Photophysical and photosensitizing characterization of 5-Chloro-Soranjidiol obtained from Heterophyllaea lycioides

J. DIMMER; L.R. COMINI; F. E. MORÁN VIEYRA; R.A. MIGNONE; S.C. NÚÑEZ MONTOYA; V. REY; C.S. MENDOZA; J.L. CABRERA; C.D. BORSARELLI

Córdoba

Congreso; 16th INTERNATIONAL CONGRESS ON PHOTOBIOLOGY; 2014

International Union of Photobiology

Heterophyllaea J.D. Hook. (Rubiaceaea) is a South American genus represented by only two species, that were described as phototoxic plants: Heterophyllaea pustulata Hook f. grows in the Andean northwest of Argentina, Bolivia and Perú and Heterophyllaea lycioides (Rusby) Sandwith, which grows in the Andean region of Bolivia and Peru [1]. Our research group succeeded in the isolation and identification of nine AQs (soranjidiol, soranjidiol-1-methyl ether, rubiadin, rubiadin-1-methyl ether, damnacanthal, damnacanthol, heterophylline, pustuline and 5,5-bisoranjidiol) from the first species. We demonstrated that these AQs possess photosensitizing properties type I and/or type II and these results led us to study them as anticancer and antimicrobial agents to be used in photodynamic therapy, obtaining satisfactory results [2,3]. Recently we have started with the phytochemical study of the second species, Heterophyllaea lycioide and we have isolated and identified five AQs from their aerial parts, where four of them have previously been isolated from H. pustulata and the additional new one 5-Chloro-Soranjidiol, recently described for this family of compounds [4]. The aim of this work is to determine photophysical and photosensitizing properties of 5-Cl-Soranjidiol compared with those of the parent compound, using steady-state and time-resolved absorption and emission spectroscopies, and the main results are summarized as follows. The results indicate that both compounds have similar photophysical properties, with a 3-exponential fluorescence decay component with a remarkable Stokes shift, probably by presence of several emitting states due to the formation of tautomeric species by intramolecular H-transfer, favoring non-radiative decay processes. However, the quantum yield of photosensitized formation of singlet molecular oxygen 1O2 for both compounds was similar and relatively efficient (0.25), confirming the potential photodynamic activity of the soranjidiol derivatives