EU Regulation 396/2005: Pesticide Residue Testing and the Critical Role of QuEChERS Evaporation in Food Safety

<div><div><p><strong>Researchers led by </strong><a target="_blank" rel="noopener noreferrer" href="https://kudova.group.uochb.cz/en"><strong>Eva Kudová</strong></a><strong> from IOCB Prague and Jitka Viktorová from UCT Prague have identified new androstane-based steroid derivatives that can significantly improve the effectiveness of existing antibiotics against multidrug-resistant </strong><i><strong>Staphylococcus aureus</strong></i><strong>.</strong></p></div></div><div><p>The team screened dozens of natural steroidal hormones and synthetic derivatives to see whether they could block bacterial efflux pumps – mechanisms that bacteria use to eject antibiotics and survive treatment. Two compounds emerged as particularly promising: they inhibited efflux pumps and lowered the effective doses of antibiotics such as ciprofloxacin and erythromycin.</p><p>Further analysis showed that one of the compounds also suppressed genes linked to bacterial virulence. Another key finding is that the most active molecules are non-toxic to human immune cells and showed no detectable endocrine activity, suggesting a favorable safety profile.</p><p>These findings support the idea that rationally designed steroid-based molecules could act as antibiotic adjuvants, helping existing drugs overcome bacterial resistance.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/IOCB_Prague_Steroidal_hormones_and_neurosteroids_novel_therapeutic_strategies_in_bacterial_infections_8e5d2a7b48.jpg" alt="IOCB Prague: Steroidal hormones and neurosteroids – novel therapeutic strategies in bacterial infections" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_IOCB_Prague_Steroidal_hormones_and_neurosteroids_novel_therapeutic_strategies_in_bacterial_infections_8e5d2a7b48.jpg 222w," sizes="100vw" width="1258" height="886"></p><blockquote><h4><strong>Original Article</strong></h4><h4><a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0223523426001613?via%3Dihub"><strong>Steroidal hormones and neurosteroids - novel therapeutic strategies in bacterial infections: Design, synthesis, and biological evaluation</strong></a></h4><p>Daniela Brdová, Bára Křížkovská, Jan Špaček, Zdeněk Míchal, Eva Jablonská, Ondřej Strnad, Hana Chodounská, Eszter Szánti-Pintér, Marina Morozovová, Václav Hanžl, Jan Tkadlec, Martijn Riool, Jan Lipov, Jitka Viktorová, Eva Kudová&nbsp;</p><p><i><strong>Eur. J. Med. Chem., 2026, 308, 118716</strong></i></p><p><a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1016/j.ejmech.2026.118716">https://doi.org/10.1016/j.ejmech.2026.118716</a></p><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/"><strong>CC-BY 4.0</strong></a></h6></blockquote><h4><strong>Abstract</strong></h4><p>The global rise of antibiotic resistance necessitates novel therapeutic strategies for infectious diseases. Inhibition of bacterial efflux pumps, which contribute to multidrug resistance, represents a promising approach to restore or even increase the efficacy of existing antibiotics. Using fluorescence-based ethidium bromide accumulation, broth microdilution, and checkerboard assays, we evaluated 26 endogenous steroidal hormones and neurosteroids, along with 30 synthetic derivatives, for their ability to enhance antibiotic susceptibility in multidrug-resistant <i>Staphylococcus aureus</i>. Structure-activity relationship analysis identified compounds <strong>13</strong> and <strong>16</strong> as lead candidates, exhibiting strong efflux pump inhibition and marked reductions in the minimum inhibitory concentrations of ciprofloxacin and erythromycin. Both compounds showed additive effects in checkerboard assays. Modifications at C-3 (polar substitution) and C-17 (3α,5β-stereochemistry and nonpolar substitution) were essential for potent efflux inhibition and sensitization, although these modifications were not additive when combined. Transcriptome analysis further revealed that compound <strong>13</strong> significantly downregulated <i>S. aureus</i> virulence-associated genes when administered alone or in combination with antibiotics. Cytotoxicity assessment in human peripheral blood mononuclear cells and receptor transactivation assays for estrogen, androgen, and progesterone receptors indicated that the most active derivatives were non-toxic and lacked detectable endocrine activity, suggesting a favorable safety profile. Overall, these findings support the concept that rationally designed andostane-based steroidal scaffolds can function as competitive bacterial efflux pump inhibitors and serve as potential antibiotic adjuvants to mitigate efflux-mediated resistance.</p><h4><strong>Instrumentation</strong></h4><h5><strong>Structural characterization</strong></h5><ul><li><strong>AVANCE III 400 MHz NMR spectrometer</strong> (Bruker)</li><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?mainauthorItems=3&amp;search=LTQ+Orbitrap+XL"><strong>LTQ Orbitrap XL HRMS</strong></a> (Thermo Fisher Scientific, ESI)</li></ul></div>

Steroidal hormones and neurosteroids – novel therapeutic strategies in bacterial infections

<p><strong>Metformin is currently the first-line oral drug of choice for the treatment of type 2 diabetes. It reduces glucose production in the liver, improves tissue sensitivity to insulin, and does not cause weight gain or hypoglycemia, which sets it apart from some other antidiabetic drugs. Moreover, its long-term beneficial effects on the risk of cardiovascular complications and mortality in people with type 2 diabetes have been well established. Researchers from the Institute of Physiology CAS (IPHYS) have identified a new group of blood metabolites that could help physicians objectively monitor whether patients with type 2 diabetes are taking their metformin as prescribed.</strong></p><h4><strong>New biomarkers for metformin use</strong></h4><p>A team led by Tomáš Čajka from the Laboratory of Translational Metabolism at IPHYS analyzed plasma samples from <strong>637 patients with type 2 diabetes treated with metformin</strong> and <strong>143 non-diabetic controls</strong> using advanced metabolomics and lipidomics. Among 614 detected metabolites, they identified five from the group of <strong>N-lactoyl-amino acids </strong>(e.g. N‑lactoyl-phenylalanine), which had previously been seen as unknown signals due to missing reference spectra in databases. The levels of these metabolites in the blood closely reflected the plasma concentrations of metformin. In patients with the highest metformin exposure, the concentrations of these metabolites were up to 7.2 times higher than in controls.</p><h4><strong>A sensitive “fingerprint” of the drug’s effect</strong></h4><p>N-Lactoyl-amino acids are formed in cells by combining lactate and amino acids, thus reflecting the metformin-induced changes in cellular energy metabolism. “<i>Importantly, even though they occur in plasma only at nanomolar concentrations, they reliably distinguish patients who take metformin regularly from those who take it irregularly or not at all</i>,” emphasizes T. Čajka.</p><h4><strong>Metabolomics in practice and international collaboration</strong></h4><p>The study also provides a detailed description of broader metabolic changes in type 2 diabetes, including increases in lactate, organic acids, and branched-chain amino acids, as well as extensive remodelling of the lipid profile. In addition to T. Čajka’s team, collaborators from the Institute for <strong>Clinical and Experimental Medicine in Prague</strong> and the <strong>West Coast Metabolomics Center</strong> (University of California, Davis) also participated in the study.</p><p>The results demonstrate that advanced metabolomics approaches developed at IPHYS within the <strong>CarDia project</strong> can find highly practical applications both in clinical studies and in personalized monitoring of treatment in patients with diabetes.</p><blockquote><h4><strong>The original article</strong></h4><h4><a target="_blank" rel="noopener noreferrer" href="https://ascpt.onlinelibrary.wiley.com/doi/10.1002/cpt.70205"><strong>Untargeted Metabolomics Identifies N-Lactoyl-Amino Acids as Dose-Responsive Plasma Biomarkers of Metformin Adherence in Type 2 Diabetes</strong></a></h4><p>Tomas Cajka, Jiri Hricko, Lucie Rudl Kulhava, Michaela Paucova, Michaela Novakova, Veronika Hola, Stanislava Rakusanova, Oliver Fiehn, Vojtech Skop, Ivana Lankova, Iva Miskova, Terezie Pelikanova, Martin Haluzik</p><p>Clin Pharmacol Ther, 119: 1057-1069</p><p><a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1002/cpt.70205">https://doi.org/10.1002/cpt.70205</a></p><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/"><strong>CC-BY 4.0</strong></a></h6></blockquote><h4><strong>Abstract</strong></h4><p>Metformin is the most widely prescribed antidiabetic drug, yet adherence remains difficult to objectively assess. Using untargeted metabolomics and lipidomics, we analyzed plasma from 637 patients with type 2 diabetes (T2D) with confirmed metformin use and 143 nondiabetic controls, annotating 614 metabolites. Patients were stratified by plasma metformin into sub-therapeutic, therapeutic, and supra-therapeutic groups, and associations were evaluated by multiple linear regression and composite metabolite ranking. Five previously unannotated features were structurally identified as N-lactoyl-amino acids, whose levels correlated strongly with plasma metformin (ρ = 0.42–0.55, P &lt; 0.0001) and increased up to 7.2-fold in the supra-therapeutic group (&gt; 2000 ng/mL). While N-lactoyl-amino acids were consistently detected in the nanomolar range, they still displayed robust and dose-dependent associations with metformin. Broader metabolic changes in T2D included elevated lactate, organic acids, and branched-chain amino acids, together with reduced urea cycle metabolites. Lipidomics showed increases in saturated triacylglycerols and diacylglycerols and decreases in cholesteryl esters, sphingomyelins, and phospholipids. These findings establish N-lactoyl-amino acids as robust, dose-responsive plasma biomarkers of metformin exposure. Despite being up to four orders of magnitude less abundant than their amino acid precursors, they sensitively reflect mitochondrial lactate overflow and pharmacodynamic adaptation, offering objective assessment of adherence.</p>

New blood biomarkers reveal how faithfully diabetes patients take metformin

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The Czech Academy of Sciences (CAS) was established by Act No. 283/1992 Coll. as the Czech successor of the former Czechoslovak Academy of Sciences. It is set up as a complex of 54 public research institutions.

Czech Academy of Sciences

The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague) is a leading scientific institution in the Czech Republic, recognized internationally. Its primary mission is basic research in the fields of chemical biology and medicinal chemistry, organic and material oriented chemistry, chemistry of natural compounds, biochemistry and molecular biology, physical chemistry, theoretical chemistry, and analytical chemistry. 

Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences

Organomation, founded in 1959, designs and manufactures high-quality nitrogen evaporators and extraction systems. Known for innovation and durability, their lab instruments are used globally for efficient sample preparation with strong customer support.

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Thermo Scientific QuEChERS Sample Preparation Kits

QuEChERS is a versatile sample preparation method for analyzing pesticides, veterinary drugs, and other residues in various sample types before GC-MS or LC-MS analysis.

<div><div><div><h3><strong>QuEChERS sample preparation—now easier, more convenient, and affordable</strong></h3><p><strong>QuEChERS</strong> (<strong><u>Q</u></strong><u>u</u>ick, <strong><u>E</u></strong>asy, <strong><u>C</u></strong>heap, <strong><u>E</u></strong>ffective, <strong><u>R</u></strong>ugged, and <strong><u>S</u></strong>afe)is a <strong>sample preparation method</strong> that was initially developed in 2003 for <strong>analyzing veterinary drugs in food</strong>. The method was also tested for <strong>pesticide residue analysis in plant material</strong> with great success. In 2003, the <strong>detailed method was published</strong> in the journal AOAC International. Since then, the QuEChERS method has evolved into a <strong>sample preparation technique used on a variety of analytes</strong> in an <strong>expanding number of sample types</strong> before analysis by <a target="_blank" rel="noopener noreferrer" href="https://www.thermofisher.com/cz/en/home/industrial/mass-spectrometry/gas-chromatography-mass-spectrometry-gc-ms.html"><strong>GC-MS</strong></a><strong> or </strong><a target="_blank" rel="noopener noreferrer" href="https://www.thermofisher.com/cz/en/home/industrial/mass-spectrometry/liquid-chromatography-mass-spectrometry-lc-ms.html"><strong>LC-MS</strong></a>.</p><p><strong>Thermo Scientific QuEChERS kits</strong> contain <strong>pre-packaged, ready-weighed salts, sorbents, and buffers</strong> to <strong>streamline your workflow</strong> and <strong>minimize the potential for error</strong>. The kits are grouped according to your <strong>analytes of interest</strong>, <strong>sample matrix</strong>, and <strong>preferred QuEChERS method</strong>:</p><ul><li><strong>Original 2003 Method</strong></li><li><strong>AOAC 2007.01 Method</strong></li><li><strong>EN 15662 Method</strong></li><li><strong>NY/T 1380-2007 Method</strong></li></ul><p><strong>Complete packages</strong>—including both <strong>extraction and clean-up kits</strong>—are available. <strong>Extraction-only and cleanup-only kits</strong> are also offered to suit your laboratory’s sample preparation needs. These <strong>pre-packaged kits save time and money</strong>, make QuEChERS procedures <strong>easier and more convenient</strong>, and ensure <strong>quality to yield reproducible results</strong> and <strong>excellent recoveries</strong> for a wide variety of analytes.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Thermo_Scientific_Qu_E_Ch_ERS_Sample_Preparation_Kits_2_1e99f0c81b.jpg" alt="Thermo Scientific QuEChERS Sample Preparation Kits" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Thermo_Scientific_Qu_E_Ch_ERS_Sample_Preparation_Kits_2_1e99f0c81b.jpg 217w," sizes="100vw" width="891" height="640"></p><h3><strong>Typical QuEChERS workflow</strong></h3><div><div><div><div><div><p>As shown in the workflow diagram below, the <strong>QuEChERS method has four basic steps</strong>:</p><ol><li><strong>Homogenize sample</strong> (fruit or vegetable)</li><li><strong>Extract analytes of interest</strong> from a sample using <strong>extraction salts</strong> (pesticide residues, veterinary drugs, and/or mycotoxins)</li><li><strong>Clean-up the resulting supernatant</strong> using <strong>dispersive solid phase extraction (dSPE)</strong></li><li><strong>Analyze by GC-MS or LC-MS</strong></li></ol><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Thermo_Scientific_Qu_E_Ch_ERS_Sample_Preparation_Kits_496491ceff.jpeg" alt="Thermo Scientific QuEChERS Sample Preparation Kits" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Thermo_Scientific_Qu_E_Ch_ERS_Sample_Preparation_Kits_496491ceff.jpeg 245w," sizes="100vw" width="1170" height="706"></p><div><h3><strong>QuEChERS products</strong></h3></div><div><h4><strong>QuEChERS extraction kits for original 2003 method</strong></h4></div><div><p>The <strong>original QuEChERS method</strong> (Anastassiades et al, 2003) was developed by <strong>Steven J. Lehotay and Michelangelo Anastassiades</strong> in 2003 for the <strong>determination of pesticide residues in fruits and vegetables</strong>. The original method was created to <strong>analyze non-base-sensitive compounds</strong> and uses a <strong>sodium chloride buffer</strong> to <strong>reduce polar interferences</strong> and <strong>enhance extraction</strong>. <strong>Buffering</strong> is an important part of the QuEChERS procedure because it <strong>allows for analysis of pesticides and other residues</strong> that display <strong>pH dependence in their recoveries</strong>, depending on the <strong>sample matrix</strong>. <strong>Three different extraction kits</strong> are available to support the <strong>original 2003 QuEChERS method</strong>.</p><h5><strong>Chemicals used in the original 2003 method</strong></h5></div><ul><li><strong>Acetonitrile:</strong> Used to perform single-phase extraction (SPE) on a sample</li><li><strong>Anhydrous MgSO₄:</strong> Induces phase separation between water content in sample and acetonitrile layer during liquid-liquid partitioning step; removes remaining water from sample during dispersive solid phase extraction (dSPE) step</li><li><strong>NaCl:</strong> Induces phase separation between water content in sample and acetonitrile layer during liquid-liquid partitioning step; removes residual water from sample; reduces polar interference and enhances extraction</li><li><strong>PSA:</strong> Primary secondary amine, used to remove polar matrix components, citric co-extractives, and free fatty acids, from sample during dispersive solid phase extraction (dSPE) step</li></ul><div><h4><strong>QuEChERS extraction and clean-up kits for AOAC 2007.01 method</strong></h4><p>The <strong>AOAC 2007.01 QuEChERS Method</strong> was developed by <strong>Steven J. Lehotay and his co-workers</strong>, who <strong>modified the original 2003 method</strong> to accommodate the use of <strong>acetate buffering at higher concentration</strong> for <strong>greater buffering strength</strong>. <strong>Buffering</strong> is an important part of the QuEChERS procedure because it <strong>allows for analysis of pesticides and other residues</strong> that display <strong>pH dependence in their recoveries</strong>, depending on the <strong>sample matrix</strong>. These <strong>extraction and clean-up products</strong> here support the <strong>AOAC 2007.01 method</strong>.</p><div><h5><strong>Chemicals used in the AOAC 2007.01 method</strong></h5><ul><li><strong>Acetonitrile:</strong> Used to perform single-phase extraction on a sample</li><li><strong>Anhydrous MgSO₄:</strong> Induces phase separation between water content in sample and acetonitrile layer during liquid-liquid partitioning step; removes remaining water from sample during dispersive solid phase extraction (dSPE) step</li><li><strong>NaOAc:</strong> Buffers the sample to stabilize pH</li><li><strong>PSA:</strong> Primary secondary amine, used to remove polar matrix components, citric co-extractives, and free fatty acids, from sample during dispersive solid phase extraction (dSPE) step</li><li><strong>C18:</strong> Removes fats, sterols, and other non-polar interferences from sample</li><li><strong>GCB:</strong> Graphitized carbon black, removes pigment (<i>not recommended for use with planar pesticides</i>)</li></ul><div><h4><strong>QuEChERS extraction and clean-up kits for EN 15662 method</strong></h4><p>The <strong>extraction and clean-up products</strong> here support the <strong>EN 15662 method</strong>. <strong>Widely used in Europe</strong>, the EN 15662 method was developed by <strong>Michelangelo Anastassiades and co-workers</strong>, who <strong>modified the original 2003 method</strong> to accommodate the use of <strong>citrate buffering at a relatively low buffering capacity</strong>. This variation uses a <strong>sodium chloride buffer</strong> to <strong>minimize polar interferences</strong> in addition to <strong>sodium citrate dihydrate</strong> and <strong>disodium citrate sesquihydrate buffers</strong>. <strong>Buffering</strong> is an important part of the QuEChERS procedure because it <strong>allows for analysis of pesticides and other residues</strong> that display <strong>pH dependence in their recoveries</strong>, depending on the <strong>sample matrix</strong>.</p><h5><strong>Chemicals used in the EN 15662 method</strong></h5><ul><li><strong>Acetonitrile:</strong> Used to perform single-phase extraction on a sample</li><li><strong>Anhydrous MgSO₄:</strong> Induces phase separation between water content in sample and acetonitrile layer during liquid-liquid partitioning step; removes remaining water from sample during dispersive solid phase extraction (dSPE) step</li><li><strong>NaCl:</strong> Induces phase separation between water content in sample and acetonitrile layer during liquid-liquid partitioning step; removes residual water from sample</li><li><strong>Trisodium Citrate:</strong> Buffers the sample to stabilize pH</li><li><strong>Disodium Citrate Sesquihydrate:</strong> Buffers the sample to stabilize pH</li><li><strong>PSA:</strong> Primary secondary amine, used to remove polar matrix components, citric co-extractives, and free fatty acids, from sample during dispersive solid phase extraction (dSPE) step</li><li><strong>C18:</strong> Removes fats, sterols, and other non-polar interferences from sample</li><li><strong>GCB:</strong> Graphitized carbon black, removes pigment (<i>not recommended for use with planar pesticides</i>)</li></ul><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Thermo_Scientific_Qu_E_Ch_ERS_Sample_Preparation_Kits_3_721562526f.jpg" alt="Thermo Scientific QuEChERS Sample Preparation Kits" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Thermo_Scientific_Qu_E_Ch_ERS_Sample_Preparation_Kits_3_721562526f.jpg 245w," sizes="100vw" width="1471" height="488"></p><div><h4><strong>QuEChERS clean-up kit for NY/T 1380-2007 method</strong></h4></div><div><p>The <strong>NY/T 1380-2007 method</strong> is <strong>recommended by China Ministry of Agriculture</strong> for the <strong>QuEChERS Method sample preparation</strong> of <strong>51 specific pesticide residues</strong> in <strong>fruits and vegetables</strong> with <strong>analysis by GC-MS</strong>.</p><h5><strong>Chemicals used in the NY/T 1380-2007 method</strong></h5><ul><li><strong>Anhydrous MgSO₄:</strong> Induces phase separation between water content in sample and acetonitrile layer during liquid-liquid partitioning step; removes remaining water from sample during dispersive solid phase extraction (dSPE) step</li><li><strong>PSA:</strong> Primary secondary amine, used to remove polar matrix components, citric co-extractives, and free fatty acids, from sample during dSPE step</li><li><strong>C18:</strong> Removes fats, sterols, and other non-polar interferences from sample</li></ul></div></div></div></div></div></div></div></div></div></div></div></div>

Products from category SPE sample preparation from Thermo Fisher Scientific - page 1

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New blood biomarkers reveal how faithfully diabetes patients take metformin

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EU Regulation 396/2005: Pesticide Residue Testing and the Critical Role of QuEChERS Evaporation in Food Safety