Abstract
Background: Quercetin is considered one of the most studied flavonols widely found in fruits and vegetables. Food preparation and storage affect the level of quercetin in food, as these processes can cause a partial or complete reduction in flavonol levels. Quercetin, as a bioactive compound, has beneficial effects on the human body and with various diseases due to its potent antioxidant properties. Quercetin is a scavenger of free radicals and exerts its effects in various body fluids (e.g., saliva, synovial fluid, blood). Because of this, it is essential to know the effect of pH on its antioxidant properties.Objective: This study aims to determine the antioxidant capacity of quercetin against superoxide radicals depending on pH using a spectroscopic method.Methods: The antioxidant properties of quercetin in the concentration range from 5 to 50 μg/ml against superoxide radicals were measured at pH values of 6.5 to 8. Superoxide radicals were generated in the photooxidation reaction of methionine with riboflavin. Inhibition of superoxide radicals by quercetin was detected spectrophotometrically in reaction with NTB.Results: Quercetin is an effective superoxide radical scavenger with the highest antioxidant capacity observed at a slightly acidic pH of 6.5. The antioxidant activity of quercetin increased with increasing concentration; effective antioxidant capacity of quercetin was in the experiment at a concentration above 30 µg/ml.Conclusion: Quercetin is a widely occurring flavonoid with many beneficial effects on the human body related to its antioxidant properties. Quercetin is an effective scavenger of superoxide radicals. Its correct dosage, processing, and storage, which significantly affect the antioxidant properties of quercetin, have a considerable impact on the effects of quercetin in the prevention and treatment of diseases. Since pH significantly affects biochemical processes in living organisms, our results could contribute to expanding information on the antioxidant properties of quercetin as a rich natural source of medicinal substances, depending on pH.Keywords:quercetin, antioxidant, superoxide radical, spectrophotometry