The appeal of the approach lies in its elegance. Traditional routes to iron oxide nanoparticles typically demand high temperatures, strong reducing agents such as sodium borohydride, and organic solvents that raise both environmental and biological safety concerns. Green synthesis, by contrast, exploits the phytochemicals naturally present in plant tissues. Cabbage is a particularly rich reservoir of such molecules: phenolic compounds, flavonoids, alkaloids, amino acids, glucosides, tannins, steroids and carbohydrates all crowd its leaves. The phenolics and flavonoids are the workhorses of the process, possessing strong reducing capacity that allows them to strip electrons from ferric ions and, at the same time, to coat the nascent particles and keep them from clumping. The authors note that, according to their literature analysis, cabbage had not previously been used to synthesize iron oxide nanoparticles, making the study a first for this familiar vegetable.

The synthesis itself was disarmingly simple. Fresh cabbage leaves were dried, powdered and extracted with distilled water in a Soxhlet apparatus at 60 degrees Celsius. Fifty millilitres of this extract was then added dropwise to 100 millilitres of a 0.01 molar ferric nitrate solution under constant stirring. Over the course of an hour, the mixture darkened from yellowish-brown to deep brown, a visual signature of nanoparticle formation. The particles were harvested by centrifugation at 15,000 revolutions per minute, dried at 80 degrees Celsius and calcined at 300 degrees Celsius for two hours, yielding 0.9 grams of product. No toxic reagents were involved at any stage, and the entire reaction proceeded at ambient temperature and pressure.

Characterization confirmed that the product was genuine nanoscale hematite. Powder X-ray diffraction revealed diffraction peaks at angles matching the rhombohedral alpha-Fe2O3 crystal structure, indexed to the (012), (104), (110) and other characteristic planes and consistent with the standard reference card JCPDS 33-0664. Applying the Debye-Scherrer equation to the principal reflections gave crystallite sizes ranging from 13.9 to 19.8 nanometres, with an average of 16.7 plus or minus 2.1 nanometres. Minor peaks hinted at trace secondary iron oxide or oxyhydroxide phases, but the dominant reflections were sharp and intense, indicating good crystallinity. That small crystallite size matters: a high surface-to-volume ratio is precisely what gives nanoparticles their outsized chemical and biological reactivity compared with bulk material.

Spectroscopy told the story of how the plant molecules had done their job. Fourier transform infrared spectroscopy detected a broad band at 3300 to 3400 reciprocal centimetres from O-H stretching of phenolic hydroxyl groups, the very groups credited with reducing the ferric ions, along with C-H stretches from terpenoids, carbonyl and amide bands from proteins and other oxygenated biomolecules, and a decisive Fe-O lattice vibration below 600 reciprocal centimetres. Ultraviolet-visible spectroscopy showed strong absorption below 300 nanometres, attributed to ligand-to-metal charge-transfer transitions between ferric ions and the phytochemicals, and a broad band between 300 and 400 nanometres assigned to Fe-O electronic transitions. Zeta potential measurements gave a mean value of minus 24.5 plus or minus 0.4 millivolts, a negative surface charge arising from adsorbed oxygen-containing phytochemicals that provides electrostatic stabilization and helps prevent aggregation.

Electron microscopy revealed a hierarchical architecture. Field-emission scanning electron micrographs showed elongated platelet-like structures, one to two micrometres wide and eight to ten micrometres long, decorated with fine granular nanoparticles, an arrangement the authors attribute to rapid nucleation followed by growth and oriented attachment along preferred crystallographic directions, guided by the selective adsorption of phytochemicals on specific crystal facets. Transmission electron microscopy resolved the individual primary particles as quasi-spherical to irregular nanocrystals that aggregate through magnetic dipole-dipole interactions. Energy-dispersive X-ray spectroscopy detected only iron and oxygen, with elemental maps showing both distributed uniformly, confirming high purity with no detectable impurities introduced during synthesis. Thermogravimetric analysis added a final flourish: total weight loss across three stages amounted to roughly eight percent, mostly residual moisture and phytochemical capping agents, leaving a robust inorganic residue of about 83.4 percent and demonstrating excellent thermal stability up to 600 degrees Celsius.

The biological screening produced a nuanced picture. Against four bacterial pathogens, the nanoparticles showed moderate activity, producing inhibition zones of 9.52 millimetres against Bacillus subtilis and 10.32 millimetres against Escherichia coli, while showing no detectable effect on Staphylococcus aureus or Pseudomonas aeruginosa. The reference antibiotic chloramphenicol, unsurprisingly, outperformed them with zones of 19.45 to 27.10 millimetres. The authors attribute the nanoparticles’ antibacterial action to reactive oxygen species that oxidize membrane lipids, proteins and nucleic acids, compounded by electrostatic interactions with the bacterial cell envelope. The resistance of the two unaffected strains likely reflects their intrinsic defence mechanisms together with the particles’ size, surface charge and degree of agglomeration, all of which govern adhesion, uptake and ROS generation.

The antifungal results were similarly selective. The nanoparticles inhibited Aspergillus niger with a 14.65 millimetre zone of inhibition, approaching the 18.03 millimetres achieved by amphotericin-B, but showed no significant activity against Candida albicans. The team points to differences in cell wall architecture and membrane composition between the two fungi as plausible explanations, and notes that antifungal efficacy in iron oxide nanoparticles is highly sensitive to particle size, concentration, crystallinity and the nature of the phytochemical capping layer. Antioxidant testing with the DPPH radical assay told a more encouraging story: radical scavenging rose in a dose-dependent fashion from 19.69 percent at 10 micrograms per millilitre to 56.06 percent at 50 micrograms per millilitre, yielding an IC50 of 44.68 micrograms per millilitre. The mechanism is electron transfer, with surface-active oxygen species and adsorbed phytochemical groups donating electrons to neutralize the nitrogen-centred DPPH radical.

Two further assays extended the therapeutic profile. In a protein denaturation assay, a standard proxy for anti-inflammatory activity, the nanoparticles inhibited denaturation of hen egg albumin in a concentration-dependent manner, from 8.61 percent at 10 parts per million to 40.30 percent at 50 parts per million, with an estimated IC50 of 34.72 micrograms per millilitre, compared against the non-steroidal anti-inflammatory drug ibuprofen as a reference. More strikingly, a Neutral Red Uptake assay on A549 human lung adenocarcinoma cells, conducted by the contract research organization Aakar Biotech in Lucknow, revealed a clear dose-dependent cytotoxicity. Viability was essentially unaffected at low concentrations, and even showed a slight hormetic increase at some doses, but fell to roughly 56 percent at 250 micrograms per millilitre and 44 percent at 1000 micrograms per millilitre, giving an IC50 of 144.9 micrograms per millilitre. Under the classification criteria of the U.S. National Cancer Institute, that places the particles in the moderately active category for anticancer agents.

The authors are careful to flag the limits of their evidence. The proposed anticancer mechanism, involving Fenton-like reactive oxygen species generation, lipid peroxidation, mitochondrial dysfunction and apoptosis, remains a plausible explanation rather than direct experimental proof, since ROS markers and apoptosis biomarkers were not measured. Nor was the cabbage extract itself tested independently, so the contribution of the plant’s own phytochemicals cannot be disentangled from that of the nanoparticles. Even so, the study demonstrates that a vegetable costing pennies can seed a multifunctional nanomaterial with credible activity across five biological fronts, and that thermal robustness and colloidal stability suitable for catalysis, environmental remediation and beyond. The path from a 96-well plate to a clinic is long, and the authors themselves call for surface functionalization studies, mechanistic work, pharmacokinetic profiling and in vivo validation. But as a demonstration that sustainable chemistry and biomedical ambition can share a shopping list, the cabbage-derived nanoparticle is hard to beat.

Subject of Research: Green synthesis of iron oxide nanoparticles using cabbage extract and evaluation of their biological activities

Article Title: Brassica oleracea mediated green synthesis of iron oxide nanoparticles and evaluation of their biological activities

Article References: Shaikh, R., Anis, M., Baig, M. I., Isankar, R. D., Pathan, A., & Mardikar, S. P. (2026). Brassica oleracea mediated green synthesis of iron oxide nanoparticles and evaluation of their biological activities. Discover Chemistry, 3(1), Article 515. https://doi.org/10.1007/s44371-026-00968-z

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00968-z

Keywords: green synthesis, iron oxide nanoparticles, Brassica oleracea, hematite, antibacterial, antifungal, antioxidant, anti-inflammatory, anticancer, phytochemicals, nanotechnology, X-ray diffraction