Antioxidant Properties of Phycocyanin from Lithuania

Abstract

Oxidative stress is involved in many diseases. Antioxidants are important as they can delay or stop the formation of free radicals by giving hydrogen atoms or scavenging them [3]. An antioxidant can be defined as any molecule capable of preventing or delaying oxidation of other molecules, usually such as lipids, proteins or nucleic acids [2, 3]. Phycocyanin belongs to the family of phycobiliproteins present in cyanobacteria [1]. Phycocyanin contains a high level of glutamic acid, aspartic acid, alanine, leucine, arginine, isoleucine, serine, glycine, and threonine. These amino acids are reported to be related to antioxidant activity [4]. Many authors state the antioxidant activity of phycocyanin. DPPH test is widely used for measuring the antioxidant activity of phycocyanin. Different authors use different markers for the calculation of the antioxidant activity of phycocyanin. Among them mainly are Trolox and ascorbic acid [1, 4]. Materials and methods. Phycocyanin was obtained from cyanobacteria collected in the Šventoji River (Lithuania). The antioxidant activity of the obtained sample was determined according to the elaborated procedure of the DPPH test. The hydrogen atom or electrons donating ability of phycocyanin was measured from the change of the purple colour of the ethanol solution of DPPH. The free radical scavenging activity of the phycocyanin solution of an appropriate concentration, based on the scavenging activity of the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, was measured. The phycocyanin solution was added to ethanolic solution DPPH in an appropriate ratio. The absorbance was read at a wavelength of 515 nm after 10, 20, 30 and 40 min, and the percentage scavenging activity was calculated using the formula given below. The solution of DPPH without the test sample was used as a control. The scavenging activity of the obtained phycocyanin was calculated according to the following formula: % Scavenging activity = [(A0 – A1) / A0] × 100 %, where A0 — absorbance of the control, A1 — absorbance of the test sample. In the process of our studies, the following issues were sorted out: the concentration of ethanol in the solution of DPPH was selected to avoid precipitation in the reaction mixtures, the ratio of the pigment solution to the DPPH solution, the calibration curves of quercetin and rutin were constructed (y = 0.6232x - 4.5352, R² = 0.9774 and y = 0.228x + 7.0992, R² = 0.9945, respectively).