Researchers in Maharashtra, India have turned the leaves of a traditional Ayurvedic medicinal tree into a factory for one of nanotechnology’s most versatile materials. In a study published in Discover Green Chemistry, a team led by Sumangal S. Kale of Shri Pancham Khemraj Mahavidyalaya, Sawantwadi, used a simple aqueous extract of Zanthoxylum rhetsa (Roxb.) DC. leaves to synthesize nickel oxide nanoparticles without any of the toxic solvents, hazardous reducing agents, or energy-hungry furnaces that dominate conventional nanoparticle manufacturing. The resulting particles, dubbed ZR-NiONPs, proved to be crystalline, ferromagnetic, and biologically active across an unusually broad front, inhibiting bacteria, fungi, free radicals, inflammatory protein denaturation, a key digestive enzyme, Mycobacterium tuberculosis, and breast cancer cells while leaving normal fibroblast cells largely unharmed.
The appeal of the approach lies in its chemistry of substitution. Standard routes to nickel oxide nanoparticles, including sol-gel processing, chemical precipitation, hydrothermal synthesis, combustion methods, and thermal decomposition, typically demand high temperatures, expensive instrumentation, and reagents that generate environmentally harmful by-products. Plant-mediated synthesis replaces all of that with phytochemicals. Leaves of Zanthoxylum rhetsa, a Rutaceae family tree distributed across South and Southeast Asia and long used in Ayurvedic medicine, are rich in flavonoids, phenolics, alkaloids, and essential oils. In the synthesis, these biomolecules perform double duty: they chemically reduce nickel ions from a nickel chloride precursor into nanoscale nickel oxide, and they cap the growing particles, preventing them from clumping and controlling their size and shape.
The practical procedure was strikingly simple. Fresh leaves collected from Satarda village in the Sawantwadi region of Sindhudurg were shade-dried, ground, and boiled in distilled water for an hour to extract the phytochemicals. The filtered extract was then mixed one-to-one with a 0.1 molar nickel chloride solution and stirred magnetically for eight hours, during which a deep brown precipitate appeared, signaling nanoparticle formation. After centrifugation, repeated washing, drying at 110 degrees Celsius, and calcination at 550 degrees Celsius, the team obtained phase-pure brown ZR-NiONPs ready for characterization and biological testing.
X-ray diffraction confirmed that the material was genuine face-centered cubic nickel oxide, with diffraction peaks matching the standard reference pattern and indexing to the (111), (200), (220), (311), and (222) crystal planes. Applying the Scherrer equation to the peak widths gave an average crystallite size of just 12.88 nanometers, and the sharpness of the peaks indicated high crystallinity with minimal lattice strain. Ultraviolet-visible spectroscopy added a second confirmation: while the raw leaf extract absorbed at 289 nanometers, a signature of the aromatic polyphenols and flavonoids within it, the finished nanoparticles showed a distinct new absorption band at 476 nanometers, reflecting defect-induced electronic transitions characteristic of nickel oxide nanoscale particles.
Infrared spectroscopy told the mechanistic story in detail. The extract spectrum displayed a rich catalog of functional groups, including broad hydroxyl stretching from phenols, aliphatic carbon-hydrogen stretches from terpenoids, carbonyl and amide bands from proteins and phenolic compounds, and aromatic ring vibrations typical of flavonoids. After synthesis, several of these bands shifted or weakened, evidence that those biomolecules had been consumed in reducing and capping the particles, and a set of entirely new peaks between roughly 550 and 430 inverse centimeters appeared, corresponding to nickel-oxygen stretching vibrations. Electron microscopy completed the physical portrait: field emission scanning electron microscopy revealed spherical to irregular, agglomerated, rough-surfaced particles, while transmission electron microscopy resolved individual particles ranging from 10 to 42 nanometers, with a selected area electron diffraction pattern of bright concentric rings confirming their polycrystalline nature.
Two further measurements rounded out the physicochemical profile. Zeta potential analysis gave a value of minus 10.2 millivolts, indicating a moderately negative surface charge and only moderate colloidal stability, a common feature of plant-capped metal oxide nanoparticles whose stability derives from both electrostatic repulsion and steric shielding by adsorbed biomolecules. More dramatically, vibrating sample magnetometry revealed a saturation magnetization of approximately plus or minus 55 emu per gram with near-zero coercivity and remanence, a soft ferromagnetic signature. That magnetic character matters beyond the laboratory bench: soft ferromagnetic nanoparticles are candidates for spintronic devices, magnetic data storage, heterogeneous catalysis, and, in a biomedical context, magnetically guided delivery.
The biological results were the study’s most eye-catching element. In agar well diffusion tests, the nanoparticles produced inhibition zones of 18 to 23 millimeters against four clinically relevant bacterial strains, with the strongest effect against Staphylococcus aureus, followed by Bacillus cereus, Escherichia coli, and Proteus vulgaris. The authors attribute this activity primarily to reactive oxygen species. Nickel oxide nanoparticles generate superoxide radicals, hydroxyl radicals, and hydrogen peroxide at the cell surface, and these species attack membrane lipids, proteins, and DNA, ultimately rupturing the bacterial cell. Released nickel ions may add a second mechanism by binding thiol groups in cellular enzymes. Notably, the particles performed better against Gram-positive bacteria, whose thick peptidoglycan wall lacks the outer lipopolysaccharide membrane that shields Gram-negative species from nanoparticle penetration.
The antifungal and metabolic assays painted a picture of moderate but genuine multifunctionality. The nanoparticles inhibited Candida albicans with an 11 millimeter zone and Aspergillus niger with 9 millimeters, below the performance of standard drugs but consistent with other plant-derived nickel oxide systems. In a DPPH free radical scavenging assay they achieved an IC50 of 92.56 micrograms per milliliter, roughly double the potency of ascorbic acid in the same test, and in a heat-induced protein denaturation model of inflammation they reached 48.83 percent inhibition at 100 micrograms per milliliter. They also inhibited the alpha-amylase enzyme central to starch digestion with an IC50 of 97.71 micrograms per milliliter, suggesting potential as a complementary agent in managing postprandial blood glucose, and they suppressed Mycobacterium tuberculosis growth by 46.24 percent at the highest tested concentration of 1000 micrograms per milliliter in an Alamar Blue viability assay.
Perhaps the most clinically significant finding came from the cell culture work. Against MCF-7 human breast cancer cells, the nanoparticles showed dose-dependent cytotoxicity with an IC50 of 88.52 micrograms per milliliter, an effect the authors link to the same reactive oxygen species machinery that kills bacteria: excessive oxidative stress in cancer cells damages mitochondria, fragments DNA, and triggers apoptosis, with surface-bound Zanthoxylum phytochemicals potentially enhancing uptake across cancer cell membranes. Crucially, when the same particles were tested against L929 mouse fibroblast cells, a standard model for normal tissue biocompatibility, inhibition never exceeded 29.40 percent even at 1000 micrograms per milliliter, and no IC50 could be determined. The phytochemical capping layer, the researchers suggest, moderates surface reactivity and limits oxidative damage in healthy cells, which possess their own antioxidant defenses, while cancer cells, already living near their redox limits, succumb.
The authors are candid about the caveats. Plant-mediated synthesis remains difficult to standardize, since phytochemical composition varies with plant origin, season, and extraction method, and scaling the process to industrial levels is unproven. No in vivo toxicology or long-term environmental assessment has yet been performed, and the anticancer and anti-tubercular effects, while real, trail standard drugs by a considerable margin. Even so, the study stands out for integrating a full physicochemical characterization with a systematic panel of biomedical assays in a single investigation, something the authors note is rare in the field. If subsequent animal studies confirm the safety margin seen in fibroblasts, these leaf-forged ferromagnetic particles could find roles in antimicrobial coatings, drug delivery platforms, biosensors, and wound healing formulations, all built from a tree that traditional medicine has valued for centuries.
Subject of Research: Green synthesis of nickel oxide nanoparticles using Zanthoxylum rhetsa leaf extract and their multifunctional biomedical activities
Article Title: Green synthesis of nickel oxide nanoparticles using Zanthoxylum rhetsa (Roxb.) DC. leaf extract, comprehensive physicochemical characterisation and multifunctional biomedical applications
Article References: Kale, S. S., Nikum, A. P., Pawar, Y. A., Gurav, V. L., & Sathe, G. B. (2026). Green synthesis of nickel oxide nanoparticles using Zanthoxylum rhetsa (Roxb.) DC. leaf extract, comprehensive physicochemical characterisation and multifunctional biomedical applications. Discover Green Chemistry, 1(1), Article 15. https://doi.org/10.1007/s44509-026-00018-y
Image Credits: AI Generated
DOI: 10.1007/s44509-026-00018-y
Keywords: green synthesis, nickel oxide nanoparticles, Zanthoxylum rhetsa, phytochemicals, antibacterial activity, anticancer activity, ferromagnetism, nanomedicine, reactive oxygen species, MCF-7 breast cancer cells, biocompatibility, Ayurvedic medicinal plants
Cite Scienmag News
APA MLA Chicago
Bethany Barker. (September 23, 2026). Tree Leaf Extract Yields Ferromagnetic Nickel Oxide Nanoparticles With Wide-Ranging Biomedical Activity. Scienmag. https://scienmag.com/tree-leaf-extract-yields-ferromagnetic-nickel-oxide-nanoparticles-with-wide-ranging-biomedical-activity/
Bethany Barker. “Tree Leaf Extract Yields Ferromagnetic Nickel Oxide Nanoparticles With Wide-Ranging Biomedical Activity.” Scienmag, 23 September 2026, https://scienmag.com/tree-leaf-extract-yields-ferromagnetic-nickel-oxide-nanoparticles-with-wide-ranging-biomedical-activity/. Accessed 23 September 2026.
Bethany Barker. “Tree Leaf Extract Yields Ferromagnetic Nickel Oxide Nanoparticles With Wide-Ranging Biomedical Activity.” Scienmag. September 23, 2026. https://scienmag.com/tree-leaf-extract-yields-ferromagnetic-nickel-oxide-nanoparticles-with-wide-ranging-biomedical-activity/
Copy citation Download RIS
Tags: antibacterial activityanticancer activityantimicrobial and anticancer properties of plant-derived nanoparticlesAyurvedic medicinal plant extracts in nanotechnologyAyurvedic medicinal plantsbioactive nanoparticles inhibiting bacteria and fungibiocompatibilityenvironmentally friendly nanomaterial productionferromagnetic nickel oxide nanoparticles for biomedical applicationsferromagnetismgreen synthesisgreen synthesis of nanomaterials using leaf extractsMCF-7 breast cancer cellsNanomedicinenanotechnology for infectious disease and cancer treatmentnickel oxide nanoparticlesnickel oxide nanoparticles for inflammatory and digestive enzyme modulationphytochemical reduction of metal oxidesphytochemicalsplant-based greenPlant-mediated nickel oxide nanoparticle synthesisreactive oxygen speciessustainable nanomaterial manufacturing methodsZanthoxylum rhetsa
