Yves Chevalier

A novel and rapid spectrofluorimetric method for histamine (HA) detection in food matrices was developed based on its complexation with europium(III) chloride (EuCl₃) in an aqueous medium. Although histamine is intrinsically nonfluorescent, coordination with Eu³⁺ induces a strong characteristic red emission centered at 620 nm. The fluorescence response was markedly enhanced by optimizing the physicochemical parameters, particularly europium concentration and solution pH, which govern histamine protonation and complex stability. Under optimal conditions, a linear fluorescence response was obtained over the investigated concentration range, with an excellent correlation coefficient (R² = 0.9935). The limits of detection and quantification were determined to be 0.175 mg L^–1 and 0.576 mg L^–1, respectively. The method was fully validated in accordance with international guidelines, demonstrating good repeatability, reproducibility, and satisfactory recoveries (73–98%) when applied to real milk samples, with minimal matrix interference. Job’s plot analysis revealed a 1:2 stoichiometry for the Eu–HA complex. Structural elucidation by ¹H NMR spectroscopy confirmed histamine coordination mainly through its amine and imidazole nitrogen atoms. Density Functional Theory (DFT) calculations supported the experimental findings, highlighting charge redistribution and ligand-to-metal charge transfer effects that contribute to the enhanced luminescence. These combined spectroscopic, analytical, and theoretical results demonstrate that europium(III) complexation provides a simple, stable, and sensitive platform for histamine detection in food safety applications.

Pharmaceutical and personal care products, such as paracetamol, are emerging contaminants frequently detected in aquatic environments, raising concerns due to their persistence and resistance to conventional wastewater treatment methods. This study reports the development of a sustainable bifunctional bioadsorbent by grafting β-cyclodextrin (β-CD) onto fibers of Posidonia oceanica, a Mediterranean seagrass rich in lignocellulosic components. The grafting was achieved using citric acid as a green, non-toxic crosslinker and potassium dihydrogen phosphate as a catalyst, yielding the Pos-βCD material. The most suitable CD type for being grafted was selected from the determination to the binding affinities of paracetamol to α-, β-, and γ-CD. The latter were evaluated in solution by ¹H NMR experiments. β-CD formed the most stable 1:1 inclusion complex. The Pos-βCD materials were synthesized at different grafting ratios and thoroughly characterized by IR, ζ-potential, TGA, BET, optical microscopy, SEM, and light scattering. IR spectroscopy confirmed the formation of ester bonds and successful surface modification. Morphological analyses by BET, optical microscopy, and SEM showed the preservation of the fiber structure after grafting along with improved thermal stability disclosed by TGA. Zeta potential measurements showed that the Pos-βCD had a negative charge over the whole pH range. The successful grafting of β-CD onto pure cellulose and pure lignin showed that β-CD was grafted to both these two components of Pos. Adsorption of Paracetamol showed the potential of Pos-βCD bioadsorbents for the removal of pharmaceutical substances from contaminated water, providing an environmentally friendly and cost-effective alternative to conventional adsorbents. This work also highlights the valorization of marine biomass waste within a circular economy framework. Graphical Abstract

This study investigates the formation of inclusion complexes using the cyclodextrins, specifically HP-β-CD and HP-γ-CD, with bioactive molecules that mask the unpleasant tastes found in herbal extracts, such as horehound, eucalyptus, plantain, and thyme. The selected bioactive molecules (BAMs), including thymol, carvacrol, and eucalyptol, were subjected to inclusion complexation with host hydroxypropyl-cyclodextrins (HP-CDs) and studied by ¹H nuclear magnetic resonance (NMR) spectroscopy. The stoichiometry of the complexes was determined to be 1:1 (HP-CD:BAM). The analysis of ¹H chemical shift changes in BAM NMR spectra allowed the calculation of binding constants, indicating better stability with HP-γ-CD due to its larger cavity size and enhanced flexibility, which favors stronger and more stable inclusion with bioactive molecules. Two-dimensional rotating-frame Overhauser effect spectroscopy experiments provided insight into the binding mode. A simple thermodynamic model highlighted the hydrogen bonding contribution to complexation. Furthermore, the inclusion complex of the carvacrol and eucalyptol mixture showed that carvacrol consistently maintains the most stable complex, even in the presence of both active compounds combined with HP-CD.