Purification, characterization, and biological activities of melanin pigment isolated from Indian squid Uroteuthis duvaucelii

Melanin is a natural pigment present in plants, animals, humans, and pigment-producing bacteria. Due to their biocompatibility and versatile biological activities, it was heavily used in cosmetic and pharmaceutical industries and also has market demand. The objective of this study is to develop a strategic method to convert the ink biomass obtained from the Indian squid Uroteuthis duvaucelii into a valuable and sensible healthcare product such as melanin. Initially, the squid was collected and processed and the ink was isolated and the powdered form was purified by 150-μm sieve with the respective procedure. Then, they were characterized by UV-Vis spectroscopy, field electron scanning electron microscopy, Fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry. The presence of melanin was confirmed by FE-SEM and the elements present were analyzed using energy-dispersive spectroscopy. In addition, their biological activities such as antioxidant and antibacterial properties were evaluated. DPPH free radical scavenging activity revealed that the powdered ink sample has significant antioxidant potential with increasing concentrations. Also, it showed potent antibacterial properties against Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa. From the present study, we conclude that the melanin was extracted from the Indian squid, and it showed significant antioxidant and antibacterial activities. Furthermore, in the near future, this Uroteuthis duvaucelii biomass has to be studied further to formulate value-added products in healthcare and cosmetics by replacing synthetic compounds and formulations.