Neurodegenerative disorders like Parkinson’s and Alzheimer’s disease affect millions of people around the world. Oxidative stress has been implicated in the pathogenesis of a number of neurodegenerative disorders, cancer and ischemia. The brain is particularly vulnerable to oxidative damage because of its high utilisation of oxygen, high levels of polyunsaturated fatty acids, relatively high levels of redox transition metal ions and low levels of antioxidants. Oxidative stress occurs due to an imbalance in the pro–oxidant and antioxidant levels. Reactive oxygen/nitrogen species (ROS/RNS) is a collective term used for free radicals and related molecules, promoting oxidative stress within cells and ultimately leading to neurodegeneration. Antioxidants counteract the excess in ROS/RNS, and is therefore of interest in the treatment and prevention of neurodegenerative disorders. Monoamine oxidases, especially monoamine oxidase B (MAO–B), also play an important role in neurodegenerative disorders. MAO–B is the main enzyme responsible for the oxidative deamination of dopamine in the substantia nigra of the brain. By inhibiting MAO–B, dopamine is increased in the brain providing symptomatic relief in Parkinson’s disease. The focus of the current study was to synthesise multifunctional compounds that could be used in the treatment and/or prevention of neurodegenerative diseases. In this study flavonoids were selected because of their wide spectrum of biological activities, including antioxidant activity and its monoamine oxidase inhibition. Flavones and chalcones are both classified under flavonoids and both structures were included. The amantadine moiety was included because of its known ability to inhibit calcium flux through the N–methyl–D–aspartate (NMDA) receptor channel. Six amantadine–flavonoid derivatives were synthesised using standard laboratory procedures and structures were determined with standard methods such as NMR, IR and mass spectrometry. The synthesised compounds were tested in a selection of biological assays, to establish the relative antioxidant properties and MAO inhibitory activity. The biological assays employed to test antioxidant properties were the thiobarbituric acid (TBA) and nitro–blue tetrazolium (NBT) assays. The TBA assay relies on the assessment of lipid peroxidation, induced via hydroxyl anions (OH), generating a pink colour with the complex formation between malondialdehyde (MDA) and TBA, which is measured spectrophotometrically at 532 nm. The principal of the NBT assay is the reduction of NBT to nitro–blue diformazan (NBD), producing a purple colour in the presence of superoxide anions (O2 –). The synthesised compounds were also evaluated for their MAO inhibitory activity toward recombinant human MAO–A and -B and inhibition values were expressed as IC50 values. The experimental data obtained in the NBT and TBA assay indicated a weak but a significant ability to scavenge O2 – and OH. In the NBT assay N–(adamantan–1–yl)–2–{3–hydroxy–4–[(2E)– 3–(3–methoxyphenyl)pro–2–enoyl]phenoxy}acetamide (6) had the best results with a 50.47 ± 1.31 uM/mg protein reduction in NBD formation, indicating that the hydroxyl group contributed to activity. The synthesised compounds were compared to the toxin (KCN) with a reduction in NDB formation of 69.88 ± 1.59 uM/mg protein. Results obtained from the TBA assay indicated that the flavone moiety had better OH scavenging ability than that of the chalcone moiety with N–(adamantan–1–yl)–2–[(5–hydroxy–4–oxo–2–phenyl–4H–chromen–7– yl)oxy]acetamide (3) showing the best activity at 0.967 ± 0.063 nmol MDA/mg tissue. The synthesised compounds were compared to the toxin (H2O2) 1.316 ± 0.028 nmol MDA/mg tissue. None of the test compounds could be compared to the results obtained with Trolox®. The IC50 values obtained for inhibition of recombinant human MAO indicated that the chalcone moiety (N–(adamantan–1–yl)–4–[(1E)–3–oxo–3–phenylpro–1–en–1–yl]benzamide (5)) showed the best inhibition of MAO–B with an IC50 of 0.717 ± 0.009 M and of MAO–A with an IC50 of 24.987 ± 5.988 M. It was further confirmed that N–(adamantan–1–yl)–4–[(1E)–3–oxo–3– phenylpro–1–en–1–yl]benzamide (5) binds reversible to MAO–B and that the mode of inhibition is competitive. Docking studies revealed that N–(adamantan–1–yl)–4–[(1E)–3–oxo–3–phenylpro– 1–en–1–yl]benzamide (5) traverses both cavities of MAO–B with the chalcone moiety orientated towards the FAD co–factor while the amantadine moiety protrudes into the entrance cavity. / Thesis (M.Sc. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2012.

Neurodegenerative disorders like Parkinson’s and Alzheimer’s disease affect millions of people around the world. Oxidative stress has been implicated in the pathogenesis of a number of neurodegenerative disorders, cancer and ischemia. The brain is particularly vulnerable to oxidative damage because of its high utilisation of oxygen, high levels of polyunsaturated fatty acids, relatively high levels of redox transition metal ions and low levels of antioxidants. Oxidative stress occurs due to an imbalance in the pro–oxidant and antioxidant levels. Reactive oxygen/nitrogen species (ROS/RNS) is a collective term used for free radicals and related molecules, promoting oxidative stress within cells and ultimately leading to neurodegeneration. Antioxidants counteract the excess in ROS/RNS, and is therefore of interest in the treatment and prevention of neurodegenerative disorders. Monoamine oxidases, especially monoamine oxidase B (MAO–B), also play an important role in neurodegenerative disorders. MAO–B is the main enzyme responsible for the oxidative deamination of dopamine in the substantia nigra of the brain. By inhibiting MAO–B, dopamine is increased in the brain providing symptomatic relief in Parkinson’s disease. The focus of the current study was to synthesise multifunctional compounds that could be used in the treatment and/or prevention of neurodegenerative diseases. In this study flavonoids were selected because of their wide spectrum of biological activities, including antioxidant activity and its monoamine oxidase inhibition. Flavones and chalcones are both classified under flavonoids and both structures were included. The amantadine moiety was included because of its known ability to inhibit calcium flux through the N–methyl–D–aspartate (NMDA) receptor channel. Six amantadine–flavonoid derivatives were synthesised using standard laboratory procedures and structures were determined with standard methods such as NMR, IR and mass spectrometry. The synthesised compounds were tested in a selection of biological assays, to establish the relative antioxidant properties and MAO inhibitory activity. The biological assays employed to test antioxidant properties were the thiobarbituric acid (TBA) and nitro–blue tetrazolium (NBT) assays. The TBA assay relies on the assessment of lipid peroxidation, induced via hydroxyl anions (OH), generating a pink colour with the complex formation between malondialdehyde (MDA) and TBA, which is measured spectrophotometrically at 532 nm. The principal of the NBT assay is the reduction of NBT to nitro–blue diformazan (NBD), producing a purple colour in the presence of superoxide anions (O2 –). The synthesised compounds were also evaluated for their MAO inhibitory activity toward recombinant human MAO–A and -B and inhibition values were expressed as IC50 values. The experimental data obtained in the NBT and TBA assay indicated a weak but a significant ability to scavenge O2 – and OH. In the NBT assay N–(adamantan–1–yl)–2–{3–hydroxy–4–[(2E)– 3–(3–methoxyphenyl)pro–2–enoyl]phenoxy}acetamide (6) had the best results with a 50.47 ± 1.31 uM/mg protein reduction in NBD formation, indicating that the hydroxyl group contributed to activity. The synthesised compounds were compared to the toxin (KCN) with a reduction in NDB formation of 69.88 ± 1.59 uM/mg protein. Results obtained from the TBA assay indicated that the flavone moiety had better OH scavenging ability than that of the chalcone moiety with N–(adamantan–1–yl)–2–[(5–hydroxy–4–oxo–2–phenyl–4H–chromen–7– yl)oxy]acetamide (3) showing the best activity at 0.967 ± 0.063 nmol MDA/mg tissue. The synthesised compounds were compared to the toxin (H2O2) 1.316 ± 0.028 nmol MDA/mg tissue. None of the test compounds could be compared to the results obtained with Trolox®. The IC50 values obtained for inhibition of recombinant human MAO indicated that the chalcone moiety (N–(adamantan–1–yl)–4–[(1E)–3–oxo–3–phenylpro–1–en–1–yl]benzamide (5)) showed the best inhibition of MAO–B with an IC50 of 0.717 ± 0.009 M and of MAO–A with an IC50 of 24.987 ± 5.988 M. It was further confirmed that N–(adamantan–1–yl)–4–[(1E)–3–oxo–3– phenylpro–1–en–1–yl]benzamide (5) binds reversible to MAO–B and that the mode of inhibition is competitive. Docking studies revealed that N–(adamantan–1–yl)–4–[(1E)–3–oxo–3–phenylpro– 1–en–1–yl]benzamide (5) traverses both cavities of MAO–B with the chalcone moiety orientated towards the FAD co–factor while the amantadine moiety protrudes into the entrance cavity. / Thesis (M.Sc. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2012.