INVESTIGADORES
PODEROSO Juan Jose
congresos y reuniones científicas
Título:
NADH oxidation by peroxynitrite. II Effects of flavonoids.
Autor/es:
ALVAREZ S; VALDEZ L; SCHÖPFER F; PODEROSO JJ; BOVERIS A
Lugar:
Santa Bárbara, EEUU
Reunión:
Congreso; World Congress Oxidant and antioxidants in Biology"; 1999
Institución organizadora:
Oxygen Club of California
Resumen:
Peroxynitrite (ONOO-) is a powerful oxidant (E (ONOO-/·NO2) = +1.4 V) formed in a diffusion-controlled termination reaction of the free radicals nitric oxide (·NO) and superoxide anion (O2·). Some flavonoids have been reported to posess biological activities, as free radical scavenging. The aim of the present work is to compare the reducing activities of several favonoids ((+) catechin, (-) epicatechin, caffeic acid, and chlorogenic acid) in their reactions with ONOO-. Ginkgo biloba and grape seeds extracts, that contain flavonoids among the active compounds, were also tested for ONOO- scavenging activity. We used a model of simple competition that involves the participation of ONOO-, NADH, and the flavonoids as competitive reductants for ONOO. An indirect fluorometric technique was used to estimate the IC50 of the flavonoids tested. The reaction of ONOO- with NADH was followed at 37°C, using 340 and 463 nm as excitation and emission wavelengths, respectively. The reaction medium consisted of 50 mM phosphate buffer, 0.1 mM DTPA, pH 7.0, 100 µM NADH and 100-700 µM ONOO-. The IC50 calculated were: 275 ± 23 µM for (+) catechin, 313 ± 23 µM for (-) epicatechin, 144 ± 29 µM for caffeic acid, and 173 ± 36 µM for chlorogenic acid. The IC50 calculated for the extracts were: 85 ± 11 µg/ml for Ginkgo biloba and 118 ± 16 µg/ml for grape seed extract. Among the number of flavonoids tested the following order of potency was observed: caffeic acid > chlorogenic acid > (+) catechin > (-) epicatechin, and Ginkgo biloba extract > grape seed extract.