Determination of the antioxidant capacity of samples of different types of tea, or of beverages based on tea or other herbal products, using a superoxide dismutase biosensor.

Research was performed to experimentally evaluate the antioxidant capacity of different plant products sold by herbalists (ginger, dog rose, ginseng and camomile) and of several types of tea (ordinary tea, green tea, detheinated tea, lemon and peach flavoured tea) using a superoxide dismutase (SOD) biosensor recently developed by the present authors. Measurements were carried out by comparing biosensor response to the superoxide radical produced in solution using the xanthine-xanthine oxidase system, both in the presence and absence of the antioxidant sample considered. Precision of antioxidant capacity measures for herbal products and for non diluted samples was good, generally with a R.S.D.%< or =10% and a LOD value about 0.1 for relative antioxidant capacity. Also a "pool" of polyphenols from different tea samples was measured using a tyrosinase biosensor (LOD approximately 2 microM).