Photodynamic compounds

This photodynamic compound causes a photosensitive disease called bighead in sheep that consume it (42). Related compounds, the... 

Wacker, A. Molecular mechanisms of photodynamic compounds. In Research progress in organic, biological and medicinal chemistry, Vol. Ill, Part 1, (eds. U. Gallo and L. Santamaria). Amsterdam North-Holland Publ. Company 1972. 

Pawlaczyk, J. and Turowska, W. (1976) Photochemistry of photodynamic compounds. VII. Identification of some products of photolysis of sulphanilamide aqueous solutions, Acta Polon. Pharm., 33, 505-509. 

Photodynamic compounds, including many natural products, have been... 

However, a problem with these chemicals is their indiscriminate toxicity in the presence of light and molecular oxygen. This toxicity precludes their use as pesticides. Safe alternatives are to treat target organisms with chemicals that either are selectively metabolized to photodynamic compounds or cause the target organism to produce toxic levels of natural photodynamic compounds with its own biochemical machinery. This review examines one aspect of the latter alternative - treatment of plants with compounds that cause the accumulation of herbicidal levels of photodynamic porphyrins. 

Despite investigations by many laboratories, the nature of the photoreceptor for the photodynamic damage remained an enigma for more than two decades. Studies demonstrating that there was a metabolic requirement before the herbicide could cause effects like a photodynamic dye (24 28, 30> 43) should have provided a clue to the actual mechanism - the induction of the accumulation of a natural photodynamic compound. 

Anthrone and anthraquinone derivatives are used as laxatives (F 2). The compounds formed in plants may repel potential predators (E 5.5.3). Hypericin, a photodynamic compound, is a feeding deterrent from Hypericum perforatum St. Johns wort, E 5.5.3). 

Table II. Toxicity of Photodynamic Compounds to the Housefly and Corn Earworm by Feeding and Topical Application...

Given stringent requirements for effective sensitizers and the desire to use wavelengths further to the red for therapeutic appHcations, definition of newer sensitizers has been a principal area of research since about 1987. Expanded theoretical and experimental understanding of photophysics has been a key element in identifying new classes of potential sensitizers (93—98). Research has focused on cationic derivatives of Nile Blue (93), metaHo-phthalocyanines (94), naphthalocyanines (95), chlorin-type compounds (96), expanded ring porphyrinoids (97), as well as porphyrins other than hematoporphyrin and its derivatives (98). This work has also been reviewed (10,91). Instmmentation for photodynamic therapy has been reviewed (99). 

An interesting application of the photodynamic properties of porphyrins is their possible use in the treatment of certain types of cancer, a procedure called cancer phototherapy. Tumors often take up more porphyrins than do normal tissues. Thus, hematopor-phyrin or other related compounds are administered to a patient with an appropriate mmor. The mmor is then exposed to an argon laser, which excites the porphyrins, producing cytotoxic effects. 

The photodynamic effect of chloroaluminum(III) phthalocyanine ((47), with C1A1 in place of Zn), a commercial product, was reported by Ben-Hur and Rosenthal.302 The photosensitizer was delivered in ethanol to cultures of Chinese hamster fibroblasts. After equilibration (16 h), exposure to visible light (fluence rate 64 Wm-2) of a suspension in PBS for 2 min gave a 3 log kill. Lack of water solubility is a problem, and for in vivo PDT of EMT-6 mammary tumors in mice a Cremophor emulsion was employed.303 The compound was a more effective PDT sensitizer than... 

In the photodynamic therapy of cancer, for example, macrocyclic tetrapyrrholic compounds named porphyrins are used. Porphyrin-containing wastewaters can negatively affect the aquatic ecosystems (plants and fish population), even in very small concentrations. Recent studies present a method adequate for the advanced purification of medical wastewaters containing such porphyrins [94],... 

In two recent reports (Mroz et al., 2007b Tegos et al., 2005) we studied the photosensitizer properties of two series of three functionalized fullerene compounds, one series with polar diserinol groups (BF1-BF3), and a second series of three compounds with quaternary pyrrolidinium groups (BF4-BF6) (Fig. 4.5). The bis-substituted and tris-substituted fullerenes are actually mixtures of regioisomers of the same molecular formula due to reaction with different double bonds. We asked the question whether the photodynamic effects displayed by these compounds operated... 

We have shown, in a series of reported experiments that cationic fullerenes fulfill many, but not all the aforementioned criteria. Our laboratory was the first to demonstrate that the soluble functionalized fullerenes described above, especially the cationic compounds BF4-BF6, were efficient antimicrobial PS and could mediate photodynamic inactivation (PDI) of various classes of microbial cells (Tegos et al., 2005). We used a broadband-pass filter giving an output of the entire visible spectrum (400-700 nm) to excite the fullerenes that maximized the absorption. 

Fullerenes should have a photodynamic effect on tumors, if (a) the compound is accumulated in the tumor tissue, (b) a reasonably efficient way to administer the compound to tumor bearing animals is found, and (c) enough excitation light can be delivered to the photosensitized tumors. The first report of fullerenes being used to cany out PDT of actual tumors was by Tabata in 1997 (Tabata et al., 1997). They chemically modified the water-insoluble C60 with polyethylene glycol (PEG), not only to make it soluble in water, but also to enlarge its molecular size. When injected intravenously into mice carrying a subcutaneous tumor on the back, the... 

The most reasonable explanation for the observed differences in fullerene behavior as a part of complex C60/PVP in chemical and biological systems is the fact that the complex itself is stable in the pure water media. Dissolution in the saline causes the formation of fullerene precipitate, which, naturally reveals the photodynamic properties. But a basic difference between water-soluble C60 complexes with organic compounds (PVP, y-CD, etc.) from other forms used for biological investigations is the low degree of fullerene molecules association... 

Intensive research interest in peripherally functionalized porphyrazines dnring the last decade has shown that these tetrapyrol derivatives shonld be considered as alternatives to the phthalocyanines that have fonnd extensive apphcations in mat r fields. These include material science and the photodynamic therapy of tnmors as well as pigments and dyes [1]. These compounds have been nsed electrophotography, optical data, photodynamic therapy of tnmois, liquid crystals, pigments and dyes. Porphyrazines have been of considerable interest to spectroscopist and theoreticians for their high symmetrical, planar stractnre and electron delocalisation [2]. 

Compared to other classes of dyes, few attempts have been made to establish photosensitizing dyes as pure diagnostic agents, as in this context two major drawbacks of these compounds appeared (i) the strong photodynamic activity and sometimes prolonged persistence of photosensitivity in several organs, particularly the skin, which is regarded as a potential safety concern, and (ii) the... 

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