Tasya Ulfika, Maged M. Basuliman, Ilham Maulana, M. Hazwan Hussin
Coconut husk, an abundant lignocellulosic residue, represents an underutilized source of technical lignin with inherent antioxidant and antimicrobial potential. In this study, lignin was isolated through alkaline extraction and subsequently complexed with zinc sulfate under mild aqueous conditions to produce Zn–Lignin hybrids with varying zinc loadings. Structural characterization using FTIR, UV–Vis spectroscopy, SEM–EDS, and XRD confirmed successful coordination between Zn2+ ions and lignin functional groups, accompanied by the formation of Osakaite-type zinc sulfate hydroxide domains within the amorphous polymer matrix. Among the synthesized materials, the intermediate zinc loading (10 mL precursor) showed the most efficient Zn2+–lignin coordination at the molecular level, while higher loading (15 mL) resulted in more pronounced bulk structural and morphological changes. Biological assessments revealed that native lignin was essentially non-toxic in the Artemia salina assay, whereas Zn–Lignin hybrids exhibited progressively higher toxicity with increasing Zn content. Antimicrobial testing demonstrated that zinc incorporation significantly enhanced lignin's activity, particularly against Staphylococcus aureus and Candida albicans , where Zn–Lignin (20%) produced inhibition zones comparable to commercial reference drugs. Simultaneous antimicrobial and toxicity evaluations were conducted to elucidate the relationship between zinc coordination, bioactivity, and biological safety. Overall, this work establishes a simple, low-temperature strategy to produce bioactive Zn–Lignin hybrids from renewable biomass, highlighting their potential for antimicrobial coatings, packaging, and environmentally friendly biocidal applications. © 2026 Indian Chemical Society.
Master Program of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Syiah Kuala, Aceh, Banda Aceh, 23111, Indonesia; Materials Technology Research Group (MaTReC), School of Chemical Sciences, Universiti Sains Malaysia, Minden, Penang, 11800, Malaysia; Department of Chemical Science, College of Science, Hadhramout University, Mukalla, Yemen
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