Antioxidant potential of melanin pigment from marine sponge-associated actinomycete Micromonospora sp.

Melanin pigment is a dark-colored natural biopolymer produced by microbes, such as actinomycetes. Melanin has various potential bioactivities, including antioxidant activity. This study aimed to determine the antioxidant and photoprotective properties of melanin extracted from the marine sponge-associated actinomycete Micromonospora fulva HV6. Antioxidant properties were measured by spectrometric techniques using 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods, and photoprotective properties were evaluated by measuring the sun protection factor (SPF). The IC50 values exhibited potent antioxidant activity of melanin in reducing DPPH and ABTS in vitro at concentrations of 31.55 ± 0.60 μg/ml and 63.07 ± 3.29 μg/ml, respectively. At the cellular level, 240 μg/ml melanin improved the viability of Schizosaccharomyces pombe under severe H2O2-induced stress better than L-ascorbic acid did, indicating its potential to prolong the longevity of yeast cells. Melanin also increased mitochondrial activity and induced oxidative stress tolerance, likely through mitochondrial adaptive reactive oxygen species signaling, similar to the response induced by calorie restriction. Melanin exhibited photoprotective properties with an SPF value of 20.78. In summary, the melanin pigment extracted from M. fulva HV6 showed potential as a natural antioxidant from a rare actinomycete group for medical and pharmacological applications.