Antioxidant potential of UV-screening pigment scytonemin isolated from the cyanobacterium Scytonema sp. HKAR-8

Abstract

The most promising class of photosynthetic microorganisms, cyanobacteria, can produce a wide range of useful natural products. Some cyanobacteria are capable of biosynthesizing the indole-alkaloid scytonemin, a secondary metabolite of significant ecological and medicinal value. Scytonemin is a small, yellow-brown, 544-Da molecular mass, lipid-soluble compound that can screen UV-A radiation. In this study, scytonemin was extracted and purified from the cyanobacterium Scytonema sp. HKAR-8. Further, nuclear magnetic resonance (NMR) spectroscopy was used to identify and characterize scytonemin. The antioxidant potentials of scytonemin were assessed using several in vitro antioxidant tests, including DPPH, ABTS, and H<inf>2</inf>O<inf>2</inf> scavenging activity. Scytonemin extracted from this cyanobacterium showed dose-dependent in vitro antioxidant activity as compared to ascorbic acid. By producing the photoprotective compound scytonemin, cyanobacteria can colonize and thrive in harsh environmental conditions by reducing the negative effects of UV radiation. This UV-shielding compound, scytonemin may be of significant importance for the formation of natural and sustainable sunscreen in the cosmetic and other therapeutic industries because of its significant antioxidant capacity and photoprotective activity. © The Author(s) under exclusive licence to Society for Plant Research 2025.