Nowadays, due to our fast-paced lifestyle, we are exposed to stress, which we only become aware of when certain diseases break out. The stress caused by reactive oxygen and nitrogen species is called oxidative stress. Reactive species are very dangerous and harmful when they are produced excessively in the body, as they can damage deoxyribonucleic acid, lipids and proteins. The risk of damage to biological molecules can be prevented by taking antioxidants that limit oxidative damage to biomolecules. Many antioxidants are present in fruits and vegetables, so by eating them we can contribute to a better antioxidant defence.
In the Master's thesis, we evaluated the antioxidant capacity of selected quinazolinones using the copper(II) ion reduction antioxidant capacity (CUPRAC) method. The method is based on the reduction of copper(II) ion to copper(I) ion with the compound being evaluated. During reduction, the blue colour of the copper(II) ion complex with neocuproine changes to an orange-yellow colour. A water-soluble analog of α-tocopherol Trolox® was used as a standard. We found that some of the tested compounds show better antioxidant capacity than Trolox (5 compounds), while others show worse (compounds 8, 9, 10) or no antioxidant properties at all (compound 1). To evaluate the results, we calculated the ratio of antioxidant capacity equivalent to Trolox TEACCUPRAC from the molar absorption coefficient (ε) of the compound and the molar absorption coefficient (ε) of the standard (Trolox). We found that the antioxidant capacity of quinazolinones is influenced by the position and number of phenolic -OH groups. The more hydroxyl groups attached to the aromatic ring, the greater the antioxidant capacity, the better the antioxidant. We also found that the presence of the methoxy group significantly increases the antioxidant capacity, depending on the position relative to the hydroxyl group. Replacing the methoxy group with an ethoxy group did not significantly affect the increase in antioxidant capacity.
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