Plants have been used as medicines for thousands of years. They have been applied for the preparation of ingredients and drugs in the treatment of diseases [1-4]. Clinical studies revealed that a diet rich in fruits and vegetables decreased risk of cardiovascular diseases and cancers. These beneficial health effects have emanated from the presence of antioxidant compounds in the plants. Oxidation is one of the most important chemical and biochemical processes. Free radicals can oxidize nucleic acids, proteins and lipids, initiating degenerative diseases. Antioxidants such as phenolic compounds are compounds known to react with free oxygen radicals and thus preventing their cell-damaging action. Therefore, screening for antioxidant properties of plant extracts is prominent in their pharmaceutical applications. Different methods have been reported for the evaluation of antioxidant capacity of medicinal plant extracts. In the present research cyclic voltammetry have been used for antioxidant screening of medicinal plant extracts. Since, electrochemical techniques are low-cost and enable rapid analysis of sample. Cyclic voltammetry on carbon nanotube modified electrode appears to be a suitable tool in antioxidant assays. It can provide information about the number of compounds redox states and the stability of these states [5].

In this work, leaves of matricaria ineora, as a medicinal plant, were dried at shadow and at room temperature. The 3.0 g powdered leaves of the plant were macerated with 50 mL of ethanol:water (20:80) for 24 h and sonicated for 12 min. The extracts were filtered using filter paper.

The voltammograms were obtained for electrochemical oxidation of antioxidant compounds on the bare and modified electrodes in two separate experiments in buffer solution (pH 7.2). It have been compared the cyclic voltammograms of matricaria ineora extract at a bare and single-walled carbon nanotube (SWCNT) modified glassy carbon electrodes. The cyclic voltammetric responses for electrochemical oxidation of extract on the bare electrode containing one pair redox peak and modified electrode containing two pair redox peaks at 100 mV/s. The peak current increased significantly on the SWNTs modified electrode as compared with the bare electrode. The electrode surface modification with SWCNTs augmented its effective surface area and the oxidation currents of antioxidants. The first redox peaks are related to compounds which also were oxidized on the bare glassy carbon electrode. Second peaks are related to compounds which cannot oxidize on the bare electrode but due to nanotubes electrocatalysis property oxidized them on the modified electrode.

References:

1. H. Benmehdi, O. Hasnaoui, O. Benali, F. Salhi, J. Mater. Environ. Sci. 3 (2012) 320-237.
2. O. Maschi, E. Dal Cero, G.V. Galli, D. Caruso, E. Bosisio, M. Agli, J. Agric. Food Chem. 56 (2008) 5015-5020.
3. A. Ghorbani, B. Gravendeel, S. Selliah, S. Zarreo, H. de Boer, Mol. Ecol. Resour. (2016) doi:10.1111/1755-0998.12615
4. L. Barros, L. Cabrita, M.V. Boas, A.M. Carvalho, I. Ferreira, Food Chem. 127 (2011) 1600-1608.
5. L. Campanella, E. Martini, M. Tomassetti, Talanta 66 (2005) 902-911.