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

Article

Product

Environment

Food

Health

Scientific article

Science and research

Laboratories

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.

Organomation

KNAUER Eurospher II 100 C18P (U)HPLC Columns (USP L1)

KNAUER´s most unpolar C18P phase with excellent shape selectivity. It features polymeric, high efficiency endcapping of 99 % and 20 % carbon content, exceptional pH stability in the range of 1–12.

<p class="cke-user_style-important"><strong>C18P columns with trifunctional modifications (USP L1): Hydrophobic and stearic interactions</strong></p><p><strong>KNAUER´s most unpolar C18P phase</strong> with excellent shape selectivity. It features polymeric, high efficiency endcapping of <strong>99 % and 20 % carbon content</strong>, exceptional <strong>pH stability</strong> in the range of <strong>1–12</strong>, and outstanding mechanical and chemical stability.</p><h5><strong>Properties</strong></h5><ul><li><strong>Separation mechanism</strong>: Hydrophobic and stearic interaction</li><li><strong>Ultra pure, </strong>spherical high performance HPLC phase based on silica gel</li><li><strong>Unpolar, trifunctional C18 (</strong>Octadecyl) modification, high efficiency endcapping, with 20 % carbon content (~ 99 % endcapping)&nbsp;</li></ul><h5><strong>Key features</strong></h5><ul><li>KNAUER´s most unpolar C18 phase, polymeric, high efficiency endcapping of 99 % and 20 % carbon content, higher pH stability in the range of 1-12, outstanding mechanical and chemical stability, suited for analytical as well as semi preparative and preparative applications.</li></ul><h5><strong>Recommended application areas</strong></h5><ul><li>Alternative selectivity to standard C18; stationary phase in Eurospher II C18 family with the highest carbon load; fully endcapped; excellent shape selectivity and pH stability.</li></ul><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_C18_P_f093126fa9.webp" alt="KNAUER: C18P" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_C18_P_f093126fa9.webp 245w," sizes="100vw" width="278" height="174"></p><blockquote><p><strong>Tip: </strong>Not all C18 phases are comparable! When replacing an existing column, always have a close look at the characteristics like carbon load, pore size and specific surface area.</p></blockquote><p class="cke-user_style-important"><strong>Stationary phase Eurospher II 100 C18P is provided in these column types: </strong>analytical, semi-preparative and preparative.</p><p><strong>Eurospher II 100 C18P Analytical Columns </strong>are available with these parameters:</p><ul><li><strong>Column length (mm): </strong>50, 100, 150, 250</li><li><strong>Column ID (mm): </strong>2, 3, 4, 4.6</li><li><strong>Particle size (µm): </strong>2, 3, 5</li></ul><p><strong>Eurospher II 100 C18P Semi-Preparative Standard Columns </strong>are available with these parameters:</p><ul><li><strong>Column length (mm): </strong>30,<strong> </strong>50, 125, 150, 250</li><li><strong>Column ID (mm): </strong>8, 16</li><li><strong>Particle size (µm): </strong>5, 10</li></ul><h3><strong>KNAUER (U)HPLC Columns</strong></h3><p><strong>Widest range of HPLC and UHPLC columns for all separation modes and applications.</strong></p><ul><li><strong>Safe Investment</strong>: Robust and reliable columns for attractive price&nbsp;</li><li><strong>Separation Mode</strong>: Reversed Phase, HILIC, Normale</li><li><strong>Simplicity: </strong>Easy purchase via our online store with fast delivery</li><li><strong>Application: </strong>All-rounder for research or highly specialised for high-throughput analysis? We have the best column for your requirements.</li><li><strong>Flexibility:</strong> Wide selection of column and particle sizes, for (U)HPLC applications up to 1000 bar</li></ul><p><strong>KNAUER offers the perfect column for any small molecule separation.</strong> No matter which separation mode, molecule and the mobile phase, we offer a suitable (U)HPLC stationary phase. Choose from a wide range of modifications, particle sizes and column dimensions to suit your application. To elongate the lifetime of your column, you can choose to use a suitable precolumn.</p><figure class="image"><img style="aspect-ratio:787/674;" src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_KNAUER_U_HPLC_C8_and_C8_A_Columns_083c60f401.webp" alt="KNAUER: KNAUER (U)HPLC Columns" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_KNAUER_U_HPLC_C8_and_C8_A_Columns_083c60f401.webp 182w," sizes="100vw" width="787" height="674"></figure>

Products from category C18 HPLC columns distributed by KNAUER - page 2

Related content

New blood biomarkers reveal how faithfully diabetes patients take metformin

Steroidal hormones and neurosteroids – novel therapeutic strategies in bacterial infections

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