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Curcuma longa (turmeric) has an extensive history of ethnomedical use for common ailments, and “curcumin”-containing dietary supplements (CDS) are a highly visible portion of today’s self-medication market. Owing to raw material cost pressure, CDS products are affected by economically motivated, nefarious adulteration with synthetic curcumin (“syncumin”), possibly leading to unexpected toxicological issues due to “residual” impurities. Using a combination of targeted and untargeted (phyto)chemical analysis, this study investigated the botanical integrity of two commercial “turmeric” CDS with vitamin and other additives that were associated with reported clinical cases of hepatotoxicity. Analyzing multisolvent extracts of the CDS by 100% quantitative 1H NMR (qHNMR), alone and in combination with countercurrent separation (CCS), provided chemical fingerprints that allowed both the targeted identification and quantification of declared components and the untargeted recognition of adulteration. While confirming the presence of curcumin as a major constituent, the universal detection capability of NMR spectroscopy identification of significant residual impurities, including potentially toxic components. While the loss-free nature of CCS captured a wide polarity range of declared and unwanted chemical components, and also increased the dynamic range of the analysis, (q)HNMR determined their mass proportions and chemical constitutions. The results demonstrate that NMR spectroscopy can recognize undeclared constituents even if they represent only a fraction of the mass balance of a dietary supplement product. The chemical information associated with the missing 4.8% and 7.4% (m/m) in the two commercial samples, exhibiting an otherwise adequate curcumin content of 95.2% and 92.6%, respectively, pointed to a product integrity issue and adulteration with undeclared synthetic curcumin. Impurities from synthesis are most plausibly the cause of the observed adverse clinical effects. The study exemplifies how the simultaneously targeted and untargeted analytical principle of the 100% qHNMR method, performed with entry-level high-field instrumentation (400 MHz), can enhance the safety of dietary supplements by identifying adulterated, non-natural “natural” products.

This Perspective of the published essential medicinal chemistry of cannabidiol (CBD) provides evidence that the popularization of CBD-fortified or CBD-labeled health products and CBD-associated health claims lacks a rigorous scientific foundation. CBD’s reputation as a cure-all puts it in the same class as other “natural” panaceas, where valid ethnobotanicals are reduced to single, purportedly active ingredients. Such reductionist approaches oversimplify useful, chemically complex mixtures in an attempt to rationalize the commercial utility of natural compounds and exploit the “natural” label. Literature evidence associates CBD with certain semiubiquitous, broadly screened, primarily plant-based substances of undocumented purity that interfere with bioassays and have a low likelihood of becoming therapeutic agents. Widespread health challenges and pandemic crises such as SARS-CoV-2 create circumstances under which scientists must be particularly vigilant about healing claims that lack solid foundational data. Herein, we offer a critical review of the published medicinal chemistry properties of CBD, as well as precise definitions of CBD-containing substances and products, distilled to reveal the essential factors that impact its development as a therapeutic agent.

Chlorophylls are present in all extracts from the aerial parts of green plant materials. Chlorophylls may act as in vitro bioassay nuisance compounds, possibly preventing the reproducibility and accurate measurement of readouts due to their UV/vis absorbance, fluorescence properties, and tendency to precipitate in aqueous media. Despite the diversity of methods used traditionally to remove chlorophylls, details about their mode of operation, specificity, and reproducibility are scarce. Herein, we report a selective and efficient 45 min liquid–liquid/countercurrent chlorophyll cleanup method using Centrifugal Partition Chromatography (CPC) with a solvent system composed of hexanes–EtOAc–MeOH–water (5:5:5:5, v/v) in elution-extrusion mode. The broader utility of the method was assessed with four different extracts prepared from three well-characterized plant materials: Epimedium sagittatum (leaves), Senna alexandrina (leaves), and Trifolium pratense (aerial parts). The reproducibility of the method, the selectivity of the chlorophyll removal, as well as the preservation of the phytochemical integrity of the resulting chlorophyll-free (“degreened”) extracts were evaluated using HPTLC, UHPLC-UV, 1H NMR spectroscopy, and LC-MS as orthogonal phytochemical methods. The cleanup process adequately preserves the metabolomic diversity as well as the integrity of the original extracts. This method was found to be sufficiently rapid for the “degreening” of botanical extracts in higher-throughput sample preparation for further biological screening.

The notion of data transparency is gaining a strong awareness among the scientific community. The availability of raw data is actually regarded as a fundamental way to advance science by promoting both integrity and reproducibility of research outcomes. Particularly, in the field of natural product and chemical research, NMR spectroscopy is a fundamental tool for structural elucidation and quantification (qNMR). As such, the accessibility of original NMR data, i.e., Free Induction Decays (FIDs), fosters transparency in chemical research and optimizes both peer review and reproducibility of reports by offering the fundamental tools to perform efficient structural verification. Although original NMR data are known to contain a wealth of information, they are rarely accessible along with published data. This viewpoint discusses the relevance of the availability of original NMR data as part of good research practices not only to promote structural correctness, but also to enhance traceability and reproducibility of both chemical and biological results.

The revision of the structure of the sesquiterpene aquatolide from a bicyclo[2.2.0]hexane to a bicyclo[2.1.1]hexane structure using compelling NMR data, X-ray crystallography, and the recent confirmation via full synthesis exemplify that the achievement of “structural correctness” depends on the completeness of the experimental evidence. Archived FIDs and newly acquired aquatolide spectra demonstrate that archiving and rigorous interpretation of 1D 1H NMR data may enhance the reproducibility of (bio)chemical research and curb the growing trend of structural misassignments. Despite being the most accessible NMR experiment, 1D 1H spectra encode a wealth of information about bonds and molecular geometry that may be fully mined by 1H iterative full spin analysis (HiFSA). Fully characterized 1D 1H spectra are unideterminant for a given structure. The corresponding FIDs may be readily submitted with publications and collected in databases. Proton NMR spectra are indispensable for structural characterization even in conjunction with 2D data. Quantum interaction and linkage tables (QuILTs) are introduced for a more intuitive visualization of 1D J-coupling relationships, NOESY correlations, and heteronuclear experiments. Overall, this study represents a significant contribution to best practices in NMR-based structural analysis and dereplication.

High-throughput biology has contributed a wealth of data on chemicals, including natural products (NPs). Recently, attention was drawn to certain, predominantly synthetic, compounds that are responsible for disproportionate percentages of hits but are false actives. Spurious bioassay interference led to their designation as pan-assay interference compounds (PAINS). NPs lack comparable scrutiny, which this study aims to rectify. Systematic mining of 80+ years of the phytochemistry and biology literature, using the NAPRALERT database, revealed that only 39 compounds represent the NPs most reported by occurrence, activity, and distinct activity. Over 50% are not explained by phenomena known for synthetic libraries, and all had manifold ascribed bioactivities, designating them as invalid metabolic panaceas (IMPs). Cumulative distributions of ∼200,000 NPs uncovered that NP research follows power-law characteristics typical for behavioral phenomena. Projection into occurrence–bioactivity–effort space produces the hyperbolic black hole of NPs, where IMPs populate the high-effort base.

The acquisition of 1D 1H NMR (HNMR) spectra is one of earliest steps in characterizing natural products and other organic molecules. For publication, HNMR information usually is “converted” into a table format, and sometimes spectral plots are provided. However, this transformation is lossy and frequently insufficient for unambiguous dereplication. This ambiguity can even lead to structural revision, such as in the recent case of aquatolide (1), a sesquiterpene lactone from Asteriscus aquaticus. Our study demonstrates that public dissemination of original (digital) HNMR data (FIDs) can be a powerful means of enhancing the reproducibility of structural assignments and, thus, any downstream biological studies. Using the archived 800 MHz HNMR spectrum, and employing a semi-automated quantum mechanics-driven spectral analysis (HiFSA), we were able to rule out the initial assignment (1a), confirm the revision (1b), and achieve the full interpretation of the HNMR fingerprints. Using additional examples of constitutional and diastereomeric isomers which exhibit complex and near-identical HNMR spectra, we show that the public sharing of original HNMR data (FIDs) is not only essential for robust structural assignments, but can enhance the reproducibility of research with bioactive natural products and other organic molecules simply and productively.

C-glycosylated flavones, including orientin, isoorientin, vitexin, and isovitexin, are minor but biologically significant constituents of fruit extracts of the chaste-tree (Vitex agnus-castus L.), a botanical supplement used to treat PMS and postmenopausal symptoms. The partition coefficient, or K-value, is the ratio of the concentration of a compound in each phase of a biphasic solvent mixture and is a physicochemical property of a particular compound in a particular solvent system. This value can be used to predict retention volume (V ret) in a countercurrent separation procedure. The K-values of C-glycosylflavones present in complex botanical fractions have been determined in a number of solvent system families (HEMWat, EBWat, HterAcWat, terAcWat) using the shake-flask technique combined with relative LC-MS quantification. This K-value database has been used to develop targeted centrifugal partition (CPC) and high-speed countercurrent chromatography (HSCCC) methods. In each separation procedure the actual K value and V ret was reasonably predicted by the shake-flask partition experiment, confirming the utility of this approach in choosing a solvent system and targeting the fraction that contains the desired compound. This K-value database allowed for the efficient isolation of C-glycosylflavones from V. agnus-castus using orthogonal CCC and CPC methods.