A validated 1H NMR method for quantitative analysis of α-bisabolol in essential oils of Eremanthus erythropappus

Larvicidal Activity of Hemp Extracts and Cannabidiol against the Yellow Fever Mosquito Aedes aegypti

To mitigate pyrethroid resistance in mosquito vectors of emerging and re-emerging human pathogens, there is an urgent need to discover insecticides with novel modes of action. Natural alternatives, such as extracts derived from plants, may serve as substitutes for traditional synthetic insecticides if they prove to be sustainable, cost-effective, and safe for non-target organisms. Hemp (Cannabis sativa) is a sustainable plant known to produce various secondary metabolites with insecticidal properties, including terpenoids and flavonoids. The goal of this study was to assess the larvicidal activity of hemp leaf extract on mosquito larvae from both pyrethroid-susceptible (PS) and pyrethroid-resistant (PR) strains of Aedes aegypti. Another goal was to identify which components of the extract were responsible for any observed larvicidal activity. We found that a methanol extract of hemp leaves induced similar concentration-dependent larvicidal activity against PS (LC50: 4.4 ppm) and PR (LC50: 4.3 ppm) strains within 48 h. Partitioning of the leaf extract between methanol and hexane fractions revealed that full larvicidal activity was restricted to the methanol fraction. Analysis of this fraction by gas chromatography-mass spectrometry and nuclear magnetic resonance showed it to be dominated by cannabidiol (CBD). Larvicidal assays using authentic CBD confirmed this compound was primarily responsible for the toxicity of the hemp leaf extract against both strains. We conclude that hemp leaf extracts and CBD have the potential to serve as viable sources for the development of novel mosquito larvicides.

A Validated 1H NMR Method for the Quantitation of 5-Hydroxymethyl-2(5H)-Furanone, a Valuable Chemical Intermediate, In a Dichloromethane Extract of Helleborus lividus subsp: Corsicus Leaves from Corsica

An experimental procedure using ¹H NMR was developed and validated to quantify 5-hydroxymethyl-2(5H)-furanone, a valuable chemical synthon ((S)-enantiomer), in a dichloromethane extract of Helleborus lividus subsp. corsicus leaves. This method, using vanillin as the internal standard, exhibited a perfect linearity of measurements (R ² = 1) associated with very good accuracy (relative errors comprised between -1.62% and 4.25%) and precision (reproducibility 30.51 mg ± 0.4%). The limit of detection and the limit of quantitation have been measured at 0.14 mg and 0.59 mg, respectively. The experiment time is very short since a single analysis is at the minute level. 5-Hydroxymethyl-2(5H)-furanone accounted for nearly 85% in the dichloromethane extract of H. lividus subsp. corsicus leaves (1.7% of the mass of fresh leaves). This plant represents an important and natural source of (S)-5-hydroxymethyl-2(5H)-furanone (main enantiomer; determined using a GC chiral analysis).

Applicable and cost-efficient microplastic analysis by quantitative 1 H-NMR spectroscopy using benchtop NMR and NoD methods

In continuation of our work on the proof-of-concept that quantitative NMR spectroscopy may be a valuable tool in microplastic (MP) analysis and quantification, we present here investigations using low-field NMR spectrometers and nondeuterated solvents for the analysis of solutions of MP particles in suitable solvents. The use of low-field NMR spectrometers (benchtop NMR) that are considerably more cost-effective in terms of purchase and operating costs compared with high-field NMR spectrometers and the use of nondeuterated solvents (NoD method) leads to an applicable and cost-efficient method for mass-based MP analysis. For benchtop 80-MHz NMR, limits of detection for polyvinylchloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS) are in the same range as if a high-field 500-MHz NMR spectrometer was used for quantification (500 MHz: PET 1 μg/ml, PVC 42 μg/ml, and PS 9 μg/ml; 80 MHz: PET 4 μg/ml, PVC 19 μg/ml, and PS 21 μg/ml) for polymers being dissolved in deuterated solvents. The same is true for the corresponding limits of quantification. Moreover, it is shown for the first time that quantitative determination of the mass concentration of PET, PVC, and PS is also possible using NoD methods by evaluating the integrals of polymer-specific signals relative to an internal or external standard. Detection limits for NoD methods are in a similar range as if deuterated solvents were used (PET 2 μg/ml, PVC 39 μg/ml, and PS 8 μg/ml) using a high-field 500-MHz spectrometer or the 80-MHz spectrometer (PET 5 μg/ml).

A Novel Dual-Stage Phase Separation Process for CO2 Absorption into a Biphasic Solvent with Low Energy Penalty

An amine-based biphasic solvent is promising to cut down the energy penalty of CO₂ capture. However, the high viscosity of the CO₂-enriched solvent retards its industrial application. This work proposed a novel dual-stage phase separation process using a triethylenetetramine and 2-(diethylamino)ethanol blend as a biphasic solvent, which separates a certain proportion of CO₂-enriched phase during CO₂ absorption to reduce its viscosity. Experimental results showed that the proposed dual-stage phase separation process improved the phase separation behavior and effectively enhanced the absorption rate by 49% at 50 °C, when 50 vol % CO₂-enriched phase was separated at 0.3 mol mol^-1. Kinetic analysis showed that the absorption rate was mainly controlled by liquid-side mass transfer. The regeneration heat of the dual-stage phase separation process cut down the energy penalty by 33% compared with the monoethanolamine-based process. Compared with the conventional biphasic solvent-based process, the heat duty was further declined by 8%. The ¹H nuclear magnetic resonance analysis showed that the dual-stage phase separation process could effectively control the generation of absorption products and intensify the interphase migration of tertiary amines.

Research Progress of NMR in Natural Product Quantification

In the fields of medicine and health, traditional high-performance liquid chromatography or UV-visible spectrophotometry is generally used for substance quantification. However, over time, nuclear magnetic resonance spectroscopy (NMR) has gradually become more mature. Nuclear magnetic resonance spectroscopy has certain advantages in the quantitative analysis of substances, such as being nondestructive, having a high flux and short analysis time. Nuclear magnetic resonance spectroscopy has been included in the pharmacopoeiae of various countries. In this paper, the principle of nuclear magnetic resonance spectroscopy and the recent progress in the quantitative study of natural products by NMR are reviewed, and its application in the quantitative study of natural products is proposed. At the same time, the problems of using NMR alone to quantify natural products are summarized and corresponding suggestions are put forward.

Rapid identification model based on decision tree algorithm coupling with 1H NMR and feature analysis by UHPLC-QTOFMS spectrometry for sandalwood

Sandalwood is one of the most valuable woods in the world. However, today's counterfeits are widespread, it is difficult to distinguish authenticity. In this paper, similar genus (Dalbergia and Pterocarpus) and confused species (Gluta sp.) of sandalwood were quickly and efficiently identified. Rapid identification model based on ¹H NMR and decision tree (DT) algorithm was firstly developed for the identification of sandalwood, and the accuracy was improved by introducing the AdaBoost algorithm. The accuracy of the final model was above 95%. And the feature components between different species of sandalwood were further explored using UHPLC-QTOFMS and NMR spectrometry. The results showed that 183 compounds were identified, among which 99 were known components, 84 were unknown components. The ¹H NMR and ¹³C NMR signals of 505 samples were assigned, among them, 14 compounds were attributed, characteristic chemical shift intervals with great differences in the model were analysed. Furthermore, the fragmentation pattern of different compounds from sandalwood, in both positive and negative ion ESI modes, was summarized. The results showed a potential and rapid tool based on DT, NMR spectroscopy and UHPLC-QTOFMS, which had performed great potential for rapid identification and feature analysis of sandalwood.

Quantitative 1H-NMR spectroscopy as an efficient method for identification and quantification of PVC, ABS and PA microparticles

This work presents a new, size-independent, fast, mass based MP-analysis of PVC, ABS and PA 6.6 using quantitative ¹H-NMR spectroscopy.

1 H-NMR and GC for detection of adulteration in commercial essential oils of Cymbopogon ssp

INTRODUCTION

Essential oils of Cymbopogon nardus and C. winterianus have fungicidal, bactericidal, and insect repellent activities. In addition, they are components of fragrances, cosmetics, and household products. The growing demand for essential oils has intensified adulteration practices of such products.

OBJECTIVES

To evaluate the authenticity and quality of citronella commercial essential oils based on chemical composition [by gas chromatography mass spectrometry (GC-MS)] and the contents of its major constituents [by ¹ H-NMR, and gas chromatography with a flame ionisation detector using internal standardisation (GC-IS)].

MATERIALS AND METHODS

The chemical composition of essential oil was determined by GC-MS. Major components were quantified by ¹ H-NMR and the results compared to those obtained by GC-IS.

RESULTS

The adulteration of oils was verified by GC and ¹ H-NMR. In the pure oils, the results obtained by ¹ H-NMR were similar to those obtained by GC-IS for most of the oils. However, in adulterated oils, signal overlap prevented the quantification of citronellol and geraniol by NMR. Importantly, due to dilution with dipropylene glycol it was not possible to quantify citronellal using ¹ H-NMR. However, for both pure and adulterated oils, GC-IS method proved successful in quantifying notable constituents.

CONCLUSION

All the methods used proved efficient in detecting adulteration. However, whilst GC-IS provided quantification of constituents of interest, both in pure and adulterated oils, their quantification by NMR was only possible in non-adulterated samples. None of the oils evaluated presented a composition within the threshold established by British Pharmacopoeia quality standards.

Identification and Quantitation of Ursolic and Oleanolic Acids in Ilex aquifolium L. Leaf Extracts Using 13C and 1H-NMR Spectroscopy

Leaves of Ilex aquifolium L. have been used for their therapeutic properties. In previous studies, components contained in the leaves were first isolated by various chromatographic techniques. Then, quantitation of oleanolic and ursolic acids, which are responsible for the biological and therapeutic activities of the plant, was performed by HPLC, HPTLC, and somewhat by GC-MS. Our objective was to develop a simple method that allows the identification of compounds contained in the leaves of Corsican I. aquifolium and to quantify ursolic and oleanolic acids. Leaves were successively extracted with hexane and dichloromethane. The extracts were chromatographed on silica gel and the fractions of column chromatography submitted to 13C-NMR analysis, following a computerized method developed in the laboratory. 13C-NMR allowed the identification of various triterpenes including ursolic acid and oleanolic acid. Quantitation of both acids was achieved, for the first time, by 1H-NMR after validation of the method (accuracy, precision, linearity, limit of detection and limit of quantitation). Ursolic and oleanolic acids accounted for 55.3% and 20.8% of the dichloromethane extract, respectively. This represents 1.3% and 0.5% of the mass of dried leaves. 1H-NMR spectroscopy appeared as a powerful tool for a rapid quantitation of biologically active compounds from I. aquifolium.

A validated 1H qNMR method for direct and simultaneous quantification of esculin, fraxin and (-)-epicatechin in Hippocastani cortex

A fast and precise qNMR method was developed for quantification of major bioactive constituents in the bark of horse chestnut and dry extracts prepared thereof. The method was optimised using 600 MHz spectrometer, and the final acquisition parameters (90°-pulse, acquisition time - 3.0 s, relaxation delay - 27 s, number of transients - 16) allowed for performing of quantitative experiments in under 15 min. The contents of three analytes were determined using specific ¹H resonances at δ7.45 ppm for esculin, δ5.00 ppm for fraxin, and δ5.94 ppm for (-)-epicatechin. The validation showed good precision (RSD < 1.5%) and accuracy (95-103%), and adequate sensitivity (LODs in the range of 3.3-5.9 µg) of the measurements. The determined levels in commercial samples of Hippocastani cortex were in the range of 25.89-38.94 mg/g dry weight (dw) of the bark for esculin, 12.58-17.13 mg/g dw for fraxin and 10.42-13.96 mg/g dw for (-)-epicatechin, and in the dry extracts prepared thereof 97.02-143.51 mg/g, 45.78-58.92 mg/g and 28.07-46.29 mg/g, respectively. The obtained results were cross-validated by a HPLC-PDA method with the use of a fused-core column, and no statistical differences were found between the results obtained by both methodologies, but with the advantage of higher precision of the qNMR assay. The relevant variability in quantitative composition of the commercial samples emphasise the need to introduce quality control studies in production of preparations containing horse chestnut bark and the developed method was proved suitable for this purpose.

Leishmanicidal activity of α-bisabolol from Tunisian chamomile essential oil

According to the World Health Organization, leishmaniasis is considered as a major neglected tropical disease causing an enormous impact on global public health. Available treatments were complicated due to the high resistance, toxicity, and high cost. Therefore, the search for novel sources of anti-leishmania agents is an urgent need. In the present study, an in vitro evaluation of the leishmanicidal activity of the essential oil of Tunisian chamomile (Matricaria recutita L.) was carried out. Chamomile essential oil exhibits a good activity on promastigotes forms of L. amazonensis and L. infantum with a low inhibitory concentration at 50% (IC₅₀) (10.8 ± 1.4 and 10.4 ± 0.6 μg/mL, respectively). Bio-guided fractionation was developed and led to the identification of (-)-α-bisabolol as the most active molecule with low IC₅₀ (16.0 ± 1.2 and 9.5 ± 0.1 μg/mL for L. amazonensis and L. infantum, respectively). This isolated sesquiterpene alcohol was studied for its activity on amastigotes forms (IC₅₀ = 5.9 ± 1.2 and 4.8 ± 1.3 μg/mL, respectively) and its cytotoxicity (selectivity indexes (SI) were 5.4 and 6.6, respectively). The obtained results showed that (-)-α-bisabolol was able to activate a programmed cell death process in the promastigote stage of the parasite. It causes phosphatidylserine externalization and membrane damage. Moreover, it decreases the mitochondrial membrane potential and total ATP levels. These results highlight the potential use of (-)-α-bisabolol against both L. amazonensis and L. infantum, and further studies should be undertaken to establish it as novel leishmanicidal therapeutic agents.