Exploring the UVB-protective efficacy of melanin precursor extracted from marine imperfect fungus: Featuring...

The present study explores the production, characterization, and application of a potentially stable melanin precursor from marine imperfect non-spore-forming Aspergillus nidulans sp. strain SG 28. Growth of the culture in artificial seawater with galactose and monosodium glutamate, pH at 7.2-7.5, and temperature at 35 ± 0.5 °C exhibits pigment production with the yield of 0.700-0.800 g/L. The characterization studies revealed that the pigment is orange reddish pink in color, soluble in water, insoluble in both polar and non-polar organic solvents, and decolorized when exposed to H₂O₂, KMnO₄, and K₂Cr₂O₇. UV-visible spectrum exhibits maximum absorption peak at 330 nm and mild shoulders at 400 and 500 nm. The pigment displayed both antioxidant and reducing power properties when exposed with ABTS and ferricyanide, respectively. The sun protection factor of the pigment was determined as 9.9. The cytocompatibility of the obtained pigment studied using HaCaT cells revealed that the cells are viable up to 500 μM. Experiments on UVB protection of the pigment using HaCat cells demonstrated the appreciable protective effect by reducing the ROS generation upon UVB exposure. In conclusion, the pigment obtained from the marine imperfect fungus showed structural similarity with DHICA which is confirmed by LC-MS. The presence of metal ions in the growth medium mediates the reaction to proceed towards DHICA formation. The SPF analysis, antioxidant property, and the UVB protection studies authenticate the potential use of pigment for skin care.