Photosensitizing activity

Photosensitizing and Catalytic Properties of PCSs 5.1. Photosensitizing Activity... 

Low-molecular semiconductors and, in particular, phthalocyanines are known to exhibit photosensitizing properties268. The photosensitizing activity of these substances has been studied in most detail for the reaction of oxidation of ascorbic acid. 

Bearing in mind the semiconductive properties of PCSs one might expect that these substances, being p-type semiconductors in air, possess photosensitizing activity. We, indeed, have demonstrated40 that PCSs, such as poly(schiff base)s, salts of poly(propynoic acid), or polyquinoline, are active photosensitizers of... 

Ivie, G.W. and Casida, J.E. Sensitized photodecomposition and photosensitizer activity of pesticide chemicals exposed to sunlight of silica gel chromatoplates, J. Agric. Food Chem., 19(3) 405-409, 1971. 

Persistent photosensitivity developed in eight men after occupational exposure to hot epoxy resin fiimes. The condition was limited to sites contacted by the resin. Small doses of ultraviolet-A light evoked abnormal reactions consisting of erythema, edema, and papules in the clinically involved skin. Positive photopatch tests were observed to epoxy resin in four subjects and to bisphenol A in all subjects. Another study showed that bisphenol A can be released during the thermal decomposition of epoxy resin in the temperature range of 250-350°C. Photosensitizing activity was explained by the formation of ftee radicals during exposure to ultraviolet-B radiation of bisphenol A vapor, to form a semiquinone derivative of bisphenol A ... 

MB also demonstrated very wide photosensitizing activity (Peloi et ah, 2008 Prates et ah, 2009). It was reported to be effective against bacteria and fungi. A methylene blue based PDT was shown to eradicate Pseudomonas aeruginosa both in planktonic and biofilm cultures (Street et ah, 2009). 

Ferro, S., Jori, G., Sortino, S., Stancanelli, R., Nikolov, P., Tongon, G., Ricchelli, F., and Mazzaglia, A. (2009). Inclusion of 5-[4-(l-dodecanoylpyridinium)-10,15,20-triphenylpor-phine in supramolecular aggregates of cationic amphiphilic cyclodextrines Physic-chemical characterization of the complexes and strengthening of the antimicrobial photosensitizing activity. Biomacromolecules 10(9), 2592-2600. 

Despite the hypothesis that the evolutionary significance of phototoxic secondary substances may be linked to their ability to discourage Insect herbivores, most research has been directed toward their effects on human skin and range animals (42). In an attempt to extend our knowledge of insect photosensitizers we have screened a number of plant secondary substances (TABLE TI) for their photosensitizing activity to 4th instar mosquito larvae Aedes atropalpus under solar simulating lamps. 

Only one class of benzofuran derivative, natural or synthetic, shows this property—the furocoumarins-, these are important for plant biosynthesis, since they take part in the elaboration of chlorophyll.308 13 Among linear furocoumarins, psoralene (27a) is particularly active. Angelicin (28), another fundamental furocoumarin heterocycle with an angular structure, has only about 12% of the photosensitizing activity of 27a.74-75 On the other hand, it has antibiotic activity. Furochromones have no photosensitizing properties. 

In related studies of metal ions, Krasnovski learned that the oxides of titanium, zinc, or tungsten possess high photosensitizing activity in redox reactions comparable to the activity of porphyrins and chlorophylls 15). 

A photosensitized activation of carbon-selenium bonds was also used for performing phenylseleno group transfer reactions. This process involves a photosensitized electron transfer (PET) as the initial step in the reaction sequence. Fragmentation affords a radical and phenylselenolate, which is oxidized to diphenyl diselenide in the presence of oxygen. The cyclized radical is then trapped by diphenyl diselenide to afford the final product. This process is quite general for intramolecular radical reactions.70,266... 

Zhou W, Moore DE. Photosensitizing activity of the antibacterial drugs sulfamethoxazole and trimethoprim. Photochem Photobiol 1997 39 63-72. 

Figure 13. Examples of photosensitizers activated by UV-B solar radiation found in plants.

Large photosensitizing activity of HAC - LI is successfully explained by the fact that compound (LI) may have two tautomeric resonance states, in one of which it contains free aminogroups, owing to which it displays photosensitizing properties, that quite well agrees with [10]. 

Table 2 Pressure Effects on Photosensitization Activation Enthalpies, Entropies, and Volumes for Four Crowded Sensitizers...

Vargas, F., Mendez, H., Fuentes, A., Sequera, J., Fraile, G., Velasques, G., Caceres, G., and Cuello, K. (2001) Photosensitizing activity of thiocolchicoside photochemical and in vitro phototoxicity studies, Pharmazie, 56, 83-88. 

This is the outcome of many years of research by the United States department of the Army. It belongs to the 4-quinoline methanol series, several of which were foimd to have potent schizonticidal activity but could not be used clinically, because they possessed photosensitizing activity in man. Mefloquine is devoid of this effect. 

Athar M, Elmets C A, Bickers D R, et al. (1989). A novel mechanism for the generation of superoxide anions in hematoporphyrin derivativemediated cutaneous photosensitization. Activation of the xanthine oxidase pathway. J. Clin. Invest. 83 1137-1143. 

Fig. (1). The pyramid of relative skin photosensitizing activity among several psoralens. The furanocoumarins at the bottom are almost inactive.

The mechanism of photooxidation of petroleum probably includes significant contributions from both radical and singlet oxygen pathways. Petroleum contains polycyclic aromatic hydrocarbons and other compounds with known photosensitizing activity Lichtenthaler et al. (1989) demonstrated quantum yields for O2 formation ranging from 0.5 to 0.8 for a number of crude oils. The photooxidation of a 2 fuel oil was inhibited by /3-carotene, an excellent quencher of O2 and free radicals, at concentrations > lO" M (Larson and Hunt, 1978). A mechanism incorporating... 

Photosensitizing activity of the compound quinine and derivatives has been reported (Spikes 1998 Waddell et al. 

The compounds psoralen and angelicin extracted from psoralea demonstrated photosensitizing activity after topical application to guinea pigs (Innocenti et al. 1977). 

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