89 research outputs found
Analytical, biological and chemical investigations on selected classes of alkaloids
No full textAbstract: This PhD project focuses on the phytochemical, antiviral and analytical investigation of selected classes of alkaloids. The thesis contains two distinct parts; the first one dealing with Amaryllidaceae alkaloids and potential antiviral agents, more in particular against SARS-CoV-2; and the second one dealing with quality control of alkaloid-containing food supplements based on Maca (Lepidium meyenii). A general structure elucidation workflow was established, combining the power of computer-assisted structure elucidation (CASE) by DFT (density functional theory) calculations with various chromatographic and spectroscopic techniques. The workflow was successfully applied to determine 2D and 3D structures of all compounds in this study. In addition, the structure of a mistakenly assigned compound named \u201cmacaridine\u201d was revised to macapyrrolin C by DFT calculation of chemical shifts. The phytochemical investigations of the four plant species (Hymenocallis littoralis, Pancratium maritimum, Scadoxus multiflorus, Lepidium meyenii) led to the discovery of nine novel alkaloids as well as extended the phytochemical profiles of the plant species. A library of Amaryllidaceae alkaloids was built and screened in vitro against the emerging SARS-CoV-2 and cytotoxicity on Vero-E6 cell line. As a result, thirteen compounds displayed moderate inhibition of SARS-CoV-2 replication (EC50 = 39 \u2013 100 \ub5M); ten compounds were devoid of activity and cytotoxicity, and twelve compounds lacked selective activity, since they were cytotoxic. Preliminary evaluation of structure-activity relationships revealed four skeleton-types (lycorine, homolycorine, crinine, and galanthamine) as promising scaffolds for further research. A new UPLC-TQD-MS/MS method was developed and validated for quality control of alkaloids in Maca-containing food supplements, because of their suspected toxicity. This represents the first analytical method for this purpose. Results obtained from analyses of commercial products indicate the alkaloid content of 500 \u2013 600 ppm in pure Maca powder. From a regulatory point of view, and based on safety concerns about the alkaloidal constituents of L. meyenii, it may be advisable to establish a maximum level of particular alkaloids or alkaloid classes in food supplements containing Maca, rather than to request their total absence. Also, we recommend the use of lepidilines as chemical markers for characterization of Maca in all types of commercial preparation due to their high content, exclusive existence in Maca and ultra-sensitivity to MS detection
Cyclopeptide alkaloids : isolation, structure elucidation, antiplasmodial activity and AGEs inhibiting properties
No full textAntifungal Activity of Extracts, Fractions, and Constituents from <i>Coccoloba cowellii</i> Leaves
No full textCoccoloba cowellii Britton (Polygonaceae, order Caryophyllales) is an endemic and critically endangered plant species that only grows in the municipality of Camagüey, a province of Cuba. A preliminary investigation of its total methanolic extract led to the discovery of promising antifungal activity. In this study, a bioassay-guided fractionation allowed the isolation of quercetin and four methoxyflavonoids: 3-O-methylquercetin, myricetin 3,3′,4′-trimethyl ether, 6-methoxymyricetin 3,4′-dimethyl ether, and 6-methoxymyricetin 3,3′,4′-trimethyl ether. The leaf extract, fractions, and compounds were tested against various fungi and showed strong in vitro antifungal activity against Cryptococcus neoformans and various Candida spp. with no cytotoxicity (CC50 > 64.0 µg/mL) on MRC-5 SV2 cells, determined by a resazurin assay. A Candida albicans SC5314 antibiofilm assay indicated that the antifungal activity of C. cowellii extracts and constituents is mainly targeted to planktonic cells. The total methanolic extract showed higher and broader activity compared with the fractions and mixture of compounds
Mood Components in Cocoa and Chocolate: The Mood Pyramid
No full textAbstractCocoa and chocolate, prepared from cocoa beans that originate from the fruits of the cocoa tree Theobroma cacao, have a long-standing reputation as healthy food, including mood-enhancing effects. In spite of many clinical trials with chocolate, cocoa, or its constituents, the mechanisms of action on mood and cognition remain unclear. More in particular, it is still controversial which constituents may contribute to the psychopharmacological activities, ranging from the major cacao flavanols and methylxanthines to the minor amines, amides, and alkaloids. In this review a critical appraisal is made of recent studies on mood and cognition, with a special emphasis on analytical characterization of the test samples. It is concluded that the mood and cognition-enhancing effects of cocoa and chocolate can be ranked from more general activities associated with flavanols and methylxanthines, to more specific activities related to minor constituents such as salsolinol, with on top the orosensory properties of chocolate. Therefore, the “mood pyramid” of cocoa and chocolate is proposed as a new concept. To understand the role and interactions of the different major and minor constituents of cocoa, it is recommended that all test samples used in future in vitro, in vivo, or human studies should be phytochemically characterized in much more detail than is common practice today.</jats:p
Mood components in cocoa and chocolate : the mood pyramid
No full textAbstract: Cocoa and chocolate, prepared from cocoa beans that originate from the fruits of the cocoa tree Theobroma cacao, have a long-standing reputation as healthy food, including mood-enhancing effects. In spite of many clinical trials with chocolate, cocoa, or its constituents, the mechanisms of action on mood and cognition remain unclear. More in particular, it is still controversial which constituents may contribute to the psychopharmacological activities, ranging from the major cacao flavanols and methylxanthines to the minor amines, amides, and alkaloids. In this review a critical appraisal is made of recent studies on mood and cognition, with a special emphasis on analytical characterization of the test samples. It is concluded that the mood and cognition-enhancing effects of cocoa and chocolate can be ranked from more general activities associated with flavanols and methylxanthines, to more specific activities related to minor constituents such as salsolinol, with on top the orosensory properties of chocolate. Therefore, the mood pyramid of cocoa and chocolate is proposed as a new concept. To understand the role and interactions of the different major and minor constituents of cocoa, it is recommended that all test samples used in future in vitro, in vivo, or human studies should be phytochemically characterized in much more detail than is common practice today
Muskusratten zonder bestrijding?: Ontwerp van een onderzoek aan de gevolgen van tijdelijk niet bestrijden
No full textOnderzoek naar de effecten van een eventuele veldproef waarbij voor een langere tijd in een bepaald gebied muskusratten niet bestreden worden.Muskusrattenbestrijdin
Isolation and structure elucidation of cyclopeptide alkaloids from <i>Ziziphus nummularia</i> and <i>Ziziphus spina-christi</i> by HPLC-DAD-MS and HPLC-PDA-HRMS-SPE-NMR
No full textCyclopeptide alkaloids
No full textAbstract: Cyclopeptide alkaloids are macrocyclic compounds, the ring system of which consists of a hydroxystyrylamine moiety, an amino acid and a \u3b2-hydroxy amino acid, and which is substituted with one or two additional units. This review covers scientific literature published since 2006 until today. In the past decade, 39 new cyclopeptide alkaloids have been reported. In addition, absolute or relative configurations of known compounds have been established. New sources of known compounds are listed: Plant families from which cyclopeptide alkaloids have been obtained during the past decade include the Acanthaceae, Malvaceae, Phyllanthaceae and Rubiaceae. Some development concerning total synthesis of cyclopeptide alkaloids are discussed. Finally, a critical overview is given of various biological activities that have been reported, i.e. on the central nervous system (CNS), antimicrobial activity and others
The emergence of a novel synthetic nicotine analog 6-methyl nicotine (6-MN) in proclaimed tobacco- and nicotine-free pouches available in Europe
No full textAbstract: A new nicotine delivery system in the form of tobacco-free nicotine pouches was introduced in Europe in 2019. These nicotine bags did not fall under the Tobacco Products Directive (TPD) II, which brought forward regulatory requirements for both cigarettes, related products, and e-liquids. As these pouches did not fall under the scope of the TPD, it was up to the member states to decide which action to be taken if any. Some EU member states banned these nicotine pouches, while others put restrictions on the amount of nicotine, warning messages, and presentation and packaging of the product, and some member states did not take any action. Likely as a result of the ban or restrictions, soon after also, tobacco and nicotine-free pouches became available in the European Union (EU). Early 2024, "NoNIC" pouches, claiming to be tobacco- and nicotine-free, became available on the European market. These pouches are promoted online and clearly target a younger population with a youth-appealing package design and enticing flavors. Upon analysis of different samples utilizing gas chromatography coupled to MS (GC-MS), liquid chromatography coupled to high-resolution tandem mass spectrometry (HRAM LC-MS2), and nuclear magnetic resonance spectroscopy (NMR), it was demonstrated that these pouches were indeed devoid of nicotine but contained the synthetic nicotine homolog 6-methyl nicotine (6-MN) and this up to 20 mg per pouch. Nonetheless, a part of a likely unaware/misled young adult subpopulation has easy access to these products, containing a novel molecule for which limited to no clinical effects are known
Isolation and structure elucidation of cyclopeptide alkaloids from **Ziziphus nummularia** and **Ziziphus spina-christi** by HPLC-DAD-MS and HPLC-PDA-(HRMS)-SPE-NMR
No full textAbstract: Seven cyclopeptide alkaloids were isolated from the stem bark of Ziziphus nummularia and Ziziphus spina-christi. Three previously undescribed compounds were identified: nummularine-U, spinanine-B and spinanine-C, together with the known compounds mauritine-F, nummularine-D, nummularine-E and amphibine-D. For their purification either semi-preparative HPLC with DAD and ESIMS detection or HPLC-PDA-(HRMS)-SPE-NMR was applied, together with conventional separation methods. Their structures were elucidated by spectroscopic means
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