2D and 3D DOSY 1H NMR, a useful tool for analysis of complex mixtures: application to herbal drugs or dietary supplements for erectile dysfunction

Exploring the Significance, Extraction, and Characterization of Plant-Derived Secondary Metabolites in Complex Mixtures

Secondary metabolites are essential components for the survival of plants. Secondary metabolites in complex mixtures from plants have been adopted and documented by different traditional medicinal systems worldwide for the treatment of various human diseases. The extraction strategies are the key components for therapeutic development from natural sources. Polarity-dependent solvent-selective extraction, acidic and basic solution-based extraction, and microwave- and ultrasound-assisted extraction are some of the most important strategies for the extraction of natural products from plants. The method needs to be optimized to isolate a specific class of compounds. Therefore, to establish the mechanism of action, the characterization of the secondary metabolites, in a mixture or in their pure forms, is equally important. LC-MS, GC-MS, and extensive NMR spectroscopic strategies are established techniques for the profiling of metabolites in crude extracts. Various protocols for the extraction and characterization of a wide range of classes of compounds have been developed by various research groups and are described in this review. Additionally, the possible means of characterizing the compounds in the mixture and their uniqueness are also discussed. Hyphenated techniques are crucial for profiling because of their ability to analyze a vast range of compounds. In contrast, inherent chemical shifts make NMR an indispensable tool for structure elucidation in complex mixtures.

Spectroscopic determination of hydrophobic adulterant tadalafil by aptasensor based ellipsometry

Tadalafil is one of the selective phosphodiesterase type 5 inhibitors (PDE5) and serves as the active compound in drugs used for the treatment of erectile dysfunction. These PDE5 inhibitors are prescribed under medical supervision. However, cases of adulteration of dietary supplements with PDE5 inhibitors or their unapproved analogs have been reported worldwide. The presence of the PDE5 inhibitors in such supplements poses a serious health risk to consumers, particularly when combined with certain nitrate-containing drugs, as their toxic effects have not been thoroughly assessed and may result in unpredictable adverse reactions. Therefore, it is crucial to detect adulteration in these dietary supplements. However, current methods for PDE5 inhibitor detection rely on time-consuming and expensive analytical techniques, although they are sensitive. In this study, we propose an aptasensor based on ellipsometry for the detection of PDE5 inhibitors. To enhance the detection specificity for PDE5 inhibitors, we designed an aptamer with a hydrophobic pocket that incorporates a guanine base-rich region and a three-way junction. This design is particularly effective considering the poor aqueous solubility of PDE5 inhibitors. Preliminary results demonstrate that tadalafil detection in various media can be achieved within the range of 1-2000 ng/mL. The limit of detection for the active compound of tadalafil is as low as 1.82 ng/mL.

Review on NMR as a tool to analyse natural products extract directly: Molecular structure elucidation and biological activity analysis

INTRODUCTION

Natural products, the small organic molecules produced by plants, microbes and invertebrates, often present in the form of a mixture, this leads to the structural characterisation of natural extracts often requiring time-consuming multistep purification procedures. Nuclear magnetic resonance (NMR) technology is traditionally utilised as a tool for the structural elucidation of pure compounds. Contemporarily, an up-to-date trend in the application of NMR in natural product research is shifting to the direct NMR analysis of crude mixtures, to obtain molecular structure and biological activity information without performing cumbersome separation.

OBJECTIVE

To review works of literature on the evolution, principle and progress of NMR technologies for analysing mixtures, we focus on the successful application of NMR technologies in direct analysis of natural product extracts.

METHODOLOGY

Based on our research experience, academic tracking and extensive literature search, which involved, but not limited to, the use of various databases, like Web of Knowledge and PubMed. The keywords used, in various combinations, to retrieve recent literature on the successful application of NMR technologies to sheer natural product extracts, and excluded artificially natural product mixture and biofluid.

RESULTS

NMR technologies for direct natural extracts analysis, including two-dimensional J-resolved spectroscopy (2D-JRES), pure shift NMR, diffusion-ordered NMR spectroscopy (DOSY), statistical correlation spectroscopy (STOCSY), concentration-ordered NMR spectroscopy (CORDY), saturation transfer difference (STD) and water-ligand observed via gradient spectroscopy (WaterLOGSY) were illustrated.

CONCLUSIONS

By these methods, molecular structure and biological activity information will be directly obtained from NMR analysis of natural products extract, aiming to save experimental time and expenses.

The POWER saga from 2007 to 2022: An example of a sexual enhancement dietary supplement tainted by different adulterants and still on the market

Ten POWER dietary supplements, chronologically called tabs, pills then caps, and advertised as 100% natural aphrodisiacs, were analyzed by ¹H NMR from 2007 to 2022. They were all tainted by PDE-5 inhibitors. Eight different adulterants were identified (sildenafil (1), sildenafil analogues (6), and vardenafil analogue (1)). Their amounts ranged from 15 to 145 mg/capsule. Four supplements contained at least 100 mg/capsule of PDE-5 inhibitor or analogue, the maximal recommended dose of sildenafil. The nature of the adulterant has changed over time, probably to evade its detection by regulatory agencies routine screening tests. Despite several warnings and/or seizures from several European food and/or health authorities, the dietary supplement POWER is still on sale on the Internet, thus demonstrating the impossibility of controlling this market. Faced with this situation, the consumer should be better informed by establishing at the European level a public database of tainted dietary supplements on the model of that of the US Food and Drug Administration. It should indicate the product name, its photo, the adulterant name, and be easily accessible to everyone.

Theoretical analysis of flow effects in spatially encoded diffusion NMR

The measurement of translational diffusion coefficients by nuclear magnetic resonance (NMR) spectroscopy is essential in a broad range of fields, including organic, inorganic, polymer, and supramolecular chemistry. It is also a powerful method for mixture analysis. Spatially encoded diffusion NMR (SPEN DNMR)" is a time efficient technique to collect diffusion NMR data, which is particularly relevant for the analysis of samples that evolve in time. In many cases, motion other than diffusion is present in NMR samples. This is, for example, the case of flow NMR experiments, such as in online reaction monitoring and in the presence of sample convection. Such motion is deleterious for the accuracy of DNMR experiments in general and for SPEN DNMR in particular. Limited theoretical understanding of flow effects in SPEN DNMR experiments is an obstacle for their broader experimental implementation. Here, we present a detailed theoretical analysis of flow effects in SPEN DNMR and of their compensation, throughout the relevant pulse sequences. This analysis is validated by comparison with numerical simulation performed with the Fokker-Planck formalism. We then consider, through numerical simulation, the specific cases of constant, laminar, and convection flow and the accuracy of SPEN DNMR experiments in these contexts. This analysis will be useful for the design and implementation of fast diffusion NMR experiments and for their applications.

NMR methods for the analysis of mixtures

NMR spectroscopy is a powerful approach for the analysis of mixtures. Its usefulness arises in large part from the vast landscape of methods, and corresponding pulse sequences, that have been and are being designed to tackle the specific properties of mixtures of small molecules. This feature article describes a selection of methods that aim to address the complexity, the low concentrations, and the changing nature that mixtures can display. These notably include pure-shift and diffusion NMR methods, hyperpolarisation methods, and fast 2D NMR methods such as ultrafast 2D NMR and non-uniform sampling. Examples or applications are also described, in fields such as reaction monitoring and metabolomics, to illustrate the relevance and limitations of different methods.

NMR-Based Metabolomic Approach for Evaluation of the Harvesting Time and Cooking Characteristics of Different Cassava Genotypes

Cassava is an important staple food for low-income countries. However, its cooking characteristics are especially affected by genotype. In this study, two groups of genotypes, namely hard to cook (HTC) and easy to cook (ETC), were harvested at different times (9 and 15 months), and evaluated by NMR coupled to chemometrics. Additionally, lignin of these materials was studied by ¹H-¹³C HSQC NMR. The carbohydrates were the most important class of compounds to differentiate the cassava genotypes. The correlation of NMR with cooking time and starch content showed that the higher content of primary metabolites, mostly glucose, can be associated with longer cooking times and reduction of starch, corroborating the metabolic pathways analysis. Furthermore, it was observed that the lignin from cell walls did not differentiate the cooking performance of the genotypes.

Lodenafil

Lodenafil is a class of drugs called an inhibitor of PDE5 which also include a wide range of other erectile medicines, such as sildenafil, tadalafil and vardenafil. It is part of a new generation of PDE5 inhibitors that includes udenafil and avanafil. Lodenafil is a prodrug manufactured in the form of lodenafil carbonate, the carbonate dimer that divides in the body into two active drug lodenafil molecules. The oral bioavailability of this formulation is higher than that of the parent drug. This article discusses, by a critical comprehensive review of the literature on lodenafil in terms of its description, names, formulae, elemental composition, appearance, and therapeutic uses. The article also discusses the methods for preparation of lodenafil, its physical-chemical properties, analytical methods for its determination, pharmacological-toxicological properties, and dosing information.

NMR technique and methodology in botanical health product analysis and quality control

Botanicals have played an important role in maintaining human health and well-being throughout history. During the past few decades in particular, the use of botanical health products has gained more popularity. Whereas, quality, safety and efficacy concerns have continuously been critical issues due to the intrinsic chemical complexity of botanicals. Chemical analytical technologies play an imperative role in addressing these issues. Nuclear magnetic resonance (NMR) spectroscopy has proven to be a powerful and useful tool for the investigation of botanical health products. In this review, NMR techniques and methodologies that have been successfully applied to the research and development of botanical health products in all stages, from plants to products, are discussed and summarized. Furthermore, applications of NMR together with other analytical techniques in a variety of domains of botanical health products investigation, such as plant species differentiation, adulteration detection, and bio-activity evaluation, are discussed and illustrated with typical examples. This article provides an overview of the potential uses of NMR techniques and methodologies in an attempt to further promote their recognition and utilization in the field of botanical health products analysis and quality control.

Novel Strategy for the Recognition of Adulterant Vegetable Oils in Essential Oils Commonly Used in Food Industries by Applying 13C NMR Spectroscopy

Essential oils (EOs) are valuable products commonly employed in the food industry and intensively studied as biopreservatives for the extension of food shelf-life. Unfortunately, EOs might be counterfeit to increase industrial profits. Among the possible adulterants, vegetable oils (VOs) must be considered for their characteristics and low costs. We aimed to apply nuclear magnetic resonance (NMR) spectroscopy for the detection and identification of VOs in mixtures with EOs. This innovative strategy is based on comparing the peak area ratio matrices of characteristic VO ¹³C NMR fatty acid signals with those of adulterated EOs. The identification of the VOs was achieved by calculating the matrix similarity at different confidence levels. The strategy demonstrated the capacity to efficiently recognize the presence of adulteration and the type of VO adulterant in mixtures. Thus, the method was applied to 20 commercial EOs, and VOs were detected and then identified in four samples.

Structural Determination, Biological Function, and Molecular Modelling Studies of Sulfoaildenafil Adulterated in Herbal Dietary Supplement

Unapproved ingredients included in herbal medicines and dietary supplements have been detected as adulterated synthetic drugs used for erectile dysfunction. Extraction from a dietary supplement was performed to isolate the compounds by HPLC analysis. The structural characterization was confirmed using mass spectrometry (ESI-TOF/MS and LC-MS/MS), 1H NMR, and 13C NMR spectroscopy techniques. Results identified the thus-obtained compound to be sulfoaildenafil, a thioketone analogue of sildenafil. The biological activities of this active compound have been focused for the first time by the experimental point of view performance in vitro. The results revealed that sulfoaildenafil can affect the therapeutic level of nitric oxide through the upregulation of nitric oxide synthase and phosphodiesterase type 5 (PDE5) gene expressions. This bulk material, which displays structural similarity to sildenafil, was analyzed for the presence of a PDE5 inhibitor using a theoretical calculation. These unique features of the potential activity of PDE5 protein and its inhibitors, sildenafil and sulfoaildenafil, may play a key consideration for understanding the mode of actions and predicting the biological activities of PDE5 inhibitors.

Hemisynthesis of coumarin derivatives from Ammodaucus leucotrichus oil extract: organobase-catalyzed reaction, analytical study by diffusion-ordered spectroscopy NMR and differential scanning calorimetry

This paper presents an in-depth chemical and analytical study of a natural substance extracted from Ammodaucus leucotrichus Coss. & Dur and its derivatives after hemisynthesis. The analysis was performed using Diffusion-Ordered Spectroscopy (NMR DOSY) and Differential Scanning Calorimetry (DSC) as general methods. The results show an interesting chemical reactivity towards coumarin-derived bisnucleophiles (4-hydroxycoumarin and triacetic acid lactone), and products obtained by hemisynthesis of pyrano[4,3-b]pyrane derivatives following Knoevenagel condensation and Michael's addition on this natural substance with the use of 4-pyrolidinopyridine organobase as catalyst.

Determination of d-Cycloserine Impurities in Pharmaceutical Dosage Forms: Comparison of the International Pharmacopoeia HPLC-UV Method and the DOSY NMR Method

d-cycloserine is a broad-spectrum antibiotic that is currently being used as a secondary choice in the treatment of tuberculosis. In recent years, it has become more popular, due to its effect on the nervous system. In this current study, we provide evidence that The International Pharmacopoeia HPLC–UV method for d-cycloserine impurity profiling is not repeatable due to the variable response of cycloserine dimer, one of d-cycloserine impurities. Therefore, we introduced the DOSY (diffusion ordered spectroscopy) NMR (nuclear magnetic resonance) technique to determine the levels of d-cycloserine impurities in pharmaceutical dosage forms. The DOSY NMR technique allowed separation of d-cycloserine, its degradation products, and key process impurities in concentrations below pharmacopoeial specification limits. The proposed DOSY NMR method allowed accurate identification and quantification of the cycloserine dimer, which was not possible through the use of the pharmacopoeial HPLC method. The current method has the potential for practical use in analytical laboratories of the pharmaceutical industry.

Metabolomics in the Context of Plant Natural Products Research: From Sample Preparation to Metabolite Analysis

Plant-derived natural products have long been considered a valuable source of lead compounds for drug development. Natural extracts are usually composed of hundreds to thousands of metabolites, whereby the bioactivity of natural extracts can be represented by synergism between several metabolites. However, isolating every single compound from a natural extract is not always possible due to the complex chemistry and presence of most secondary metabolites at very low levels. Metabolomics has emerged in recent years as an indispensable tool for the analysis of thousands of metabolites from crude natural extracts, leading to a paradigm shift in natural products drug research. Analytical methods such as mass spectrometry (MS) and nuclear magnetic resonance (NMR) are used to comprehensively annotate the constituents of plant natural products for screening, drug discovery as well as for quality control purposes such as those required for phytomedicine. In this review, the current advancements in plant sample preparation, sample measurements, and data analysis are presented alongside a few case studies of the successful applications of these processes in plant natural product drug discovery.

Exploring the Role of Solvent on Carbohydrate-Aryl Interactions by Diffusion NMR-Based Studies

Carbohydrate-protein interactions play an important role in many molecular recognition processes. An exquisite combination of multiple factors favors the interaction of the receptor with one specific type of sugar, whereas others are excluded. Stacking CH-aromatic interactions within the binding site provide a relevant contribution to the stabilization of the resulting sugar-protein complex. Being experimentally difficult to detect and analyze, the key CH-π interaction features have been very often dissected using a variety of techniques and simple model systems. In the present work, diffusion NMR spectroscopy has been employed to separate the components of sugar mixtures in different solvents on the basis of their differential ability to interact through CH-π interactions with one particular aromatic cosolute in solution. The experimental data show that the properties of the solvent did also influence the diffusion behavior of the sugars present in the mixture, inhibiting or improving their separation. Overall, the results showed that, for the considered monosaccharide derivatives, their diffusion coefficient values and, consequently, their apparent molecular sizes and/or shapes depend on the balance between solute/cosolute as well as solute/solvent interactions. Thus, in certain media and in the presence of the aromatic cosolute, the studied saccharides that are more suited to display CH-π interactions exhibited a lower diffusion coefficient than the noncomplexing sugars in the mixture. However, when dissolved in another medium, the interaction with the solvent strongly competes with that of the aromatic cosolute.

Mutual Diffusion Driven NMR: a new approach for the analysis of mixtures by spatially resolved NMR spectroscopy

We introduce a new approach for resolving the NMR spectra of mixtures that relies on the mutual diffusion of dissolved species when a concentration gradient is established within the NMR tube. This is achieved by cooling down a biphasic mixture of triethylamine and deuterated water below its mixing temperature, where a single phase is expected. Until equilibrium is reached, a gradient of concentration, from 'pure' triethylamine to 'pure' water, establishes within the tube. The amount of time required to reach this equilibrium is controlled by the mutual diffusion coefficient of both species. Moreover, a gradient of concentration exists for each additional compound dissolved in this system, related to the partition coefficient for that compound in the original biphasic state. Using slice selective experiments, it was possible to measure these concentration gradients and use them to separate signals from all the present species. We show the results acquired for a mixture composed of n-octanol, methanol, acetonitrile and benzene and compare them with those obtained by pulse field gradient NMR. Copyright © 2016 John Wiley & Sons, Ltd.

1H NMR spectra dataset and solid-state NMR data of cowpea (Vigna unguiculata)

In this article the NMR data from chemical shifts, coupling constants, and structures of all the characterized compounds were provided, beyond a complementary PCA evaluation for the corresponding manuscript (E.G. Alves Filho, L.M.A. Silva, E.M. Teofilo, F.H. Larsen, E.S. de Brito, 2017) [3]. In addition, a complementary assessment from solid-state NMR data was provided. For further chemometric analysis, numerical matrices from the raw ¹H NMR data were made available in Microsoft Excel workbook format (.xls).

Pulsed-field gradient nuclear magnetic resonance measurements (PFG NMR) for diffusion ordered spectroscopy (DOSY) mapping

The advent of Diffusion Ordered SpectroscopY (DOSY) NMR has enabled diffusion coefficients to be routinely measured and used to characterize chemical systems in solution. Indeed, DOSY NMR allows the separation of the chemical entities present in multicomponent systems and provides information on their intermolecular interactions as well as on their size and shape.

Design, synthesis, structure, toxicology and in vitro testing of three novel agents for Alzheimer’s disease

This article describes the synthesis of three novel compounds for the treatment of Alzheimer’s disease (AD).

PALMA, an improved algorithm for DOSY signal processing

NMR is a tool of choice for the measurement of diffusion coefficients of species in solution.

LC-ESI-MS/MS analysis of phosphodiesterase-5 inhibitors and their analogues in foods and dietary supplements in Korea

A number of 188 food and dietary supplement samples were collected from 2009 to the first half of 2013 in Korean online and offline stores. A method to identify phosphodiesterase-5 (PDE-5) inhibitors and their analogues using liquid chromatography-electrospray ionisation-mass spectrometry/mass spectrometry (LC-ESI-MS/MS) was validated. Limit of detection and limit of quantitation of liquid-type and solid-type negative samples ranged from 0.05 to 3.33 ng/mL or ng/g and from 0.15 to 10.00 ng/mL or ng/g, respectively. Recoveries ranged from 83% to 112%. Nineteen PDE-5 inhibitors and their analogues were detected, with tadalafil group compounds being the most frequently observed (53.0%), followed by the sildenafil group (42.5%). Tadalafil concentrations ranged from 0.08 to 138.69 mg/g. Compounds were most frequently detected in capsules (in 40 of 80 adulterated samples). To protect public health and food safety, appropriate monitoring of PDE-5 inhibitors and their analogues in foods and dietary supplements is recommended.

Anti-inflammatory and toxicological evaluation of Moussonia deppeana (Schldl. & Cham) Hanst and Verbascoside as a main active metabolite

ETHNOPHARMACOLOGICAL RELEVANCE

Moussonia deppeana, known as Tlachichinole, is a Mexican medicinal plant used for treatment of inflammatory diseases, influenza, diarrhea, gastrointestinal disorders and arthritis.

AIM OF THE STUDY

In this paper the antioxidant and anti-inflammatory activities as well as the acute and sub-acute toxicological effects were evaluated for the ethanolic extract from aerial parts of M. deppeana, also its phytochemical analysis is described.

MATERIALS AND METHODS

Phytochemical analysis and compound isolation were performed with thin layer chromatography. The chemical identification of the main compound was performed by (1)H NMR (COSY, NOESY, HSQC and HMBC) spectra. In vitro antioxidant capacity and total phenolic content for the ethanolic extract and its primary fractions was determined by DPPH and Folin-Ciocalteu reagent. Acute and subacute toxicity tests were evaluated on Balb/C mice. Finally acute anti-inflammatory evaluation was tested for a local (TPA) and systemic (carrageenan) murine model.

RESULTS

The main compound isolated from the ethanolic extract of M. deppeana was Verbascoside, which was isolated from F3 and was identified by (1)H NMR and COSY data. Furthermore oleanolic and ursolic acids were isolated from primary fractions F1 and F2. Ethanolic extract showed IC50 = 6.71mg/mL for DPPH test and 664.12µg QE/mL for the total phenolic content. The LD50 value was >2g/kg by i.g. route in male and female mice. Sub-acute administration (28 days) of the ethanolic extract (1g/kg) did not cause lethality or alter any hematological and biochemical parameters, in addition, histological analysis of the major organs exhibited no structural changes. Anti-inflammatory activity of the ethanolic extract showed an ED50 = 1.5mg/ear and 450mg/kg for TPA and carrageenan test, respectively. Primary fractions generated moderate local and systemic anti-inflammatory activity.

CONCLUSION

The ethanolic extract from the aerial parts of M. deppeana did not cause any lethality or adverse effect in either of the acute and sub-acute toxicity tests. This exhibited an important local and systemic anti-inflammatory activity and also moderate antioxidant capacity. Moreover, the primary fraction F2 was more active for the TPA model while the primary fraction F3 was most active in the carrageenan model in vivo. The main compound isolated from F3 was verbascoside; on the other hand also ursolic and oleanolic acids were isolated from F1 and F2.

Adulteration of Dietary Supplements by the Illegal Addition of Synthetic Drugs: A Review

In the last few years, the consumption of dietary supplements, especially those having plants as ingredients, has been increasing due to the common idea that they are natural products posing no risks to human health. In the European Union and the United States, dietary supplements are legally considered as foods/special category of foods, thus are not being submitted to any safety assessment prior to their commercialization. Among the issues that can affect safety, adulteration by the illegal addition of pharmaceutical substances or their analogs is of major concern since unscrupulous producers can falsify these products to provide for quick effects and to increase sales. This review discusses the various classes of synthetic drugs most frequently described as being illegally added to dietary supplements marketed for weight loss, muscle building/sport performance and sexual performance enhancement. Information regarding regulation and consumption is also presented. Finally, several conventional and advanced analytical techniques used to detect and identify different adulterants in dietary supplements and therefore also in foods, with particular emphasis on plant food supplements, are critically described. This review demonstrates that dietary supplement adulteration is an emerging food safety problem and that an effective control by food regulatory authorities is needed to safeguard consumers.

Evaluation of a benchtop cryogen-free low-field ¹H NMR spectrometer for the analysis of sexual enhancement and weight loss dietary supplements adulterated with pharmaceutical substances

Nuclear magnetic resonance (NMR) spectroscopy is a unique tool for detection, structural characterization, and quantification of compounds in complex mixtures. However, due to cost constraints, NMR is rarely used in routine quality control (QC) analysis. The recent release of benchtop cryogen-free low-field NMR spectrometers represents a technological break in the NMR field. In this paper, we evaluated the potential of a benchtop cryogen-free 60 MHz spectrometer for uncovering adulteration of "100% natural" sexual enhancement and weight loss dietary supplements. We demonstrated that the adulterant(s) can readily be detected in ≈20 min of recording after a very simple and rapid sample preparation. We also showed that the quantification by the internal standard method can be done on the low-field NMR spectrometer and leads to results similar to those obtained with high-field NMR. Considering the cost and space efficiency of these spectrometers, we anticipate their introduction in QC laboratories as well as in governmental agencies, especially in the field of fraud detection.

Detection, identification and quantification by 1H NMR of adulterants in 150 herbal dietary supplements marketed for improving sexual performance

One hundred and fifty dietary supplements (DS) marketed to increase sexual performance were analyzed. All these formulations were claimed to contain only natural compounds, plant extracts and/or vitamins. (1)H NMR spectroscopy was used for detecting the presence of adulterants and for their identification and quantification. Mass spectrometry was used as a complementary method for confirming the chemical structures. 61% of DS were adulterated with phosphodiesterase-5 inhibitors (PDE-5i) (27% with the PDE-5i medicines sildenafil, tadalafil and vardenafil, and 34% with their structurally modified analogues). Among them, 64% contained only one PDE-5i and 36% mixtures of two, three and even four. The amounts of PDE-5i medicines were higher than the maximum recommended dose in 25% of DS tainted with these drugs. Additional 5.5% DS included other drugs for the treatment of sexual dysfunction (yohimbine, flibanserin, phentolamine, dehydroepiandrosterone or testosterone). Some DS (2.5%) contained products (osthole, icariin) extracted from plants known to improve sexual performance. Only 31% of the samples could be considered as true herbal/natural products. A follow-up over time of several DS revealed that manufacturers make changes in the chemical composition of the formulations. Lack of quality or consistent manufacture (contamination possibly due to inadequate cleaning of the manufacturing chain, presence of impurities or degradation products, various compositions of a given DS with the same batch number, inadequate labelling) indicated poor manufacturing practices. In conclusion, this paper demonstrates the power of (1)H NMR spectroscopy as a first-line method for the detection of adulterated herbal/natural DS and the need for more effective quality control of purported herbal DS.

Two dimensional NMR spectroscopic approaches for exploring plant metabolome: A review

Today, most investigations of the plant metabolome tend to be based on either nuclear magnetic resonance (NMR) spectroscopy or mass spectrometry (MS), with or without hyphenation with chromatography. Although less sensitive than MS, NMR provides a powerful complementary technique for the identification and quantification of metabolites in plant extracts. NMR spectroscopy, well appreciated by phytochemists as a particularly information-rich method, showed recent paradigm shift for the improving of metabolome(s) structural and functional characterization and for advancing the understanding of many biological processes. Furthermore, two dimensional NMR (2D NMR) experiments and the use of chemometric data analysis of NMR spectra have proven highly effective at identifying novel and known metabolites that correlate with changes in genotype or phenotype. In this review, we provide an overview of the development of NMR in the field of metabolomics with special focus on 2D NMR spectroscopic techniques and their applications in phytomedicines quality control analysis and drug discovery from natural sources, raising more attention at its potential to reduce the gap between the pace of natural products research and modern drug discovery demand.

Characterization of heroin samples by 1H NMR and 2D DOSY 1H NMR

Twenty-four samples of heroin from different illicit drug seizures were analyzed using proton Nuclear Magnetic Resonance ((1)H NMR) and two-dimensional diffusion-ordered spectroscopy (2D DOSY) (1)H NMR. A careful assignment and quantification of (1)H signals enabled a comprehensive characterization of the substances present in the samples investigated: heroin, its main related impurities (6-acetylmorphine, acetylcodeine, morphine, noscapine and papaverine) and cutting agents (caffeine and acetaminophen in nearly all samples as well as lactose, lidocaine, mannitol, piracetam in one sample only), and hence to establish their spectral signatures. The good agreement between the amounts of heroin, noscapine, caffeine and acetaminophen determined by (1)H NMR and gas chromatography, the reference method in forensic laboratories, demonstrates the validity of the (1)H NMR technique. In this paper, 2D DOSY (1)H NMR offers a new approach for a whole characterization of the various components of these complex mixtures.

Sildenafil citrate monohydrate-cyclodextrin nanosuspension complexes for use in metered-dose inhalers

Sildenafil is a selective phosphodiesterase-5 inhibitor used for the treatment of erectile dysfunction and pulmonary hypertension. Sildenafil citrate monohydrate was complexed with α-, hydroxypropyl-β- and γ-cyclodextrin (α-CD, HP-β-CD and γ-CD, respectively) to enhance its water solubility. The complexes of sildenafil citrate monohydrate with all types of CDs were characterized by phase solubility diagrams, (1)H and (13)C NMR, and dielectric constants. Sildenafil citrate monohydrate complexed with CDs was developed as nanosuspensions for use in a pressurized metered-dose inhaler (pMDI). Sildenafil citrate monohydrate pMDI formulations were prepared by a bottom-up process using dried ethanol as a solvent and HFA-134a as an antisolvent and propellant in order to form nanosuspensions. A 3×3 factorial design was applied for the contents of the dried ethanol and HFA-134a propellant. The phase solubility profiles of the sildenafil and cyclodextrins were described as AL type with a mole ratio 1:1. The piperazine moiety of sildenafil formed an inclusion in the cavity of the CDs. The particle diameters of the sildenafil citrate monohydrate suspensions in pMDIs were all within a nanosuspension size range. An assay of the sildenafil content showed that the formation of complexes with CDs was close to 100%. In the case of the formulations with CDs, the emitted doses varied within 97.4±10.8%, the fine particle fractions (FPFs) were in a range of 45-81%, the fine particle dose (FPD) was 12.6±2.0 μg and the mass median aerodynamic diameters (MMADs) were 1.86±0.41 μm. In contrast, the formulations without CDs produced a low emitted dose of sildenafil (<60%). Therefore, only sildenafil citrate monohydrate pMDI formulations containing CDs were suitable for use as aerosols.