Chemical derivatization strategies for enhancing the HPLC analytical performance of natural active triterpenoids

Development and Validation of a Highly Sensitive Isotope-Coded Equivalent Reporter Ion Assay for the Semi-Quantification of Isocoumarins in Complex Matrices

The accurate quantification of multicomponents using LC-MS is pivotal for ensuring the quality control of herbal medicine, as well as the investigation of their analysis of biological tissue distribution. However, two significant challenges persist: the scarcity of authentic standards and the selection of appropriate internal standards. In this study, we present a highly sensitive isotope-coded equivalent reporter ion assay (iERIA) that combines equivalently quantitative ion and isotope-coded derivatization strategies. This method offers triple functionality: enabling the semidetermination of multiple components using a single standard, introducing stable isotope-labeled internal standards, and enhancing MS detection signals. Using four isocoumarins as a model, namely, 5-carboxylmellein, 5-hydroxymethylmellein, 5-methylmellein, and 5-hydroxymellein, we successfully quantified these compounds across various matrices, including herbal extracts, plasma, urine, and liver tissue. Reporter ions at m/z 170 and 234 generated by the dansulfonyl derivatives of isocoumarins, were subsequently detected for calculating the concentrations of samples based on the equivalent ion method. It is very beneficial for trace detection in biological samples free of any concentration steps, with an increased LOD of 50 times after dansyl chloride derivatization. Additionally, the introduction of stable isotope-labeled internal standards using d6-dansyl chloride mitigated matrix effects and instrument drift, ensuring the accuracy and precision of the semiquantification. This practical UPLC-MS/MS strategy significantly expands the applicability of multicomponent determination, with promising implications in diverse domains such as herbal medicine active ingredient analysis, food function and safety assessment, and metabolomics research.

One-pot derivatization/magnetic solid-phase extraction combined with high-performance liquid chromatography-fluorescence detection for rapid analysis of biogenic amines in alcoholic beverages

The determination of biogenic amines (BAs) in alcoholic beverages is crucial for assessing their health impact, ensuring beverage quality, and guaranteeing safety. Herein, a rapid one-pot derivatization/magnetic solid-phase extraction (OPD/MSPE) method was proposed using 6-aminoquinolinyl-N-hydroxysuccinimide carbamate as the derivatization reagent and magnetic hydroxyl-functionalized multi-walled carbon nanotubes as the extraction material. Integration of derivatization and extraction steps simplifies the sample preparation process, taking only three minutes and eliminating the need for centrifugation by utilizing magnetic sorbent. The resulting desorption solution was directly analyzed by high-performance liquid chromatography-fluorescence detection (HPLC-FLD) without any evaporation or reconstitution steps. The integrated OPD/MSPE-HPLC-FLD method demonstrates excellent linearity (R2 > 0.992), accuracy (relative recoveries: 85.1-109.2%), precision (RSDs≤9.7%) and detection limits (limits of detection: 0.3-2 ng/mL). It has been successfully applied to determine free BAs in various alcoholic beverages, including red wine, Baijiu, Huangjiu, and beer. This method enables rapid, sensitive and precise analysis of BAs in alcoholic beverages.

Preparation of alkyl microporous organic network-based capillary column for an efficient gas chromatographic separation of position isomers

The large surface area, excellent thermal stability and easy modification make microporous organic networks (MONs) good candidates in the field of gas chromatography (GC). Due to the limited species and highly conjugated networks of MONs, their applications are still in infancy and restricted. To accelerate their developments and to enrich their types in GC, here we report the first example of synthesizing alkyl MON and its capillary column for GC separation of position isomers. Linear 1,8-dibromooctane is used as the alkyl monomer instead of traditional aromatic ones to construct novel alkyl MON to decrease the inherent conjugated characteristic of MONs. The alkyl MON exhibits good thermal stability (up to 350°C), large surface area (1173 m2 g-1), and non-polar character, allowing good resolution for alkanes, alkyl benzenes, alcohols, ketones, and diverse position isomers, including dichlorobenzene, trichlorobenzene, bromotoluene, nitrotoluene, methylbenzaldehyde, and ionone with the limits of detection (0.003 mg mL-1) and limits of quantitation of (0.10 mg mL-1). The in situ growth-prepared alkyl MON column demonstrates remarkable duration time and precisions for the retention relative standard deviations, (RSDs%, intra-day, n = 7), 0.06%-0.53% (intra-day, n = 7), and 2.87%-10.59% (column-to-column, n = 3). In addition, the fabricated alkyl MON-coated capillary column offers better resolution than three commercial GC columns for the resolution of methylbenzaldehyde, bromotoluene, and chlorotoluene isomers. This work reveals the practicability for synthesizing alkyl MONs and demonstrates their prospects for position isomers separation.

Click preparation of triazole-bridged teicoplanin-bound chiral stationary phases for efficient separating amino acid enantiomers

Enantioseparation of amino acids is considered as a challenging task due to the extreme structural similarity of their enantiomers. Herein, teicoplanin was modified with different chemical equivalents of azide groups and attached to silica particles by employing Click Chemistry for resolution of chiral amino acids for the first time. Interestingly, teicoplanin modified with 5-fold the chemical equivalent of azide groups (TK-2 CSP) exhibited superior amino acid separation ability compared to two other columns: one modified with only 1-fold the chemical equivalent of azide groups (TK-1 CSP), and the other modified with excess azide groups (TK-3 CSP). Additionally, the TK-2 CSP exhibited superior enantioselectivity when separating amino acids containing hydrophobic alkyl side chains in comparison to other teicoplanin-based CSPs. The TK-2 CSP column allows the baseline separation of 7 native amino acids. Molecular docking demonstrates that effective enantioseparation arises from distinct patterns of interaction between the host and guest molecules. Moreover, (p-methyl) phenylcarbaminoylated-teicoplanin CSP (TK-4, TK-5 CSP) were prepared by post-modification from TK-1 CSP and TK-2 CSP to isolate Fmoc-modified amino acids. This work explores the impact of various modification methods on the enantioseparation effects of host molecules and paves the way for expanding the potential applications of teicoplanin and macrocyclic glycopeptide molecules.

Natural antibacterial membranes prepared using Schisandra chinensis extracts and polyvinyl alcohol in an environment-friendly manner

Foodborne pathogens can cause food spoilage and lead to food safety issues. In recent years, food packaging has received a lot of attention. Traditional packaging membranes are non-biodegradable and remain in the environment for a long time. In this study, natural antimicrobial substances were extracted from Schisandra chinensis by a green extraction process using distilled water as the solvent, and the effects of different treatment on the antimicrobial activity of the extract were compared. At the same time, four types of Schisandra chinensis antimicrobial membranes were prepared using polyvinyl alcohol (PVA) as the substrate. The whole extraction and membrane preparation process did not involve organic solvents, making the process green and environment friendly. Material characterization included inverted biological microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), tensile strength test, pore size measurement, water uptake test, etc. Among them, no extract particles were observed with the naked eye on the surfaces of MⅡ and MⅣ. MⅡ has a uniformly transparent, nearly colorless morphology and is the most tensile. MⅣ surface is flat and smooth, the microstructure is dense and uniform. At the same time, the four types of membranes were tested against common pathogenic bacteria for 12 h, and the OD600 trend revealed the excellent antimicrobial activity of the membranes against S. aureus, MRSA, E. coli, and L. monocytogenes. The membranes could also be reused at least once. This study provides a new idea for preparing natural plant-based antimicrobial membranes.