Comparative Study of the Photophysical Behavior of Fisetin

MATÍAS FUNES; N. MARIANO CORREA; JUANA J. SILBER; M ALICIA BIASUTTI

PHOTOCHEMISTRY AND PHOTOBIOLOGY

Wiley-Blackwell

Año: 2007 vol. 83 p. 486 - 493

0031-8655

The 3,3¢, 4¢,7 tetrahydroxiflavone (fisetin) is a natural therapeuticallyactive and fluorescent polyhydroxyflavone, with importantspectroscopic and biological behavior. Fisetin shows dual emission,with a normal band (N) from the S1 fi S0 transition andthe one generated in the excited state (phototautomer; PT) fromthe intramolecular proton transfer (ESIPT) process. The influenceof different interfaces on the ESIPT process of fisetin wasinvestigated in reverse micelles media (RMs) made of the anionicsodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT) and cationicbenzyl n-hexadecyl dimethylammonium chloride (BHDC) surfactants,in benzene. The studies were carried out by absorption,emission spectroscopy, steady-state anisotropy and time-resolvedfluorescence measurements. Fisetin behavior was also investigatedin homogeneous media with special emphasis in water andbenzene, which are the polar core and the organic pseudofase inthe RMs, respectively. In addition, the effect of concentration inbenzene and the variation of the pH in water were studied.Fluorescence lifetime measurements show that in water theESIPT process is independent on the concentration, while inbenzene it was possible to detect fluorescent aggregate species(Nas) formed in the ground state. The effect of the pH in waterallowed us to identify the anionic fisetin (A)) emission. Thestudies in RMs show that fisetin interacts specifically with thehead of the surfactants, which always results in diminishing theemission of the PT. Also the formation of A) is detectedparticularly at W0 > 0. Appreciable high anisotropy values areobtained in RMs, as compared with those in fluid homogeneousmedia, which are independent of the water content confirmingthat fisetin molecules are anchored in the anionic as well as in thecationic interfaces.