A native plant of North America, Aronia melanocarpa (aronia) is commonly known as black chokeberry and is now cultivated worldwide. The aronia plant, which belongs to the Rosaceae family, is very rich in anthocyanins and other phenolic compounds and has a dark purple color. With its high total polyphenol and anthocyanin content and DPPH radical scavenging activity, Aronia is known to have powerful antioxidant features compared to many other fruits [1, 2].
Aronia has a wide range of phenolic chemicals, including phenolic acids, flavonols, anthocyanins, and flavan-3-ols[3]. So far, it has been shown that aronia berry decreases cystolic blood pressure and cholesterol levels [4], which reduces the risk of chronic illnesses [5] and provides strong antioxidant protection [6].
O2 is generally not reactive to most cellular components, but ROS (reactive oxygen species) causes oxidation of lipids, proteins, RNA, DNA and many small molecules in the cell. ROS have a high reactivity to these biological components due to their changed chemistry as compared to O2, which permits them to donate an electron or transfer an excited energy state to an acceptor molecule [7]. Hydrogen peroxide (H2O2), superoxide (O2), singlet oxygen (1O2), the hydroxyl radical (HO.) and different types of organic and inorganic peroxides are the principal forms of ROS in cells, which vary widely in their characteristics and chemical reactivity [7–11]. Since ROS is very reactive and is produced independently in nearly all cell compartments, its levels must be controlled to prevent undesired cellular oxidation.
A group of polyphenolic compounds commonly found in fruits, vegetables and other food products and produced as secondary metabolites in plants are called flavonoids. In addition to other bioactivities (e.g., anti-inflammation, anti-aging), flavanoids have beneficial biochemical effects on certain diseases (eg cardiovascular disease, atherosclerosis) [12–14]. Their principal biological function is antioxidant protection. Flavonoid antioxidant activity can protect against free radical damage by scavenging reactive oxygen species, activating antioxidant enzymes, inhibiting oxidases (e.g., xanthine oxidase [XO], cyclooxygenase [COX], lipoxygenase and phosphoinositide 3-kinase [PI3K]), and reducing α-tocopheryl radicals. To decrease oxidative stress, flavonoid antioxidant activity can raise uric acid levels, metal-chelating activity, and low-molecular-weight antioxidant activity [13].
Antioxidants have been promoted as helpful agents in improving plant stand and minimizing the impacts of biotic and abiotic stressors.
Plants have many enzymatic and non-enzymatic defensive strategies against oxidative stressors caused by ROS. The antioxidant enzymes of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) have an important place in the enzymatic defense systems of plants to remove ROS [15]. SOD is the primary O2.− scavenger and results in the formation of H2O2 and O2 by enzymatic reaction. The H2O2 generated is subsequently removed by CAT [16].
Catalase (H2O2: H2O2 oxidoreductase E.C.1.11.1.6) is a kind of antioxidant enzyme found in all aerobic organisms. It is known that H2O2 is converted into water and oxygen in the cell in the presence of catalase with the realization of environmental stress. Catalase is found in all major locations of H2O2 generation in higher plants' cellular environments (such as peroxisomes, mitochondria and cytosol) [17].
Due to the importance of catalase in plant defense system, we aimed in this study to purify the enzyme from Aronia melanocarpa leaves for the first time and to determine optimum buffer, optimum ionic strength, optimum pH and optimum substrate amount in order to find new potential natural antioxidant sources.