The antioxidant activities of black mulberry (morus nigra L.) extracts andtheir effects on serum paraoxonase-1, arylesterase, catalase, and myeloperoxidase enzyme activities: an investigation

Paraoxonase (PON) is a clinical enzyme that also possesses arylesterase (ARE) activity and plays an atheroprotective role in lipoprotein metabolism. While catalase (CAT) plays a role in the elimination of hydrogen peroxide, myeloperoxidase (MPO) is an enzyme with bactericidal effects released by neutrophils during bacterial infections. Its pro-oxidant effect has been associated with cardiovascular diseases. In our study, we aimed to investigate the effects of the high polyphenolic content and antioxidant properties of the black mulberry (Morus nigra L) fruit—an important medicinal plant—on the serum activities of these enzymes under in vitro conditions. With ethical approval, a serum pool was established using patient serum from the biochemistry laboratory. Total phenolic content and total flavonoid content of all extracts of black mulberry fruit, as well as their FRAP, DPPH, ABTS, total oxidant status (TOS), and total antioxidant status (TAS) activities, were determined. Additionally, the phenolic compound content of extracts was analyzed by HPLC. Extracts were prepared at concentrations of 25, 50, 75, 100, and 200 µg/mL in serum, and their effects on PON, ARE, CAT, and MPO enzyme activities were determined spectrophotometrically and kinetically. In general, the extracts significantly reduced PON, ARE, MPO, and TOS activities compared to the control serum, while increases were observed in TAS and CAT values (p<0.05). It was observed that the extent of these increases and decreases was particularly significant at concentrations of 100 and 200 µg/mL. A total of 7 phenolic compounds were identified in the HPLC analysis. Among these, protocatechuic acid had the highest concentration. Keywords: Antioxidant, Arylesterase, Blackberry, Catalase, Myeloperoxidase, Paraoxonase