Vancomycin-sensitized photooxidation in the presence of the natural pigment vitamin B2: Interaction with excited states and photogenerated ROS

CACCIARI, R. DANIEL; REYNOSO, EUGENIA; MONTEJANO, HERNÁN; BIASUTTI, M. ALICIA

REDOX REPORT

MANEY PUBLISHING

Lugar: London; Año: 2016 vol. 22 p. 166 - 175

1351-0002

Sensitized photooxidation processes in the presence of natural pigments, may provide an alternative to antibiotics degradation since, although these compounds are transparent to natural light irradiation, can be degraded by the action of photosensitizers which absorb light and produce highly reactive species, especially those derived from molecular oxygen (ROS). Most antibiotics used currently belong to a group of pharmaceutical substances that have been considered as a new type of contaminants due to their persistence and bioaccumulation in the environment. In this context, we decided to investigate kinetic and mechanistic aspects of Vancomycin (Vanco) photosensitized degradation in the presence of the natural pigment Riboflavin (Vitamin B2, Rf) and the artificial dye Rose Bengal (RB) as comparative purposes. Thestudy was carried out in aqueous solution at different pH values in order to establish relationships between the structure of the compound and susceptibility to ROS mediated photooxidation. Experimental evidence indicates that in the presence of Rf there is considerable contribution of the radical-mediated mechanism; whereas that in the presence of RB the photooxidation process occurs exclusively through O2(1Δg), and the reactivity to this excited species increase with increasing pH of the environment. Microbiological tests on Staphylococcus aureus ATCC25923, showed that the bactericidal activity of the antibiotic on the strain studied, it was not affected by the sensitized photodegradation process suggesting that photoproducts generated eventually retain the bactericidal properties of the original antibiotic.