A non-singlet oxygen mediated reaction photoinduced by phenalenone, a universal reference for singlet oxygen sensitization

CAROLINA LORENTE; EMMANUEL ARZOUMANIAN; CAROLINA CASTAÑO; ESTHER OLIVEROS; ANDRÉS H. THOMAS

RSC Advances

Royal Society of Chemistry

Lugar: Londres; Año: 2014

2046-2069

Photosensitized oxidations involve the generation of radicals (type I mechanism) and/or the production of singlet molecular oxygen (1O2) (type II mechanism). These processes contribute to the generation of skin cancer, but have also found important applications, for example for photodynamic therapy and disinfection. It is generally accepted that the photosensitization of proteins occurs mainly through the reactions of 1O2 with tryptophan (Trp) and other amino acids. Phenalenone (PN) is one of the well-known type II photosensitizers and is widely used as a 1O2 reference sensitizer. In this work, we have studied the interaction of Trp with the excited states of PN, the production of 1O2 in the presence of Trp, the formation of radicals and the kinetics of the photodegradation of Trp under different experimental conditions. In contrast to what is usually assumed, we have proven that PN is also able to act as Type I photosensitizer. Moreover, we have demonstrated that the predominant mechanism of photosensitization of Trp by PN involves an electron transfer initiated-process.