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<p>In the present investigation, ZnO/NiO heterostructure nanocomposites (NCs) were successfully synthesized using the ethanolic leaf extract of <i>Catharanthus roseus</i> (<i>C. roseus</i>) via a facile, economical and eco-friendly green synthesis approach. Phytochemical screening confirmed the presence of various bioactive constituents that acted as effective reducing and stabilizing agents during the formation of the nanocomposites. The synthesized <i>C. roseus</i>-mediated ZnO/NiO NCs were extensively characterized by UV–visible spectroscopy, diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDAX) to investigate their optical, crystalline and morphological properties. The nanocomposites exhibited improved optical absorption characteristics with an average crystallite size of 24.44&#xa0;nm and direct and indirect band gap energies of 3.15&#xa0;eV and 1.81&#xa0;eV, respectively. The synthesized ZnO/NiO nanocomposites exhibited concentration-dependent antioxidant activity in the DPPH free radical scavenging assay and demonstrated measurable antibacterial activity against <i>Escherichia coli</i> and <i>Bacillus subtilis</i>. Their effects on rotenone-challenged SH-SY5Y cells were evaluated using the MTT assay, which revealed a concentration-dependent response. Partial recovery of cell viability was observed at lower concentrations (6.25–12.5&#xa0;µg/mL), whereas higher concentrations produced progressively increased cytotoxicity, with an IC<sub>50</sub> value of 23&#xa0;µg/mL. These findings indicate a limited concentration window associated with beneficial cellular effects rather than uniform neuroprotective activity across the tested dose range. Overall, the results provide preliminary evidence of the antioxidant, antibacterial and dose-dependent cellular responses of <i>C. roseus</i>-mediated ZnO/NiO nanocomposites. However, further mechanistic studies, comprehensive toxicity assessments and advanced biological validation are required to establish their safety profile and biomedical relevance.</p> Graphical abstract <p></p>

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Green synthesis of Catharanthus roseus-mediated ZnO/NiO nanocomposites and their antibacterial, antioxidant and in vitro cellular activities

  • 期刊论文

  • 发表日期：

    2026年7月6日

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  • K. P. Greeshma,
  • A. Mani,
  • S. Muthulingam,
  • B. Archana,
  • B. Preethi,
  • R. Thamiz Selvi,
  • Ashim Kumar Sen

摘要

In the present investigation, ZnO/NiO heterostructure nanocomposites (NCs) were successfully synthesized using the ethanolic leaf extract of Catharanthus roseus (C. roseus) via a facile, economical and eco-friendly green synthesis approach. Phytochemical screening confirmed the presence of various bioactive constituents that acted as effective reducing and stabilizing agents during the formation of the nanocomposites. The synthesized C. roseus-mediated ZnO/NiO NCs were extensively characterized by UV–visible spectroscopy, diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDAX) to investigate their optical, crystalline and morphological properties. The nanocomposites exhibited improved optical absorption characteristics with an average crystallite size of 24.44 nm and direct and indirect band gap energies of 3.15 eV and 1.81 eV, respectively. The synthesized ZnO/NiO nanocomposites exhibited concentration-dependent antioxidant activity in the DPPH free radical scavenging assay and demonstrated measurable antibacterial activity against Escherichia coli and Bacillus subtilis. Their effects on rotenone-challenged SH-SY5Y cells were evaluated using the MTT assay, which revealed a concentration-dependent response. Partial recovery of cell viability was observed at lower concentrations (6.25–12.5 µg/mL), whereas higher concentrations produced progressively increased cytotoxicity, with an IC50 value of 23 µg/mL. These findings indicate a limited concentration window associated with beneficial cellular effects rather than uniform neuroprotective activity across the tested dose range. Overall, the results provide preliminary evidence of the antioxidant, antibacterial and dose-dependent cellular responses of C. roseus-mediated ZnO/NiO nanocomposites. However, further mechanistic studies, comprehensive toxicity assessments and advanced biological validation are required to establish their safety profile and biomedical relevance.

Graphical abstract