Radiation, pollution, metabolic processes of oxigen combustion in the human body can cause production of radicals. These molecules can lead to oxidative stress disorders, injuries and diseases. The nature has provided solution for removing radicals, preventing or curing the damage caused by radicals. Polyphenoles; flavonoids and tannins are very important antioxidants in nature. They play an important role in human diet. People with weakened immune system are advised to take purified and highly concentrated polyphenols in supplements. Pycnogenol, from the French Pinus pinaster bark, is one of the already well known and mostly used antioxidants. The white fir bark extract has also some antioxidant effect. This extract contains pycnogenol – like active substances; catechin, epicatechin, quercetin and epigallocatechine gallate. In the thesis we tested and compared white fir bark extracts from different locations in Slovenia (Celje, Dolenjske Toplice, Dolenja vas, Dragomer, Idrija, Lovrenc, Metlika, Slovenske Konjice, Snežnik, Trebnje, Trojane, Zaplana), and fractions of the extract from Kočevska Reka. We used DPPH, ABTS, superoxide and hydroxil radical scavenging methods and the reducing power determinating method. We performed tests with reagents that caused colour change of the samples and their absorbance. The latter was measured with the Tecan spectrophotometer which allows the measurement of more samples simultaneausly. The obtained results confirmed the antioxidant activity (AA) of tested silver fir extracts. The most active was the sample from Metlika. It gave the best results with NADH, was also twice second, twice third and once fourth. Tests on sample fractions showed high antioxidant activity of some fractions that were comparable with standards' AA or higher. On the other side there were fractions with low or practically no AA.
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