Monitoring antioxidants by coulometry: Quantitative assessment of the strikingly high antioxidant capacity of bergamot (Citrus bergamia R.) by-products.

A recently optimized rapid, cheap, and accurate coulometric method has been exploited to determine the antioxidant capacity of bergamot (Citrus bergamia Risso) by-products, including first (FPJ) and second press juices (SPJ), in comparison to analogous products from several citrus species. Extracts from the entire edible part (i.e., juice and pulp) and de-oiled peel of bergamot were also assayed. The Coulometrically Determined Antioxidant Capacity (CDAC) data, expressed as moles of electrons per mass of sample, were evaluated with other parameters such as total phenolic compounds, ascorbic acid, total carotenoids, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical inhibition. The CDAC of bergamot FPJ (39 mmol e kg) was comparable with other citrus juices (20-65 mmol e kg range), whereas the CDAC of bergamot SPJ (816 mmol e kg) was strikingly higher than the counterparts from other citrus fruits. This value approached that of bergamot peel extracts (822 mmol e kg). Bergamot peel and SPJ also exhibited the highest DPPH inhibition. The CDAC values were associated with the HPLC-determined content of flavonoids, namely neoeriocitrin, naringin, and neohesperidin, which were 4-10-fold more concentrated in bergamot SPJ and peel than in SPJ from other citrus species. These findings contribute to point at bergamot by-products as rich sources of antioxidant compounds on a quantitative basis, highlighting their enormous potential for pharmaceutical, nutraceutical and food applications.