Photophysical and Photochemical Properties of Naturally Occurring nor melinonine F and Melinonine F Alkaloids and Structurally Related N(2)- and/or N(9)-methyl- β -carboline Derivatives

RASSE-SURIANI, FEDERICO A. O.; GARCÍA-EINSCHLAG, FERNANDO S.; RAFTI, MATÍAS; SCHMIDT DE LEÓN, TOBÍAS; DAVID GARA, PEDRO M.; ERRA-BALSELLS, ROSA; CABRERIZO, FRANCO M.

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2017

0031-8655

In the present work, we have synthesized and fully characterized the photophysical andphotochemical properties of a selected group of N-methyl-β-carboline derivatives (9-methyl-β-carbolines and iodine salts of 2-methyl- and 2,9-dimethyl-β-carbolinium) in aqueous solutions, in thepH-range 4.0 - 14.5. Moreover, despite the quite extensive studies reported in the literature regardingthe overall photophysical behaviour of N-unsubstituted βCs, this work constitutes the first full andunambiguous characterization of anionic species of N-unsubstituted βCs (norharmane, harmane andharmine), present in aqueous solution under highly alkaline conditions (pH > 13.0).Acid dissociation constants (Ka), thermal stabilities, room temperature UV-visible absorptionand fluorescence emission and excitation spectra, fluorescence quantum yields (ФF) and fluorescencelifetimes (τF), as well as quantum yields of singlet oxygen production (ФΔ) have been measured for allthe 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 theequilibria and species involved. The impact of all the foregoing observations on the biological role, aswell as, the potential biotechnological applications of these compounds is discussed.