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Kumari S, Carmona AV, Tiwari AK, Trippier PC. Amide Bond Bioisosteres: Strategies, Synthesis, and Successes. J Med Chem 2020; 63:12290-12358. [PMID: 32686940 DOI: 10.1021/acs.jmedchem.0c00530] [Citation(s) in RCA: 209] [Impact Index Per Article: 52.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The amide functional group plays a key role in the composition of biomolecules, including many clinically approved drugs. Bioisosterism is widely employed in the rational modification of lead compounds, being used to increase potency, enhance selectivity, improve pharmacokinetic properties, eliminate toxicity, and acquire novel chemical space to secure intellectual property. The introduction of a bioisostere leads to structural changes in molecular size, shape, electronic distribution, polarity, pKa, dipole or polarizability, which can be either favorable or detrimental to biological activity. This approach has opened up new avenues in drug design and development resulting in more efficient drug candidates introduced onto the market as well as in the clinical pipeline. Herein, we review the strategic decisions in selecting an amide bioisostere (the why), synthetic routes to each (the how), and success stories of each bioisostere (the implementation) to provide a comprehensive overview of this important toolbox for medicinal chemists.
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Affiliation(s)
- Shikha Kumari
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
| | - Angelica V Carmona
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
| | - Amit K Tiwari
- Department of Pharmacology and Experimental Therapeutics, College of Pharmacy and Pharmaceutical Sciences, The University of Toledo, Toledo, Ohio 43614, United States
| | - Paul C Trippier
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States.,Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States.,UNMC Center for Drug Discovery, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
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Cassell RJ, Sharma KK, Su H, Cummins BR, Cui H, Mores KL, Blaine AT, Altman RA, van Rijn RM. The Meta-Position of Phe 4 in Leu-Enkephalin Regulates Potency, Selectivity, Functional Activity, and Signaling Bias at the Delta and Mu Opioid Receptors. Molecules 2019; 24:molecules24244542. [PMID: 31842282 PMCID: PMC6943441 DOI: 10.3390/molecules24244542] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 12/08/2019] [Accepted: 12/10/2019] [Indexed: 01/10/2023] Open
Abstract
As tool compounds to study cardiac ischemia, the endogenous δ-opioid receptors (δOR) agonist Leu5-enkephalin and the more metabolically stable synthetic peptide (d-Ala2, d-Leu5)-enkephalin are frequently employed. However, both peptides have similar pharmacological profiles that restrict detailed investigation of the cellular mechanism of the δOR’s protective role during ischemic events. Thus, a need remains for δOR peptides with improved selectivity and unique signaling properties for investigating the specific roles for δOR signaling in cardiac ischemia. To this end, we explored substitution at the Phe4 position of Leu5-enkephalin for its ability to modulate receptor function and selectivity. Peptides were assessed for their affinity to bind to δORs and µ-opioid receptors (µORs) and potency to inhibit cAMP signaling and to recruit β-arrestin 2. Additionally, peptide stability was measured in rat plasma. Substitution of the meta-position of Phe4 of Leu5-enkephalin provided high-affinity ligands with varying levels of selectivity and bias at both the δOR and µOR and improved peptide stability, while substitution with picoline derivatives produced lower-affinity ligands with G protein biases at both receptors. Overall, these favorable substitutions at the meta-position of Phe4 may be combined with other modifications to Leu5-enkephalin to deliver improved agonists with finely tuned potency, selectivity, bias and drug-like properties.
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MESH Headings
- Animals
- CHO Cells
- Cricetulus
- Enkephalin, Leucine/genetics
- Enkephalin, Leucine/pharmacology
- Humans
- Phenylalanine
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Signal Transduction/drug effects
- Signal Transduction/genetics
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Affiliation(s)
- Robert J. Cassell
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (R.J.C.); (H.S.); (K.L.M.); (A.T.B.)
| | - Krishna K. Sharma
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045, USA;
| | - Hongyu Su
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (R.J.C.); (H.S.); (K.L.M.); (A.T.B.)
| | | | - Haoyue Cui
- College of Wuya, Shenyang Pharmaceutical University, Shenyang 110016, China;
| | - Kendall L. Mores
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (R.J.C.); (H.S.); (K.L.M.); (A.T.B.)
| | - Arryn T. Blaine
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (R.J.C.); (H.S.); (K.L.M.); (A.T.B.)
| | - Ryan A. Altman
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045, USA;
- Correspondence: (R.A.A.); (R.M.v.R.)
| | - Richard M. van Rijn
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA; (R.J.C.); (H.S.); (K.L.M.); (A.T.B.)
- Purdue Institute for Drug Discovery, Purdue University, West Lafayette, IN 47907, USA
- Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN 47907, USA
- Correspondence: (R.A.A.); (R.M.v.R.)
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3
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Sun S, Jia Q, Zhang Z. Applications of amide isosteres in medicinal chemistry. Bioorg Med Chem Lett 2019; 29:2535-2550. [PMID: 31377035 DOI: 10.1016/j.bmcl.2019.07.033] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/17/2019] [Accepted: 07/19/2019] [Indexed: 12/18/2022]
Abstract
Isosteric replacement of amide groups is a classic practice in medicinal chemistry. This digest highlights the applications of most commonly employed amide isosteres in drug design aiming at improving potency and selectivity, optimizing physicochemical and pharmacokinetic properties, eliminating or modifying toxicophores, as well as providing novel intellectual property of lead compounds.
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Affiliation(s)
- Shaoyi Sun
- Xenon Pharmaceuticals Inc., 200-3650 Gilmore Way, Burnaby, BC V5G 4W8, Canada.
| | - Qi Jia
- Xenon Pharmaceuticals Inc., 200-3650 Gilmore Way, Burnaby, BC V5G 4W8, Canada
| | - Zaihui Zhang
- Signalchem Lifesciences Corp., 110-13210, Vanier Place, Richmond, BC V6V 2J2, Canada
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Synthesis of Leu-enkephalin peptidomimetics containing trifluoromethylalkenes as amide isopolar mimics. J Fluor Chem 2019; 218:90-98. [DOI: 10.1016/j.jfluchem.2018.12.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Altman RA, Sharma KK, Rajewski LG, Toren PC, Baltezor MJ, Pal M, Karad SN. Tyr 1-ψ[( Z)CF═CH]-Gly 2 Fluorinated Peptidomimetic Improves Distribution and Metabolism Properties of Leu-Enkephalin. ACS Chem Neurosci 2018; 9:1735-1742. [PMID: 29648788 DOI: 10.1021/acschemneuro.8b00085] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Opioid peptides are key regulators in cellular and intercellular physiological responses, and could be therapeutically useful for modulating several pathological conditions. Unfortunately, the use of peptide-based agonists to target centrally located opioid receptors is limited by poor physicochemical (PC), distribution, metabolic, and pharmacokinetic (DMPK) properties that restrict penetration across the blood-brain barrier via passive diffusion. To address these problems, the present paper exploits fluorinated peptidomimetics to simultaneously modify PC and DMPK properties, thus facilitating entry into the central nervous system. As an initial example, the present paper exploited the Tyr1-ψ[( Z)CF═CH]-Gly2 peptidomimetic to improve PC druglike characteristics (computational), plasma and microsomal degradation, and systemic and CNS distribution of Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu). Thus, the fluoroalkene replacement transformed an instable in vitro tool compound into a stable and centrally distributed in vivo probe. In contrast, the Tyr1-ψ[CF3CH2-NH]-Gly2 peptidomimetic decreased stability by accelerating proteolysis at the Gly3-Phe4 position.
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Affiliation(s)
- Ryan A. Altman
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Krishna K. Sharma
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Lian G. Rajewski
- Biotechnology Innovation and Optimization Center, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Paul C. Toren
- Biotechnology Innovation and Optimization Center, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Michael J. Baltezor
- Biotechnology Innovation and Optimization Center, The University of Kansas, Lawrence, Kansas 66045, United States
| | - Mohan Pal
- Department of Pathology, Michigan Medicine, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Somnath N. Karad
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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Karad SN, Pal M, Crowley RS, Prisinzano TE, Altman RA. Synthesis and Opioid Activity of Tyr 1 -ψ[(Z)CF=CH]-Gly 2 and Tyr 1 -ψ[(S)/(R)-CF 3 CH-NH]-Gly 2 Leu-enkephalin Fluorinated Peptidomimetics. ChemMedChem 2017; 12:571-576. [PMID: 28296145 PMCID: PMC5486982 DOI: 10.1002/cmdc.201700103] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 03/13/2017] [Indexed: 12/16/2022]
Abstract
We describe the design, synthesis, and opioid activity of fluoroalkene (Tyr1 -ψ[(Z)CF=CH]-Gly2 ) and trifluoroethylamine (Tyr1 -ψ[(S)/(R)-CF3 CH-NH]-Gly2 ) analogues of the endogenous opioid neuropeptide, Leu-enkephalin. The fluoroalkene peptidomimetic exhibited low nanomolar functional activity (5.0±2 nm and 60±15 nm for δ- and μ-opioid receptors, respectively) with a μ/δ-selectivity ratio that mimics that of the natural peptide. However, the trifluoroethylamine peptidomimetics, irrespective of stereochemistry, did not activate the opioid receptors, which suggest that bulky CF3 substituents are not tolerated at this position.
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Affiliation(s)
- Somnath Narayan Karad
- Department of Medicinal Chemistry, The University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas, 66045, USA
| | - Mohan Pal
- Department of Medicinal Chemistry, The University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas, 66045, USA
| | - Rachel S Crowley
- Department of Medicinal Chemistry, The University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas, 66045, USA
| | - Thomas E Prisinzano
- Department of Medicinal Chemistry, The University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas, 66045, USA
| | - Ryan A Altman
- Department of Medicinal Chemistry, The University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas, 66045, USA
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Kuhnline Sloan CD, Nandi P, Linz TH, Aldrich JV, Audus KL, Lunte SM. Analytical and biological methods for probing the blood-brain barrier. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2012; 5:505-31. [PMID: 22708905 PMCID: PMC3744104 DOI: 10.1146/annurev-anchem-062011-143002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The blood-brain barrier (BBB) is an important interface between the peripheral and central nervous systems. It protects the brain against the infiltration of harmful substances and regulates the permeation of beneficial endogenous substances from the blood into the extracellular fluid of the brain. It can also present a major obstacle in the development of drugs that are targeted for the central nervous system. Several methods have been developed to investigate the transport and metabolism of drugs, peptides, and endogenous compounds at the BBB. In vivo methods include intravenous injection, brain perfusion, positron emission tomography, and microdialysis sampling. Researchers have also developed in vitro cell-culture models that can be employed to investigate transport and metabolism at the BBB without the complication of systemic involvement. All these methods require sensitive and selective analytical methods to monitor the transport and metabolism of the compounds of interest at the BBB.
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DesMarteau DD, Lu C. Syntheses and lipophilicity measurement of Nα/N-terminus-1,1-dihydroperfluoroalkylated α-amino acids and small peptides. J Fluor Chem 2007. [DOI: 10.1016/j.jfluchem.2007.07.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Chappa AK, Cooper JD, Audus KL, Lunte SM. Investigation of the metabolism of substance P at the blood-brain barrier using LC-MS/MS. J Pharm Biomed Anal 2006; 43:1409-15. [PMID: 17118606 PMCID: PMC1945052 DOI: 10.1016/j.jpba.2006.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2006] [Revised: 10/02/2006] [Accepted: 10/10/2006] [Indexed: 11/19/2022]
Abstract
Substance P (SP) has been associated with pain and depression as well as neurodegenerative diseases. Many of these diverse actions of SP can potentially be attributed to SP metabolites generated at the blood-brain barrier (BBB). In this study, the metabolism of SP was investigated using an in vitro model of the BBB and LC-MS/MS. Substance P metabolism was found to be non-saturable in the concentration range of 100 nM to 10 microM, with approximately 70% of the peptide remaining intact after 5 h. The major metabolites of SP were identified by MS as 3-11 and 5-11. Two previously unreported metabolites, 5-11 and 6-11, were also found in our studies. Several additional minor SP metabolites, including 1-9 and 2-11, were also identified. A profile of the SP metabolites generated by the BBB over time was obtained. The results from the present study provide a better understanding of the role of the blood-brain barrier in the pharmacology of SP.
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Affiliation(s)
- Arvind K Chappa
- Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, KS 66047, USA
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Mehrotra S, Prajapati RK, Haq W, Singh VK. Immunomodulation by biphalin, dimeric synthetic opioid peptide, and its analog. Immunopharmacol Immunotoxicol 2002; 24:83-96. [PMID: 12022447 DOI: 10.1081/iph-120003405] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The opioid pentapeptides called enkephalins were originally described as the endogenous ligands for the opioid receptors. Although their precise physiological significance still remains elusive, the enkephalins have been reported to exhibit analgesic, antidepressant, antianxiety and anticonvulsant activities. In addition, enkephalins have also been shown to act as immunomodulator. The first generation of dimeric peptides was derived from enkephalins. Biphalin [(Tyr-D-Ala-Gly-Phe-NH)2] is a bivalent opioid analog containing two tyrosine residues. We have evaluated the immunomodulatory properties of biphalin and its analogs in various in vitro tests. We report that biphalin and one of its analogs [Tyr-D-Ala-Gly-Phe-NH.NH-Phe(p-Cl)-H] stimulate human T cell proliferation, natural killer (NK) cell cytotoxicity in vitro and interleukin-2 (IL-2) production. Biphalin and its analog also released chemokine like factor in the culture supernatant that was responsible for increased chemotaxis of monocytes. Furthermore, these peptides inhibited tumor necrosis factor (TNF-alpha) production in lipopolysaccharide (LPS) stimulated peripheral blood mononuclear cells (PBMC) and nitric oxide (NO) production in mouse macrophage cells, RAW 264.7. Our observations suggest immunomodulatory property of biphalin and its analog.
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Affiliation(s)
- S Mehrotra
- Department of Immunology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India
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11
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Abstract
The transport of substance P (SP) was investigated using the bovine brain microvessel endothelial cell culture model of the blood-brain barrier (BBB). The samples were derivatized precolumn with naphthalene dialdehyde, then analyzed by cyclodextrin-modified micellar electrokinetic chromatography with laser-induced fluorescence detection. SP crossed the BBB in both the apical-to-basolateral and basolateral-to-apical directions through an active transport mechanism. The transport of SP from the apical side was demonstrated to be via transcytosis. The N-terminal (SP(1-4)) and C-terminal (SP(3-11)) fragments were also found to permeate the BBB from the apical side.
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Affiliation(s)
- Anita L Freed
- Department of Pharmaceutical Chemistry, The University of Kansas, School of Pharmacy, Lawrence KS 66047, USA.
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12
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Freed AL, Audus KL, Lunte SM. Investigation of the metabolism of substance P at the blood-brain barrier using capillary electrophoresis with laser-induced fluorescence detection. Electrophoresis 2001; 22:3778-84. [PMID: 11699918 DOI: 10.1002/1522-2683(200109)22:17<3778::aid-elps3778>3.0.co;2-e] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Substance P (SP) metabolism was investigated upon exposure to a monolayer of bovine brain microvessel endothelial cells (BBMECs), a cell culture model of the blood-brain barrier. SP was incubated with the BBMECs and its metabolism was followed as a function of time over a 5-h period. The resulting samples were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA)/cyanide, separated, and detected using cyclodextrin-modified electrokinetic chromatography with laser-induced fluorescence detection (CDMEKC-LIF). Upon exposure to the BBMEC monolayer, SP rapidly degraded to produce the N-terminal (1-9), (1-4) and (1-7) and C-terminal (2-11) and (3-11) fragments. These results were compared with those in an earlier report from our laboratory, where SP metabolism was investigated in vivo by microdialysis sampling in rat striatum.
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Affiliation(s)
- A L Freed
- Department of Pharmaceutical Chemistry and the Center for Bioanalytical Research, University of Kansas, Lawrence, USA
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Gawron AJ, Lunte SM. Detection of neuropeptides using on-capillary copper complexation and capillary electrophoresis with electrochemical detection. Electrophoresis 2000; 21:3205-11. [PMID: 11001219 DOI: 10.1002/1522-2683(20000901)21:15<3205::aid-elps3205>3.0.co;2-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Capillary electrophoresis with electrochemical detection using a carbon fiber electrode in conjunction with on-capillary copper complexation was evaluated for the determination of peptides in standard and biological matrices. Peptides composed of 2-10 amino acids were investigated. A comparison was made between the responses obtained for peptides containing the oxidizable residue tyrosine and those obtained for their respective copper complexes. Electrochemical detection of non-tyrosine-containing peptides and a cyclic peptide was also demonstrated. A separation of leucine (Leu)-enkephalin and five metabolites was developed and then used for the investigation of Leu-enkephalin metabolism in plasma. The appearance of the des-tyrosine (des-Tyr) Leu-enkephalin, which cannot be detected directly at a carbon electrode, was monitored using the on-capillary complexation technique. Direct injection of the plasma sample was possible using this methodology.
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Affiliation(s)
- A J Gawron
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66047, USA
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Bak A, Fich M, Larsen BD, Frokjaer S, Friis GJ. N-terminal 4-imidazolidinone prodrugs of Leu-enkephalin: synthesis, chemical and enzymatic stability studies. Eur J Pharm Sci 1999; 7:317-23. [PMID: 9971915 DOI: 10.1016/s0928-0987(98)00044-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Four N-terminal 4-imidazolidinone prodrugs of Leu-enkephalin are prepared and characterized. Their enzymatic and chemical stability are assessed using high-performance liquid chromatography. The prodrug derivatives are shown to degrade stoichiometrically to Leu-enkephalin in phosphate buffer [t1/2 (0.05 M phosphate buffer without KCl): acetone prodrug (II) 930 min; cyclopentanone prodrug (III): 216 min; cyclohexanone prodrug (IV): 432 min; 4-methylcyclohexanone prodrug (V): 792 min]. Furthermore, the prodrugs are shown to afford global stabilization of the Leu-enkephalin molecule towards the enzymes, aminopeptidase N and angiotensin converting enzyme, primarily responsible for degradation of Leu-enkephalin at the blood-brain barrier and in plasma. Therefore, the 4-imidazolidinones, being metabolic stable and bioreversible, may be suitable prodrug candidates for delivery of Leu-enkephalin to important target areas such as the brain, if given intravenously.
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Affiliation(s)
- A Bak
- Department of Analytical and Pharmaceutical Chemistry, The Royal Danish School of Pharmacy, Universitetsparken 2, Copenhagen DK-2100, Denmark
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Lund L, Bak A, Friis G, Hovgaard L, Christrup L. The enzymatic degradation and transport of leucine–enkephalin and 4-imidazolidinone enkephalin prodrugs at the blood–brain barrier. Int J Pharm 1998. [DOI: 10.1016/s0378-5173(98)00192-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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16
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Audus KL, Ng L, Wang W, Borchardt RT. Brain microvessel endothelial cell culture systems. PHARMACEUTICAL BIOTECHNOLOGY 1996; 8:239-58. [PMID: 8791813 DOI: 10.1007/978-1-4899-1863-5_13] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- K L Audus
- Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence 66045, USA
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Brudel M, Kertscher U, Schröder D, Melzig MF, Mehlis B. Liquid chromatographic-mass spectrometric studies on the enzymatic degradation of beta-endorphin by endothelial cells. J Chromatogr A 1995; 712:169-75. [PMID: 8556149 DOI: 10.1016/0021-9673(95)00564-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
An on-line HPLC-mass spectrometric procedure with an electrospray atmospheric pressure ionization (ESI-API) ion source was developed to identify the enzymatic degradation products (peptides) generated by incubation of human beta-endorphin (h beta E) with cultured aortic endothelial cells. The samples from the complex incubation mixture were prepurified and enriched using a small reversed-phase (RP) perfusion precolumn. Flow switching was applied to transfer the peptides from this precolumn to the analytical RP column of 2 or 0.32 mm I.D. and to separate them by gradient elution. The peptides were detected by means of an on-line coupled triple quadrupole mass spectrometer (TSQ 700) with an ESI-API ion source operated in the positive ion mode. This MS system behaves as a concentration sensitive detector at flow-rates from 5 to 150 microliters/min. MS-MS experiments supported the unambiguous assignment of the peptide structures. Thus most of the peptide fractions were identified and the region 16-17-18 (-L-F-K-) of h beta E was found to be primarily attacked by the enzymes of the endothelial cells.
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Affiliation(s)
- M Brudel
- Institute of Molecular Pharmacology, Berlin, Germany
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