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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Phenomenex Strata C8 Solid Phase Extraction (SPE)

An end-capped C8 sorbent that offers moderate hydrophobic retention with negligible secondary polar interactions from active silanol groups. 

Reversed Phase Solid Phase Extraction (SPE)An end-capped C8 sorbent that offers moderate hydrophobic retention with negligible secondary polar interactions from active silanol groups. &nbsp;Ideal for compounds that may interact too strongly with a C18 sorbent.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_C8_9efc4274c5.webp" alt="Phenomenex: Strata C8" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_C8_9efc4274c5.webp 245w," sizes="100vw" width="500" height="150"><ul><li>Surface Area (m²/g): -</li><li>Separation Mode: Reversed Phase</li><li>Particle Size: 25, 55</li><li>Recommended Use: Extraction of extremely hydrophobic compounds that are retained too tightly on C18-E.</li></ul><h4>Starting Method</h4><h5>Strata Reversed Phase</h5><ul><li>Condition: 1 mL Methanol</li><li>Equilibrate: 1 mL DI Water</li><li>Load: Pretreated sample</li><li>Wash: 1 mL 5% Methanol in DI Water, dry under vacuum for 2-5 min</li><li>Elute: 1 mL Methanol</li></ul>Based on 100 mg/1 mL sorbent mass. The above is a convenient starting point for SPE method development, further optimization may be required to tailor the method for your specific extraction needs.

Phenomenex Strata Phenyl Solid Phase Extraction (SPE)

A short alkyl chain with a phenyl group provides moderate hydrophobic selectivity and aromatic selectivity through π−π interactions.

Retention of Aromatic CompoundsA short alkyl chain with a phenyl group provides moderate hydrophobic selectivity and aromatic selectivity through π−π interactions.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_Phenyl_5bc4ec65e4.webp" alt="Phenomenex: Strata Phenyl" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_Phenyl_5bc4ec65e4.webp 245w," sizes="100vw" width="500" height="150"><ul><li>Surface Area (m²/g): 500</li><li>Separation Mode: Reversed Phase</li><li>Pore size: 70</li><li>Particle Size: 55</li><li>Recommended Use: Extraction of aromatic and hydrophobic compounds</li></ul><h4>Starting Method</h4><h5>Strata Reversed Phase</h5><ul><li>Condition: 1 mL Methanol</li><li>Equilibrate: 1 mL DI Water</li><li>Load: Pretreated sample</li><li>Wash: 1 mL 5% Methanol in DI Water, dry under vacuum for 2-5 min</li><li>Elute: 1 mL Methanol</li></ul>Based on 100 mg/1 mL sorbent mass. The above is a convenient starting point for SPE method development, further optimization may be required to tailor the method for your specific extraction needs.

Phenomenex Strata SDB-L Solid Phase Extraction (SPE)

A rugged polymer sorbent that is pH stable from 1-14 and offers hydrophobic and aromatic selectivity for reversed phase applications.

Styrene-Divinylbenzene Solid Phase Extraction (SPE) SorbentA rugged polymer sorbent that is pH stable from 1-14 and offers hydrophobic and aromatic selectivity for reversed phase applications.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_SDB_L_49e276aab1.jpg" alt="Phenomenex: Strata-SDB-L" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_SDB_L_49e276aab1.jpg 193w," sizes="100vw" width="208" height="168"><ul><li>Surface Area (m²/g): 500</li><li>Separation Mode: Reversed Phase</li><li>Pore size: 260</li><li>Particle Size: 100</li><li>Recommended Use: Extraction of hydrophobic and aromatic compounds</li></ul><h4>Starting Method</h4><h5>Strata Reversed Phase</h5><ul><li>Condition: 1 mL Methanol</li><li>Equilibrate: 1 mL DI Water</li><li>Load: Pretreated sample</li><li>Wash: 1 mL 5% Methanol in DI Water, dry under vacuum for 2-5 min</li><li>Elute: 1 mL Methanol</li></ul>Based on 100 mg/1 mL sorbent mass. The above is a convenient starting point for SPE method development, further optimization may be required to tailor the method for your specific extraction needs.

Phenomenex Strata Eco Screen Solid Phase Extraction (SPE)

This proprietary normal phase sorbent is topped with sodium sulfate to remove any excess water and is used for the extraction of hydrocarbons from environmental samples.

Specialty Solid Phase Extraction (SPE) SorbentThis proprietary normal phase sorbent is topped with sodium sulfate to remove any excess water and is used for the extraction of hydrocarbons from environmental samples, resulting in high recoveries of naphthalene.

Phenomenex Strata EPH Solid Phase Extraction (SPE)

This specialty normal phase sorbent was developed for the fractionation of aliphatic and aromatic hydrocarbons from environmental samples.

Specialty Solid Phase Extraction (SPE) SorbentThis specialty normal phase sorbent was developed for the fractionation of aliphatic and aromatic hydrocarbons from environmental samples.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_eph_6f99720a51.webp" alt="Phenomenex: Strata-EPH" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_eph_6f99720a51.webp 245w," sizes="100vw" width="500" height="150"><ul><li>Surface Area (m²/g): -</li><li>Separation Mode: Multi-mode</li><li>Particle Size: 200</li><li>Recommended Use: Fractionation of aliphatic and aromatic hydrocarbons from environmental samples</li></ul><h4>Starting Method</h4><h5>Strata EPH Normal Phase</h5><ul><li>Condition: IPA/DCM</li><li>Equilibrate: Hexane</li><li>Load: Pretreated sample</li><li>Wash: 5 % DCM in Hexane</li><li>Elute: 1:1 Hexane / DCM or 1:1 Hexane / IPA</li></ul>Based on 100 mg/1 mL sorbent mass. The above is a convenient starting point for SPE method development, further optimization may be required to tailor the method for your specific extraction needs.

Phenomenex Strata PAH Solid Phase Extraction (SPE)

Strata PAH is a proprietary sorbent designed to provide high recoveries of polycyclic aromatic hydrocarbons from water.

Specialty Solid Phase Extraction (SPE) SorbentStrata PAH (Polycyclic Aromatic Hydrocarbons) is a proprietary sorbent designed to provide high recoveries of polycyclic aromatic hydrocarbons from water (as specified in EPA Method 550.1) while simultaneously removing humic acids from the extract.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_pah_c48e1fab83.webp" alt="Phenomenex: Strata-PAH" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_pah_c48e1fab83.webp 245w," sizes="100vw" width="500" height="150"><ul><li>Surface Area (m²/g): -</li><li>Separation Mode: Reversed Phase</li><li>Particle Size: 55</li><li>Recommended Use: Extraction of polycyclic aromatic hydrocarbons from water (as specified in EPA Method 550.1) while simultaneously removing humic acids from the extract</li></ul>

Phenomenex Strata PFAS Solid Phase Extraction (SPE)

A new stacked cartridge able to offer 2x gains in productivity and reduce the need for multiple tubes, transfer steps, and wasted time. 

Specialty Solid Phase Extraction (SPE) SorbentA new stacked cartridge able to offer 2x gains in productivity and reduce the need for multiple tubes, transfer steps, and wasted time. This product is recommended to be used for EPA 1633 and DOD QSM 5.1/5.3 guidelines to minimize multiple sample but still provide high recoveries of low level PFAS (Per- and Polyfluoroalkyl Substances) in solid samples, soils, biota, sediments, or non-drinking water samples.<ul><li>Surface Area (m²/g): -</li><li>Separation Mode: Multi-Mode</li><li>Pore Size: 0</li><li>Recommended Use: for EPA 1633 and DOD QSM 5.1/5.3 applications for diverse matrices and non-drinking water PFAS applications</li></ul><h4>Stacked SPE Cartridges for Efficient PFAS Extraction</h4>Strata PFAS is a stacked solid phase extraction cartridge for EPA method 1633 and DOD QSM 5.1/5.3 applications.<ul><li>Reliable SPE with 2x gains in productivity</li><li>Reproducible extraction</li><li>Reduced need for multiple tubes, transfer steps, and wasted time</li></ul>

Phenomenex Strata CN Solid Phase Extraction (SPE)

Strata CN is a polar phase with slight hydrophobic selectivity in reversed phase mode and moderate polar selectivity in normal phase mode.

Normal Phase Solid Phase Extraction (SPE)A polar phase with slight hydrophobic selectivity in reversed phase mode and moderate polar selectivity in normal phase mode.<figure class="image"><img style="aspect-ratio:500/150;" src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_cn_769c96c476.webp" alt="Phenomenex: Strata-CN" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_cn_769c96c476.webp 245w," sizes="100vw" width="500" height="150"></figure><ul><li>Surface Area (m²/g): -</li><li>Separation Mode: Normal Phase</li><li>Particle Size: 55</li><li>Recommended Use: Extraction of polar compounds such as those that contain hydroxyl groups.</li></ul><h4>Starting Method</h4><ul><li>Condition: IPA/DCM</li><li>Equilibrate: Hexane</li><li>Load: Pretreated sample</li><li>Wash: 5 % DCM in Hexane</li><li>Elute: 1:1 Hexane / DCM or 1:1 Hexane / IPA</li></ul>Based on 100 mg/1 mL sorbent mass. The above is a convenient starting point for SPE method development, further optimization may be required to tailor the method for your specific extraction needs.

Phenomenex Strata Silica (Si-1) Solid Phase Extraction (SPE)

Strata Silica (Si-1) is a normal phase SPE sorbent with unbonded silica particle that offers strong polar selectivity.

Normal Phase Solid Phase Extraction (SPE)A polar phase with slight hydrophobic selectivity in reversed phase mode and moderate polar selectivity in normal phase mode.<figure class="image"><img style="aspect-ratio:500/150;" src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Phenomenex_Strata_si_e4eb885006.webp" alt="Phenomenex: Strata-Silica (Si-1)" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Phenomenex_Strata_si_e4eb885006.webp 245w," sizes="100vw" width="500" height="150"></figure><ul><li>Surface Area (m²/g): 550, m²/g, null m²/g, 490 m²/g</li><li>Separation Mode: Normal Phase</li><li>Pore Size: 70</li><li>Particle Size: 55</li><li>Recommended Use: Extraction of polar compounds that are similar in structure</li></ul><h4>Starting Method</h4><h5>Strata Normal Phase Method</h5><ul><li>Condition: IPA/DCM</li><li>Equilibrate: Hexane</li><li>Load: Pretreated sample</li><li>Wash: 5 % DCM in Hexane</li><li>Elute: 1:1 Hexane / DCM or 1:1 Hexane / IPA</li></ul>Based on 100 mg/1 mL sorbent mass. The above is a convenient starting point for SPE method development, further optimization may be required to tailor the method for your specific extraction needs.

Phenomenex Strata Melamine Solid Phase Extraction (SPE)

A proprietary phase that allows for the simultaneous extraction of melamine and cyanuric acid out of food and biological samples.

Specialty Solid Phase Extraction (SPE) SorbentA proprietary phase that allows for the simultaneous extraction of melamine and cyanuric acid out of food and biological samples.

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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