New insights into the photophysics and photochemistry of harmalol in aqueous media

JUAN G. YAÑUK; M. PAULA DENOFRIO; MARÍA L. ALOMAR; M. MICAELA GONZALEZ; ROSA ERRA-BALSELLS; FRANCO M. CABRERIZO

Córdoba

Congreso; 16th International Congress of Photobiology; 2014

Harmalol is a naturally occurring alkaloid that belongs to the family of β-carbolines (βCs). βCs comprise both fully aromatic alkaloids and partially reduced derivatives such as 3,4-dihydro- and 1,2,3,4-tetrahydro-βCs. In terms of its chemical structure, harmalol is a 3,4-dihydro-βC. During the last decades, the photophysics and photochemistry of some βCs, in aqueous media, has been well investigated [1-3]. Briefly, in aqueous solution, these alkaloids may show several acid?base equilibria. However, for some dihydro- and tetrahydro-βCs, the information published in the literature is, in somehow, contradictory, negligible or null [4-8]. In the present work we have investigated the acid-base equilibria and species present in the pH range of 2-13. The corresponding pKa values, chemical structure of each harmalol acid-base specie, as well as the corresponding absorption and emission spectra observed in aqueous solution are reported. Moreover, the pH-effect on the thermal and photochemical stability of harmalol is also reported.