The research, published in the Journal of the Saudi Chemical Society by a team led by Mohamed S. Abdelwahab of Matrouh University together with colleagues at Qassim University, Alexandria University, and the National Institute of Oceanography and Fisheries, describes a green synthesis route for what the researchers call CQDs-F: carbon quantum dots functionalized with an extract of fennel seed, Foeniculum vulgare. The approach is disarmingly simple. Sucrose was dissolved in water, purified by liquid-liquid extraction, and then subjected to a staged thermal decomposition in a sealed crucible—five minutes at 300 degrees Celsius, five minutes at 400, and twenty minutes at 500. The resulting black carbonaceous residue was ground, sieved, and then blended with a methanolic fennel seed extract in a mortar, where the extract’s phytochemicals passivated and decorated the nanoparticle surfaces as the mixture dried at room temperature.

What makes this functionalization more than a gimmick is the chemistry of fennel itself. Before making any nanoparticles, the team ran the fennel extract through ultra-performance liquid chromatography coupled to high-resolution mass spectrometry, operating in both positive and negative electrospray ionization modes to catch the widest possible range of molecules. The dual-mode analysis revealed a rich phytochemical arsenal: chlorogenic acid and its isomers, coumarin, p-coumaric acid, anethole and estragole derivatives—including a glycosylated form—the flavonoids quercetin and kaempferol, sesquiterpene oxides, epoxy fatty acids, and unsaturated fatty acids such as linoleic acid. These are precisely the classes of compounds associated with antioxidant, antimicrobial, and anticancer activity in the ethnobotanical literature, and the researchers hypothesized that anchoring them to the carbon dot surface would imbue the nanoparticles with biological functions that bare carbon dots lack.

The characterization data told a compelling story of successful marriage between plant chemistry and carbon nanostructure. Fourier-transform infrared spectroscopy of CQDs-F showed the characteristic 852 per centimeter band of para-disubstituted benzene rings—the unmistakable fingerprint of trans-anethole, fennel’s principal phenylpropanoid—alongside aryl-ether stretches and broadened hydroxyl absorption indicating reinforced hydrogen-bonding networks from adsorbed polyphenols. X-ray diffraction revealed that the (002) graphitic peak had broadened relative to the pristine dots, shrinking the crystallite size to roughly 0.8 to 1.0 nanometers by the Scherrer equation, evidence that the adsorbed plant molecules were distorting the carbon lattice. High-resolution transmission electron microscopy confirmed quasi-spherical particles spanning 4.05 to 6.9 nanometers, averaging 5.6 nanometers, well dispersed without large aggregates. Energy-dispersive X-ray spectroscopy found a carbon- and oxygen-dominated composition with no intentional metal doping, and nitrogen physisorption measured a spacious BET surface area of about 232 square meters per gram for the functionalized dots, with a predominantly mesoporous texture.

Then came the biology. Against a panel of four bacterial pathogens, CQDs-F showed a striking selectivity for Gram-negative Escherichia coli. At the highest tested concentration of 1000 micrograms per milliliter, the nanoparticles produced an inhibition zone of 23.33 millimeters against E. coli—roughly four times the effect seen against the Gram-positive strains Staphylococcus aureus and Bacillus subtilis and the Gram-negative opportunist Pseudomonas aeruginosa. The minimum inhibitory concentration told the same story: 62.5 micrograms per milliliter for E. coli versus 125 for the other three organisms. Critically, the minimum bactericidal concentrations—125 micrograms per milliliter for E. coli, 250 for S. aureus and B. subtilis, and 500 for P. aeruginosa—yielded MBC-to-MIC ratios between 2 and 4, all within the accepted bactericidal threshold, meaning the dots do not merely stall bacterial growth but actually kill the cells.

Why would a sugar-derived carbon dot wrapped in fennel phytochemicals be such an effective antibacterial agent? The authors point to a two-pronged mechanism. Carbon quantum dots are known to disrupt bacterial membrane permeability and integrity, and their heteroatom content promotes the generation of reactive oxygen species that damage microbial cells. Layered on top of that is the chemical firepower of the fennel-derived surface molecules, which can interact directly with microbial membranes and modulate oxidative stress. The pronounced susceptibility of E. coli, with its outer membrane architecture, suggests the phytochemical-functionalized surface may interact particularly well with Gram-negative cell envelopes, although the precise molecular basis remains a question for future work.

The antioxidant results were equally impressive. In the standard DPPH assay, which tracks the fading of a deep violet free radical as it is quenched, CQDs-F achieved an IC50 of just 12.75 micrograms per milliliter—meaning that tiny amounts of the material neutralized half of the radicals present. Ascorbic acid, the vitamin C benchmark, was still stronger at 2.993 micrograms per milliliter, but the nanoparticles dramatically outperformed many previously reported carbon dots, such as those derived from pineapple waste or citrus peels, which required hundreds of times higher concentrations. The team attributes this potency to the synergistic radical-scavenging effects of the hydroxyl-rich polyphenols tethered to the nanoparticle surface, whose electron- and hydrogen-donating capacity is amplified by the oxygen-containing functional groups of the carbon core.

Perhaps the most medically significant findings came from the cell culture experiments. On Vero cells—normal African green monkey kidney cells used as a standard toxicity yardstick—CQDs-F was essentially harmless below 250 micrograms per milliliter, with measurable toxicity only appearing at 500 micrograms per milliliter and climbing steeply beyond that. But on human cancer cells the story was different. The dots showed an IC50 of 160.2 micrograms per milliliter against Caco-2 colon carcinoma cells and, most strikingly, 134.8 micrograms per milliliter against MCF-7 breast cancer cells. The resulting selectivity index of 3.56 for MCF-7 means the nanoparticles are preferentially toxic to the cancer cells relative to normal ones—a property the authors attribute to differences in cellular metabolism, membrane permeability, nanoparticle uptake, and sensitivity to oxidative stress between malignant and healthy cells. For a material made from table sugar and a spice, that is a remarkable therapeutic profile, even at this preliminary in vitro stage.

The context makes these results more than a curiosity. Antimicrobial resistance is one of the most pressing threats in modern medicine, and carbon quantum dots have attracted attention as low-toxicity alternatives or complements to conventional antibiotics, capable of breaking down biofilms and, in some studies, showing activity against drug-resistant pathogens without triggering detectable bacterial resistance. On the cancer front, carbon dots are being explored as drug-delivery vehicles, imaging agents, and even standalone therapeutics, with previous studies showing that functionalization—whether with glutathione, curcumin, doxorubicin, or plant metabolites—consistently enhances their therapeutic reach. This study adds fennel phytochemicals to that growing toolbox, and uniquely ties the biological activity to a fully mapped phytochemical inventory verified by dual-mode mass spectrometry.

The authors are careful to frame this as a preliminary study, and the caveats matter: the cytotoxicity work was done on cell lines in dishes, not in living organisms, and scaling a mortar-and-crucible synthesis to industrial volumes will require optimization of yield and reproducibility. Still, the synthesis itself is a persuasive argument for the green chemistry approach. It used inexpensive, renewable precursors, mild conditions, no hazardous reducing agents, and no elaborate instrumentation—the kind of process that could, in principle, be replicated almost anywhere. If subsequent in vivo studies validate the safety and efficacy suggested here, the idea that tomorrow’s antibacterial coatings, antioxidant supplements, or even cancer-targeted nanomedicines might begin life as caramelized sugar dusted with fennel extract will seem less like science fiction and more like the sensible future of sustainable nanotechnology.

Subject of Research: Green synthesis of fennel extract-functionalized carbon quantum dots and their antibacterial, antioxidant, and anticancer activities

Article Title: UPLC-MS analysis and green synthesis of fennel extract-carbon quantum dots: an assessment of antibacterial, anticancer, and antioxidant potentials

Article References: Abdelwahab, M. S., Al-Harby, N. F., El Batouti, M., & Metwally, R. A. (2026). UPLC-MS analysis and green synthesis of fennel extract-carbon quantum dots: an assessment of antibacterial, anticancer, and antioxidant potentials. Journal of Saudi Chemical Society, 30(4), Article 45. https://doi.org/10.1007/s44442-026-00096-4

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00096-4

Keywords: carbon quantum dots, fennel, green synthesis, antibacterial, antioxidant, anticancer, UPLC-MS, nanotechnology, phytochemicals, E. coli, MCF-7, sucrose pyrolysis

The scale of the problem the researchers set out to address is substantial. Muscle injuries remain one of the leading causes of time lost from training and competition in professional football, and the biological response to a given training load is highly individual, shaped by a complex web of metabolic, inflammatory, and recovery processes. Current monitoring strategies rely predominantly on external load metrics derived from electronic performance tracking systems, which the authors argue do not fully capture the individual physiological stress and biological cost of training. Metabolomics, the systematic measurement of small molecules that represent the final products of cellular regulation, provides a downstream functional readout of physiology that integrates genomic, proteomic, and environmental influences. Because urine can be collected non-invasively and repeatedly, it is an attractive medium for tracking these processes in athletes who are tested constantly.

The study’s design reflected the realities of elite sport. Of the 287 samples, 30 were collected during ten clinically confirmed muscle injury and rehabilitation periods from ten distinct players, while the remaining 257 came from healthy periods and served as controls. Injuries were defined and recorded according to UEFA consensus recommendations, diagnosed by the same medical staff throughout, and supported by ultrasound and magnetic resonance imaging when clinically indicated. The injury set spanned the spectrum of lesions common in professional football, including grade 2b and 3c hamstring strains affecting the biceps femoris, semimembranosus, semitendinosus, and rectus femoris muscles. Samples were collected at a median of 22 days post-injury, with the majority drawn during early and late rehabilitation phases rather than the acute window.

On the analytical side, the team used targeted ultra-performance liquid chromatography coupled to tandem mass spectrometry to quantify amino acids and tryptophan-related metabolites. Absolute concentrations were normalized to creatinine to correct for urinary dilution, and tryptophan pathway metabolites were additionally normalized to tryptophan itself, yielding 71 metabolite ratios for statistical analysis. Quality control relied on calibration standards, procedural blanks, retention-time matching, and stable isotope-labeled internal standards added to every sample. Before any supervised modeling, principal component analysis confirmed that injury status was not the dominant source of variance in the dataset, an expected result given that injury-related perturbations are subtle against the broad physiological variability inherent to elite athletes. No analytical outliers or season-related batch effects were detected.

Despite that subtlety, univariate statistics combining Welch’s test, fold-change assessment, and Hedge’s g effect sizes revealed a coherent biochemical story. The most striking signals involved tryptophan metabolism: injured players showed substantially elevated levels of xanthurenic acid, kynurenic acid, and elevated tryptamine-to-tryptophan ratios, alongside higher S-adenosylmethionine. The kynurenine pathway, through which tryptophan is degraded, is strongly regulated by immune signaling and inflammatory mediators and has been widely implicated in exercise-induced adaptation, making its perturbation one of the most biologically relevant responses to muscle damage. Conversely, aminophenol, proline, ornithine, and lysine were reduced in the injury group, consistent with altered protein turnover as the body repools amino acids for tissue repair.

Two further metabolic themes emerged. The first involved purine degradation, particularly hypoxanthine, a well-established marker of energetic stress that accumulates when ATP is broken down faster than it can be regenerated. In the context of muscle injury, elevated hypoxanthine likely reflects both localized energy depletion within damaged fibers and the systemic metabolic cost of sustaining tissue repair. The second theme involved amino acids directly implicated in structural remodeling: proline and ornithine are closely linked to collagen synthesis and connective tissue repair, while elevated beta-aminoisobutyric acid, or BAIBA, has been associated with muscle stress adaptation and mitochondrial remodeling. Changes in alanine, glutamic acid, taurine, beta-alanine, and phenylacetylglutamine reinforced the picture of coordinated protein turnover. Pathway over-representation analysis using the KEGG database pointed to significant enrichment of amino acid metabolic pathways, particularly arginine and proline metabolism, although the authors caution that because the panel was targeted, this enrichment is exploratory rather than definitive mechanistic evidence.

The multivariate analysis was where the findings took on their most clinically suggestive form. Using partial least squares discriminant analysis with leave-one-out cross-validation and 300-fold permutation testing to guard against overfitting, the researchers built a model that separated injured from non-injured samples with a cross-validated area under the receiver operating characteristic curve of 0.88, correctly identifying 73 percent of injury samples and 88 percent of controls, with statistical significance at p less than 0.003. The most influential discriminant metabolites were BAIBA, hypoxanthine, xanthurenic acid, beta-alanine, and alanine, largely consistent with the univariate results. Backward stepwise feature selection then pared the model down to a restricted subset of metabolites that preserved an AUROC of 0.81, a simplification the authors highlight as important for translation, since small targeted panels are more analytically robust and easier to validate in routine clinical settings than full metabolomic profiles.

The team was careful to stress-test its own statistics. Because 30 injury samples came from only ten players, they repeated validation using a stricter leave-one-player-out scheme, under which performance dropped to an AUROC of 0.72. They attribute this decline to the severe class imbalance and the concentration of injury samples among few individuals, and they emphasize that independent player-level validation in larger cohorts is essential before any clinical deployment. The imbalance also shaped other performance metrics: the positive predictive value was a modest 41 percent, while the negative predictive value reached 97 percent, meaning the current score is far better at ruling out injury-related metabolic stress than confirming it. The authors also note that nutritional intake, acute workload, and medication, all of which can influence the urinary metabolome, were not recorded and represent potential confounders.

Perhaps the most visually compelling element of the study is the longitudinal perspective. For eight of the ten injured players, serial samples collected across rehabilitation allowed the researchers to track individual trajectories of a metabolite-based injury score. In a descriptive, exploratory assessment, these trajectories suggested progressive normalization of the metabolic profile during rehabilitation, approaching baseline values by the return-to-play milestone, and players who never sustained injuries showed baseline stability in the score. The study juxtaposes these chemical trajectories with serial 3-Tesla MRI examinations of a 24-year-old player who suffered a complete proximal hamstring aponeurosis tear, documenting the anatomical progression from acute edema and tendon retraction through scar bridging, maturation, and remodeling over eight weeks. The authors argue that macro-structural healing on MRI does not necessarily reflect the resolution of local energetic or systemic inflammatory stress, so mapping metabolomic trajectories against structural lesion evolution could, in principle, reveal whether cellular homeostasis has truly recovered even when imaging looks normal.

The researchers are measured about what their findings can and cannot support. Urinary profiles reflect systemic metabolic balance rather than local tissue remodeling, and the signatures cannot currently be used to guide return-to-play decisions. The observational design limits causal interpretation, and the single-center cohort restricts generalizability. Nevertheless, the demonstration that a coordinated, statistically robust metabolic signature of muscle injury can be captured non-invasively in urine marks a meaningful step toward complementing external load monitoring with an internal readout of biological stress. Future multicenter studies that integrate longitudinal metabolomics with structural imaging, biochemical markers, and clinical assessment will determine whether this multimodal approach adds clinically meaningful value, potentially transforming how the world’s most expensive athletes are monitored, rehabilitated, and returned to competition.

Subject of Research: Urinary metabolomic biomarkers of muscle injury and recovery in professional football players

Article Title: Urinary metabolomic signatures of muscle injury and recovery in elite football players

Article References: Quintás, G., Pruna, R., Wong, M., Mechó, S., Madrero, P., Sanjuán-Herráez, J. D., & Rodas, G. (2026). Urinary metabolomic signatures of muscle injury and recovery in elite football players. Metabolomics, 22(5), Article 158. https://doi.org/10.1007/s11306-026-02530-5

Image Credits: AI Generated

DOI: 10.1007/s11306-026-02530-5

Keywords: metabolomics, muscle injury, football, sports medicine, urine biomarkers, tryptophan metabolism, purine metabolism, PLS-DA, FC Barcelona, athlete monitoring, rehabilitation, UPLC-MS