Photophysical and Photochemical Properties of Naturally Occurring normelinonine F and Melinonine F Alkaloids and Structurally Related N(2)- and/or N(9)-methyl-beta-carboline Derivatives.
Rasse-Suriani, F. A. O., Garcia-Einschlag, F. S., Rafti, M., Schmidt De Leon, T., David Gara, P. M., Erra-Balsells, R. and Cabrerizo, F. M.
Instituto de Investigaciones Biotecnologicas - Instituto Tecnologico de Chascomus (IIB-INTECH), Universidad Nacional de San Martin (UNSAM) - Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Chascomus, Argentina.
INIFTA - CONICET, Universidad Nacional de La Plata, La Plata, Argentina.
Facultad de Ciencias Exactas y Naturales, Departamento de Quimica Organica, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina.
Centro de Investigacion en Hidratos de Carbono (CIHIDECAR - CONICET), Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina.
Centro de Investigaciones Opticas (CIOP - CONICET - CIC), Universidad Nacional de La Plata, La Plata, Argentina.
In the present work, we have synthesized and fully characterized the photophysical and photochemical properties of a selected group of N-methyl-beta-carboline derivatives (9-methyl-beta-carbolines and iodine salts of 2-methyl- and 2,9-dimethyl-beta-carbolinium) in aqueous solutions, in the pH range 4.0-14.5. Moreover, despite the quite extensive studies reported in the literature regarding the overall photophysical behavior of N-unsubstituted betaCs, this work constitutes the first full and unambiguous characterization of anionic species of N-unsubstituted betaCs (norharmane, harmane and harmine), present in aqueous solution under highly alkaline conditions (pH > 13.0). Acid dissociation constants (Ka ), thermal stabilities, room temperature UV-visible absorption and fluorescence emission and excitation spectra, fluorescence quantum yields (capital EF, CyrillicF ) and fluorescence lifetimes (tauF ), as well as quantum yields of singlet oxygen production (capital EF, CyrillicDelta ) have been measured for all the studied compounds. Furthermore, for the first time to our knowledge, chemometric techniques (MCR-ALS and PARAFAC) were applied on these systems, providing relevant information about the equilibria and species involved. The impact of all the foregoing observations on the biological role, as well as the potential biotechnological applications of these compounds, is discussed.
Photochemistry and Photobiology 94(1): 36-51 (2018)