1
|
Sviben I, Glavaš M, Erben A, Bachelart T, Pavlović Saftić D, Piantanida I, Basarić N. Dipeptides Containing Pyrene and Modified Photochemically Reactive Tyrosine: Noncovalent and Covalent Binding to Polynucleotides. Molecules 2023; 28:7533. [PMID: 38005255 PMCID: PMC10672942 DOI: 10.3390/molecules28227533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 11/06/2023] [Accepted: 11/08/2023] [Indexed: 11/26/2023] Open
Abstract
Dipeptides 1 and 2 were synthesized from unnatural amino acids containing pyrene as a fluorescent label and polynucleotide binding unit, and modified tyrosine as a photochemically reactive unit. Photophysical properties of the peptides were investigated by steady-state and time-resolved fluorescence. Both peptides are fluorescent (Φf = 0.3-0.4) and do not show a tendency to form pyrene excimers in the concentration range < 10-5 M, which is important for their application in the fluorescent labeling of polynucleotides. Furthermore, both peptides are photochemically reactive and undergo deamination delivering quinone methides (QMs) (ΦR = 0.01-0.02), as indicated from the preparative photomethanolysis study of the corresponding N-Boc protected derivatives 7 and 8. Both peptides form stable complexes with polynucleotides (log Ka > 6) by noncovalent interactions and similar affinities, binding to minor grooves, preferably to the AT reach regions. Peptide 2 with a longer spacer between the fluorophore and the photo-activable unit undergoes a more efficient deamination reaction, based on the comparison with the N-Boc protected derivatives. Upon light excitation of the complex 2·oligoAT10, the photo-generation of QM initiates the alkylation, which results in the fluorescent labeling of the oligonucleotide. This study demonstrated, as a proof of principle, that small molecules can combine dual forms of fluorescent labeling of polynucleotides, whereby initial addition of the dye rapidly forms a reversible high-affinity noncovalent complex with ds-DNA/RNA, which can be, upon irradiation by light, converted to the irreversible (covalent) form. Such a dual labeling ability of a dye could have many applications in biomedicinal sciences.
Collapse
Affiliation(s)
| | | | | | | | | | - Ivo Piantanida
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (I.S.); (M.G.); (A.E.); (T.B.); (D.P.S.)
| | - Nikola Basarić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (I.S.); (M.G.); (A.E.); (T.B.); (D.P.S.)
| |
Collapse
|
2
|
Stockhammer L, Radetzky M, Khatoon SS, Bechmann M, Waser M. Chiral Lewis Base-Catalysed Asymmetric Syntheses of Benzo-fused ϵ-Lactones. European J Org Chem 2023; 26:e202300704. [PMID: 38601860 PMCID: PMC11005097 DOI: 10.1002/ejoc.202300704] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/24/2023] [Indexed: 04/12/2024]
Abstract
We herein report a two-step protocol for the asymmetric synthesis of novel chiral benzofused ϵ-lactones starting from O-protected hydroxymethyl-para-quinone methides and activated aryl esters. By using chiral isothiourea Lewis base catalysts a broad variety of differently substituted products could be obtained in yields of around 50 % over both steps with high levels of enantioselectivities, albeit low diastereoselectivities only.
Collapse
Affiliation(s)
- Lotte Stockhammer
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Maximilian Radetzky
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Syeda Sadia Khatoon
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Matthias Bechmann
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Mario Waser
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| |
Collapse
|
3
|
Sugumaran M, Evans JJ. Catecholamine Derivatives as Novel Crosslinkers for the Synthesis of Versatile Biopolymers. J Funct Biomater 2023; 14:449. [PMID: 37754863 PMCID: PMC10531651 DOI: 10.3390/jfb14090449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/07/2023] [Accepted: 08/29/2023] [Indexed: 09/28/2023] Open
Abstract
Catecholamine metabolites are not only involved in primary metabolism, but also in secondary metabolism, serving a diverse array of physiologically and biochemically important functions. Melanin, which originates from dopa and dopamine, found in the hair, eye, and skin of all animals, is an important biopolymeric pigment. It provides protection against damaging solar radiation to animals. N-Acetyldopamine and N-β-alanyldopamine play a crucial role in the hardening of the exoskeletons of all insects. In addition, insects and other arthropods utilize the melanogenic process as a key component of their defense systems. Many marine organisms utilize dopyl peptides and proteins as bonding materials to adhere to various substrata. Moreover, the complex dopa derivatives that are precursors to the formation of the exoskeletons of numerous marine organisms also exhibit antibiotic properties. The biochemistry and mechanistic transformations of different catecholamine derivatives to produce various biomaterials with antioxidant, antibiotic, crosslinking, and gluing capabilities are highlighted. These reactivities are exhibited through the transient and highly reactive quinones, quinone methides, and quinone methide imine amide intermediates, as well as chelation to metal ions. A careful consideration of the reactivities summarized in this review will inspire numerous strategies for synthesizing novel biomaterials for future medical and industrial use.
Collapse
Affiliation(s)
- Manickam Sugumaran
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA;
| | - Jason J. Evans
- Department of Chemistry, University of Massachusetts Boston, Boston, MA 02125, USA
| |
Collapse
|
4
|
Gibadullina E, Neganova M, Aleksandrova Y, Nguyen HBT, Voloshina A, Khrizanforov M, Nguyen TT, Vinyukova E, Volcho K, Tsypyshev D, Lyubina A, Amerhanova S, Strelnik A, Voronina J, Islamov D, Zhapparbergenov R, Appazov N, Chabuka B, Christopher K, Burilov A, Salakhutdinov N, Sinyashin O, Alabugin I. Hybrids of Sterically Hindered Phenols and Diaryl Ureas: Synthesis, Switch from Antioxidant Activity to ROS Generation and Induction of Apoptosis. Int J Mol Sci 2023; 24:12637. [PMID: 37628818 PMCID: PMC10454409 DOI: 10.3390/ijms241612637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 08/03/2023] [Accepted: 08/07/2023] [Indexed: 08/27/2023] Open
Abstract
The utility of sterically hindered phenols (SHPs) in drug design is based on their chameleonic ability to switch from an antioxidant that can protect healthy tissues to highly cytotoxic species that can target tumor cells. This work explores the biological activity of a family of 45 new hybrid molecules that combine SHPs equipped with an activating phosphonate moiety at the benzylic position with additional urea/thiourea fragments. The target compounds were synthesized by reaction of iso(thio)cyanates with C-arylphosphorylated phenols containing pendant 2,6-diaminopyridine and 1,3-diaminobenzene moieties. The SHP/urea hybrids display cytotoxic activity against a number of tumor lines. Mechanistic studies confirm the paradoxical nature of these substances which combine pronounced antioxidant properties in radical trapping assays with increased reactive oxygen species generation in tumor cells. Moreover, the most cytotoxic compounds inhibited the process of glycolysis in SH-SY5Y cells and caused pronounced dissipation of the mitochondrial membrane of isolated rat liver mitochondria. Molecular docking of the most active compounds identified the activator allosteric center of pyruvate kinase M2 as one of the possible targets. For the most promising compounds, 11b and 17b, this combination of properties results in the ability to induce apoptosis in HuTu 80 cells along the intrinsic mitochondrial pathway. Cyclic voltammetry studies reveal complex redox behavior which can be simplified by addition of a large excess of acid that can protect some of the oxidizable groups by protonations. Interestingly, the re-reduction behavior of the oxidized species shows considerable variations, indicating different degrees of reversibility. Such reversibility (or quasi-reversibility) suggests that the shift of the phenol-quinone equilibrium toward the original phenol at the lower pH may be associated with lower cytotoxicity.
Collapse
Affiliation(s)
- Elmira Gibadullina
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Margarita Neganova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
- Institute of Physiologically Active Compounds at Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, Severnij Pr. 1, Chernogolovka 142432, Russia;
| | - Yulia Aleksandrova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
- Institute of Physiologically Active Compounds at Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, Severnij Pr. 1, Chernogolovka 142432, Russia;
| | - Hoang Bao Tran Nguyen
- The Department of General Organic and Petrochemical Synthesis Technology, The Kazan National Research Technological University, Karl Marx St. 68, Kazan 420015, Russia; (H.B.T.N.); (T.T.N.)
| | - Alexandra Voloshina
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Mikhail Khrizanforov
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Thi Thu Nguyen
- The Department of General Organic and Petrochemical Synthesis Technology, The Kazan National Research Technological University, Karl Marx St. 68, Kazan 420015, Russia; (H.B.T.N.); (T.T.N.)
| | - Ekaterina Vinyukova
- Institute of Physiologically Active Compounds at Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, Severnij Pr. 1, Chernogolovka 142432, Russia;
| | - Konstantin Volcho
- Department of Medicinal Chemistry, Novosibirsk Institute of Organic Chemistry, Lavrentiev Av. 9, Novosibirsk 630090, Russia (D.T.); (N.S.)
| | - Dmitry Tsypyshev
- Department of Medicinal Chemistry, Novosibirsk Institute of Organic Chemistry, Lavrentiev Av. 9, Novosibirsk 630090, Russia (D.T.); (N.S.)
| | - Anna Lyubina
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Syumbelya Amerhanova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Anna Strelnik
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Julia Voronina
- Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Leninskii Prospekt, 31, Moscow 119071, Russia;
| | - Daut Islamov
- Laboratory for Structural Analysis of Biomacromolecules, Kazan Scientific Center of Russian Academy of Science, 31, Kremlevskaya, Kazan 420008, Russia;
| | - Rakhmetulla Zhapparbergenov
- Laboratory of Engineering Profile, Department of Engineering Technology, Korkyt Ata Kyzylorda University, 29A, Aiteke Bi Street, Kyzylorda 120014, Kazakhstan;
| | - Nurbol Appazov
- Laboratory of Engineering Profile, Department of Engineering Technology, Korkyt Ata Kyzylorda University, 29A, Aiteke Bi Street, Kyzylorda 120014, Kazakhstan;
| | - Beauty Chabuka
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.C.)
| | - Kimberley Christopher
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.C.)
| | - Alexander Burilov
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Nariman Salakhutdinov
- Department of Medicinal Chemistry, Novosibirsk Institute of Organic Chemistry, Lavrentiev Av. 9, Novosibirsk 630090, Russia (D.T.); (N.S.)
| | - Oleg Sinyashin
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
| | - Igor Alabugin
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, Akad. Arbuzov St. 8, Kazan 420088, Russia; (M.N.); (Y.A.); (A.V.); (M.K.); (A.L.); (S.A.); (A.S.); (A.B.); (O.S.); (I.A.)
- Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, FL 32306-3290, USA; (B.C.)
| |
Collapse
|
5
|
Li Y, Wang Y, Zhang N, Zhou S, Peng Y, Zheng J. Glutathione conjugation and protein modification resulting from metabolic activation of venlafaxine in vitro and in vivo. Xenobiotica 2021; 51:1303-1317. [PMID: 34160341 DOI: 10.1080/00498254.2021.1946204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Venlafaxine (VLF), an antidepressant agent, is widely used to combat major depressive disorders, particularly for the treatment of selective serotonin reuptake inhibitor-resistant depression. VLF has been shown to cause liver injury. The present study aimed to investigate the metabolic activation of VLF and explore the mechanisms of hepatotoxicity induced by VLF.One glutathione (GSH) conjugate and one cysteine conjugate were both detected in mouse and human liver microsomal incubations containing VLF and GSH or cysteine. The two conjugates were also detected in cultured mouse primary hepatocytes and bile of rats after exposure to VLF. The in vitro and in vivo studies demonstrated that VLF was metabolized to a quinone methide intermediate reactive to GSH and cysteine residues of hepatic protein. The observed protein covalent binding revealed dose-dependency. The metabolic activation of VLF was P450-dependent, and CYP3A4 was found as the predominant enzyme involved in the bioactivation process.These findings facilitate better understanding of the metabolic activation-hepatotoxicity relationship of VLF and provide chemists with information about new potential structural alerts during drug design process.
Collapse
Affiliation(s)
- Yilin Li
- Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P. R. China
| | - Yang Wang
- Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P. R. China
| | - Na Zhang
- Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P. R. China
| | - Shenzhi Zhou
- Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P. R. China
| | - Ying Peng
- Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P. R. China
| | - Jiang Zheng
- Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P. R. China.,State Key Laboratory of Functions and Applications of Medicinal Plants, Key Laboratory of Pharmaceutics of Guizhou Province, Guizhou Medical University, Guiyang, Guizhou 550025, P. R. China.,Key Laboratory of Environmental Pollution, Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang, Guizhou 550025, P. R. China
| |
Collapse
|
6
|
Sambol M, Benčić P, Erben A, Matković M, Mihaljević B, Piantanida I, Kralj M, Basarić N. Photochemical Reactivity of Naphthol-Naphthalimide Conjugates and Their Biological Activity. Molecules 2021; 26:3355. [PMID: 34199541 DOI: 10.3390/molecules26113355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/21/2021] [Accepted: 05/28/2021] [Indexed: 11/17/2022] Open
Abstract
Quinone methide precursors 1a–e, with different alkyl linkers between the naphthol and the naphthalimide chromophore, were synthesized. Their photophysical properties and photochemical reactivity were investigated and connected with biological activity. Upon excitation of the naphthol, Förster resonance energy transfer (FRET) to the naphthalimide takes place and the quantum yields of fluorescence are low (ΦF ≈ 10−2). Due to FRET, photodehydration of naphthols to QMs takes place inefficiently (ΦR ≈ 10−5). However, the formation of QMs can also be initiated upon excitation of naphthalimide, the lower energy chromophore, in a process that involves photoinduced electron transfer (PET) from the naphthol to the naphthalimide. Fluorescence titrations revealed that 1a and 1e form complexes with ct-DNA with moderate association constants Ka ≈ 105–106 M−1, as well as with bovine serum albumin (BSA) Ka ≈ 105 M−1 (1:1 complex). The irradiation of the complex 1e@BSA resulted in the alkylation of the protein, probably via QM. The antiproliferative activity of 1a–e against two human cancer cell lines (H460 and MCF 7) was investigated with the cells kept in the dark or irradiated at 350 nm, whereupon cytotoxicity increased, particularly for 1e (>100 times). Although the enhancement of this activity upon UV irradiation has no imminent therapeutic application, the results presented have importance in the rational design of new generations of anticancer phototherapeutics that absorb visible light.
Collapse
|
7
|
Elder T, Rencoret J, del Río JC, Kim H, Ralph J. Radical Coupling Reactions of Hydroxystilbene Glucosides and Coniferyl Alcohol: A Density Functional Theory Study. Front Plant Sci 2021; 12:642848. [PMID: 33737945 PMCID: PMC7960926 DOI: 10.3389/fpls.2021.642848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/10/2021] [Indexed: 06/12/2023]
Abstract
The monolignols, p-coumaryl, coniferyl, and sinapyl alcohol, arise from the general phenylpropanoid biosynthetic pathway. Increasingly, however, authentic lignin monomers derived from outside this process are being identified and found to be fully incorporated into the lignin polymer. Among them, hydroxystilbene glucosides, which are produced through a hybrid process that combines the phenylpropanoid and acetate/malonate pathways, have been experimentally detected in the bark lignin of Norway spruce (Picea abies). Several interunit linkages have been identified and proposed to occur through homo-coupling of the hydroxystilbene glucosides and their cross-coupling with coniferyl alcohol. In the current work, the thermodynamics of these coupling modes and subsequent rearomatization reactions have been evaluated by the application of density functional theory (DFT) calculations. The objective of this paper is to determine favorable coupling and cross-coupling modes to help explain the experimental observations and attempt to predict other favorable pathways that might be further elucidated via in vitro polymerization aided by synthetic models and detailed structural studies.
Collapse
Affiliation(s)
- Thomas Elder
- USDA-Forest Service, Southern Research Station, Auburn, AL, United States
| | - Jorge Rencoret
- Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Seville, Spain
| | - José C. del Río
- Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Seville, Spain
| | - Hoon Kim
- Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin, Madison, WI, United States
| | - John Ralph
- Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, University of Wisconsin, Madison, WI, United States
- Department of Biochemistry, University of Wisconsin, Madison, WI, United States
| |
Collapse
|
8
|
Ito S, Sugumaran M, Wakamatsu K. Chemical Reactivities of ortho-Quinones Produced in Living Organisms: Fate of Quinonoid Products Formed by Tyrosinase and Phenoloxidase Action on Phenols and Catechols. Int J Mol Sci 2020; 21:ijms21176080. [PMID: 32846902 PMCID: PMC7504153 DOI: 10.3390/ijms21176080] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/19/2020] [Accepted: 08/20/2020] [Indexed: 12/27/2022] Open
Abstract
Tyrosinase catalyzes the oxidation of phenols and catechols (o-diphenols) to o-quinones. The reactivities of o-quinones thus generated are responsible for oxidative browning of plant products, sclerotization of insect cuticle, defense reaction in arthropods, tunichrome biochemistry in tunicates, production of mussel glue, and most importantly melanin biosynthesis in all organisms. These reactions also form a set of major reactions that are of nonenzymatic origin in nature. In this review, we summarized the chemical fates of o-quinones. Many of the reactions of o-quinones proceed extremely fast with a half-life of less than a second. As a result, the corresponding quinone production can only be detected through rapid scanning spectrophotometry. Michael-1,6-addition with thiols, intramolecular cyclization reaction with side chain amino groups, and the redox regeneration to original catechol represent some of the fast reactions exhibited by o-quinones, while, nucleophilic addition of carboxyl group, alcoholic group, and water are mostly slow reactions. A variety of catecholamines also exhibit side chain desaturation through tautomeric quinone methide formation. Therefore, quinone methide tautomers also play a pivotal role in the fate of numerous o-quinones. Armed with such wide and dangerous reactivity, o-quinones are capable of modifying the structure of important cellular components especially proteins and DNA and causing severe cytotoxicity and carcinogenic effects. The reactivities of different o-quinones involved in these processes along with special emphasis on mechanism of melanogenesis are discussed.
Collapse
Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
- Correspondence: (S.I.); (K.W.); Tel.: +81-562-93-9849 (S.I. & K.W.); Fax: +81-562-93-4595 (S.I. & K.W.)
| | - Manickam Sugumaran
- Department of Biology, University of Massachusetts, Boston, MA 02125, USA;
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
- Correspondence: (S.I.); (K.W.); Tel.: +81-562-93-9849 (S.I. & K.W.); Fax: +81-562-93-4595 (S.I. & K.W.)
| |
Collapse
|
9
|
Meng Q, Moinuddin SGA, Kim SJ, Bedgar DL, Costa MA, Thomas DG, Young RP, Smith CA, Cort JR, Davin LB, Lewis NG. Pterocarpan synthase (PTS) structures suggest a common quinone methide-stabilizing function in dirigent proteins and proteins with dirigent-like domains. J Biol Chem 2020; 295:11584-11601. [PMID: 32565424 PMCID: PMC7450108 DOI: 10.1074/jbc.ra120.012444] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 06/17/2020] [Indexed: 11/28/2022] Open
Abstract
The biochemical activities of dirigent proteins (DPs) give rise to distinct complex classes of plant phenolics. DPs apparently began to emerge during the aquatic-to-land transition, with phylogenetic analyses revealing the presence of numerous DP subfamilies in the plant kingdom. The vast majority (>95%) of DPs in these large multigene families still await discovery of their biochemical functions. Here, we elucidated the 3D structures of two pterocarpan-forming proteins with dirigent-like domains. Both proteins stereospecifically convert distinct diastereomeric chiral isoflavonoid precursors to the chiral pterocarpans, (-)- and (+)-medicarpin, respectively. Their 3D structures enabled comparisons with stereoselective lignan- and aromatic terpenoid-forming DP orthologs. Each protein provides entry into diverse plant natural products classes, and our experiments suggest a common biochemical mechanism in binding and stabilizing distinct plant phenol-derived mono- and bis-quinone methide intermediates during different C-C and C-O bond-forming processes. These observations provide key insights into both their appearance and functional diversification of DPs during land plant evolution/adaptation. The proposed biochemical mechanisms based on our findings provide important clues to how additional physiological roles for DPs and proteins harboring dirigent-like domains can now be rationally and systematically identified.
Collapse
Affiliation(s)
- Qingyan Meng
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - Syed G A Moinuddin
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - Sung-Jin Kim
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - Diana L Bedgar
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - Michael A Costa
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - Dennis G Thomas
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Robert P Young
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Clyde A Smith
- Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, California, USA
| | - John R Cort
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Laurence B Davin
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| | - Norman G Lewis
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA
| |
Collapse
|
10
|
Yang M, Basada J, Gronert S, Erden I. An Oxy-anion Accelerated [1,5]- o-Quinone Methide Shift During the Nucleophilic Epoxidation of Salicylfulvene. European J Org Chem 2020; 2020:362-366. [PMID: 33071627 PMCID: PMC7565285 DOI: 10.1002/ejoc.201901620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Indexed: 11/11/2022]
Abstract
A new facet of nucleophilic fulvene epoxidations has been uncovered. 6-Arylfulvenes containing an ortho or para hydroxyl group react with basic hydrogen peroxide in an unusual manner; the epoxidation of the fulvene exocyclic double bond is followed by a phenoxide ion initiated epoxide ring opening to form an o-quinone methide (o-QM) intermediate. The resulting cyclopentadienolate undergoes an unusual oxy-anion accelerated [1,5]-sigmatropic o-QM shift. Computational studies reveal that the activation energy for the [1,5]-QM-shift in the cyclopentadienolate intermediate is quite low, signifying the acceleration caused by the oxy-anion group. Placement of a second hydroxyl group in the 6-aryl ring at C5 epoxidation via electron donation to the o-QM carbon; instead, an intramolecular oxa-6-π-electrocyclization of the o-QM intermediate onto the cyclopentadiene is observed.
Collapse
Affiliation(s)
- Mingwei Yang
- San Francisco State university, Department of Chemistry and Biochemistry, 1600 Holloway Avenue, San Francisco California, 94132, USA
| | - John Basada
- San Francisco State university, Department of Chemistry and Biochemistry, 1600 Holloway Avenue, San Francisco California, 94132, USA
| | - Scott Gronert
- University of Wisconsin Wisconsin - Milwaukee, Department of Chemistry and Biochemistry, Cramer St., Milwaukee, WI 53211 USA
| | - Ihsan Erden
- San Francisco State university, Department of Chemistry and Biochemistry, 1600 Holloway Avenue, San Francisco California, 94132, USA
| |
Collapse
|
11
|
Romero KJ, Galliher MS, Raycroft MAR, Chauvin JPR, Bosque I, Pratt DA, Stephenson CRJ. Electrochemical Dimerization of Phenylpropenoids and the Surprising Antioxidant Activity of the Resultant Quinone Methide Dimers. Angew Chem Int Ed Engl 2018; 57:17125-17129. [PMID: 30474921 DOI: 10.1002/anie.201810870] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Indexed: 12/12/2022]
Abstract
A simple method for the dimerization of phenylpropenoid derivatives is reported. It leverages electrochemical oxidation of p-unsaturated phenols to access the dimeric materials in a biomimetic fashion. The mild nature of the transformation provides excellent functional group tolerance, resulting in a unified approach for the synthesis of a range of natural products and related analogues with excellent regiocontrol. The operational simplicity of the method allows for greater efficiency in the synthesis of complex natural products. Interestingly, the quinone methide dimer intermediates are potent radical-trapping antioxidants; more so than the phenols from which they are derived-or transformed to-despite the fact that they do not possess a labile H-atom for transfer to the peroxyl radicals that propagate autoxidation.
Collapse
Affiliation(s)
- Kevin J Romero
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Matthew S Galliher
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Mark A R Raycroft
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Jean-Philippe R Chauvin
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Irene Bosque
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Derek A Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | | |
Collapse
|
12
|
Abstract
The formal (4+1)-cyclization between in situ generated achiral carbonyl-stabilized ammonium ylides and vinylogous p-quinone methides can be carried out under operationally simple conditions, leading to two different double bond regioisomers depending on the used conditions. Besides these racemic approaches, also a first proof-of-concept for enantioselective versions of these reactions has been obtained.
Collapse
Affiliation(s)
- Lukas Roiser
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria
| | - Katharina Zielke
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria
| | - Mario Waser
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria
| |
Collapse
|
13
|
Škalamera Đ, Antol I, Mlinarić-Majerski K, Vančik H, Phillips DL, Ma J, Basarić N. Ultrafast Adiabatic Photodehydration of 2-Hydroxymethylphenol and the Formation of Quinone Methide. Chemistry 2018; 24:9426-9435. [PMID: 29677402 DOI: 10.1002/chem.201801543] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Indexed: 12/13/2022]
Abstract
The photochemical reactivity of 2-hydroxymethylphenol (1) was investigated experimentally by photochemistry under cryogenic conditions, by detecting reactive intermediates by IR spectroscopy, and by using nanosecond and femtosecond transient absorption spectroscopic methods in solution at room temperature. In addition, theoretical studies were performed to facilitate the interpretation of the experimental results and also to simulate the reaction pathway to obtain a better understanding of the reaction mechanism. The main finding of this work is that photodehydration of 1 takes place in an ultrafast adiabatic photochemical reaction without any clear intermediate, delivering quinone methide (QM) in the excited state. Upon photoexcitation to a higher vibrational level of the singlet excited state, 1 undergoes vibrational relaxation leading to two photochemical pathways, one by which synchronous elimination of H2 O gives QM 2 in its S1 state and the other by which homolytic cleavage of the phenolic O-H bond produces a phenoxyl radical (S0 ). Both are ultrafast processes that occur within a picosecond. The excited state of QM 2 (S1 ) probably deactivates to S0 through a conical intersection to give QM 2 (S0 ), which subsequently delivers benzoxete 4. Elucidation of the reaction mechanisms for the photodehydration of phenols by which QMs are formed is important to tune the reactivity of QMs with DNA and proteins for the potential application of QMs in medicine as therapeutic agents.
Collapse
Affiliation(s)
- Đani Škalamera
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia.,Department of Organic Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000, Zagreb, Croatia
| | - Ivana Antol
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia
| | - Kata Mlinarić-Majerski
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia
| | - Hrvoj Vančik
- Department of Organic Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000, Zagreb, Croatia
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P.R. China
| | - Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of, Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an, P.R. China
| | - Nikola Basarić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia
| |
Collapse
|
14
|
Meisinger N, Roiser L, Monkowius U, Himmelsbach M, Robiette R, Waser M. Asymmetric Synthesis of 2,3-Dihydrobenzofurans by a [4+1] Annulation Between Ammonium Ylides and In Situ Generated o- Quinone Methides. Chemistry 2017; 23:5137-5142. [PMID: 28165173 PMCID: PMC5419452 DOI: 10.1002/chem.201700171] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Indexed: 12/31/2022]
Abstract
A highly enantio‐ and diastereoselective [4+1] annulation between in situ generated ammonium ylides and o‐quinone methides for the synthesis of a variety of 2,3‐dihydrobenzofurans has been developed. The key factors controlling the reactivity and stereoselectivity were systematically investigated by experimental and computational means and the energy profiles obtained provide a deeper insight into the mechanistic details of this reaction.
Collapse
Affiliation(s)
- Nicole Meisinger
- Johannes Kepler University Linz, Institute of Organic Chemistry, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Lukas Roiser
- Johannes Kepler University Linz, Institute of Organic Chemistry, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Uwe Monkowius
- Johannes Kepler University Linz, Institute of Inorganic Chemistry, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Markus Himmelsbach
- Johannes Kepler University Linz, Institute of Analytical Chemistry, Altenbergerstrasse 69, 4040, Linz, Austria
| | - Raphaël Robiette
- Université catholique de Louvain, Institute of Condensed Matter and Nanosciences, Place Louis Pasteur 1 box L4.01.02, 1348, Louvain-la-Neuve, Belgium
| | - Mario Waser
- Johannes Kepler University Linz, Institute of Organic Chemistry, Altenbergerstrasse 69, 4040, Linz, Austria
| |
Collapse
|
15
|
Sugumaran M. Reactivities of Quinone Methides versus o-Quinones in Catecholamine Metabolism and Eumelanin Biosynthesis. Int J Mol Sci 2016; 17:ijms17091576. [PMID: 27657049 PMCID: PMC5037842 DOI: 10.3390/ijms17091576] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 09/08/2016] [Accepted: 09/12/2016] [Indexed: 12/18/2022] Open
Abstract
Melanin is an important biopolymeric pigment produced in a vast majority of organisms. Tyrosine and its hydroxylated product, dopa, form the starting material for melanin biosynthesis. Earlier studies by Raper and Mason resulted in the identification of dopachrome and dihydroxyindoles as important intermediates and paved way for the establishment of well-known Raper-Mason pathway for the biogenesis of brown to black eumelanins. Tyrosinase catalyzes the oxidation of tyrosine as well as dopa to dopaquinone. Dopaquinone thus formed, undergoes intramolecular cyclization to form leucochrome, which is further oxidized to dopachrome. Dopachrome is either converted into 5,6-dihydroxyindole by decarboxylative aromatization or isomerized into 5,6-dihydroxyindole-2-carboxylic acid. Oxidative polymerization of these two dihydroxyindoles eventually produces eumelanin pigments via melanochrome. While the role of quinones in the biosynthetic pathway is very well acknowledged, that of isomeric quinone methides, however, remained marginalized. This review article summarizes the key role of quinone methides during the oxidative transformation of a vast array of catecholamine derivatives and brings out the importance of these transient reactive species during the melanogenic process. In addition, possible reactions of quinone methides at various stages of melanogenesis are discussed.
Collapse
Affiliation(s)
- Manickam Sugumaran
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA.
| |
Collapse
|
16
|
Richard MA, Hamels D, Pigeon P, Top S, Dansette PM, Lee HZS, Vessières A, Mansuy D, Jaouen G. Oxidative metabolism of ferrocene analogues of tamoxifen: characterization and antiproliferative activities of the metabolites. ChemMedChem 2015; 10:981-90. [PMID: 25882581 DOI: 10.1002/cmdc.201500075] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 11/05/2022]
Abstract
Ferrociphenols have been found to have high antiproliferative activity against estrogen-independent breast cancer cells. The rat and human liver microsome-mediated metabolism of three compounds of the ferrocifen (FC) family, 1,1-bis(4-hydroxyphenyl)-2-ferrocenyl-but-1-ene (FC1), 1-(4-hydroxyphenyl)-1-(phenyl)-2-ferrocenyl-but-1-ene (FC2), and 1-[4-(3-dimethylaminopropoxy)phenyl]-1-(4-hydroxyphenyl)-2-ferrocenyl-but-1-ene (FC3), was studied. Three main metabolite classes were identified: quinone methides (QMs) deriving from two-electron oxidation of FCs, cyclic indene products (CPs) deriving from acid-catalyzed cyclization of QMs, and allylic alcohols (AAs) deriving from hydroxylation of FCs. These metabolites are generated by cytochromes P450 (P450s), as shown by experiments with either N-benzylimidazole as a P450 inhibitor or recombinant human P450s. Such P450-dependent oxidation of the phenol function and hydroxylation of the allylic CH2 group of FCs leads to the formation of QM and AA metabolites, respectively. Some of the new ferrociphenols obtained in this study were found to exhibit remarkable antiproliferative effects toward MDA-MB-231 hormone-independent breast cancer cells.
Collapse
Affiliation(s)
- Marie-Aude Richard
- PSL, Chimie ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France).,Sorbonne Universités, UPMC Univ. Paris 6, UMR 8232, IPCM, 4 place Jussieu, 75005 Paris (France).,CNRS, UMR 8232, IPCM, 75005 Paris (France)
| | - Didier Hamels
- PSL, Chimie ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France)
| | - Pascal Pigeon
- PSL, Chimie ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France).,Sorbonne Universités, UPMC Univ. Paris 6, UMR 8232, IPCM, 4 place Jussieu, 75005 Paris (France).,CNRS, UMR 8232, IPCM, 75005 Paris (France)
| | - Siden Top
- Sorbonne Universités, UPMC Univ. Paris 6, UMR 8232, IPCM, 4 place Jussieu, 75005 Paris (France). .,CNRS, UMR 8232, IPCM, 75005 Paris (France).
| | - Patrick M Dansette
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris Descartes, PRES Paris Cité Sorbonne, 45 rue des Saints Pères, 75270, Paris Cedex 06 (France)
| | - Hui Zhi Shirley Lee
- PSL, Chimie ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France).,Sorbonne Universités, UPMC Univ. Paris 6, UMR 8232, IPCM, 4 place Jussieu, 75005 Paris (France).,CNRS, UMR 8232, IPCM, 75005 Paris (France)
| | - Anne Vessières
- Sorbonne Universités, UPMC Univ. Paris 6, UMR 8232, IPCM, 4 place Jussieu, 75005 Paris (France).,CNRS, UMR 8232, IPCM, 75005 Paris (France)
| | - Daniel Mansuy
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris Descartes, PRES Paris Cité Sorbonne, 45 rue des Saints Pères, 75270, Paris Cedex 06 (France).
| | - Gérard Jaouen
- PSL, Chimie ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris (France). .,Sorbonne Universités, UPMC Univ. Paris 6, UMR 8232, IPCM, 4 place Jussieu, 75005 Paris (France). .,CNRS, UMR 8232, IPCM, 75005 Paris (France).
| |
Collapse
|
17
|
Matsuura BS, Keylor MH, Li B, Lin Y, Allison S, Pratt DA, Stephenson CRJ. A scalable biomimetic synthesis of resveratrol dimers and systematic evaluation of their antioxidant activities. Angew Chem Int Ed Engl 2015; 54:3754-7. [PMID: 25650836 DOI: 10.1002/anie.201409773] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Revised: 11/11/2014] [Indexed: 01/12/2023]
Abstract
An efficient synthetic route to the resveratrol oligomers quadrangularin A and pallidol is reported. It features a scalable biomimetic oxidative dimerization that proceeds in excellent yield and with complete regioselectivity. A systematic evaluation of the natural products and their synthetic precursors as radical-trapping antioxidants has revealed that, contrary to popular belief, this mode of action is unlikely to account for their observed biological activity.
Collapse
Affiliation(s)
- Bryan S Matsuura
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109 (USA)
| | | | | | | | | | | | | |
Collapse
|