitamin B
a pulse radiolysis study
RAVI JOSHI, S. KAPOOR and T. MUKHERJEE
Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre,
Mumbai 400 085, India
Received 21 September 2001; accepted 22 May 2002
Abstract—Redox reactions of pyridoxal (P-OH) with e
and various organo-
haloperoxyl radicals have been studied using pulse radiolysis technique. The rate constants for the
reaction of P-OH or P-O
with the above-mentioned radicals and the transient absorption spectra
have been measured. The transients formed in the reaction of hydrated electron and oxidizing radicals
with pyridoxal have been assigned. An attempt has been made to nd a correlation between the rate
constants and Taft parameter for the reactions with the organo-haloperoxyl radicals. It has also been
observed that the one-electron oxidized radical of pyridoxal is repaired by uric acid. The reduction
potential for the P-OH
/P-OH couple at pH 7, as measured by cyclic voltammetry, has been found to
: Pyridoxal; pulse radiolysis; oxidizing radicals; repair.
Recently, dietary antioxidants have found importance in anti-carcinogenesis and
degenerative diseases due to their free radical scavenging characteristics [1– 5].
The concept that free radicals play a signi cant role in the pathogenesis of certain
human diseases and the role of antioxidants in diseases and oxidative stress
has been increasingly recognized [6– 11]. Similarly, radiation chemical studies
on vitamins have become important in connection with radiation sterilization of
food and medical products [12, 13]. In recent years, the use of pesticides and
related organo-halogens has increased enormously and their toxicity is known to
be due to the formation of organo-haloperoxyl radicals. Pulse radiolysis offers a
clean method for studying such redox reactions of various biologically important
compounds [14– 16].
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