RESUMO
The photostability of quercetin in alcoholic solutions was studied. Both UVA and UVB light induced degradation of quercetin, yielding a single product 1 deriving from oxidation and addition of an alcohol molecule to the 2,3 double bond. The same mechanism operated when quercetin was dissolved in alkaline solutions, and again a product 2 due to oxidation and addition of water was characterized. Comparison with quercetin analogs confirmed that, despite the presence of five hydroxy groups in quercetin, those in positions 3, 3', and 4' are mainly involved in the antioxidant activity of the compound , as well as in its photolability.
Assuntos
Quercetina/análogos & derivados , Quercetina/química , Raios Ultravioleta , Amônia/química , Apigenina/química , Apigenina/efeitos da radiação , Estabilidade de Medicamentos , Etanol/química , Flavonoides/química , Flavonoides/efeitos da radiação , Concentração de Íons de Hidrogênio , Quempferóis/química , Quempferóis/efeitos da radiação , Metanol/química , Oxirredução , Processos Fotoquímicos , Quercetina/efeitos da radiação , Rutina/química , Rutina/efeitos da radiação , Soluções , Solventes/química , Espectrofotometria UltravioletaRESUMO
This work studied the radiation resistance of Listeria monocytogenes and Salmonella species and the effect of irradiation on leaf flavonoid content and sensory acceptability of minimally processed arugula. Immersion in ozone-treated water reduced the analyzed microorganisms by 1 log. L. monocytogenes and Salmonella were not isolated from samples. Samples of this vegetable were inoculated with a cocktail of Salmonella spp. and L. monocytogenes and exposed to gamma irradiation. D10 values for Salmonella ranged from 0.16 to 0.19 kGy and for L. monocytogenes from 0.37 to 0.48 kGy. Kaempferol glycoside levels were 4 and ca. 3 times higher in samples exposed to 1 and 2 kGy, respectively, than in control samples. An increase in quercetin glycoside was also observed mainly in samples exposed to 1 kGy. In sensory evaluation, arugula had good acceptability, even after exposure to 2 and 4 kGy. These results indicate that irradiation has potential as a practical processing step to improve the safety of arugula.