Physicochemical Properties and Biological Activities of Melanin Extracted from Sunflower Testae

Abstract

Melanin extracted from sunflower testae was isolated, purified and the physicochemical properties, antioxidant activities, metal ion removal activity and anti-radiation were investigated. The physical and chemical characterization showed that it was acid-resistant, alkali soluble and insoluble in most of the organic solvents and distilled water and the similar redox properties to synthetic melanin from sigma. The melanin was precipitated on treatment with FeCl₃, ammoniacal AgNO₃, potassium ferricyanide and was bleached in the presence of oxidants and reductants. It was also confirmed as one of melanins based on the Ultraviolet visibl. (UV-vis) absorption spectroscopy, Fourier transform infrared spectrometry (FT-IR), Electron paramagnetic resonance (EPR) spectroscopy, and Scanning electron microscopy (SEM) spectroscopic techniques apart from physiochemical analysis. Elemental composition analysis revealed that the melanin was pheomelanin or allomelanins. The melanin also showed the antioxidant potential observed in the in vitro evaluation of diphenyl picryl hydrazinyl radical scavenging activity, superoxide-scavenging activity, hydroxyl-scavenging activity, reducing power, metal ion removal activity and anti-radiation activity. The activities examined indicated that melanin from sunflower testae could be considered as a novel potential antioxidant, heavy metal adsorbent, and UV protection agent. The results suggested that the melanin could potentially be used as a natural antioxidant in the food, cosmetic and other industries.