Guido F. Pauli

# Publications/

OpenAccess The Essential Medicinal Chemistry of Curcumin

Journal: Journal of Medicinal Chemistry (RoMEO status: White) Published on
Categories: publications
Subjects: Pharmacognosy Phytochemistry Curcumin IMPs PAINS Review

Curcumin is a constituent (up to ∼5%) of the traditional medicine known as turmeric. Interest in the therapeutic use of turmeric and the relative ease of isolation of curcuminoids has led to their extensive investigation. Curcumin has recently been classified as both a PAINS (pan-assay interference compounds) and an IMPS (invalid metabolic panaceas) candidate. The likely false activity of curcumin in vitro and in vivo has resulted in >120 clinical trials of curcuminoids against several diseases.

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# Posters/

NAPRALERT, from an historical information silo to a linked resource able to address the new challenges in Natural Products Chemistry and Pharmacognosy.

Abstract from conference NAPRALERT is a database on natural products, including data on ethnobotany, chemistry, pharmacology, toxicology, and clinical trials from literature dating back to the 19th century. Established in 1975 by Norman R. Farnsworth, it became a web accessible resource in 2005 but soon became stagnant while literature grew exponentially. After a complete rewrite of the platform, the focus is now on connecting this resource to the rest of the existing databases and expanding its usability.

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# Publications/

Dissemination of Original NMR Data Enhances Reproducibility and Integrity in Chemical Research

Journal: Natural Product Reports (RoMEO status: Yellow) Published on
Categories: publications
Subjects: Fundamental research NMR raw data

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.

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# Posters/

Grape Seed Proanthocyanidins: A Novel Source Of Dental Biomaterials And Unique Phytochemistry

Composite-based, tooth colored dental restorations, in spite of their aesthetic appeal, are limited by a short life span. Every subsequent restoration results in the loss of healthy dental tissue. Thus, a bio-mimetic approach has been developed to enhance the mechanical strength of dentin using plant-derived proanthocyanidins (PACs). From a panel of eight active plants, grape seed extract showed the highest dentin biomodification potential, a 15-fold enhancement of dentin stiffness measured in MPa.

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# Posters/

Reviving NAPRALERT and Making It Ready For Improvement and New Challenges In Natural Products Chemistry and Pharmacognosy

NAPRALERT is a database on natural products, including data on the ethnobotany, chemistry, pharmacology, toxicology, and clinical trials. It was established in 1975 by the late Norman R. Farnsworth, at a time when computerized databases were just starting. It became web-accessible in 2005. Due to resource constraints, few enhancements were made to the existing database structure. Now, 10 years later, NAPRALERT faces the challenge of catching-up with other well-established resources.

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# Publications/

OpenAccess Toward Structural Correctness: Aquatolide and the Importance of 1D Proton NMR FID Archiving

Journal: Journal of Organic Chemistry (RoMEO status: White) Published on
Categories: publications
Subjects: Pharmacognosy Phytochemistry NMR FID raw data Spin simulation

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.

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# Publications/

OpenAccess Can Invalid Bioactives Undermine Natural Product-Based Drug Discovery?

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.

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# Publications/

Bioadhesive properties of enriched proanthocyanidins primers

Journal: Dental Materials (RoMEO status: Green) Published on
Categories: publications
Subjects: Pharmacognosy Phytochemistry Dentistry OPAC NMR

Plant derived proanthocyanidins are well-established compounds exhibiting high dentin biomodification potency. Among the effects, enhanced tissue biomechanics and biostability are of relevance to restorative dentistry. This study evaluated the adhesive properties of an enriched proanthocyanidin primer on the bond strength of experimental resin-based adhesives containing variable concentrations of HEMA.

# Publications/

Subtle Chemical Shifts Explain the NMR Fingerprints of Oligomeric Proanthocyanidins with High Dentin Biomodification Potency

Journal: Journal of Organic Chemistry (RoMEO status: White) Published on
Categories: publications
Subjects: Pharmacognosy Phytochemistry Dentistry OPAC NMR

The ability of certain oligomeric proanthocyanidins (OPACs) to enhance the biomechanical properties of dentin involves collagen cross-linking of the 1.3–4.5 nm wide space via protein–polyphenol interactions. A systematic interdisciplinary search for the bioactive principles of pine bark has yielded the trimeric PAC, ent-epicatechin-(4β→8)-epicatechin-(2β→O→7,4β→8)-catechin (3), representing the hitherto most potent single chemical entity capable of enhancing dentin stiffness. Building the case from two congeneric PAC dimers, a detailed structural analysis decoded the stereochemistry, spatial arrangement, and chemical properties of three dentin biomodifiers.

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# Posters/

Chemical nano shifts explain the NMR fingerprints of dentin-enhancing oligomeric proanthocyanidins

1D NMR spectra contain a wealth of vital structural information that can enhance the description of bioactive molecules. The present study demonstrates how quantum-mechanics driven 1H iterative Full Spin Analysis (QM-HiFSA) is capable of distinguishing spectral detail that cannot be interpreted manually or visually, but provides important information of the 3D structure and bonding (re-)activity of the molecules. This approach is established by analyzing 1D NMR spectra of oligomeric proanthocyanidins (OPACs), which exhibit high dentin bioactivity, and were isolated from the inner bark of pine.

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# Posters/

Dissemination of original NMR data enhances the reproducibility of natural product research

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.

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# Posters/

K-targeted isolation of C-glycosylflavones from Vitex agnus-castus by countercurrent methodology

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.

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# Posters/

Minimizing the problems with “PIMPs”

A recent article by Baell(1) on the problems experienced by medicinal chemists with pan-assay interference compounds (PAINS) and Shoichet’s work(2) on the impact of aggregation occurring in high throughput screening libraries, prompts a consideration of how these and other similar problems are experienced by pharmacognosists with promiscuous invalid metabolites as panaceas (PIMPs). Contrary to the classical definition of secondary metabolites as being species specific (or near specific), several natural products, particularly in the more extensively investigated plant kingdom, are common across species, genera, and even families (e.

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# Publications/

Mimicking the Hierarchical Functions of Dentin Collagen Cross-Links with Plant Derived Phenols and Phenolic Acids

Journal: Langmuir (RoMEO status: White) Published on
Categories: publications
Subjects: Pharmacognosy Phytochemistry Dentistry Polyphenols NMR

Proanthocyanidins (PACs) are secondary plant metabolites that mediate nonenzymatic collagen cross-linking and enhance the properties of collagen based tissue, such as dentin. The extent and nature of cross-linking is influenced by the composition and specific chemical structure of the bioactive compounds present in certain PAC-rich extracts. This study investigated the effect of the molecular weight and stereochemistry of polyphenol compounds on two important properties of dentin, biomechanics, and biostability. For that, purified phenols, a phenolic acid, and some of its derivatives were selected: PAC dimers (A1, A2, B1, and B2) and a trimer (C1), gallic acid (Ga), its esters methyl-gallate (MGa) and propyl-gallate (PGa), and a pentagalloyl ester of glucose (PGG).

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# Publications/

OpenAccess Essential Parameters for Structural Analysis and Dereplication by 1H NMR Spectroscopy

Journal: Journal of Natural Products (RoMEO status: White) Published on
Categories: publications
Subjects: Pharmacognosy Phytochemistry NMR Spin simulation

The present study demonstrates the importance of adequate precision when reporting the δ and J parameters of frequency domain 1H NMR (HNMR) data. Using a variety of structural classes (terpenoids, phenolics, alkaloids) from different taxa (plants, cyanobacteria), this study develops rationales that explain the importance of enhanced precision in NMR spectroscopic analysis and rationalizes the need for reporting Δδ and ΔJ values at the 0.1–1 ppb and 10 mHz level, respectively.

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