Autori: Moţ, A.C., Coman, C., Miron, C., Damian, G., Sarbu, C., Silaghi-Dumitrescu, R.

Editorial: Elsevier, Food Chemistry , 143, p.214-222 , 2014.

Rezumat:

A transient species may be detected with UV-vis and EPR spectroscopy during turnover of a laccase with quercetin; this species is assigned as a quercetin-derived radical, based on EPR spectra as well the observed UV-vis similarities (a 540. nm centred band) with previously reported data. The rates of formation and decay of this species correlate well (. r=. 0.9946) with the pro-oxidant reactivity manifested by flavonoids in the presence of laccase. An assay for the pro-oxidant reactivity of natural products is hence proposed based on the results reported here; its application is demonstrated for a series of pure compounds as well as for several propolis extracts. This assay has the advantages of using a biologically relevant process (haemoglobin oxidation), and not requiring the addition of oxidising agents such as peroxide or superoxide. Correlations, or the lack thereof, between the pro-oxidant parameters and the redox potentials, antioxidant capacities and lipophilicities, were analysed. The laccase employed in our study does display reactivity-related similarities to a range of other proteins, including human plasma ceruloplasmin

Cuvinte cheie: EPR; Flavonoid; Laccase; Met-haemoglobin; Pro-oxidant, antioxidant; Quercetin; Radical