Abstract
Proline-Ninhydrin (PN) complex has earlier been reported by us to be an excellent free radical scavenger and also examined for in vitro and in vivo radioprotection. Here we present mechanism of reaction of PN complex with hydroxyl ({sup .}OH) radicals and other oxidants and compared the results with proline and ninhydrin independently. PN complex was prepared by mixing in 1:1 stoichiometric ratio of proline and ninhydrin in a ball mill at 40 degree C and purified by crystallisation. Parent absorption spectra of PN complex show peak at 300 nm and 304 nm with a ground state pK{sub a} of 9.3. The reaction of {sup .}OH radical and other one-electron oxidants were studied using 7 MeV electron pulses from LINAC and the dose determined by aerated KSCN dosimeter. {sup .}OH radical reaction with PN studied at pH 6.8 produced a transients having broad absorption band at 400 nm. The reaction of {sup .}OH with PN complex was found to be dependent on the pH of the solution, at pH > 8 the transient absorption band shifted to 360 nm. The pK{sub a} of the transient was measured by following these absorption changes with varying the pH from 2 to 11 to
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Barik, A;
Priyadarsini, K I;
[1]
Prabhakar, K R;
Veerapur, V P;
Unnikrishnan, M K
[2]
- Radiation and Photochemistry Division, Behabha Atomic Research Centre, Trombay, Mumbai (India)
- Department of Pharmacology, Manipal College of Pharmaceutical Sciences (India)
Citation Formats
Barik, A, Priyadarsini, K I, Prabhakar, K R, Veerapur, V P, and Unnikrishnan, M K.
Pulse radiolysis studies of proline-ninhydrin complex.
China: N. p.,
2006.
Web.
Barik, A, Priyadarsini, K I, Prabhakar, K R, Veerapur, V P, & Unnikrishnan, M K.
Pulse radiolysis studies of proline-ninhydrin complex.
China.
Barik, A, Priyadarsini, K I, Prabhakar, K R, Veerapur, V P, and Unnikrishnan, M K.
2006.
"Pulse radiolysis studies of proline-ninhydrin complex."
China.
@misc{etde_21605573,
title = {Pulse radiolysis studies of proline-ninhydrin complex}
author = {Barik, A, Priyadarsini, K I, Prabhakar, K R, Veerapur, V P, and Unnikrishnan, M K}
abstractNote = {Proline-Ninhydrin (PN) complex has earlier been reported by us to be an excellent free radical scavenger and also examined for in vitro and in vivo radioprotection. Here we present mechanism of reaction of PN complex with hydroxyl ({sup .}OH) radicals and other oxidants and compared the results with proline and ninhydrin independently. PN complex was prepared by mixing in 1:1 stoichiometric ratio of proline and ninhydrin in a ball mill at 40 degree C and purified by crystallisation. Parent absorption spectra of PN complex show peak at 300 nm and 304 nm with a ground state pK{sub a} of 9.3. The reaction of {sup .}OH radical and other one-electron oxidants were studied using 7 MeV electron pulses from LINAC and the dose determined by aerated KSCN dosimeter. {sup .}OH radical reaction with PN studied at pH 6.8 produced a transients having broad absorption band at 400 nm. The reaction of {sup .}OH with PN complex was found to be dependent on the pH of the solution, at pH > 8 the transient absorption band shifted to 360 nm. The pK{sub a} of the transient was measured by following these absorption changes with varying the pH from 2 to 11 to be 6.9. OH radical reactions with the organic substrates is non-selective in nature and in order to establish the nature of the transient absorption band, pulse radiolysis studied were carried out with specific one electron oxidants, SO{sub 4}{sup .-} radical and Cl{sub 2}{sup .-} radical, which showed the transient absorption band with maximum at 440 nm and 350 nm respectively, indicating that the reaction {sup .}OH with PN complex at pH 7 is not by oxidation but by addition reaction to the aromatic ring. The reaction of H atom with PN complex was carried out in presence of tert-butanol at pH 1. The transient showed similar spectrum as observed with reaction OH radical reaction. As the H atom proceeds through mostly abstraction reaction, the transient formed by H atom and OH radical at low pH produces H atom abstracted species of the PN complex. Pulse radiolysis studies of ninhydrin and proline were studied independently, from which it has been confirmed that the OH radical attack in PN complex occurs preferably on the ninhydrin site only. (authors)}
place = {China}
year = {2006}
month = {Jul}
}
title = {Pulse radiolysis studies of proline-ninhydrin complex}
author = {Barik, A, Priyadarsini, K I, Prabhakar, K R, Veerapur, V P, and Unnikrishnan, M K}
abstractNote = {Proline-Ninhydrin (PN) complex has earlier been reported by us to be an excellent free radical scavenger and also examined for in vitro and in vivo radioprotection. Here we present mechanism of reaction of PN complex with hydroxyl ({sup .}OH) radicals and other oxidants and compared the results with proline and ninhydrin independently. PN complex was prepared by mixing in 1:1 stoichiometric ratio of proline and ninhydrin in a ball mill at 40 degree C and purified by crystallisation. Parent absorption spectra of PN complex show peak at 300 nm and 304 nm with a ground state pK{sub a} of 9.3. The reaction of {sup .}OH radical and other one-electron oxidants were studied using 7 MeV electron pulses from LINAC and the dose determined by aerated KSCN dosimeter. {sup .}OH radical reaction with PN studied at pH 6.8 produced a transients having broad absorption band at 400 nm. The reaction of {sup .}OH with PN complex was found to be dependent on the pH of the solution, at pH > 8 the transient absorption band shifted to 360 nm. The pK{sub a} of the transient was measured by following these absorption changes with varying the pH from 2 to 11 to be 6.9. OH radical reactions with the organic substrates is non-selective in nature and in order to establish the nature of the transient absorption band, pulse radiolysis studied were carried out with specific one electron oxidants, SO{sub 4}{sup .-} radical and Cl{sub 2}{sup .-} radical, which showed the transient absorption band with maximum at 440 nm and 350 nm respectively, indicating that the reaction {sup .}OH with PN complex at pH 7 is not by oxidation but by addition reaction to the aromatic ring. The reaction of H atom with PN complex was carried out in presence of tert-butanol at pH 1. The transient showed similar spectrum as observed with reaction OH radical reaction. As the H atom proceeds through mostly abstraction reaction, the transient formed by H atom and OH radical at low pH produces H atom abstracted species of the PN complex. Pulse radiolysis studies of ninhydrin and proline were studied independently, from which it has been confirmed that the OH radical attack in PN complex occurs preferably on the ninhydrin site only. (authors)}
place = {China}
year = {2006}
month = {Jul}
}