Development of Biosensors for Determination of the Total Antioxidant Capacity of Olive Leaf Extract

Oguz Bayraktar, Secil Coban

In the present work, a laccase biosensor was investigated for determination of the oleuropein concentration that is the biological active component of olive leaf and contributes dominantly to the total antioxidant capacity. The biosensor was prepared by immobilization of laccase from Trametesversicolor by addition of cross-linking agent, glutaraldehyde, into the carbon paste electrode. The best biosensor performance was determined for biosensor having glutaraldehyde amount of 12.03 % and 5 mg/ml of laccase enzyme. The scan rate of 10 mV/s was decided to be the optimum for the amperometric detection of oleuropein based on the fastest response and maximum reduction current. Biosensor performance was also investigated for olive leave extract fractions varying in their oleuropein amounts. Therefore, biosensor performance was investigated for fractions containing different types of phenolic compounds. High Performance Liquid Chromatography (HPLC), total phenol content and antioxidant capacity analyses of the fractions were also carried out for comparison with biosensor results.