β-Diketones and Their Derivatives: Synthesis, Characterization and Biomedical Applications

A special issue of Pharmaceuticals (ISSN 1424-8247). This special issue belongs to the section "Medicinal Chemistry".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 18782

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Department of Science and High Technology, Università degli Studi dell’Insubria, Via Valleggio, 9, 22100 Como, CO, Italy
Interests: coordination and organometallic chemistry; homogeneous catalysis; new inorganic materials; metal–organic frameworks (MOF)
Special Issues, Collections and Topics in MDPI journals
Department of Science and High Technology, Università degli Studi dell’Insubria, Via Valleggio, 11-22100 Como (CO), Italy
Interests: advanced fluorescence spectroscopy techniques; molecular biophysics; spectroscopic evaluation and optimization of drugs and drug delivery systems; photosensitizers; amyloid aggregation; new materials; polymeric metal-organic compounds
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Dept. of Science and High Technology, Università degli Studi dell’Insubria, Via Valleggio, 9, 22100 Como (CO), Italy
Interests: indole alkaloids; organometallic chemistry; organic electrochemistry; magnetic resonance imaging contrast agents; non-conventional techniques in organic synthesis

Special Issue Information

Dear Colleagues,

β-diketones are widely studied organic compounds that exhibit rich tautomerism patterns and peculiar chemical reactivity. The characteristic b-diketo moiety displays metal chelating and H-bonding affinities and can undergo radicalization as well as act as radical scavenger.

The above endowments make β-diketones particularly promising scaffolds for the development of novel drug substances and pharmacological active principles. Moreover, β-diketones may find applications as either carriers for metal-based drugs (e.g., Pt-based antineoplastic agents) or cages for contrast agents in diagnostic and medical imaging due to their ability to form supramolecular organic as well as metal-organic complexes. Finally, β-diketones are endowed with rather interesting spectroscopic properties. First, several β-diketones emit sizeable fluorescence, thus opening new avenues for theranostics applications, not only as they are drugs whose intra-tissue and intra-cellular localization and quantification can be straightforwardly achieved, but also because they can act as tracers for metals within biological tissues. Secondly, some β-diketones display photosensitized cytotoxicity.

Some biologically active β-diketones occur naturally and can be extracted from plants, disclosing exciting perspectives in phytopharmacy. The usage as traditional remedies of β-diketone-rich extracts obtained by plants like Turmeric and Hypericum Perforatum dates back to ancient times, and their beneficial effects are historically recognized. However, recent efforts in the design and production of new β-diketone molecules and individuation of optimized synthetic pathways and strategies have given new impulse to their exploitation in pharmacology. Moreover, β-diketones were recently pointed out as promising reaction intermediates or catalysts for the synthesis of other drug compounds.

This Special Issue of Pharmaceutics devoted to “β-diketones and derivatives” does not have the ambition to constitute an exhaustive panorama of the state of art in β-diketones chemistry and biomedical applications. It is rather intended to provide an interdisciplinary forum for the many different communities involved in the research on these fascinating and versatile compounds, giving a glance on the several interconnected aspects to be tackled in the next future, in the hope to offer a less sectorial point of view and, possibly, an occasion to develop new networks for the actors in play. Accordingly, high quality original research articles in a wealth of topics including, but not limited to, β-diketones synthesis, complexation and supramolecular arrangement, characterization, spectroscopy, in-silico modelling, and wide-spectrum biomedical applications are welcomed, provided their relevance and technical soundness. Well documented reviews on any aspect of the study of either β-diketones in general or any particular class of β-diketones are also solicited, as they will help potential readers to orient within this astonishingly heterogeneous universe.

Prof. Dr. Angelo Maspero
Dr. Luca Nardo
Dr. Giovanni Palmisano
Guest Editors

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Keywords

  • β-diketone
  • Drug compound
  • Drug synthesis
  • Metal complexation
  • Metal sensing
  • Contrast media for diagnostic imaging
  • Drug delivery
  • Spectroscopy
  • Photoreactivity
  • Theranostics
  • In-silico drug design

Published Papers (5 papers)

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Research

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22 pages, 3203 KiB  
Article
Curcumin-Based β-Diketo Ligands for Ga3+: Thermodynamic Investigation of Potential Metal-Based Drugs
by Matteo Mari, Debora Carrozza, Gianluca Malavasi, Ettore Venturi, Giulia Avino, Pier Cesare Capponi, Michele Iori, Sara Rubagotti, Silvia Belluti, Mattia Asti and Erika Ferrari
Pharmaceuticals 2022, 15(7), 854; https://doi.org/10.3390/ph15070854 - 12 Jul 2022
Cited by 7 | Viewed by 2186
Abstract
Curcumin is known for its therapeutic properties; among these, antioxidant, anti-inflammatory and anti-cancer ones stand out. Besides, curcumin metal complexes have shown widespread application in medicine and can be exploited as lead structures for developing metal-based drugs. Unfortunately, curcumin is poorly bioavailable, mainly [...] Read more.
Curcumin is known for its therapeutic properties; among these, antioxidant, anti-inflammatory and anti-cancer ones stand out. Besides, curcumin metal complexes have shown widespread application in medicine and can be exploited as lead structures for developing metal-based drugs. Unfortunately, curcumin is poorly bioavailable, mainly due to its instability in physiological conditions; this weakness is tightly connected to the presence of the β-diketo moiety undergoing tautomeric equilibrium. Stability and metal-chelating ability can be tuned by modulating the electronic effects and steric hindrance close to the β-diketo moiety; in addition, formation of a metal complex shifts the tautomeric equilibrium towards the β-keto–enol form and increases stability in biological media. Among the metals used in clinical therapy, gallium nitrate has shown to have significant antitumor activity against non-Hodgkin lymphoma and bladder cancer, thus indicating that gallium-based drugs have potential for further development as antineoplastic agents with improved therapeutic activity. Curcuminoids have demonstrated high affinity for gallium(III), allowing the formation of stable positively charged M:L 1:2 β-diketonate complexes that benefit from the therapeutic activity of both the metal and the ligand. Seven new curcumin derivatives were synthesized and completely characterized. The new derivatives retain the solvent-dependent keto–enol tautomerism, with the prevalence of the diketo form in aqueous solution. Enhanced stability in simulated physiological conditions was observed in comparison to the lead compound curcumin. The presence of Ga3+ anticipates the dissociation of the enolic proton, allowing chelate complex formation, and simultaneously it shifts the tautomeric equilibrium towards the keto–enol form. A complete 1H/13C NMR and UV–Vis study was performed to define the metal-to-ligand stoichiometry ratio and the overall stability constants. In addition, we demonstrated that some of the derivatives have increased antiproliferative activity on colon cancer cells compared to curcumin and antioxidant properties. On the whole, the synthesized curcumin-based molecules may act as new gallium(III) chelators with improved stability with respect to curcumin and could open interesting perspectives for the development of novel therapeutic agents for cancer. Full article
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17 pages, 3462 KiB  
Article
Synthesis, Characterization and DNA-Binding Affinity of a New Zinc(II) Bis(5-methoxy-indol-3-yl)propane-1,3-dione Complex
by Luca Scapinello, Guglielmo Vesco, Luca Nardo, Angelo Maspero, Federico Vavassori, Simona Galli and Andrea Penoni
Pharmaceuticals 2021, 14(8), 760; https://doi.org/10.3390/ph14080760 - 03 Aug 2021
Cited by 3 | Viewed by 2211
Abstract
The novel zinc(II) µ-oxo-bridged-dimeric complex [Zn2(µ-O)2(BMIP)2] (BMIP = 1,3-bis(5-methoxy-1-methyl-1H-indol-3-yl)propane-1,3-dione), 1, was synthetized and fully characterized. The spectral data indicate a zincoxane molecular structure, with the BMIP ligand coordinating in its neutral form via its [...] Read more.
The novel zinc(II) µ-oxo-bridged-dimeric complex [Zn2(µ-O)2(BMIP)2] (BMIP = 1,3-bis(5-methoxy-1-methyl-1H-indol-3-yl)propane-1,3-dione), 1, was synthetized and fully characterized. The spectral data indicate a zincoxane molecular structure, with the BMIP ligand coordinating in its neutral form via its oxygen atoms. Structural changes in 1 in dimethylsulfoxide (DMSO) were evidenced by means of spectroscopic techniques including infrared absorption and nuclear magnetic resonance, showing DMSO entrance in the coordination sphere of the metal ion. The resulting complex [Zn2(µ-O)2(BMIP)2(DMSO)], 2, readily reacts in the presence of N-methyl-imidazole (NMI), a liquid-phase nucleoside mimic, to form [Zn2(µ-O)2(BMIP)2(NMI)], 3, through DMSO displacement. The three complexes show high thermal stability, demonstrating that 1 has high affinity for hard nucleophiles. Finally, with the aim of probing the suitability of this system as model scaffold for new potential anticancer metallodrugs, the interactions of 1 with calf thymus DNA were investigated in vitro in pseudo-physiological environment through UV-Vis absorption and fluorescence emission spectroscopy, as well as time-resolved fluorescence studies. The latter analyses revealed that [Zn2(µ-O)2(BMIP)2(DMSO)] binds to DNA with high affinity upon DMSO displacement, opening new perspectives for the development of optimized drug substances. Full article
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24 pages, 5460 KiB  
Article
Comparison of Solution Chemical Properties and Biological Activity of Ruthenium Complexes of Selected β-Diketone, 8-Hydroxyquinoline and Pyrithione Ligands
by Tamás Pivarcsik, Gábor Tóth, Nikoletta Szemerédi, Anita Bogdanov, Gabriella Spengler, Jakob Kljun, Jerneja Kladnik, Iztok Turel and Éva A. Enyedy
Pharmaceuticals 2021, 14(6), 518; https://doi.org/10.3390/ph14060518 - 27 May 2021
Cited by 10 | Viewed by 3460
Abstract
In this work, the various biological activities of eight organoruthenium(II) complexes were evaluated to reveal correlations with their stability and reactivity in aqueous media. Complexes with general formula [Ru(η6-p-cymene)(X,Y)(Z)] were prepared, where (X,Y) represents either an O,O [...] Read more.
In this work, the various biological activities of eight organoruthenium(II) complexes were evaluated to reveal correlations with their stability and reactivity in aqueous media. Complexes with general formula [Ru(η6-p-cymene)(X,Y)(Z)] were prepared, where (X,Y) represents either an O,O-ligand (β-diketone), N,O-ligand (8-hydroxyquinoline) or O,S-pyrithione-type ligands (pyrithione = 1-hydroxypyridine-2(1H)-thione) with Cl or 1,3,5-triaza-7-phosphaadamantane (PTA) as a co-ligand (Z). The tested complexes inhibit the chlamydial growth on HeLa cells, and one of the complexes inhibits the growth of the human herpes simplex virus-2. The chlorido complexes with N,O- and O,S-ligands displayed strong antibacterial activity on Gram-positive strains including the resistant S. aureus (MRSA) and were cytotoxic in adenocarcinoma cell lines. Effect of the structural variation on the biological properties and solution stability was clearly revealed. The decreased bioactivity of the β-diketone complexes can be related to their lower stability in solution. In contrast, the O,S-pyrithione-type complexes are highly stable in solution and the complexation prevents the oxidation of the O,S-ligands. Comparing the binding of PTA and the chlorido co-ligands, it can be concluded that PTA is generally more strongly coordinated to ruthenium, which at the same time decreased the reactivity of complexes with human serum albumin or 1-methylimidazole as well as diminished their bioactivity. Full article
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Review

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18 pages, 3381 KiB  
Review
Structural Studies of β-Diketones and Their Implications on Biological Effects
by Poul Erik Hansen
Pharmaceuticals 2021, 14(11), 1189; https://doi.org/10.3390/ph14111189 - 20 Nov 2021
Cited by 22 | Viewed by 3054
Abstract
The paper briefly summarizes methods to determine the structure of β-diketones with emphasis on NMR methods. Density functional calculations are also briefly treated. Emphasis is on the tautomeric equilibria of β-diketones in relation to biological effects. Relevant physical parameters such as acidity and [...] Read more.
The paper briefly summarizes methods to determine the structure of β-diketones with emphasis on NMR methods. Density functional calculations are also briefly treated. Emphasis is on the tautomeric equilibria of β-diketones in relation to biological effects. Relevant physical parameters such as acidity and solubility are treated. A series of biologically active molecules are treated with respect to structure (tautomerism). Characteristic molecules or groups of molecules are usnic acids, tetramic and tetronic acids, o-hydroxydibenzoylmethanes, curcumines, lupulones, and hyperforines. Full article
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25 pages, 6443 KiB  
Review
Recent Developments in the Synthesis of β-Diketones
by Gonzalo de Gonzalo and Andrés R. Alcántara
Pharmaceuticals 2021, 14(10), 1043; https://doi.org/10.3390/ph14101043 - 13 Oct 2021
Cited by 16 | Viewed by 5434
Abstract
Apart from being one of the most important intermediates in chemical synthesis, broadly used in the formation of C–C bonds among other processes, the β-dicarbonyl structure is present in a huge number of biologically and pharmaceutically active compounds. In fact, mainly derived from [...] Read more.
Apart from being one of the most important intermediates in chemical synthesis, broadly used in the formation of C–C bonds among other processes, the β-dicarbonyl structure is present in a huge number of biologically and pharmaceutically active compounds. In fact, mainly derived from the well-known antioxidant capability associated with the corresponding enol tautomer, β-diketones are valuable compounds in the treatment of many pathological disorders, such as cardiovascular and liver diseases, hypertension, obesity, diabetes, neurological disorders, inflammation, skin diseases, fibrosis, or arthritis; therefore, the synthesis of these structures is an area of overwhelming interest for organic chemists. This paper is devoted to the advances achieved in the last ten years for the preparation of 1,3-diketones, using different chemical (Claisen, hydration of alkynones, decarboxylative coupling) or catalytic (biocatalysis, organocatalytic, metal-based catalysis) methodologies: Additionally, the preparation of branched β-dicarbonyl compounds by means of α-functionalization of non-substituted 1,3-diketones are also discussed. Full article
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