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

<div><div>Researchers led by <a target="_blank" rel="noopener noreferrer" href="https://kudova.group.uochb.cz/en">Eva Kudová</a> 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 Staphylococcus aureus.</div></div><div>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.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.These findings support the idea that rationally designed steroid-based molecules could act as antibiotic adjuvants, helping existing drugs overcome bacterial resistance.<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"><blockquote><h4>Original Article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0223523426001613?via%3Dihub">Steroidal hormones and neurosteroids - novel therapeutic strategies in bacterial infections: Design, synthesis, and biological evaluation</a></h4>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;Eur. J. Med. Chem., 2026, 308, 118716<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><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/">CC-BY 4.0</a></h6></blockquote><h4>Abstract</h4>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 Staphylococcus aureus. Structure-activity relationship analysis identified compounds 13 and 16 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 13 significantly downregulated S. aureus 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.<h4>Instrumentation</h4><h5>Structural characterization</h5><ul><li>AVANCE III 400 MHz NMR spectrometer (Bruker)</li><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?mainauthorItems=3&amp;search=LTQ+Orbitrap+XL">LTQ Orbitrap XL HRMS</a> (Thermo Fisher Scientific, ESI)</li></ul></div>

Steroidal hormones and neurosteroids – novel therapeutic strategies in bacterial infections

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.<h4>New biomarkers for metformin use</h4>A team led by Tomáš Čajka from the Laboratory of Translational Metabolism at IPHYS analyzed plasma samples from 637 patients with type 2 diabetes treated with metformin and 143 non-diabetic controls using advanced metabolomics and lipidomics. Among 614 detected metabolites, they identified five from the group of N-lactoyl-amino acids (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.<h4>A sensitive “fingerprint” of the drug’s effect</h4>N-Lactoyl-amino acids are formed in cells by combining lactate and amino acids, thus reflecting the metformin-induced changes in cellular energy metabolism. “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,” emphasizes T. Čajka.<h4>Metabolomics in practice and international collaboration</h4>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 Clinical and Experimental Medicine in Prague and the West Coast Metabolomics Center (University of California, Davis) also participated in the study.The results demonstrate that advanced metabolomics approaches developed at IPHYS within the CarDia project can find highly practical applications both in clinical studies and in personalized monitoring of treatment in patients with diabetes.<blockquote><h4>The original article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://ascpt.onlinelibrary.wiley.com/doi/10.1002/cpt.70205">Untargeted Metabolomics Identifies N-Lactoyl-Amino Acids as Dose-Responsive Plasma Biomarkers of Metformin Adherence in Type 2 Diabetes</a></h4>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 HaluzikClin Pharmacol Ther, 119: 1057-1069<a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1002/cpt.70205">https://doi.org/10.1002/cpt.70205</a><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/">CC-BY 4.0</a></h6></blockquote><h4>Abstract</h4>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.

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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KNAUER Eurospher II 100 C8 & C8A (U)HPLC Columns (USP L7)

C8 is a silica gel based stationary phase in reversed phase mode with alternative selectivity compared to C18 phases. 

Classical and hydrophilic/aqueous C8 columns for HPLC and UHPLC (USP L7)C8 is a silica gel based stationary phase in reversed phase mode with alternative selectivity compared to C18 phases. Compared to C18 phases, these columns show less retention due to the lower hydrophobicity.<ul><li>Ultra pure, spherical high performance HPLC phase based on silica gel</li><li>Monomeric C8 (Octyl) modification, standard endcapping, with 10 % carbon content (~ 50 % endcapping)</li></ul><h5>Properties</h5><ul><li>Separation mechanism: Hydrophobic interaction(lower compared to C18 phases)</li></ul><h5>Key features</h5><ul><li>Classical C8 phase, standard 50 % endcapping and 10 % carbon load, outstanding mechanical and chemical stability, suited for analytical as well as semi preparative and preparative applications.</li></ul><h5>Recommended application areas</h5><ul><li>Similar selectivity to C18 phase but less retention due to the lower hydrophobicity; useful for determination of:<ul><li>Water soluble vitamins</li><li>Steroids</li><li>Catecholamines</li><li>Sedatives</li></ul></li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_C8_rp_non_endcapped_3f7727d3fd.webp" alt="KNAUER: C8 RP Non-endcapped" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_C8_rp_non_endcapped_3f7727d3fd.webp 148w," sizes="100vw" width="304" height="321">Hydrophilic C8A phase offers an alternative, more polar selectivity. It is suited for highly polar reversed phase applications with up to 100 % aqueous mobile phases.&nbsp;<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_C8_A_e1f371165e.webp" alt="KNAUER: C8A" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_C8_A_e1f371165e.webp 198w," sizes="100vw" width="473" height="373"><blockquote>Tip: Caution! Even for short term storage all buffer solutions have to be rinsed from the column to prevent crystallization effects.</blockquote>Stationary phases Eurospher II 100 C8 and C8A are provided in these column types: analytical, semi-preparative and preparative.Eurospher II 100 C8 and C8A Analytical Columns are available with these parameters:<ul><li>Column length (mm): 50, 100, 150, 250</li><li>Column ID (mm): 2, 3, 4, 4.6</li><li>Particle size (µm): 2, 3, 5</li></ul>Eurospher II 100 C8 and C8A Semi-Preparative Standard Columns are available with these parameters:<ul><li>Column length (mm): 30, 50, 125, 150, 250</li><li>Column ID (mm): 8, 16</li><li>Particle size (µm): 5, 10</li></ul><h3>KNAUER (U)HPLC Columns</h3>Widest range of HPLC and UHPLC columns for all separation modes and applications.<ul><li>Safe Investment: Robust and reliable columns for attractive price&nbsp;</li><li>Separation Mode: Reversed Phase, HILIC, Normale</li><li>Simplicity: Easy purchase via our online store with fast delivery</li><li>Application: All-rounder for research or highly specialised for high-throughput analysis? We have the best column for your requirements.</li><li>Flexibility: Wide selection of column and particle sizes, for (U)HPLC applications up to 1000 bar</li></ul>KNAUER offers the perfect column for any small molecule separation. 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.<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>

KNAUER Eurosil Bioselect 300 C8 HPLC Columns (USP L7)

Eurosil Bioselect C8 has been specifically developed for the determination and purification of peptides, proteins, and oligonucleotides up to a molecular weight of approximately 20 kDa.

Analytical wide pore phase for the determination of biomolecules bigger than 5000 DaEurosil Bioselect C8 has been specifically developed for the determination and purification of peptides, proteins, and oligonucleotides up to a molecular weight of approximately 20 kDa.<h5>Properties</h5><ul><li>Ultra pure, spherical wide pore HPLC phase based on wide pore silica gel</li><li>Unpolar, monomeric C8 modification, endcapped</li><li>4.5 % carbon content (conventional endcapping)</li><li>Separation mechanism: hydrophobic interaction</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_C8_hydrosphob_6986c292b4.webp" alt="KNAUER: C8" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_C8_hydrosphob_6986c292b4.webp 144w," sizes="100vw" width="381" height="413"><h5>Recommended application areas</h5><ul><li>Hydrophilic biomolecules, peptides, peptide mapping after enzymatic digestion</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Eurosil_Bioselect_Phases_98acc32d0e.jpg" alt="KNAUER: Eurosil Bioselect - Phases and recommended sizes of molecules" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Eurosil_Bioselect_Phases_98acc32d0e.jpg 245w," sizes="100vw" width="1385" height="778"><h3>KNAUER Wide pore HPLC columns</h3>For enhanced resolution, capacity and recovery of proteins and other biomolecules<ul><li>Material: Silica or polymer particles</li><li>Separation Ranges: 2–100 kDa</li><li>Column Brands: Eurosil Bioselect or AppliChrom®</li><li>Particle sizes: 3–10 µm</li><li>Pore Sizes: 300 or 100–1000 Å</li><li>Specific surface: 90 ± 5 m2/g</li><li>Pore volume: 0.8 ml/g</li><li>Density: 450 g/l</li><li>Applications: Peptides exceeding approximately 50 amino acids and oligonucleotides greater than 25 residues</li><li>Customize: Bioanalysis requires a lot of flexibility in the pore size, the pH range, the temperatures and the solvents used. To achieve this, we cross phase limits.</li></ul><h4>Characteristics&nbsp;</h4><ul><li>Eurosil Bioselect columns are available in 4 modifications, useful for a wide range of separation tasks involving large molecules up to 100 000 Da.</li><li>Strict manufacturing procedures ensure a very narrow pore size distribution.</li><li>Interfering anions or heavy metal ions on the silica surface are not present in Eurosil Bioselect columns because only ultra pure silica gel and high quality chemical modifications are employed.</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Eurosil_Bioselect_85cfc2d201.jpg" alt="KNAUER: Eurosil Bioselect" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Eurosil_Bioselect_85cfc2d201.jpg 222w," sizes="100vw" width="1114" height="782"><h4>Separation mechanism of Eurosil Bioselect</h4>To separate larger molecules, they need to freely access the interior of the pores of the packing material. Therefore, the analytes’ diameter must be smaller than the average pore diameter.&nbsp;For higher molecular weight solutes, the use of lower pore size materials (60-120 Å) as typically used for the analysis of small molecules may result restricted diffusion in the material´s pores and therewith reduced column efficiency.&nbsp;<h4>Modifications</h4>The recommended modification of Eurosil Bioselect depends on the molecular weight of the analytes.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Eurosil_Bioselect_chemical_modifications_1fd5d87f7b.jpg" alt="KNAUER: Eurosil Bioselect - chemical modifications" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Eurosil_Bioselect_chemical_modifications_1fd5d87f7b.jpg 245w," sizes="100vw" width="955" height="505"> &nbsp;

KNAUER Eurospher II 100 C8 & C8A Prep HPLC Columns (USP L7)

Classical and hydrophilic/aqueous C8 columns for HPLC and UHPLC (USP L7)C8 is a silica gel based stationary phase in reversed phase mode with alternative selectivity compared to C18 phases. Compared to C18 phases, these columns show less retention due to the lower hydrophobicity.<ul><li>Ultra pure, spherical high performance HPLC phase based on silica gel</li><li>Monomeric C8 (Octyl) modification, standard endcapping, with 10 % carbon content (~ 50 % endcapping)</li></ul><h5>Properties</h5><ul><li>Separation mechanism: Hydrophobic interaction(lower compared to C18 phases)</li></ul><h5>Key features</h5><ul><li>Classical C8 phase, standard 50 % endcapping and 10 % carbon load, outstanding mechanical and chemical stability, suited for analytical as well as semi preparative and preparative applications.</li></ul><h5>Recommended application areas</h5><ul><li>Similar selectivity to C18 phase but less retention due to the lower hydrophobicity; useful for determination of:<ul><li>Water soluble vitamins</li><li>Steroids</li><li>Catecholamines</li><li>Sedatives</li></ul></li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_C8_rp_non_endcapped_3f7727d3fd.webp" alt="KNAUER: C8 RP Non-endcapped" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_C8_rp_non_endcapped_3f7727d3fd.webp 148w," sizes="100vw" width="304" height="321">Hydrophilic C8A phase offers an alternative, more polar selectivity. It is suited for highly polar reversed phase applications with up to 100 % aqueous mobile phases.&nbsp;<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_C8_A_e1f371165e.webp" alt="KNAUER: C8A" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_C8_A_e1f371165e.webp 198w," sizes="100vw" width="473" height="373"><blockquote>Tip: Caution! Even for short term storage all buffer solutions have to be rinsed from the column to prevent crystallization effects.</blockquote>Stationary phases Eurospher II 100 C8 and C8A are provided in these column types: analytical, semi-preparative and preparative.Eurospher II 100 C8 and C8A Preparative Standard Columns are available with these parameters:<ul><li>Column length (mm): 50, 150, 250</li><li>Column ID (mm): 20, 30, 50</li><li>Particle size (µm): 5, 10, 15</li></ul>Eurospher II 100 C8 and C8A Preparative dAX Columns with dynamic axial compression are available with these parameters:<ul><li>Column length (mm): 50, 150, 250</li><li>Column ID (mm): 25, 30, 50</li><li>Particle size (µm): 5, 10, 15</li></ul><h3>KNAUER Preparative HPLC Columns</h3>The right choice for all dimensions from semi-prep to batch chromatography to SMB.<ul><li>Modifications: Reversed Phase, HILIC, Normale Phase</li><li>Max. Pressure: 400–600 bar</li><li>Column Inner Diameter (ID): 16–50 mm in our shop, more on request</li><li>Column Brands: Eurospher, Eurospher II</li><li>Safe Investment: Robustness and durability based on superior technology</li><li>Application: Easy upscaling, as all materials are available from ultra high performance to preparative scale HPLC. You can also use our upscaling calculator.</li><li>Customizable: Standard flanged hardware &amp; dAX hardware with static or dynamic axial compression available</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Preparative_HPLC_Columns_31bc2477c3.webp" alt="KNAUER: KNAUER Preparative HPLC Columns" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Preparative_HPLC_Columns_31bc2477c3.webp 221w," sizes="100vw" width="1024" height="724"><h5>Preparative HPLC columns can be offered with two different hardware types:</h5><ul><li>Versatile standard flanged hardware for nearly any application task in batch chromatography</li><li>dAX Hardware with static and dynamic axial compression for an extended lifetime and multi-column chromatography like SMB processes</li></ul>

Products from category C8 HPLC columns focused on Consumables distributed by KNAUER - 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