|
NISCAIR ONLINE PERIODICALS REPOSITORY (NOPR) >
NISCAIR PUBLICATIONS >
Research Journals >
Indian Journal of Biochemistry and Biophysics (IJBB) >
IJBB Vol.47 [2010] >
IJBB Vol.47(5) [October 2010] >
| Title: | Kinetics and mechanisms of oxidation of some antioxidants with photochemically generated tert-butoxyl radicals |
| Authors: | Vijayalakshmi, G
Adinarayana, M
Rao, Jayaprakash |
| Keywords: | Oxidation
t-BuOยท(t-BuO).radicals
Caffeic acid
Chlorogenic acid
Rosmarinic acid
Gallic acid |
| Issue Date: | Oct-2010 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | Dietary antioxidants play an important role
in the prevention of several chronic diseases including cardiovascular
diseases, cancer, ageing and diabetes. In order to understand the mechanism of
oxidation of antioxidants viz., gallic acid (GA), caffeic acid (CA), rosmarinic
acid (RA) and chlorogenic acid (CGA), a systematic kinetic study of these
antioxidants with photochemically generated tertiary butoxyl (t-BuO). radicals was carried out. The oxidation of antioxidants by
t-BuO. radicals was followed spectrophotometrically by measuring
the absorbance of GA (266 nm), CA (310 nm), RA (324 nm) and CGA (328 nm) at
their respective lmax.
The initial rates of oxidation of antioxidants were calculated from the plot of
absorbance vs time and were found to
increase with increase in [antioxidant], [t-BuOOH]
and light intensity in all the cases. The quantum yields (f) were calculated from the initial rates of oxidation of antioxidant
and the measured light intensity at 254 nm, the wavelength at which the tert-butyl hydroperoxide (t-BuOOH) was activated to radicals. The
quantum yields were found to depend on [antioxidant] and [t-BuOOH], and were independent of light intensity. The order with
respect to [antioxidant], [t-BuOOH]
were found to be fractional whereas order with respect to intensity was one.
The order of reactivity was found to be: CA > CGA > RA > GA. The
products were identified by mass spectral data. On the basis of kinetic results
and product analysis, probable mechanisms were suggested. |
| Page(s): | 292-297 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-0959 (Online); 0301-1208 (Print) |
| Source: | IJBB Vol.47(5) [October 2010]
|
|
