Mechanisms involved in the chemical inhibition of the eosin-sensitized photooxidation of trypsin

Rizzuto, Frank; Spikes, John D.

doi:10.1007/bf01327349

Cited by 12 publications

(3 citation statements)

References 33 publications

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“…Decay rates of the hematoporphyrin transients were determined from photographs of the oscillascope traces with the assistance of a Hewlett-Packard Model 9810A programmable calculator. The methodology is described in greater detail elsewhere (Rizzuto and Spikes, 1975). Anaerobic samples were prepared by bubbling with prepurified nitrogen and the usual freeze-thaw techniques (Vaish and Tollin, 1970); both techniques gave similar results.…”

Section: Methodsmentioning

confidence: 99%

The Effect of Chemical Structure on the Photosensitizing Efficiencies of Porphyrins

Cauzzo

Gennari

Jori

et al. 1977

Photochem & Photobiology

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Abstract— A kinetic investigation was performed on the photooxidation of methionine sensitized by various porphyrins at different oxygen concentrations. The rate of photooxidation was found to be strongly dependent on the nature of the sensitizer. In the case of hematoporphyrin, chelation of Mg2+ and Zn2+ and especially of Cu2+ and Fe2+ caused a significant decrease of the photosensitizing efficiency. Fluorescence and/or flash photolysis studies showed that such a decrease is ascribed to an enhancement of the non‐radiative decay of the first excited singlet state as well as to a reduction of the triplet lifetime. The sensitizing efficiency is also dependent on the nature of the porphyrin side chains. A reaction mechanism involving 1O2 as the oxidizing agent is proposed.

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Section: Methodsmentioning

confidence: 99%

The Effect of Chemical Structure on the Photosensitizing Efficiencies of Porphyrins

Cauzzo

Gennari

Jori

et al. 1977

Photochem & Photobiology

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“…213 A reversible electron transfer reaction between triplet state eosin and p-phenylendiamine with regeneration of sensitizer ground state and unaltered quencher has been proposed to explain inhibition of eosin-sensitized photooxidation of trypsin. 214 The structure activity relationship of many physical quencher substances is difficult to predict, especially under physiological conditions. Although some general requirements must be fulfilled to allow physical quenching, e.g.…”

Section: Physical Triplet State Quenchersmentioning

confidence: 99%

Endogenous UVA-photosensitizers: mediators of skin photodamage and novel targets for skin photoprotection

Wondrak

Jacobson

2006

Photochem Photobiol Sci

364

313

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Endogenous chromophores in human skin serve as photosensitizers involved in skin photocarcinogenesis and photoaging. Absorption of solar photons, particularly in the UVA region, induces the formation of photoexcited states of skin photosensitizers with subsequent generation of reactive oxygen species (ROS), organic free radicals and other toxic photoproducts that mediate skin photooxidative stress. The complexity of endogenous skin photosensitizers with regard to molecular structure, pathways of formation, mechanisms of action, and the diversity of relevant skin targets has hampered progress in this area of photobiology and most likely contributed to an underestimation of the importance of endogenous sensitizers in skin photodamage. Recently, UVA-fluorophores in extracellular matrix proteins formed posttranslationally as a consequence of enzymatic maturation or spontaneous chemical damage during chronological and actinic aging have been identified as an abundant source of light-driven ROS formation in skin upstream of photooxidative cellular stress. Importantly, sensitized skin cell photodamage by this bystander mechanism occurs after photoexcitation of sensitizers contained in skin structural proteins without direct cellular photon absorption thereby enhancing the potency and range of phototoxic UVA action in deeper layers of skin. The causative role of photoexcited states in skin photodamage suggests that direct molecular antagonism of photosensitization reactions using physical quenchers of photoexcited states offers a novel chemopreventive opportunity for skin photoprotection.

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“…Then, by reverse electron transfer, ground state eosin and Propyl Gallate were regenerated. Photodynamic activation occurred with the formation of a free radical, and Propyl Gallate acted by inhibiting free-radical formation (Rizzuto and Spikes 1975). Propyl Gallate also inhibited mild oxidation of serum lowdensity lipoprotein.…”

Section: Antioxidant-related Effectsmentioning

confidence: 99%

Final Report on the Amended Safety Assessment of Propyl Gallate1

2007

Int J Toxicol

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Propyl Gallate is the n-propyl ester of gallic acid (3,4,5-trihydroxybenzoic acid). It is soluble in ethanol, ethyl ether, oil, lard, and aqueous solutions of polyethylene glycol (PEG) ethers of cetyl alcohol, but only slightly soluble in water. Propyl Gallate currently is used as an antioxidant in a reported 167 cosmetic products at maximum concentrations of 0.1%. Propyl Gallate is a generally recognized as safe (GRAS) antioxidant to protect fats, oils, and fat-containing food from rancidity that results from the formation of peroxides. Data on dermal absorption are not available, but Propyl Gallate is absorbed when ingested, then methylated, conjugated, and excreted in the urine. The biological activity of Propyl Gallate is consistent with its free-radical scavenging ability, with effects that include antimicrobial activity, enzyme inhibition, inhibition of biosynthetic processes, inhibition of the formation of nitrosamines, anesthesia, inhibition of neuromuscular response to chemicals, ionizing/ultraviolet (UV) radiation protection, chemoprotection, antimutagenesis, anticarcinogenesis and antitumorigenesis, antiteratogenesis, and anticariogenesis. Animal toxicity studies indicate that Propyl Gallate was slightly toxic when ingested, but no systemic effects were noted with dermal application. Propyl Gallate is a strong sensitizer when tested intradermally, less sensitizing when tested topically, and nonsensitizing topically at 0.1% in one study. In a second study, Propyl Gallate (15 mg dissolved in 8 ml vehicle) was sensitizing to guinea pigs. Acute eye irritation tests conducted on nine cosmetic formulations, each containing less than 1% Propyl Gallate, were negative. A phototoxicity study conducted on a cosmetic formulation containing 0.003% Propyl Gallate determined that the product was not phototoxic to guinea pigs. In one study, female rats fed 0.5 g Propyl Gallate had substantially increased fetal resorption rates when compared to controls, but in four other studies, Propyl Gallate at doses up to 2.04 g/kg was nonteratogenic in rats, rabbits, mice, and hamsters. In clinical cumulative irritancy tests, Propyl Gallate was nonirritating at concentrations up to 10%. Patch tests at concentrations less than 1% yielded positive elicitation responses. Repeat-insult patch tests using cosmetic formulations with 0.003% Propyl Gallate produced no irritation or sensitization. Propyl Gallate at a concentration of 10% in alcohol was nonphototoxic in 25 subjects. Cosmetic formulations, each containing 0.003% Propyl Gallate, produced no signs of photosensitization or phototoxicity in a total of 371 subjects. Although Propyl Gallate is not a skin irritant in clinical tests, the available data demonstrate that it is a skin sensitizer and that it may be a sensitizer at lower concentrations than originally thought, i.e., at concentrations less than 1%. In actual practice, cosmetic formulations contain Propyl Gallate at concentrations up to 0.1% and usage has increased over the past 20 years. In spite of the increased exposure...

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Mechanisms involved in the chemical inhibition of the eosin-sensitized photooxidation of trypsin

Cited by 12 publications

References 33 publications

The Effect of Chemical Structure on the Photosensitizing Efficiencies of Porphyrins

The Effect of Chemical Structure on the Photosensitizing Efficiencies of Porphyrins

Endogenous UVA-photosensitizers: mediators of skin photodamage and novel targets for skin photoprotection

Final Report on the Amended Safety Assessment of Propyl Gallate1

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