Antioxidants Properties of Apocynin in Zea Mays Leaves are Mediated by an Increased Nitric Oxide (NO) Production

TOSSI, V; LAMATTINA, L.; CASSIA, R.

Rosario, Argentina

Congreso; XXVII Reunion de la Sociedad Argentina de Fisiologia Vegetal; 2008

Sociedad Argentina de Fisiologia Vegetal

Apocynin is a natural antioxidant compound. In this work, we have evaluated if antioxidant properties of apocynin may be originated by a NO induction in maize leaves. For NO detection, maize leaves were loaded with the specific NO probe 4,5-diamino-fluorescein, (DAF-FM-DA) . The optimal apocynin concentration for NO induction was 100 ìM. NO was detected mainly in epidermal cells and vascular tissues. The apocynin-induced NO production was reduced to 50% by L-NAME, a nitric oxide synthase (NOS) inhibitor. Diphenylene iodonium (DPI), a plant NADPH oxidase inhibitor did not induces NO production. Maize seedlings treated with H2O, apocynin, apocynin + L-NAME and DPI were UV-B irradiated. To characterize the antioxidant properties of apocynin.ROS production was detected by diaminobenzidine (DAB) staining and cell damage by ion leakage. ROS and cell damage were strongly increased by UV-B in H2O-treated leaves. Apocynin protected maize leaves against the UV-B-induced damage, and this protection was inhibited by L-NAME. DPI did not protects. When maize leaves were pre-treated with H2O and then placed in 1M H2O2 for 24h, the chlorophyll (Chl) content shut down to 0.12 mg g-1FW. As expected, 100 and 200 ìM apocynin protected leaf discs from H2O2 stress and chlorophyll breakdown. These results demonstrate that apocynin induces endogenous NO in maize leaves by a NOS like activity, in a NADPH oxidase-independent mechanism. This NO induction is required for the protection provided by apocynin against the oxidative stress generated by UV-B and H2O2. Financed by Conicet, ANPCyT and UNMDP.