Monoamine Oxidase Inhibition by Kavalactones from Kava (Piper Methysticum).

Monoamine oxidases (MAOs) are key metabolic enzymes for neurotransmitter and dietary amines and are targets for the treatment of neuropsychiatric and neurodegenerative disorders. This study examined the MAO inhibition potential of kavain and other kavalactones from the roots of kava (Piper methysticum), a plant that has been used for its anxiolytic properties. (±)-Kavain was found to be a good potency in vitro inhibitor of human MAO-B with an IC50 of 5.34 µM. (±)-Kavain is a weaker MAO-A inhibitor with an IC50 of 19.0 µM. Under the same experimental conditions, the reference MAO inhibitor, curcumin, displays IC50 values of 5.01 µM and 2.55 µM for the inhibition of MAO-A and MAO-B, respectively. It was further established that (±)-kavain interacts reversibly and competitively with MAO-A and MAO-B with enzyme-inhibitor dissociation constants (Ki) of 7.72 and 5.10 µM, respectively. Curcumin in turn, displays a Ki value of 3.08 µM for the inhibition of MAO-A. Based on these findings, other kavalactones (dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin) were also evaluated as MAO inhibitors in this study. Yangonin proved to be the most potent MAO inhibitor with IC50 values of 1.29 and 0.085 µM for MAO-A and MAO-B, respectively. It may be concluded that some of the central effects (e.g., anxiolytic) of kava may be mediated by MAO inhibition.

S-nitrosylation and attenuation of excessive calcium flux by pentacycloundecane derivatives.

A novel series of polycyclic amines, containing nitrogen monoxide donating moieties, were synthesised and tested for calcium channel and N-methyl-D-aspartate receptor modulating activity. The synthesised compounds were classified into two groups, based on their nitrogen monoxide donating moieties: unsaturated nitro compounds (1, 2 and 3) and nitro esters, or nitrates (4, 5 and 6). The nitrates were obtained via the reaction of hydroxyl functionalities with thionylchloride nitrate. All of the compounds synthesised exhibited significant (p<0.01) S-nitrosylation capacity. The calcium channel activity of the polycyclic amines was evaluated using a KCl mediated fluorescent calcium flux assay. All the compounds exhibited better calcium channel antagonism than the lead structure, NGP1-01, with compound 1 exhibiting calcium channel blockade comparable to the commercially available nimodipine at concentrations of 10 µM and 1 µM. Compounds 3 and 4 inhibited calcium flux to these levels at 10 µM concentrations. NMDA/glycine mediated N-methyl-D-aspartate receptor (NMDAR) calcium influx inhibition was evaluated at a 100 µM concentration using a fluorescent calcium flux assay. All the compounds exhibited NMDAR antagonism with compounds 1 (25.4%), 2 (20.24%), 3 (33.14%) and 6 (24.55%) showing the most significant NMDAR inhibitory activity (p<0.01). No clear correlation was observed between the S-nitrosylation capabilities of the compounds and their calcium channel activity or NMDAR channel antagonism, indicating that other factors probably play a more decisive role in the mechanism of pentacycloundecylamine channel modulation. This could include the geometric and steric bulk considerations that have been described to contribute to the channel activities of the pentacycloundecylamines. All the compounds synthesised exhibited promising calcium channel and NMDAR channel inhibitory activity and show promise as potential lead compounds for drug development against neurodegeneration.

Antioxidant properties of 4-quinolones and structurally related flavones.

Neurodegenerative disorders are frequently associated with increased oxidative damage to the brain as a result of free radicals produced by cellular respiration. The onset and progression of neurodegeneration may therefore be curbed by exogenous hydrogen-donating antioxidant moieties such as the naturally occurring flavonoids. A series of 2-phenylquinolin-4(1H)-ones was synthesised and displayed moderate to high antioxidant activity when compared to structurally related flavones and quinolines. Activity of the hydroxy-2-phenylquinolin-4(1H)-ones (8-10) was established in reducing ferrous ions and diminishing hydrogen peroxide and hydroxyl radical production, in the FRAP (1.41-97.71% Trolox equivalents), ORAC (9.18-15.27 µM Trolox equivalents at 0.00 1mM) and TBARS (0.05-0.72 nmol MDA/mg tissue) assays, respectively. The results indicated that the additional hydrogen donating groups on the synthesised 2-phenylquinolin-4(1H)-one series increased antioxidant activity.

Synthesis, evaluation and application of polycyclic fluorescent analogues as N-methyl-D-aspartate receptor and voltage gated calcium channel ligands.

A series of polycyclic fluorescent ligands were synthesised and evaluated in murine striatal synaptoneurosomes for N-methyl-D-aspartate receptor (NMDAR) mediated calcium flux inhibition and inhibition of calcium influx through voltage gated calcium channels (VGCC). Amantadine (a) and N-(1-adamantyl)-1,3-propanediamine (c) substituted with 1-cyanoisoindole (3), indazole (5), dinitrobenzene (7, 8), dansyl (9, 10) and coumarin (11) moieties showed moderate to high inhibition of the NMDAR. A high degree of VGCC inhibition was observed for the cyanoisoindole compounds (3, 4) the dansyl compounds (9, 10) and the coumarin compound (12). Fluorophores conjugated to hydroxy-4-aza-8-oxoheptacyclotetradecane (13, 14) did not exhibit any significant VGCC inhibition, but the indazole conjugate (14) showed promising NMDAR activity. Dose response curves were calculated for selected NMDAR inhibitors (8-11) and N-[3-(1-adamantylamino)propyl]-5-dimethylaminonaphthalene-1-sulfonamide (10) exhibited the highest activity of the novel compounds. Compound 10 was further used as a fluorescent NMDAR ligand in a fluorescent competition assay utilizing MK-801, NGP1-01 and amantadine as known NMDAR inhibitors to demonstrate the possible applications of the novel fluorescent compounds. These small molecule fluorescent ligands can be considered as possible pharmacological tools in assay development and/or other investigations in the study of neurodegeneration.

Synthesis and evaluation of fluorescent heterocyclic aminoadamantanes as multifunctional neuroprotective agents.

A series of fluorescent heterocyclic adamantane amines were synthesised with the goal to develop novel fluorescent ligands for neurological assay development. These derivatives demonstrated multifunctional neuroprotective activity through inhibition of the N-methyl-d-aspartate receptor/ion channel, calcium channels and the enzyme nitric oxide synthase. It also exhibited a high degree of free radical scavenging potential. N-(1-adamantyl)-2-oxo-chromene-3-carboxamide (8), N-adamantan-1-yl-5-dimethyl-amino-1-naphthalenesulfonic acid (11) and N-(1-cyano-2H-isoindol-2-yl) adamantan-1-amine (12) were found to possess a high degree of multifunctionality with favourable physical-chemical properties for bioavailability and blood-brain barrier permeability. The ability of these heterocyclic adamantane amine derivatives as nitric oxide synthase inhibitors, calcium channel modulators, NMDAR inhibitors and effective antioxidants, indicate that they may find application as multifunctional drugs in neuroprotection.

Polycyclic cage structures as carrier molecules for neuroprotective non-steroidal anti-inflammatory drugs.

The blood-brain barrier is formed by the brain capillary endothelium and plays the predominant role in controlling the passage of substances between the blood and the brain. Recent studies on polycyclic structures, i.e. pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane and amantadine, indicated favourable distribution thereof to the brain and it was concluded that these polycyclic structures and their derivatives penetrate the blood-brain barrier readily. A series of novel polycyclic prodrugs incorporating the well known non-steroidal anti-inflammatory drugs (NSAIDs), acetylsalicylic acid and ibuprofen, were synthesised and screened for blood-brain barrier permeability and antioxidant activity. Increased levels of both NSAIDs were detected in the brain tissue of C57BL/6 mice after administration of the synthesised prodrugs, indicating favourable blood-brain barrier permeation. Results from a lipid peroxidation assay indicated that the ester and amide prodrugs significantly increased the ability of the drugs to attenuate lipid peroxidation. These novel prodrugs thus readily penetrate the blood-brain barrier and exhibit increased antioxidant activity when compared to the free NSAIDs.

Fluorescent polycyclic ligands for nitric oxide synthase (NOS) inhibition.

In recent years polycyclic compounds have been shown to exhibit pharmacological profiles of importance in the symptomatic and proposed curative treatment of neurodegenerative diseases (e.g., Parkinson's and Alzheimer's disease). These structures also show modification and improvement of the pharmacokinetic and pharmacodynamic properties of drugs in current use. Nitric oxide (NO) is a molecular messenger involved in a number of physiological processes in mammals. It is synthesised by nitric oxide synthase (NOS) from L-arginine and its overproduction could lead to a number of neurological disorders. The aim of this study was to synthesise a series of novel indazole, indole and other fluorescent derivatives conjugated to polycyclic structures for evaluation in NOS assays. NOS is a target system where fluorescent techniques and fluorescently labelled NOS inhibitors can be used for detecting the biophysical properties of enzyme-ligand interactions and thus facilitate development of novel inhibitors of neurodegeneration. This could lead to a greater insight into the neuroprotective mechanism and a possible cure/treatment for neurodegenerative diseases. A series of compounds incorporating polycyclic structures such as 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.0.(2,10)0.(3,14)0.(4,9)0.(9,13)0(12,15)]tetradecane and amantadine as well as suitable fluorescent moieties were selected for synthesis. In the biological evaluation the oxyhaemoglobin (oxyHb) assay was employed to determine the activity of the novel compounds at an enzymatic level of NOS. IC(50) values of the novel fluorescent compounds were compared to that of aminoguanidine (AG) and 7-nitroindazole (7-NI), two known NOS inhibitors, and showed moderate to high affinity (IC(50) values ranging from 7.73 microM to 0.291 microM) for the NOS enzyme.

The activity of p-methoxybenzylisothiocyanate against Neisseria gonorrhoeae, Haemophilus ducreyi, and other microorganisms.

p-Methoxybenzylisothiocyanate was isolated from Lepidium bonariense and found to be responsible for the plants antimicrobial and STD activity. MIC determinations were conducted for p-methoxybenzylisothiocyanate on Haemophilus ducreyi, Neisseria gonorrheae, Candida albicans, Bacillus subtilus, Micrococcus luteus, Staphylococcus aureus, Enterobacter sp., Escherichia coli, Klebsiella pneumoniae, and Psuedomanas aeruginosa. An in vitro cellular toxicity assay showed that at 100 microM (17,9 microg/mL) p-methoxybenzylisothiocyanate is not toxic to living cells.

Antimalarial compounds from Parinari capensis.

The antimalarial activity of the raw petroleum ether and dichloromethane extracts of the stems of Parinari capensis (Chrysobalanceae) was determined. Phytochemical investigation of these extracts led to the isolation of three diterpene lactones that possess antimalarial activity with IC(50) values of 0.54, 0.67, and 1.57 microg/mL. Although their antimalarial activity is promising, the toxicity profiles of these diterpene lactones prevent further biological evaluation. They could however be used effectively as lead compounds in the synthesis of novel antimalarial agents.