PHOTOGENERATION OF SUPEROXIDE and DECARBOXYLATED PEPTIDE RADICALS BY CARBOQUONE, MITOMYCIN C and STREPTONIGRIN. AN ELECTRON SPIN RESONANCE and SPIN TRAPPING STUDY

Abstract

Abstract— Visible light (405–615 nm) excitation of carboquone, mitomycin C, and streptonigrin dissolved in dimethylsulfoxide in the presence of oxygen generates superoxide anion radicals (O2−). The quantum yields for these reactions range from 4.2 times 10−2 (carboquone, λ= 615 ± 10 nm) to 7.3 times 10−6 (streptonigrin, λ=545 ± 10 nm). O2− radicals were spin trapped with 5,5‐dimethyl‐1‐pyrroline‐1‐oxide (DMPO) and identified by electron spin resonance (ESR). The efficiency of DMPO to spin trap O2− in dimethylsulfoxide was determined and indicated that 91% of the O2− present in dimethylsulfoxide is trapped by DMPO. The oxidation of the photoexcited drug molecules occurs via a direct electron transfer to dissolved oxygen in solution. Ultraviolet irradiation (λ= 313 ± 10 nm) of the aminoquinone drug solutions (80% H2O, 20% dimethylsulfoxide) in the presence of peptides results in the decarboxylation of the peptides. In this case the photoexcited drugs are reduced, abstracting an electron from the C‐terminal carboxyl group of the peptides. The reaction is specific to the C‐terminal amino acid of the peptide. The decarboxylated peptide radicals were spin trapped with 2‐methyl‐2‐nitrosopropane (MNP) and identified by ESR.

Antioxidant and cell growth activities of beet root pomace extracts

“…The ESR hyperfine splitting constants of the DMPO-OH adduct were: a N = 12.65 G; a H = 10.4 G; a H = 1.3 G, which is in accordance with literature data (Carmichael, Samuni, & Riesz, 1985). All beetroot extracts have efficiently scavenged reactive superoxide anion radicals (Fig.…”

“…In all cases a typical ESR spectrum of DPPH radicals, with five lines of relative intensities 1:2:3:2:1 and hyperfine splitting constant a N = 9.03, was observed (Ć etković , Djilas, Č anadanović - Brunet, & Tumbas, 2004). The H-transfer reactions from antioxidants, present in beetroot pomace extracts, to DPPH Å were monitored by recording the decay of the DPPH Å ESR signal.…”

Spectroscopic Studies of Cutaneous Photosensitizing Agents–xvi. Isperse Blue 35

“…3 was observed. The ESR signal is identified as the DMPO/O; adduct on the basis of its characteristic pattern and values of hf coupling constants aN = 12.7 G, a; = 10.3 G and a; = 1.3 G, which are in agreement with those reported earlier for the same type of radical (Harbour and Hair, 1978;Carmichael et a / . , 1985).…”

ENHANCEMENT OF ANTITUMOR DRUG CYTOTOXICITY via LASER PHOTOACTIVATION

“…These authors have demonstrated that, in the presence of oxygen, photoexcited D and DX transfer an electron to oxygen generating superoxide anion 0; which eventually yields OH'. Carmichael et al (1983) have also reported that irradiation of air-saturated solutions of MX, at variance with D and DX, does not generate 0; or any other oxygen-activated radical species. Reszka er al.…”

“…Consequently, MX was classified as a poor photosensitizer compared to both dauno-797 mycin and adriamycin (Carmichael et af., 1983;Carmichael and Riesz, 1985). Furthermore, a number of photosensitized effects on biomolecules and biosubstrates have been reported for anthracyclines, which involve nor only photochemical generation of radical species (Gray et al, 1982;Carmichael et a!. , 1983;Li and Chignell, 1987) but also other excitedstate reactions such as photobinding to DNA (Daugherty et af., 1979;Gray and Phillips, 1980) or cell surface proteins (Yee et al, 1984).…”