Parietin, an anthraquinone derivative isolated from Teloschistes flavicans, as photosensitizer type I

L.R. COMINI, S.C. NÚÑEZ MONTOYA, N. JELICICH, G. VERGARA, J. MARIONI, J.L. CABRERA.

Maresias

Encuentro; XII Encuentro Latinoamericano de Fotoquimica y Fotobiologia; 2015

For several years, anthraquinone (AQs) derivatives have been thoroughly studied in relation to their photosensitizing properties in photodynamic reactions. Some of them have shown good antibacterial and antiviral effects by means of photosensitization, in where reactive oxygen species (ROS) are increased, such as superoxide anion (O2.¯) (Type I mechanism) and singlet molecular oxygen (1O2) (Type II mechanism), and the subsequent oxidative damage is observed [1].This time we report the type I photosensitizer properties of parietin (PTN), an AQ isolated from the lichen species: Teleoschistes flavicans (SW) Norm. (Telochistaceae) [2].The production of O2.¯ was detected and quantified with an indirect photobiological method, which measures the reduction of Nitroblue Tetrazolium (NBT) to blue formazan by O2.¯ generated inside human leukocytes, when an oxidizer (AQ-PTN) is present in the dark and under continuous UV-Vis radiation (380?480 nm, with a maximum at 420 nm - 0.65 mW/cm2). The absorbance of blue NBT formazan intracellular was measured with respect to basal production and was expressed in percentage. According to the results, PTN causes an increase in the production of O2-. under irradiation compared to darkness condition at 5 and 10 mg / ml (Table 1). At 20 mg/mL and darkness, the percentage of production of O2-. is less than those generated to 5 and 10 mg/mL and even under irradiation, this percentage was equal to the condition basal (0.0 ± 0.0). These latter results could be due to an excessive generation of ROS in dark condition and even more under irradiation at 20 mg/mL, causing a major oxidative damage in the leukocytes with the eventual cell death.In conclusion, it was shown that PTN is a good photosensitizer type I and this is directly dependent on the concentration used.