The rates of photo oxidation of thiamine in presence of peroxydiphosphate (PDP) has been determined by measuring the absorbance of thiamine at 264 nm spectre metrically. The rates and quantum yields of oxidation. Of thiamine by phosphate radical anion have been determined in the presence of different concentrations of caffecic acid. Increase in (caffeic acid) is found to decrease the rate of oxidation of thiamine suggesting that caffecic acid acts as an efficient scavenger of PO4-2 and protects thiamine from it. Phosphate radical anion compacts for thiamine as well as caffeic acid the rate constant for phosphate radical anion with caffeic acid has been calculated to be 1.3059 X 10-8 litres mol-1.s-1. The quantum yields of photo oxidation of thiamine have been calculated from the rates of oxidation of thiamine and the light intensity absorbed by PDP at 264 nm. The wave length at which PDP is activated to phosphate radical anion. From the results of experimentally determined quantum yields (exp+) and the quantum yields calculated (cal) assuming caffeic acid concentration and corrected for PO.-4. Scavenging by caffeic acid are also found to be greater than experiment values. These observations suggest that thiamine radicals are repaired by caffeic acid in addition to scavenging of phosphate radical anions. Bansal and Fessenden have used sulphate radical anion (So4) a strong electro phillic radical to create radical cation in uracil and substituted uracils. In the paper we report the results on the protection of thiamine from phosphate radical anion by caffeic acid the rate constant of PO.-4 reaction with caffeic acid has been evaluated. Further an attempt has also been made to evaluate the extent of repair of thiamine radicals by caffeic acid.

1. IJSRD - International Journal for Scientific Research & Development| Vol. 2, Issue 07, 2014 | ISSN (online): 2321-0613
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Kinetics and Mechanism of Protection of Thiamine from Phosphate
Radical
Biyyala Sreedhar Rao1
M. Anand Rao2
1
Osmania University, India
Abstract— The rates of photo oxidation of thiamine in
presence of peroxydiphosphate (PDP) has been determined
by measuring the absorbance of thiamine at 264 nm spectre
metrically. The rates and quantum yields of oxidation. Of
thiamine by phosphate radical anion have been determined
in the presence of different concentrations of caffecic acid.
Increase in (caffeic acid) is found to decrease the rate of
oxidation of thiamine suggesting that caffecic acid acts as an
efficient scavenger of PO4-2 and protects thiamine from it.
Phosphate radical anion compacts for thiamine as well as
caffeic acid the rate constant for phosphate radical anion
with caffeic acid has been calculated to be 1.3059 X 10-8
litres mol-1.s-1. The quantum yields of photo oxidation of
thiamine have been calculated from the rates of oxidation of
thiamine and the light intensity absorbed by PDP at 264 nm.
The wave length at which PDP is activated to phosphate
radical anion. From the results of experimentally determined
quantum yields (exp+) and the quantum yields calculated
(cal) assuming caffeic acid concentration and corrected for
PO.-4. Scavenging by caffeic acid are also found to be
greater than experiment values. These observations suggest
that thiamine radicals are repaired by caffeic acid in addition
to scavenging of phosphate radical anions. Bansal and
Fessenden have used sulphate radical anion (So4) a strong
electro phillic radical to create radical cation in uracil and
substituted uracils. In the paper we report the results on the
protection of thiamine from phosphate radical anion by
caffeic acid the rate constant of PO.-4 reaction with caffeic
acid has been evaluated. Further an attempt has also been
made to evaluate the extent of repair of thiamine radicals by
caffeic acid.
Key words: oxidation of caffeic acid repairing of thiamine
by caffeic acid, oxidations by phosphate radical anion.
I. INTRODUCTION
Hydroxy cinnamic acids are natural anti-oxidants and their
anti-oxidant and antifungal activity is mainly due to their
ability to scavenge several oxidizing free radicals1-4
. In
recent times focus is on the protective action of naturally
occurring anti-oxidant and in this connection studies
involving caffeic acid assume importance due to wide
spread occurrence of this anti-oxidant in nature. When DNA
is subjected to ionizing radiation many different changes can
occur in DNA ranging from various kinds of base
modifications to single and double strand breaks. Even
though sugar radicals are actually responsible for strand
break formation in DNA, Experimental results clearly
indicate that base radicals can contribute significantly via
transfer of radical site from base moiety to sugar moiety5
.
Strand breaks are considered to be every serious kind of
damage to DNA. Ionizing radiation causes damage to DNA
by direct and indirect effect.
II. EXPERIMENTAL
Thiamine and peroxydiphosphate were purchased from
EMERCK, while caffeic acid was from SIGMA. All
solutions were prepared using double distilled water. Stock
solutions of thiamine and caffeic acid were always freshly
prepared and de aerated by bubbling nitrogen. The solution
of peroxydiphosphate was prepared by using double distilled
water and standardized using cerimetry using ferroin
indicator. Peroxydiphosphate solution was added to a
measured excess of ferrous ammonium sulphate, and back
titrated with a standard cericammonium sulphate solution as
reported by Kapoor etal. At room temperature this reaction
is rapid enough for analytical purposes and equivalency of
ferrousion to PDP is 2 to 1. Required amounts of caffeic
acid were then infected as aqueous solution in to the mixture
of thiamine and PDP solution present in a specially designed
1 cm path length quartz cuvette which is suitable for both
irradiation in the quantum yield. Reactor as well as for
absorbance measurements6-8
. The absorbance measurements
were made at 264nm, which is the max of thiamine on
HITACHI/UV-Vis spectrophotometer (model 3410).
Irradiations were performed at room temperature (250
C)
with high pressure mercury lamp using quantum yield
reactor room temperature (250
C) with high pressure mercury
lamp quantum yield reactor model QYR – 20. The
irradiations were interrupted at definite intervals of time and
the absorbance was noted from which the rate of reaction
and the quantum yields of oxidation are calculated9
. The
light intensity at 264 oxidation are calculated10
. The light
intensity at 264nm was measure by PDP chemical
actinometry. The light intensity absorbed by PDP was
calculated by using the following equation.
It IPDP = Intensity of light absorbed by
peroxydiphosphate in a reaction mixture
It = total intensity of light measured from
peroxydiphosphate actinometry.
PDP = Molar absorption co. Efficient of thiamine
at 264 nm.
III. RESULTS AND DISCUSSION
N2- Saturated aqueous solution of the reaction mixture
containing 1x10-4
mol dm-3
, PDP 1x10-4
mol dm-3
and
caffeic acid were irradiated and the absorbance at 264nm
(max of thiamine) with time were noted from which the
rates of oxidation of thiamine were calculated from the plots
of absorbance versus time using a micro cal origin computer
program on personal computer (table 1, figure 1) N2-
Saturated aqueous solution of the mixture containing caffeic
acid and PDP were irradiated and the absorbance at 264 nm
(max. of caffeic acid) with time were noted from which the
rates of Oxidation of caffeic acid were calculated from the

2. Kinetics and Mechanism of Protection of Thiamine from Phosphate Radical
(IJSRD/Vol. 2/Issue 07/2014/115)
All rights reserved by www.ijsrd.com 524
plots of absorbance versus time using micro cal origin
computer program. The initial rates of caffeic acid by
Irradiation time in minutes Absorbance
0 0.695
1 0.688
2 0.684
3 0.678
5 0.667
7 0.664
9 0.651
11 0.640
13 0.632
16 0.617
19 0.595
24 0.565
30 0.529
38 0.529
48 0.408
58 0.340
68 0.268
Table 1: Oxidation Of Thiamine In Presence Of Pdp At
Various (Caffeic Acid) In Aqueous Anoxic Solutions
[Thiamine] = 1X10-4
M
[PDP] = 1X10-3
M
Temp = 305K
Absorbance at 264nm in the presence of
(caffeicacid) concentration in aqueous anoxic solutions.
Table 2: Effect Of [Pdp] On Oxidation Of Thiamine In
Presence Of Pdp
Intensity - 2.78 x 1017
q/s
λ - 264nm
E - 7.9 x 103
dm3
mol-1
cm-1
PH -
8.2
[Thiamine] - 1 x 10-4
M
[PDP] - 1 x 10-3
M
λ - 264unm
0.47 ml of thiamine + 1.51ml of PDP + 8.02 ml of water
Irradiation time in minutes Absorbance
0 0.812
0.5 0.809
2 0.799
3 0.793
5 0.783
7 0.770
9 0.767
12 0.738
15 0.697
19 0.666
24 0.631
IV. CONCLUSION
From the results of experimentally determined quantum
yields (expt) and the quantum yields calculated (cal)
assuming caffeic acid concentration and corrected for PO.-
4.
Scavenging by caffeic acid are also found to be greater than
experiment values. These observations suggest that thiamine
radicals are repaired by caffeic acid in addition to
scavenging of phosphate radical anions. Bansal and
Fessenden have used sulphate radical anion (SO4
) a strong
electro phillic radical to create radical cation in uracil and
substituted uracils. The reaction orders were determined
from the slopes of irradiation of time vs absorbance plots by
varying the concentration of PDP and thiamine
hydrochloride. The rate of reactions was measured at
different temperatures, 25˚, 30˚C under varying acid and
thiamine hydrochloride concentration. The rates were found
to increase with increasing temperature. The rates and
quantum yields of oxidation of thiamine increased with
increase in concentration of Thiamine.
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