Metabolism of the neurotoxin in MPTP by human liver monoamine oxidase B

AbstractThe neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was oxidized to dihydropyridine MPDP+ and pyridine MPP+ by preparations of monoamine oxidase B (MAO B), including pure human liver MAO B:monoclonal antibody complex. Km,app values for MPTP and benzylamine, a preferred MAO B substrate, were 316 and 64 μM, respectively. 4-Phenyl-1,2,3,6-tetrahydropyridine (PTP), the nor derivative of MPTP, was also a substrate (Km,app = 221μM). MPDP+ MPTP, and MPP+, but not PTP, were found tobe irreversible inhibitors of MAO B. Our studies support the hypothesis that MPTP is oxidized in primate brain by MAO B to MPDP+ which is then converted to MPP+ a major metabolite found in the substantia nigra

Antitumor Agents 252. Application of validated QSAR models to database mining: discovery of novel tylophorine derivatives as potential anticancer agents

A combined approach of validated QSAR modeling and virtual screening was successfully applied to the discovery of novel tylophrine derivatives as anticancer agents. QSAR models have been initially developed for 52 chemically diverse phenanthrine-based tylophrine derivatives (PBTs) with known experimental EC50 using chemical topological descriptors (calculated with the MolConnZ program) and variable selection k nearest neighbor (kNN) method. Several validation protocols have been applied to achieve robust QSAR models. The original dataset was divided into multiple training and test sets, and the models were considered acceptable only if the leave-one-out cross-validated R2 (q2) values were greater than 0.5 for the training sets and the correlation coefficient R2 values were greater than 0.6 for the test sets. Furthermore, the q2 values for the actual dataset were shown to be significantly higher than those obtained for the same dataset with randomized target properties (Y-randomization test), indicating that models were statistically significant. Ten best models were then employed to mine a commercially available ChemDiv Database (ca. 500K compounds) resulting in 34 consensus hits with moderate to high predicted activities. Ten structurally diverse hits were experimentally tested and eight were confirmed active with the highest experimental EC50 of 1.8µM implying an exceptionally high hit rate (80%). The same ten models were further applied to predict EC50 for four new PBTs, and the correlation coefficient (R2) between the experimental and predicted EC50 for these compounds plus eight active consensus hits was shown to be as high as 0.57. Our studies suggest that the approach combining validated QSAR modeling and virtual screening could be successfully used as a general tool for the discovery of novel biologically active compounds

Long-acting anticholinesterases for myasthenia gravis: synthesis and activities of quaternary phenylcarbamates of neostigmine, pyridostigmine and physostigmine

The N-monophenylcarbamate analogues of neostigmine methyl sulfate (6) and pyridostigmine bromide (8) together with their precursors (5), (7), and the N(1)-methylammonium analogues of (−)-phenserine (12), (−)-tolserine (14), (−)-cymserine (16) and (−)-phenethylcymserine (18) were synthesized to produce long-acting peripheral inhibitors of acetylcholinesterase or butyrylcholinesterase. Evaluation of their cholinesterase inhibition against human enzyme ex vivo demonstrated that, whereas compounds 5–8 possessed only marginal activity, 12, 14, 16 and 18 proved to be potent anticholinesterases. An extended duration of cholinesterase inhibition was determined in rodent, making them of potential interest as long-acting agents for myasthenia gravis

Antitumor agents 273. Design and synthesis of N-alkyl-thiocolchicinoids as potential antitumor agents

As a part of our continuing study of colchicinoids as therapeutically useful antitumor drugs, thiocolchicine derivatives, including their phosphate and other water soluble salts, were synthesized and evaluated for inhibition of tubulin polymerization and for in vitro cytotoxicity. Three compounds, 7, 10, and 11, showed potent inhibition of tubulin assembly (IC50 = 0.88 – 1.1 μM). In addition, compound 7, a water soluble succinic acid salt of N-deacetylthiocolchicine (4), showed potent cytotoxicity against a panel of tumor cell lines, suggesting it might be a potential lead to be developed as a therapeutic antitumor agent. Compound 8, a water soluble succinic acid salt of N,N-dimethyl-N-deacetylthiocolchicine (5), showed selective activities against HCT-8 and SK-BR-3 cells. N,N-Diethyl-N-deacetylthiocolchicine (6) seemed not to be a substrate for the P-gp efflux pump, based on the similar ED50 values obtained against P-gp over-expressing KBvin (0.0146 μg/mL) cells and the parent KB (0.0200 μg/mL) cell line

A cellular model of inflammation for identifying TNF-α synthesis inhibitors

Neuroinflammation is a common facet of both acute and chronic neurodegenerative conditions, exemplified by stroke and by Alzheimer’s and Parkinson’s disease, and the presence of elevated levels of the proinflammatory cytokine, tumor necrosis factor-α (TNF-α) has been documented in each. Although initial TNF-α generation is associated with a protective compensatory response, its unregulated chronic elevation is generally detrimental and can drive the disease process. In such circumstances, therapeutic strategies that can both gain access to the brain and target the production of TNF-α are predicted to be of clinical benefit. An in vitro mouse macrophage-like cellular screen, utilizing RAW 264.7 cells, was hence developed to identify novel TNF-α lowering agents incorporating lipophilic physicochemical characteristics predicted to allow penetration of the blood-brain barrier. Cultured RAW 264.7 cells exposed to lipopolysaccharide (LPS) induced a rapid, marked and concentration-dependent cellular release of TNF-α into the cell culture media, which was readily detected by Enzyme Linked ImmunoSorbent Assay (ELISA). The effects of four characterized thalidomide-based TNF-α lowering agents were assessed alongside 10 novel uncharacterized compounds synthesized on the same backbone. One of these new analogs possessed activity of sufficient magnitude to warrant further investigation. Activity determined in the cellular model translated to an in vivo rodent model of acute LPS-induced TNF-α elevation. The utility of the TNF-α cellular assay lies in its simplicity and robust nature, providing a tool for initial pharmacological screening to allow for the rapid identification novel TNF-α lowering agents

Preparation and Characterization of Tetrabenazine Enantiomers against Vesicular Monoamine Transporter 2

As a clinical medication for the treatment of hyperkinetic movement disorders, in conditions such as Huntington's disease, tetrabenazine (TBZ) has always been used in its racemic form. To establish whether or not its beneficial therapeutic actions are enantiospecific, a practical total synthetic route was developed to yield each enantiomeric form to allow their chemical and pharmacological characterization. We briefly summarize the total synthesis of TBZ and report a detailed procedure for resolution of TBZ into its enantiomers, (+)-TBZ and (−)-TBZ. This allowed determination of the optical rotation and absolute configurations of each TBZ enantiomer, based on X-ray crystallographic analysis, together with characterization of their inhibitory action at the vesicular monoamine transporter 2, where (+)-TBZ proved 3-fold more active than (−)-TBZ

Inhibition of Human Acetyl- and Butyrylcholinesterase by Novel Carbamates of (−)- and (+)-Tetrahydrofurobenzofuran and Methanobenzodioxepine

A new enantiomeric synthesis utilizing classical resolution provided two novel series of optically active inhibitors of cholinesterase: (−)- and (+)- O-carbamoyl phenols of tetrahydrofurobenzofuran and methanobenzodioxepine. An additional two series of (−)- and (+)-O-carbamoyl phenols of pyrroloindole and furoindole were obtained by known procedures, and their anticholinesterase actions were similarly quantified against freshly prepared human acetyl- (AChE) and butyrylcholinesterase (BChE). Both enantiomeric forms of each series demonstrated potent cholinesterase inhibitory activity (with IC50 values as low as 10 nM for AChE and 3 nM for BChE), with the exception of the (+)-O-carbamoyl phenols of pyrroloindole that lacked activity (IC50 values > 1 µM). Based on the biological data of these four series, a SAR analysis was provided by molecular volume calculations. In addition, a probable transition state model was established according to the known X-ray structure of a transition state complex of Torpedo californica AChE-m-(N,N,N,trimethylammonio)-2,2,2-trifluoroacetophenone (TcAChE-TMTFA). This model proved valuable in explaining the enantio-selectivity and enzyme subtype selectivity of each series. These carbamates are more or similarly potent to anticholinesterases in current clinical use; providing not only inhibitors of potential clinical relevance but also pharmacological tools to define drug-enzyme binding interactions within an enzyme crucial in the maintenance of cognition and numerous systemic physiological functions in health, aging and disease

Antitumor agents 270. Novel substituted 6-phenyl-4H-furo[3,2-c]pyran-4-one derivatives as potent and highly selective anti-breast cancer agents

6-Phenyl-4H-furo[3,2-c]pyran-4-one derivatives based on neo-tashinlactone (1) were synthesized and evaluated as novel anti-breast cancer agents. Compounds 10-13, 23, 25, and 27 showed potent inhibition against the SK-BR-3 breast cancer cell line. Importantly, 25 and 27 showed the highest cancer cell line selectivity, being approximately 100- to 250-fold more potent against SK-BR-3 (ED50 0.28 and 0.44 μM, respectively) compared with other cancer cell lines tested. In addition, 25 displayed low cytotoxicity against normal breast cell lines 184A1 and MCF10A. Compounds 25 and 27 merit further investigation in our continuing program to generate and develop selective anti-breast cancer agents

Design, synthesis and biological assessment of novel N-substituted 3-(phthalimidin-2-yl)-2,6-dioxopiperidines and 3-substituted 2,6-dioxopiperidines for TNF-α inhibitory activity

Eight novel 2-(2,6-dioxopiperidin-3-yl)phthalimidine EM-12 dithiocarbamates 9 and 10, N-substituted 3-(phthalimidin-2-yl)-2,6-dioxopiperidines 11-14 and 3-substituted 2,6-dioxopiperidines 16 and 18 were synthesized as tumor necrosis factor-α (TNF-α) synthesis inhibitors. Synthesis involved utilization of a novel condensation approach, a one-pot reaction involving addition, iminium rearrangement and elimination, to generate the phthalimidine ring required for the creation of compounds 9-14. Agents were, thereafter, quantitatively assessed for their ability to suppress the synthesis on TNF-α in a lipopolysaccharide (LPS)-challenged mouse macrophage-like cellular screen, utilizing cultured RAW 264.7 cells. Whereas compounds 9, 14 and 16 exhibited potent TNF-α lowering activity, reducing TNF-α by up to 48% at 30 μM, compounds 12, 17 and 18 presented moderate TNF-α inhibitory action. The TNF-α lowering properties of these analogs proved more potent than that of revlimid (3) and thalidomide (1). In particular, N-dithiophthalimidomethyl-3-(phthalimidin-2-yl)-2,6-dioxopiperidine 14 not only possessed the greatest potency of the analogs to reduce TNF-α synthesis, but achieved this with minor cellular toxicity at 30 μM. The pharmacological focus of the presented compounds is towards the development of well-tolerated agents to ameliorate the neuroinflammation, that is, commonly associated with neurodegenerative disorders, epitomized by Alzheimer's disease and Parkinson's disease