Protective Effects and Metal Chelating Activity of Bacterial Melanin Produced by Streptomyces Spectabilis
DOI:
https://doi.org/10.48048/tis.2026.12213Keywords:
Melanin, Streptomyces spectabilis, Antioxidant activity, UV protection, Intracellular reactive oxygen species, Heavy metal, Bioremediation, Melanin, Streptomyces spectabilis, Antioxidant activity, UV protection, Intracellular reactive oxygen species, Heavy metal, BioremediationAbstract
Melanin is a complex biopolymer widely distributed among diverse organisms and is recognized for its various biological functions, including antioxidant activity, ultraviolet (UV) protection, and metal ion chelation. In this study, melanin extracted from Streptomyces spectabilis strains AQ2 and CQ2 was analyzed in terms of its chemical characteristics and bioactivities. Experimental results indicated that melanin yields from both strains were generally comparable. Strain AQ2 exhibited slightly higher production efficiency relative to biomass, whereas strain CQ2 produced a marginally greater total amount of melanin after prolonged cultivation. The structural properties of the extracted melanin were subsequently examined using Fourier transform infrared (FTIR) and UV–visible spectroscopy. Spectroscopic analysis confirmed that the melanin displayed structural features and typical absorption characteristics of synthetic melanin. Assessment of antioxidant potential via 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and intracellular reactive oxygen species (ROS) assays using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) revealed that melanin from strain CQ2 exhibited superior free radical scavenging activity compared to AQ2. Moreover, melanin from both strains effectively reduced intracellular ROS levels following UV exposure in B16F10 and HaCaT cell lines. Additionally, both melanin demonstrated strong metal ion chelation activity, with particularly high affinity for copper ions. Collectively, these findings suggest that melanin from S. spectabilis strains AQ2 and CQ2 possess significant bioactive properties and holds promise as a natural agent for UV protection, antioxidant defense, and heavy metal remediation. Further studies should focus on optimizing production parameters and exploring broader functional applications of these natural melanin compounds.
HIGHLIGHTS
- A comparison of melanin production revealed that Streptomyces spectabilis strains AQ2 and CQ2 generated comparable yields. Strain AQ2 exhibited slightly higher efficiency relative to biomass and production time.
- FTIR and UV–visible spectroscopy confirmed that melanin from both strains exhibited structural characteristics and absorption properties similar to those of synthetic melanin.
- Melanin derived from AQ2 and CQ2 exhibited free radical scavenging activity and effectively reduced intracellular ROS levels following UV exposure in keratinocyte and melanocyte cell lines.
- Melanin derived from AQ2 and CQ2 exhibited metal ion chelation activity, particularly showing high affinity for copper ions.
GRAPHICAL ABSTRACT
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