Photophysical and photochemical properties of Bauhinia megalandra (Caesalpinaceae) extracts as new PDT photosensitizer

Franklin Ramon Vargas Tovar; C. Rivas; O. Estrada; Aristides Alfredo Marcano O.; Lorenzo Echevarria; Yrene Diaz; I. Alexander; L. Rodriguez; L. Padron; I. Ramon Rivera

doi:10.1117/12.589314

21 October 2004 Photophysical and photochemical properties of Bauhinia megalandra (Caesalpinaceae) extracts as new PDT photosensitizer

Franklin Ramon Vargas Tovar, C. Rivas, O. Estrada, Aristides Alfredo Marcano O., Lorenzo Echevarria, Yrene Diaz, I. Alexander, L. Rodriguez, L. Padron, I. Ramon Rivera

Author Affiliations +

Proceedings Volume 5622, 5th Iberoamerican Meeting on Optics and 8th Latin American Meeting on Optics, Lasers, and Their Applications; (2004) https://doi.org/10.1117/12.589314
Event: 5th Iberoamerican Meeting on Optics and 8th Latin American Meeting on Optics, Lasers, and Their Applications, 2004, Porlamar, Venezuela

Abstract

Recently new photosensitizers, chlorophyll "a and b" derivatives, for photodynamic therapy (PDT) have been presented. It already passed complete pre-clinical investigations. This prompted us to carry out an extensive study of photophysical properties of chlorine derivatives, important both for optimization of their clinic applications and for study of mechanisms of chlorine PDT&. The fresh leaves of Bauhinia megalandra (Caesalpinaceae) were extracted with methanol by percolation, and re-extract with a mixture of methanol-water (1:1), the insoluble fraction was then separated by column chromatography [RP18/hexane-ethylacetate (9:1)] to obtain four fractions named 1 to 4. These compounds were identified by NMR data. We found that 3 and 4 efficiently generates singlet oxygen when irradiated with visible light. Detection of the singlet oxygen was fulfilled by its reaction with histidine and detected by bleaching p-nitrosodimethylaniline under 440 nm irradiation. The quantum yields of singlet oxygen determined by us were 0.088 (1), 0.151 (2), 0.219 (3) and 0.301 (4). We measured absorption and fluorescence spectra of compounds 1 to 4 (Mg-chlorophyll-a, Pheophytin, Mg-chlorophyll-b and chlorophyll-b respectively) in different media and in aqueous solutions of human serum albumin. The association constant of the compounds 1, 2, 3 and 4 in the presence of HSA were estimated. The binding and quenching studies suggest that only 1 and 3 may serve as a useful fluorescence probe for structure/function studies of different chlorophyll binding proteins. No photoinduced binding was observed after irradiation by all the studied compounds in presence of human serum albumin.

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Franklin Ramon Vargas Tovar, C. Rivas, O. Estrada, Aristides Alfredo Marcano O., Lorenzo Echevarria, Yrene Diaz, I. Alexander, L. Rodriguez, L. Padron, and I. Ramon Rivera "Photophysical and photochemical properties of Bauhinia megalandra (Caesalpinaceae) extracts as new PDT photosensitizer", Proc. SPIE 5622, 5th Iberoamerican Meeting on Optics and 8th Latin American Meeting on Optics, Lasers, and Their Applications, (21 October 2004); https://doi.org/10.1117/12.589314

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KEYWORDS

Oxygen

Luminescence

Quantum efficiency

Photodynamic therapy

Absorption

Proteins

Tissue optics

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