Evaluation of selected food supplements containing antioxidants.

Seven commercial food supplements present on the Polish market were evaluated for their in vitro antioxidant capacity. The selected products were in the form of hard gelatin capsules. They contained the extracts from chokeberry, cranberry, blueberry and green tea. The mixture of vitamins and minerals as well as the product containing vitamin C in substantial dose were included into comparison. The products were examined using three methods in order to evaluate their antioxidant capacity: electron paramagnetic resonance (EPR), Trolox equivalent antioxidant capacity (TEAC), oxygen radical absorbing antioxidant capacity (ORAC) assays. Total polyphenolic content was determined according to Folin-Ciocalteu method The results were calculated per capsule. All studied preparations showed antioxidant properties and may provide substantial antioxidant protection. The in vitro antioxidant capacity varied considerably and was associated with the content of polyphenols in the capsule. The supplement with 250 mg of green tea extract was the most potent antioxidant in all assays. Nevertheless it must be remembered that the amounts of extracts were different in encapsulated products. As the quality of extracts and their properties are miscellaneous, there is a need to standardize dietary antioxidant supplements with respect to their antioxidant capacity if effective doses are to be recommended.