In this study, melanin (BgM) was obtained from Boletus griseus. The chemical composition and structure of BgM were characterized by UV-visible absorption spectrum, Fourier transform infrared spectrum, elemental analysis, nuclear magnetic resonance, pyrolysis gas chromatography mass spectrometry, and ultra-performance liquid chromatography–high resolution mass spectrometry. The percentage contents of C, H, N, S and O elements were 56.38%, 5.86%, 6.17%, 2.44%, and 28.04%, and the S/N and C/N ratios were 0.17 and 10.66, respectively. The UV-vis spectrum of BgM showed a maximum absorption peak at 214 nm. Characteristic absorption peaks were observed at 3426, 1600 and 1105 cm⁻¹, and BgM contained phenolic hydroxyl, amidogen, carbonyl, methylene, and methyl groups. Moreover, BgM is an eumelanin, and its main skeleton has both a benzene ring and an indole, and the branched chain mainly consists of alkanes, alcohols, and fatty acids. BgM was hydrolyzed by H₂O₂ and four compounds were tentatively analyzed from the UPLC-MS/MS profile. The chemical structure of BgM was characterized as 5,6-dihydroxyindole eumelanin, and the condensed molecular formula is [C₂₈(OR₁)₄(OR₂)₃H₁₁O₆N₄]_n.

In this study, Arundo donax Linnaeus was utilized as the biomass and a TH/DS (Tetra-n-butylammonium hydroxide/Dimethyl sulfoxide, C₁₆H₃₇NO/C₂H₆OS) system was employed to dissolve biomass cellulose. The optimal process for the preparation of Arundo donax L. biomass regenerated cellulose fiber was determined through process optimization. The physical properties and antimicrobial performance of the resulting products were analyzed. The results demonstrated that the physical indicators of biomass regenerated cellulose fiber, prepared from Arundo donax L. cellulose, met the requirements of the standard for Viscose Filament (Dry breaking strength ≥ 1.65 CN/dtex, Elongation at dry breaking 15.5–26.0%, and Dry elongation CV value ≤ 10.0%). Additionally, excellent antimicrobial properties were exhibited by the biomass regenerated cellulose fiber developed in this study, with antibacterial rates against Staphylococcus aureus and other three strain indexes meeting the Viscose Filament standards. Furthermore, high antiviral activity of 99.99% against H1N1 and H3N2 strains of influenza A virus was observed in the experimental samples, indicating a remarkable antiviral effect. Valuable references for the comprehensive utilization of Arundo donax L. biomass resources are provided by this research.