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

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

Waters/Wyatt Optilab On-line Differential Refractometer

The Waters Optilab is a unique dRI detector for standard HPLC/GPC with 256 times the detection power and 50 times the dynamic range of every other RI detector for chromatography in existence today, making it a valuable addition to any MALS setup.

<h4>Independent of Chromaphores</h4>Independent of chromaphores or fluorophores, differential Refractive Index (dRI) detectors serve as accurate and versatile concentration detectors in all types of solvents. dRI is part of standard instrumentation for a variety of macromolecular characterization techniques including standard chromatography, SEC-MALS, FFF-MALS and CG-MALS.<h4>Unique dRI Detector</h4>The Optilab is a unique dRI detector for standard HPLC/GPC with 256 times the detection power and 50 times the dynamic range of every other RI detector for chromatography in existence today, making it a valuable addition to any MALS setup.<h4>Product Description</h4>Using a combination of cutting-edge semiconductor photodiode technology and proprietary computer algorithms, the Optilab achieves an unprecedented combination of sensitivity and range. These features mean that it addresses both standard chromatographic applications and some challenges unique to light scattering measurements such as high concentrations, determination of sample refractive increments (dn/dc) and solvent refractive index.<h5>Key Benefits</h5><ul><li>Extraordinary dRI measurement range, -0.0047 to +0.0047 RIU (comparable to 25 mg/mL protein in PBS)</li><li>Highly sensitive, ±7.5 x 10 -10 &nbsp;RIU across the entire measurement range</li><li>Measures solvent absolute refractive index, required for MALS calculations</li><li>Measures at the same wavelength as the MALS detector, for maximum accuracy in MALS calculations</li><li>Band broadening &lt; 20 µL preserves SEC resolution</li><li>Temperature range 4 °C to 65 °C for proteins and polymers that require a range of temperatures</li><li>High-resolution, touch-screen front panel displays data graphs and diagnostics, even with the host computer turned off</li></ul><h5>Unparalleled Features</h5>Even though the Optilab offers a dRI measurement range orders of magnitude beyond that of other dRI detectors, unlike other detectors there are no range or gain settings in the Optilab. The full range of instrument detection is always present, and the full sensitivity exists over the entire range.The Optilab can also do something no other on-line refractive index detector can: it can measure the absolute refractive index of a solution. In addition, it can measure the dn/dc of a solvent at the same wavelength of light as the light scattering instrument. And just to make sure it can't be matched, you can replace the light source in the Optilab for other wavelengths (e.g., 690, 633, 488, etc.) in just minutes!The Optilab can go below ambient temperatures as easily as above ambient. No hassle temperature control can be programmed from 4 °C to 65 °C. Compatible with all HPLC systems.<h4>Specifications</h4><h5>Measurement Capabilities – Differential Refractive Index</h5>Standard Optilab Configuration<ul><li>Measurement Range: –0.0047 to +0.0047 RIU</li><li>Peak-to-Peak Noise: ±7.5 × 10⁻¹⁰ RIU (Measured per ASTM-E1303-95 at 25 °C)</li></ul>High Concentration (HC) Option<ul><li>Measurement Range: –0.0026 to +0.034 RIU</li><li>Peak-to-Peak Noise: ±1.5 × 10⁻⁹ RIU (Optimized for higher concentration samples)</li><li>Response Time: User-selectable from 0.1 to 5 seconds</li><li>Absolute Refractive Index Measurement Range: 1.2 to 1.8 RIU</li><li>Absolute RI Sensitivity: ±0.002 RIU</li></ul>Fluidics and Flow Properties<ul><li>Band Broadening: &lt;12 µL</li><li>Fill Volume (Inlet Tubing + Flow Cell): 51.4 µL</li><li>Outlet Tubing Volume (0.030" ID): 370 µL</li></ul>Pressure Ratings<ul><li>Inlet Back Pressure (0.5 mL/min H₂O @ 20 °C): &lt;22 psi (1.5 bar)</li><li>Max Outlet Back Pressure: 30 psi (2 bar)</li></ul>Temperature Control<ul><li>Sample Temperature Control Range: 4 °C to 65 °C</li><li>Regulation Stability: ±0.005 °C</li></ul>Light Source Options<ul><li>Standard: 660 nm</li><li>HC Model (Optional): 488 nm, 785 nm, or 940 nm</li></ul>Safety Features<ul><li>Built-in vapor and liquid leak sensors for enhanced lab safety</li></ul>Electronics and Connectivity<ul><li>Digital Output: 22+ bit resolution @ 10 Hz</li><li>Analog Output: ±10 V or ±1 V, 18-bit resolution</li><li>Computer Interface: Ethernet</li></ul>Auxiliary I/O Ports<ul><li>Inputs:<ul><li>Analog In (16-bit, ±10 V A/D)</li><li>Zero dRI</li><li>Purge</li><li>Recycle In</li><li>Autoinject In</li><li>Alarm In</li></ul></li><li>Outputs:<ul><li>Autoinject Retransmit</li><li>Alarm Out</li><li>Recycle Out (controls Orbit™ valve switching)</li></ul></li></ul>User Interface<ul><li>Front Panel Display: 7” (178 mm) high-resolution multi-touch screen for viewing signals, diagnostics, and adjusting instrument settings</li></ul>Instrument Dimensions<ul><li>Size: 58 cm (L) × 36 cm (W) × 18 cm (H)</li></ul><h4>Other Refractive Index Detectors</h4><ul><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/1269">microOptilab™</a> - The first RI detector specifically designed for use with all UHPLC systems.</li></ul>

Waters/Wyatt microOptilab On-line Differential Refractometer

The Waters microOptilab brings the universal detection capabilities, unsurpassed concentration range, and superb sensitivity and linearity

<h4>Independent of Chromaphores</h4>Independent of chromaphores or fluorophores, differential Refractive Index (dRI) detectors measure concentrations of all types of samples in almost all solvents. The microOptilab brings the universal detection capabilities, unsurpassed concentration range, and superb sensitivity and linearity – familiar from the Optilab™ – to the domain of UHPLC.<h4>SEC-MALS with UHPLC</h4>Like standard SEC, UHPLC-SEC analysis relying on column calibration with molecular standards is unreliable when the standards do not accurately reflect your samples in terms of conformation, non-ideal (e.g., hydrophobic) column interactions or reversible association. SEC-MALS employs a microDAWN™ MALS detector downstream of the SEC column and UV detector, to determine molar mass / molecular weight distributions of macromolecules independently of column calibration.Refractive index detection is an important component of any SEC-MALS system, and necessary for analyzing conjugated proteins or polymers devoid of chromaphores. The microOptilab connects with the microDAWN MALS detector for a complete UHP-SEC-MALS setup that transfers the many benefits of SEC-MALS analysis to the realm of UHPLC.<h5>Key benefits</h5><ul><li>Very low band broadening, &lt; 4 µL, to maintain the resolution of very narrow UHPLC peaks</li><li>Extraordinary dRI measurement range, -4.7 x 10 -3 &nbsp;to +4.7 x 10 -3 &nbsp;RIU (comparable to 25 mg/mL protein in PBS)</li><li>Highly sensitive, ± 1.5 x 10 -9 &nbsp;RIU across the entire measurement range</li><li>Measures solvent refractive index, require for MALS calculations</li><li>Measures at the same wavelength as the MALS detector, for maximum accuracy in MALS calculations</li><li>Temperature range 4 °C to 65 °C for proteins and polymers that require a range of temperatures</li><li>High-resolution, touch-screen front panel displays data graphs and instrument diagnostics, even with the host computer turned off</li></ul><h5>Unparalleled features</h5><ul><li>Considering the extremely small peak volumes of UHPLC, band broadening in the microOptilab is kept to the absolute minimum, at less than 4 µL, as compared to 20 - 40 µL or more for standard RI detectors. As a result, the superior resolution from UHPLC columns and instruments will not be compromised with the microOptilab RI detector.</li><li>Even though the microOptilab offers a dRI measurement range orders of magnitude beyond that of other UHPLC dRI detectors, unlike other detectors there are no range or gain settings in the microOptilab. The full range of instrument detection is always present, and the full sensitivity exists over the entire range. The small flow cell and proprietary temperature regulation enable stable RI baselines and signals which further enhance the detector's sensitivity.</li><li>Unlike all other dRI detectors, the microOptilab also measures absolute refractive index in order to determine solvent RI, necessary in light scattering calculations and useful in assessing the accuracy of mixing of solvent gradients.</li><li>The microOptilab can be operated below ambient temperatures as easily as above ambient. No hassle temperature control can be programmed down to 4 °C or as high as 65 °C.</li><li>The microOptilab is compatible with all UHPLC systems.</li></ul><h4>Specifications</h4><h5>Measurement Capabilities – Differential Refractive Index</h5><ul><li>Differential RI Measurement Range: –0.0047 to +0.0047 RIU</li><li>Peak-to-Peak Noise: ±1.5 × 10⁻⁹ RIU (Measured per ASTM-E1303-95 at 25 °C with a 0.5 sec collection interval)</li><li>Response Time: User-selectable from 0.04 to 5 seconds</li><li>Absolute Refractive Index Range: 1.2 to 1.8 RIU</li><li>Absolute RI Sensitivity: ±0.002 RIU</li></ul>Fluidics and Flow Properties<ul><li>Band Broadening: &lt;4 µL (at 0.3 mL/min)</li><li>Fill Volume (Inlet Tubing + Flow Cell): 13.7 µL</li><li>Outlet Tubing Volume (0.030” ID): 228 µL</li></ul>Pressure Ratings<ul><li>Inlet Back Pressure (0.5 mL/min H₂O @ 20 °C): &lt;320 psi (22 bar)</li><li>Maximum Permissible Outlet Pressure: 30 psi (2 bar)</li></ul>Temperature Control<ul><li>Control Range: 4 °C to 65 °C</li><li>Stability: ±0.005 °C for precise thermal regulation</li></ul>Optical Source and Safety<ul><li>Light Source: 660 nm wavelength</li><li>Safety Sensors: Integrated vapor and liquid leak detection</li></ul>Electronics and Connectivity<ul><li>Digital Output Rate: 25 Hz</li><li>Analog Output: ±10 V or ±1 V, 18-bit resolution</li><li>Computer Interface: Ethernet for seamless data connectivity</li></ul>Auxiliary I/O Ports<ul><li>Inputs:<ul><li>Analog In (16-bit, ±10 V A/D)</li><li>Zero dRI</li><li>Purge</li><li>Recycle In</li><li>Autoinject In</li><li>Alarm In</li></ul></li><li>Outputs:<ul><li>Autoinject Retransmit</li><li>Alarm Out</li><li>Recycle Out (Orbit™ valve switching)</li></ul></li></ul>User Interface<ul><li>Display: 7” (178 mm) high-resolution multi-touch screen for viewing live signals, diagnostics, and configuring instrument settings</li></ul>Instrument Dimensions<ul><li>Size: 58 cm (L) × 36 cm (W) × 18 cm (H)</li></ul><h4>Other Refractive Index Detectors</h4><ul><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/1268">Optilab™</a> - A unique on-line differential refractometer for measuring concentration of any macromolecule, regardless of chromophores. Temperature controlled from 4 °C to 65 °C. The high-concentration option accommodates protein concentration up to 180 mg/mL.</li></ul>

Products from category Refractive Index deteectors (RI) focused on GPC/SEC distributed by Waters Corporation (Europe) - page 1

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