A superoxide dismutase biosensor for measuring the antioxidant capacity of blueberry based integrators

Numerous studies and experimental research have indicated the involvement of reactive oxygen species (ROS) in particular, as well as of all types of free radicals in general, in the genesis of numerous pathologies[1]. The antioxidant compounds contained in many foods and beverages are capable of reacting with the radicals and thus play an important role in the prevention and defence against oxidative diseases, representing a protective factor of fundamental importance for human health. Sometimes, however, in the case of incorrect food habits or physical deficiencies, food intake alone is not sufficient to provide enough antioxidant nutrients. Therefore, in such cases, the use of food integrators is recommended. This has become a widespread practice although the antioxidant properties of these compounds are often not fully quantified. It is thus of particular and topical interest to be able to come up with new analytical methods to assess the antioxidant capacity of the various ‘over the counter’ products available in drugstores and that may be purchase without medical prescription. The aim of the present work was to investigate the antioxidant capacity of capsules containing blueberry based products which are included among the group of integrators most widely sold in drugstores owing to this capacity and produced by various drug firms. The results of the investigation are compared in order to rank these products in the order of their antioxidant capacity. Blueberries contain a relatively large amount of acids (citric, malic, etc.), sugars, pectins, tannins, mirtilline (glucoside pigment), anthocyanin (which has a beneficial effect on retina capillaries), vitamins A and C and, to a lesser extent, Vitamin B. It is therefore recommended in treating eye disorders (myopia and retinopatina), in combating eye fatigue, as an antidiarrhoic and against diabetes. It is useful for combating the fragility and excessive permeability of blood vessels [2] by exerting a protective action on capillaries. It is a known fact that the dry extract of blueberry can improve night vision [3]. In particular, black blueberry leaves and berries are rich in active principle. They contain antioxidant compounds like tannins, flavonoids, anthocyanins, glucosides and anthocyanidins. It is therefore its antiradical action that is of fundamental importance: blueberry anthocyanosides strongly inhibit free radicals as they are able to react with practically all known species of radicals [4]. In order to measure antioxidant capacity, in addition to the various spectrophotometric, voltammetric and fluorimetric methods described in the literature, our laboratory has recently developed a special electrochemical method based on a superoxide dismutase (SOD) biosensor [5] to determine the superoxide radical. Previous investigations clearly demonstrated how the results obtained using this new biosensor are comparable to those obtained using established methods (ORAC, DMPD, etc.) [6,7] and have shown the method to be a valid, “robust”, sensitive, practical and economic method. The results obtained by applying the SOD biosensor method to various blueberry based integrators were compared with the results obtained with the spectrophotometric method based on N,N–dimethyl-p-phenylenediamine (DMPD- FeCl3). The same results are currently being compared with those obtained also using the ORAC fluorimetric method, the most frequently used to determine antioxidant activity in food matrices and adopted as reference method. It is also planned to compare the antioxidant capacity of these integrators sold in drugstores with that of fresh and/or deep-frozen blueberries.