Preparation and Characterization of Manganese (II) Complexes with Potential Therapeutic Application against α-synuclein Aggregation

Transcription

1 Preparation and Characterization of Manganese (II) Complexes with Potential Therapeutic Application against α-synuclein Aggregation Kate Byrne BSc Medicinal Chemistry & Pharmaceutical Science Year 3 Project

2 Overview Aim of the Project Parkinson s Disease and Etiology α-synuclein and Lewy Bodies Project Rationale and Objectives Synthesis of the compounds Characterisation of the compounds Conclusion

3 Aim The aim of this project was to synthesize, purify and characterise three manganese(ii) complexes as part of a structure-activity relationship (SAR) study of a potential therapeutic system for Parkinson s disease

4 Parkinson s Disease Parkinson s disease, (PD) is a progressive neurological disease which is a result of the loss of dopamine producing brain cells Parkinson s disease is named after Dr. James Parkinson who first reported symptoms of the disease in 1817 when it was referred to as Paralysis Agitans Etiology Idiopathic Figure 1: Dr. James Parkinson

5 Statistics Parkinson s disease affects 6.3 million people worldwide. Over 9,000 of those affected by the disease are Irish. The disease typically develops at the age of 65 however people can develop early-onset parkinson s before reaching 50 years. Current life expectancy: 81 years Projected Life expectancy 2030: 90+ years

6 α-synuclein α-synuclein is a protein that is abundant in the human brain. In the early stages of Parkinson s disease misfolded α-synuclein proteins are converted to pathological oligomers and higher order aggregates that form fibrils leading to the formation of Lewy Bodies. Figure 2: α-synuclein aggregation stages Emil Paleek, et al., Changes in interfacial properties of α-synuclein preceding its aggregation, Analyst, 2008, 133, 76.

7 1. He-Jin Lee, et al., Extracellular α-synuclein a novel and crucial factor in Lewy body diseases, Nature Reviews Neurology, 2014, 10, D.J. Haynes, S. Lim, P.S. Donnelly, Metal complexes designed to bind to amyloid-β for diagnosis and treatment of Alzheimer s disease, Chem. Soc. Rev., 2014, 43, Lewy bodies and Parkinson s Disease Lewy bodies are abnormal α-synuclein protein aggregates that develop in nerve cells in regions of the brain that are involved in motor control. The presence of the Lewy Body protein aggregates in the brain is a pathological hallmark of Parkinson s Disease. 1 Inhibiting α-synuclein aggregation offers a therapeutic target for Parkinson s Disease and evidence in the literature suggests a role for inorganic medicinal chemistry 2

8 Lead Compound The complex salt, MD1 has been shown to be an excellent lead compound for the prevention of α-synuclein aggregation. MD1: [Mn 2 (oda)(phen) 4 (H 2 O) 2 ][Mn 2 (oda)(phen) 4 (oda) 2 ]4H 2 O Where; odah 2 = octanedioic acid; phen = 1,10-phenanthroline Figure 4: Structures of MD1 and Octanedioic Acid

9 Comprised of bi-nuclear Cationic and Anionic components (Complex salt). 1 Bridging and terminal octanedioate ligands, deprotonated octanedioic acid Highly water soluble. Exhibits antioxidant capability. 2 Reduces α-synuclein aggregation in fungal (saccharomyces cerevisiae) and mammalian (HEK293) cellular models M. McCann, M. Devereux, et al. Synthesis and structure of the Mn 2 (II,II) complex salt [Mn 2 (oda)(phen) 4 (H 2 O) 2 ] [Mn 2 (oda) 2 (phen) 4 ] (odah 2 = octanedioic acid): a catalyst for H 2 O 2 disproportionation., J. Chem. Soc., Chem. Commun., 1994, T. Ribeiro, M. McCann, M. Devereux, M. Pereira, et al., Evaluation of antioxidant activity of a Mn 2+ complex salt and its potential therapeutic use against alpha synuclein aggregation. Manuscript in preparation. (Target Journal: Nature Communications)

10 Research question What are the structural aspects of MD1 that are important for its α-synuclein aggregation inhibitory properties?

11 Objective of the Structure- Activity Relationship Study To investigate analogues of MD1 to determine how variations in structure influence the α-synuclein aggregation inhibitory potential of this class of manganese(ii) complex. Note: The analogues were varied in terms of the number of Manganese centres in the complex as well as the charge on the complex

12 Key Objectives To synthesise and characterise three known analogues of MD1 with variations in structure achieved by replacing the octanedioate ligands with aliphatic dicarboxylic acid ligands of varying chain length Octanedioic acid (odah 2 ) Hexanedioic acid (hxdah 2 ) [Mn(hxda)(phen) 2 (H 2 O)].7H 2 O 1 [Mn(pda)(phen)] 2 [Mn 2 (bda) 2 (phen) 2 (H 2 O)].2H 2 O 3 Pentanedioic acid (pdah 2 ) Butanedioic acid (bdah 2 ) 1. M. McCann, M. Devereux, et al., Manganese(II) complexes of hexanedioic and heptanedioic acids: X-ray crystal structure of [Mn(hxda)(phen) 2 (H 2 O)].7H 2 O and [Mn(phen) 2 (H 2 O)][Mn(hpda)(phen) 2 (H 2 O)](hpda).12.5H 2 O, Polyhedron, 1997, 16, Martin Curran, PhD Thesis, DIT/NUIM M. McCann, M. Devereux, et al., Synthesis, X-ray crystal structure and catalytic activities of manganese(ii) butanedioic acid complexes [Mn(bda)(phen) 2 (H 2 O) 4 ].2H 2 O and {[Mn(bda)(bipy 2 (H 2 O) 2 ].H 2 O } n, Polyhedron, 1997, 16, 2547.

13 Structure of the Analogue Complexes [Mn(hxda)(phen) 2 (H 2 O)].7H 2 O : Mononuclear (1 manganese centre), 2 phens per manganese, neutral charge [Mn(pda)(phen)]: Polymeric, 1 phen per manganese, neutral charge. [Mn 2 (bda) 2 (phen) 2 (H 2 O)].2H 2 O: Binuclear (2 manganese centres), 1 phen per manganese, neutral charge

14 Synthetic Scheme Stage One: Generation of the manganese(ii) dicarboxylate precursors Where; R = -(CH 2 ) 4 - or -(CH 2 ) 3 -or -(CH 2 ) 2 -

15 Synthetic Scheme Stage Two: Reaction of the precursor complexes with 1,10- phenanthroline to produce the analogues of MD1 {Mn(OOC-(CH 2 ) n -COO)} x + 4 phen Reflux EtOH [Mn(hxda)(phen) 2 (H 2 O)].7H 2 O (where n = 4) [Mn(pda)(phen)] (where n = 3) [Mn 2 (bda) 2 (phen) 2 (H 2 O)].2H 2 O (where n = 2)

16 Characterisation The three precursor complexes and the three analogue complexes were characterised using the following techniques: Infra-Red (IR) Spectroscopy Magnetic Susceptibility Analysis Inductively-Coupled Mass Spectrometry (ICP-MS)

17 Infrared Spectroscopy An IR spectrum was recorded of: The Ligand The Precursor Complex The Final Complex Each of the spectra was then overlayed

18 Hexanedioic Acid

19 [Mn(hxda)].H 2 O

20 [Mn(hxda)(phen) 2 (H 2 O)].7H 2 O

21 Hexanedioic Acid Spectra Overlay

22 Infrared Spectroscopy Precursor Complex and Analogue Complex Similarities Characteristic Carbonyl Peak Asymmetric Stretch cm -1 Symmetric Stretch cm -1

23 Determination of [Mn] Using ICP ICP Standards Intensity y = 66202x R² = Concentration (ppm)

24 Mn 2+ Analysis Name of Complex Theoretical Concentration (ppm) Experimental Concentration (ppm) [Mn(bda)].2H 2 O [Mn(pda)].H 2 O [Mn(hxda)].H 2 O Drug 1, [Mn 2 (bda) 2 (phen) 2 (H 2 O)].2 H 2 O x 2 Drug 2, [Mn(pda)(phen)] Drug 3, [Mn(hxda)(phen) 2 (H 2 O)].7 H 2 O

25 Magnetic Susceptibility Balance µ s.o. = n(n + 2) Where; N = number of unpaired electrons, n=5 µ s.o. = 5(5 + 2) = 35 = 5.92 µ s.o. = 5.92B.M.

26 Gram Magnetic Susceptibility Calculation Χ g = c l (R R 0) 10 9 m C= calibration constant, 1.05 L= sample length, cm R= reading taken of sample R 0 = reading taken with no sample M= sample mass (g)

27 Molar Magnetic Susceptibility Χ M = Χ g M Where; Χ M = Molar Magetic Susceptibility Χ g = Gram Magnetic Susceptibility (cm 3 g -1 ) M= Molar Mass (g mol -1 )

28 Effective Magnetic Moment µ EFF = TX M µ EFF = effective magnetic moment, B.M. T= Temperature (K), 292K X M = Molar magnetic Susceptibility, cm 3 mol -1

29 Name of Substance Theoretical Value Experimental B.M. Value B.M. [Mn(bda)].2H 2 O [Mn(pda)].H 2 O [Mn(hxda)].H 2 O Drug 1, [Mn 2 (bda) 2 (phen) 2 (H 2 O)]. 2H 2 O x 2 Drug 2, [Mn(pda)(phen)] Drug 3, [Mn(hxda)(phen) 2 (H 2 O)]. 7H 2 O

30 Conclusion 1. The complex salt [Mn 2 (oda)(phen) 4 (H 2 O) 2 ] [Mn 2 (oda)(phen) 4 (oda) 2 ]4H 2 O (MD1) is an excellent lead candidate for the prevention of α-synuclein aggregation. 2. Three known analogues of MD1 {[Mn(hxda)(phen) 2 (H 2 O)].7H 2 O; [Mn(pda)(phen)]; and [Mn 2 (bda) 2 (phen) 2 (H 2 O)].2H 2 O along with their precursor manganese(ii) dicarboxylate complexes have been synthesised using methods previously published 3. All six complexes have been characterised using a range of analytical techniques. 4. Further work is required to purify the complexes in preparation for their use in a structure-activity relationship study.

31 Acknowledgements I would like to thank my supervisors Professor Michael Devereux and Dr. Patricia Ennis for their help and support when carrying out this project. I would also like to thank the School of Chemical & Pharmaceutical Sciences for allowing me to use their equipment.

32 Thank You