Double Bond In Ring Research Articles

Screening and Characterization of a Chryseobacterium timonianum Strain with Aflatoxin B1 Removal Ability.

Aflatoxin B1 (AFB1) is a potent hepatocarcinogenic mycotoxin found in animal feed and human food components. AFB1 contamination poses severe food safety and economic consequences. In this study, we used a coumarin-selective medium to isolate bacterial strains that can remove AFB1. Among the isolated bacterial strains, strain c4a exhibited the highest AFB1 removal activity. This strain was subjected to biochemical and phylogenetic characterization. The AFB1 removal activity of the extracellular supernatant of this strain was optimized for growth medium, reaction temperature, pH, and metal ions. The degradation products were analyzed using UPLC-ESI MS/MS. Strain c4a was found to be most closely related to Chryseobacterium timonianum. The extracellular supernatant of C. timonianum c4a grown in a modified nutrient broth (with gelatin peptone and beef extract in a 4:1 ratio) demonstrated the highest AFB1 removal activity when incubated with 1 ppm AFB1 at 60°C, pH 8, and Mn2+ or Mg2+ supplementation for 72 h. Surprisingly, the autoclaved extracellular supernatant also retained AFB1 removal activity. UPLC-ESI MS/MS analysis suggested that AFB1 was transformed into a metabolite (m/z value 285.08) by water molecule addition on furan ring double bond. The AFB1 removal activity of C. timonianum c4a was extracellular, constitutive, and highly thermostable, structurally transforming AFB1 into a much less toxic product. Herein, we present the first evidence of thermostable AFB1 removal activity of a strain belonging to C. timonianum.

Structural feature-based strategy for the identification of diterpene alkaloids in Aconitum carmichaeli Debeaux

The taproot of Aconitum carmichaelii Debeaux (AC), a poisonous Traditional Chinese Medicine, has been widely used to treat joint pain, rheumatism and dysmenorrhea. Fermentation is a traditional drug processing method that reduces toxicity or increases efficacy. However, the chemical composition of AC, especially fermented AC, has not been fully elucidated. Therefore, it is necessary to establish a method to characterize the chemical composition of raw and fermented AC. In this study, a structural feature-based comprehensive strategy was employed to identify the chemical components of raw and fermented AC. A highly selective method consisting of mass defect filtering (MDF), ring double bond (RDB), nitrogen rule, and feature MS fragments filtering was established using UPLC-Q-Orbitrap-MS. By the established method, 230 diterpene alkaloids were characterized in raw AC, including 108 amine, 68 monoester, and 54 diester diterpene alkaloids. 145 of them were potential new compounds. Totals of 466 diterpene alkaloids were identified in fermented AC, including 231 amine, 162 monoester, and 73 diester diterpene alkaloids. 397 of them were potential new compounds. Ester hydrolysis, hydroxylation, and demethylation were the major transformation pathways during fermentation. An integrated approach with highly selective based on the structural feature of analytes was established and applied to identify the chemicals in AC. The strategy showed great performance in improving the accuracy and coverage of the identification by using LC-MS.

Fused Tetrahydroquinolines Are Interfering with Your Assay.

Tricyclic tetrahydroquinolines (THQs) have been repeatedly reported as hits across a diverse range of high-throughput screening (HTS) campaigns. The activities of these compounds, however, are likely due to reactive byproducts that interfere with the assay. As a lesser studied class of pan-assay interference compounds, the mechanism by which fused THQs react with protein targets remains largely unknown. During HTS follow-up, we characterized the behavior and stability of several fused tricyclic THQs. We synthesized key analogues to pinpoint the cyclopentene ring double bond as a source of reactivity of fused THQs. We found that these compounds degrade in solution under standard laboratory conditions in days. Importantly, these observations make it likely that fused THQs, which are ubiquitously found within small molecule screening libraries, are unlikely the intact parent compounds. We urge deprioritization of tricylic THQ hits in HTS follow-up and caution against the investment of resources to follow-up on these problematic compounds.

Significant acceleration of E-Z photoisomerization induced by molecular planarity breaking

E-Z photoisomerization constitutes the footstone of photosensitive proteins, molecular photoswitches and sunscreens and is believed to be controlled by photoinduced intramolecular charge transfer. In this work, we have made methylation on isomerizable alkene bond of plant sunscreen sinapate esters to break the coplanarity between phenol ring and CC double bond in ground state. Femtosecond transient absorption spectroscopy combined with time-dependent density functional theory calculations determine that this molecular planarity breaking triggers an immediate excited-state CC double bond twisting and thus accelerates the isomerization by more than one order of magnitude. These results highlight the role of molecular geometry on isomerization dynamics.

Synthesis of Gentamicin Minor Components: Gentamicin C1a and Gentamicin C2b.

Gentamicin C1a and the minor isomer C2b have been reported to have favorable properties in terms of antibacterial activity and toxicity compared to the commercial mixture from which they have previously been isolated by preparative high-performance liquid chromatography. We report straightforward syntheses of both compounds from readily available sisomicin by selective oxidation of the side chain in ring I, hydrogenation of the double bond in ring I to give the 5'-epi series, inversion of configuration at position 5' under thermodynamic conditions, and installation of the 6'-amino group by reductive amination.

Integration of offline two-dimensional chromatography and mass defect filtering-based precursor ion list data acquisition for targeted characterization of diterpenoid alkaloids in the lateral roots of Aconitum carmichaelii

The hyphenated technique of offline two-dimensional (2D) chromatography with high resolution mass spectrometry (MS) was an efficient tool for separation and characterization of components in complex systems such as herbal medicines, especially those co-eluting components or isomers. In this study, we constructed the ultra-performance convergence chromatography (UPC2) × reversed phase (RP) chromatographic separation system and developed a mass defect filtering (MDF)-based precursor ion list (PIL) acquisition method to improve the selectivity and sensitivity of this technique, and the systematic characterization of diterpenoid alkaloids in the lateral roots of Aconitum carmichaelii (namely “Fuzi” in Chinese) was used as an example. The constructed offline 2D separation system showed a good orthogonality of 0.77. Besides, the in-house databases for known and predicted C19- and C20-diterpenoid alkaloids were established by molecular design in Compound Discoverer software for MS data matching and filtering, and two MDF windows were further constructed to screen out more potential diterpenoid alkaloids with novel structures and to obtain the PIL (mass range: even values between 298 and 1020 Da, parent mass width: ±100 mDa) for data acquisition by calculating the m/z values of potential ions using mass range and corresponding mass defect in the MDF windows. In addition, an integrative structure interpretation strategy was developed by integrating elemental composition analysis, ring double bond analysis, neutral loss filtering, diagnostic ion filtering and database matching, etc. As a result, a total of 659 components in the lateral roots of A. carmichaelii were exposed and characterized, including 526 potential new compounds. This strategy showed significant advantages in improving the coverage and selectivity of screening, and could also be applied in systematic characterization of components in other herbal medicines.

Effective Parameters Controlling Sterol Transfer: A Time-Resolved Small-Angle Neutron Scattering Study.

Though cholesterol is the most prevalent and essential sterol in mammalian cellular membranes, its precursors, post-synthesis cholesterol products, as well as its oxidized derivatives play many other important physiological roles. Using a non-invasive in situ technique, time-resolved small angle neutron scattering, we report on the rate of membrane desorption and corresponding activation energy for this process for a series of sterol precursors and post-synthesis cholesterol products that vary from cholesterol by the number and position of double bonds in B ring of cholesterol's steroid core. In addition, we report on sterols that have oxidation modifications in ring A and ring B of the steroid core. We find that sterols that differ in position or the number of double bonds in ring B have similar time and energy characteristics, while oxysterols have faster transfer rates and lower activation energies than cholesterol in a manner generally consistent with known sterol characteristics, like Log P, the n-octanol/water partitioning coefficient. We find, however, that membrane/water partitioning which is dependent on lipid-sterol interactions is a better predictor, shown by the correlation of the sterols' tilt modulus with both the desorption rates and activation energy.

Removal of 26 corticosteroids, potential COVID-19 remedies, at environmentally relevant concentrations in water using UV/free chlorine, UV/monochloramine, and UV/hydrogen peroxide

Corticosteroids (CSs) with two double bonds in ring A are sensitive to UV. CSs were poorly removed by individual Cl2, NH2Cl, and H2O2 treatment. Combining UV with Cl2, NH2Cl, or H2O2 promoted UV-insensitive CS removal.

Parisvaniosides A–E, five new steroidal saponins from Paris vaniotii

The species of Paris genus is a prolific source of structurally diverse steroidal saponins responsible for multivarious biological properties. The first phytochemical investigation on the steroidal saponin constituents from the rhizomes of Paris vaniotii Lévl. led to the discovery and structural characterization of four new spirostanol saponins, named parisvaniosides A-D (1–4), and one new furostanol glycoside, named parisvanioside E (5), along with eleven known analogues (6–16). Their structures were unambiguously established on the basis of extensive spectroscopic analysis and comparison with the reported spectroscopic data. Compound 1 is a rare spirostanol saponin sharing with a C-9/C-11 double bond and a peroxy group located between C-5 and C-8 of the aglycone, whereas 3 and 4 are unusual C-27 steroidal sapoins with hydroxyl/methoxyl at both C-5 and C-6. Furthermore, 5 is the first furostanol saponin with a unique aglycone featuring two trisubstituted double bonds in ring B. All isolated saponins were evaluated for their anti-inflammatory effects on a lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production model in RAW 264.7 macrophages.

Rapid Profiling of the Marker Components in Artemisia annua L. and their Metabolites in Rats Using an Improved Liquid Chromatography-tandem Highresolution Mass Spectrometry-based Technology.

As parasite resistance to the main artemisinin drugs has emerged in Southern Asia, the traditional herb Artemisia annua L. (AAL) from which artemisinin (QHS) isolated was found to overcome resistance to QHS. However the component and metabolite profiles of AAL remain unclear. In this study, component profiling of marker compounds in AAL (amorphane sesquiterpene lactones and flavonoids) was performed and their subsequent metabolism was investigated in rats. For efficient component classification and structural characterization, an improved liquid chromatography- tandem high-resolution mass spectrometry (HRMS)-based analytical strategy was applied, i.e., background subtraction (BS) followed by ring-double-bond (RDB) filter in tandem with repeated BS processing. Structures of detected components/metabolites were characterized based on integrated information including their HRMSn patterns, RDB values, the established component/metabolite network, the biosynthesis pathways of AAL, and/or NMR data. A total of 38 amorphane sesquiterpene lactones and 35 flavonoids were found in AAL as prototype compounds, among which 26 components were previously undescribed. Major compounds were identified by comparing them with reference standards. Among 73 AAL prototypes administered, 38 were absorbed in the circulation as the prototype. Moreover, 20 metabolites of amorphane sesquiterpene lactones and 10 metabolites of flavonoids were detected in rats. The major metabolic pathways included oxidation, methylation, glucuronidation and sulfation. The component and metabolite network were established for marker components in AAL, which will be valuable to understand the synergistic antimalarial potency of QHS in A. annua L. The analytical strategy can also be applied to other herbal medicines.

An enhanced strategy integrating offline two-dimensional separation with data independent acquisition mode and deconvolution: Characterization of metabolites of Uncaria rhynchophylla in rat plasma as a case

The importance to clarify the drug metabolites is beyond doubt in view of their potential efficacy and safety. However, due to the complex matrix interference, relatively low content and the co-eluting effect, it is of a great challenge to comprehensively and systematically characterize the metabolites in vivo, especially for the traditional Chinese medicines (TCMs) due to the numerous types of components. In the present study, a comprehensive off-line two-dimensional separation system combining with data independent acquisition (DIA) mode and multi-dimensional data deconvolution method was established for chromatographic separation, data acquisition and data procession of indole alkaloids in rat plasma after intragastrically administrated with the extract of Uncaria rhynchophylla at the dose of 1 g/kg. The orthogonality of the off-line 2D separation system consisting of HILIC for first-dimensional separation and the PRLC for second-dimensional separation was valuated with the “asterisk” equations, and the results showed that off-line 2D separation system had passable orthogonality (A0 = 53.3%). Furthermore, the DIA mode was applied to capture MS/MS spectra in view of its advantage in acquiring MS data, and an effective multi-dimensional deconvolution method integrating the calculation of chemical formula, the extraction of diagnostic ion, the filter of ring double bond (RDB) and the judgement of neutral loss was established to parse the spectra for the complicated DIA data for comprehensive analysis of metabolites in rat plasma. Ultimately, a total of 127 indole alkaloids were tentatively characterized, and the main metabolic pathways were inferred as demethylation, dehydrogenation, hydroxylation and deglycosylation. The off-line two-dimensional separation system was applied for the comprehensive characterization of metabolites in vivo for the first time. This study suggested a new approach to enable the enrichment, separation and analysis of the low content components in vivo.

Dimethyl 2,5-furandicarboxylate synthesis from 2,5-furanodicarboxylic acid and dimethyl carbonate in presence of MgO-Al2O3 and tetrabutylammonium bromide

• MgO-Al 2 O 3 and MgO-La 2 O 3 bimetallic oxides were prepared by a simple hydrothermal method. • An 80.19% selectivity of DMFDCA was obtained under mild conditions. • This work provides a green and economical route for DMFDCA production. 2,5-furandicarboxylic acid (FDCA) and dimethyl 2,5-furandicarboxylate (DMFDCA) are attracting increasing attention as important biomass-based chemical feedstocks. Considering the physicochemical properties of FDCA with high polarity, poor solubility and easy decarboxylation, the synthesis of DMFDCA from FDCA is especially necessary. However, how to synthesize DMFDCA in case of avoiding a series of side reactions such as furan ring opening and double bond addition is a huge challenge. Herein, we used FDCA and dimethyl carbonate (DMC) to synthesize DMFDCA in presence of MgO-Al 2 O 3 and tetrabutylammonium bromide (TBAB), and the optimized yield and selectivity of DMFDCA came up to 76.38% and 80.19%, respectively. In addition, the used catalysts were characterized by SEM, XRD, BET, XPS and CO 2 -TPD analysis, and the structure, composition, morphology and basic site distribution of catalyst were well studied, and the relationship between catalyst structure and catalytic performance in the esterification of FDCA into DMFDCA thorough organic acid exchange reaction method was also analyzed. This work provides a promising solution for the preparation of furan-based polyester monomers.

Metabolite profiling of IMID-2, a novel anticancer molecule of piperazine derivative: In silico prediction, in vitro and in vivo metabolite characterization using UPLC-QTOF-MS/MS.

IMID-2, a newly identified piperazine-based anticancer molecule, has been shown to be cytotoxic against various cancer cell lines. The primary aim of this research was to identify and characterize possible metabolites of the molecule formed during biotransformation. A metabolite identification study was first executed using an in silico tool to predict the possible metabolism sites of IMID-2. Thereafter, metabolites generated in vitro (rat liver microsomes, rat S9 fractions and human liver microsomes) and in vivo (rat plasma, urine and feces) were identified and characterized employing UPLC-QTOF-MS/MS. A total of eight metabolites, among which were six in phase I and two in phase II reactions, were recognized. The plausible structure of the metabolites and probable metabolic pathway have been established based on the mass fragmentation pattern, mass ppm error, ring double bond calculation and nitrogen rule. The majority of phase I metabolites were generated by N-oxidation, hydroxylation, oxidative deamination followed by reduction, oxidative dechlorination, N-dearylation, and N-dealkylation. Glucuronidation played a significant role in the formation of phase II metabolites of the molecule.

Update on LIPID MAPS classification, nomenclature, and shorthand notation for MS-derived lipid structures

A comprehensive and standardized system to report lipid structures analyzed by MS is essential for the communication and storage of lipidomics data. Herein, an update on both the LIPID MAPS classification system and shorthand notation of lipid structures is presented for lipid categories Fatty Acyls (FA), Glycerolipids (GL), Glycerophospholipids (GP), Sphingolipids (SP), and Sterols (ST). With its major changes, i.e., annotation of ring double bond equivalents and number of oxygens, the updated shorthand notation facilitates reporting of newly delineated oxygenated lipid species as well. For standardized reporting in lipidomics, the hierarchical architecture of shorthand notation reflects the diverse structural resolution powers provided by mass spectrometric assays. Moreover, shorthand notation is expanded beyond mammalian phyla to lipids from plant and yeast phyla. Finally, annotation of atoms is included for the use of stable isotope-labeled compounds in metabolic labeling experiments or as internal standards. This update on lipid classification, nomenclature, and shorthand annotation for lipid mass spectra is considered a standard for lipid data presentation.

Key structural features in cis‐carane, (+)‐3‐carene, cis‐pinane, (+)‐α‐pinene, and (−)‐β‐pinene influencing red turpentine beetle primary attraction when released with ethanol

AbstractIn US Pacific Northwest ponderosa pine forests the primary attraction order shown previously for red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae), is (−)‐β‐pinene+ethanol > (+)‐3‐carene+ethanol > (+)‐α‐pinene+ethanol. The monoterpenes are bicyclic C10H16 isomers containing one 6‐carbon ring with one double bond. Both pinenes have a 4‐carbon second ring and differ only by their endocyclic or exocyclic double bond. The (+)‐3‐carene second ring has 3‐carbons; its double bond is endocyclic like (+)‐α‐pinene. Ring system and double bond influences on primary attraction were evaluated by hydrogenating (+)‐3‐carene and (+)‐α‐pinene to cis‐carane and cis‐pinane, respectively. Field test primary attraction strengths were (−)‐β‐pinene+ethanol > cis‐carane+ethanol > cis‐pinane+ethanol > ethanol. In combination with ethanol (i) a double bond is not required in either ring system to attract D. valens, (ii) the cis‐carane bicyclic 3, 6‐carbon ring system provides stronger beetle attraction than the cis‐pinane 4, 6‐carbon bicyclic ring system, and likely structural basis for stronger (+)‐3‐carene attraction over (+)‐α‐pinene, (iii) adding an exocyclic double bond to the 4, 6‐carbon ring system elevates attraction above the 3, 6‐carbon ring system with no double bond, and (iv) the 4, 6‐carbon ring system is a much stronger attractant with an exocyclic rather than endocyclic double bond.

Understanding the Mechanism and Selectivities of the Reaction of Meta-Chloroperbenzoic Acid and Dibromocarbene with β-Himachalene: A DFT Study

This study was performed to understand the site selectivity in the reaction between β-himachalene and meta-chloroperbenzoic acid (m-CPBA) in the first step followed by the addition of dibromocarbene (CBr2) to the main monoepoxidation product Pα formed in the first reaction. Calculations were performed using the Becke three-parameter hybrid exchange functional and the Lee–Yang–Parr correlation functional (B3LYP) with the 6-311 + G (d, p) basis set. Transition states were located by QST2, and their highlighting was validated by the existence of only one imaginary frequency in the Hessian matrix. The action of m-CPBA on β-himachalene was analyzed on the two double bonds of β-himachalene whose theoretical calculations show that the attack affects the most substituted double bond on α side containing hydrogen of ring junction. The obtained Pα product thereafter treated with dibromocarbene leads via an exothermic reaction to the six-membered ring double bond position of α-monoepoxide. The major products Pαα are kinetically and thermodynamically favored with a high stereoselectivity in perfect correlation with the experimental observations.

Comparative LC-MS analysis of tropolone alkaloids from in vitro cultures and native sources of Gloriosa superba by Kendrick mass defect plots.

Gloriosa superba L. is a promising antitumoural plant species as a source of colchicinoids. Ethnobotanical applications of G. superba are associated with different plant parts such as leaves, seeds, fruits, tuber and the whole plant. A comparative phytochemical study of purified extracts from in vitro cultures and native tubers of G. superba was carried out by ultrahigh-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HR-MS) in combination with the mass defect filtering (MDF) technique. The individual compounds were tentatively annotated using database correlations, retention time (Rt), accurate m/z data obtained by electrospray ionisation (ESI) (+)-HR-MS, proposed elemental composition, ring double bond equivalent (RDBeq) values and HR-MS/MS fragmentation patterns. Moreover, the identification was based on transforming the exact mass ratio (m/z) for the protonated molecular ions [М + Н]+ of the observed metabolites in Kendrick nominal masses (NKMs) and calculation of the Kendrick mass defect (KMD), which made it possible to graphically present the ion peaks in Kendrick plots. Building Kendrick plots allows easy differentiation of small structural differences such as methylation or demethylation of compounds from the same homologous series. In this way, a wide range of tropolone alkaloids was characterised. A greater variety was observed in in vitro cultures, compared to native sources. This LC-MS analysis unambiguously demonstrated the presence of tropolone alkaloids in in vitro cultures of G. superba. This approach of LC-MS data interpretation can be used to understand complex mass spectra such as those of plant extracts.

Oxidative degradation of Bisphenol A in aqueous solution using cobalt ion-activated peroxymonosulfate

The degradation of Bisphenol A (BPA) in aqueous solution by an advanced oxidation process (AOP) involving cobalt ion activation of peroxymonosulfate (PMS) was investigated, in order to optimize the effectiveness of the PMS/Co system for complete mineralization of Bisphenol A in aqueous media. Batch degradation experiments were carried out in a 500 mL capacity quartz reactor under varied conditions of Co2+ ion source, pH, oxidant and catalyst dosage/ratio and time. The effect of humic acid addition on the degradation process was as well assessed. A technique was adapted for monitoring the degradation process by means of high-performance liquid chromatography. Results obtained show clearly that Co-activated PMS was very efficient for the degradation of BPA in water, due to action of strongly oxidizing sulfate radical anion (SO4−) and hydroxyl radical (OH). Both CoSO4 and CoCl2 as catalysts yielded complete degradation of BPA under different conditions. The time interval to complete degradation increased for higher BPA concentrations, whereas the trend of degradation rate with pH was pH 5 > pH 9 > pH 7. The presence of humic acid in water hindered the degradation performance of Co/PMS in a time-dependent manner. Quantum chemical computations performed to assess the local reactivity of the BPA molecule and to identify the reactive regions in terms of radical (F) and electrophilic attack (F−), revealed that radical attack would be initiated on the aromatic ring and olefinic double bonds. The present study has revealed that the PMS/Co2+ oxidation process has the capacity to completely remove and mineralize Bisphenol A from aqueous solution.

Update on metabolism of abemaciclib: In silico, in vitro, and in vivo metabolite identification and characterization using high resolution mass spectrometry.

Abemaciclib was approved by the US Food and Drug Administration in 2015 as an advanced treatment for metastatic breast cancer. Identification and characterization of limited numbers of abemaciclib metabolites have been reported in the literature. Therefore, the current study focused on the investigation of the in vitro and in vivo metabolic fate of abemaciclib using high resolution mass spectrometry. Initially, a vulnerable site of metabolism was predicted by the Xenosite web predictor tool. Later, in vitro metabolites were identified from pooled rat liver microsomes, rat S9 fractions, and human liver microsomes. Finally, in vivo metabolites have been detected in plasma, urine, and feces matrix of male Sprague-Dawley rats. A total of 12 putative metabolites (11 phase I and 1 phase II) of abemaciclib and their metabolic pathways were proposed by considering accurate mass, mass fragmentation pattern, nitrogen rule, and ring double bonds of the detected metabolites. Abemaciclib was metabolized via hydroxylation, N-oxidation, N-dealkylation, oxidative deamination followed by reduction and sulfate conjugation. In the human liver microsomes, maximum numbers of metabolites (11 metabolites) were observed, from which M7, M8, M9, and M11 were human specific.

Characterization of pyrolytic lignin and insight into its formation mechanisms using novel techniques and DFT method

Real pyrolytic lignin (R-PLs) and pyrolytic products from model compounds (M-PL) were characterized by HPLC/Qtof-MS, GPC and 2D HSQC NMR to acquire molecular information. A huge amount of molecules were detected, analyzed and sorted into several categories according to their properties. Most compounds in R-PLs have complicated sidechains, with high molecular weight (MW) but moderate ring double bond equivalent (RDB), which might be derivatives of lignin fragments. The low MW fractions of R-PLs are considered as lignin simple monomers (LSM) and their derivatives, because the peaks of R-PLs and M-PL within low MW range of GPC are proximal. Molecules with medium MW but pretty high RDB, supposed to be coke/PAHs, were found more in M-PL than R-PLs, indicating that coke/PAHs primarily derive from LSM. Formation mechanisms of PL were proposed based on the differences between R-PLs and M-PL, which were supported by density functional theory (DFT) calculation. The results provide an in-depth understanding of pyrolytic lignin and inspire studies on high-value utilization of pyrolytic lignin.