Chlorinated anthraquinones as type I photosensitizers

DIMMER JESICA; COMINI LR .; NÚÑEZ MONTOYA SC; C.S. MENDOZA; CABRERA

Maresias

Encuentro; XII Encuentro Latinoamericano de Fotoquimica y Fotobiologia.; 2015

Heterophyllaea lycioides (Rusby) Sandwith grows in the Andean region from Bolivia and Perú, and is one of the two species which forms Heterophyllaea genus. From aerial parts, we purified two new anthraquinones (AQs) derivatives for this family of compounds, both characterized by the presence of chlorine in their structures: 5-clorosoranjidiol y 7-clbisoranjidiol. Worth noting that is the first time that AQs containing chlorine are reported for a species of Rubiaceae. Previously, we demonstrated that AQs isolated from the other vegetal specie, H. pustulata, are photosensitizers by acting through type I and/or type II mechanisms. Continuing this research line, we propose to determine whether new chlorinated AQs are able to generate superoxide anion radical (O2-.) under irradiation (type I mechanism).O2.- production was quantified by an indirect photobiological method, which measures the reduction of Nitroblue Tetrazolium (NBT) to Formazan Blue (FB) by action of the O2.- generated for human leukocytes (2 x 106 cells/ml), when an oxidizer (AQ) is present. This assay was performed under darkness vs. UV radiation (290? 400 nm, UVR). Samples were tested at two different concentrations: 10 and 20 µg/mL in Hank´s balanced salt solution (HBSS) with DMSO (1%) as co-solvent. Cell controls and samples (n=2) were incubated at 37 °C for 30 min, under both experimental conditions. Absorbance of FB was measured at 575 nm. The increased of O2-. production respect to controls was expressed in percentage (Fig. 1).Results show that 5-clorosoranjidiol only produced stimulation of O2-. at 20 μg/mL, whereas the chlorinated dimer increased it at 10 μg/mL and not at the highest concentration tested. This could be due to a high generation of this reactive species, promoted for this concentration; and thus the O2-. generated may be attacking several cellular components, leading to eventual cell death. In conclusion, we demonstrated that 5-clorosoranjidiol and 7-clorobisoranjidiol generate photosensitization in vitro by type I mechanism, which is directly dependent on the concentration used.