Naturally occurring polyphenolic inhibitors of amyloid beta aggregation.

Alzheimer's disease is the most common neurodegenerative disease and is one of the main causes of death in developed countries. Consumption of foods rich in polyphenolics is strongly correlated with reduced incidence of Alzheimer's disease. Our study has investigated the biological activity of previously untested polyphenolic compounds in preventing amyloid ß aggregation. The anti-aggregatory potential of these compounds was assessed using the Thioflavin-T assay, transmission electron microscopy, dynamic light scattering and size exclusion chromatography. Two structurally related compounds, luteolin and transilitin were identified as potent inhibitors of Aß fibril formation. Computational docking studies with an X-ray derived oligomeric structure offer a rationale for the inhibitory activity observed and may facilitate development of improved inhibitors of Aß aggregation and toxicity.

Carboxymethylated-kappa-casein: a convenient tool for the identification of polyphenolic inhibitors of amyloid fibril formation.

Reduced and carboxymethylated-kappa-casein (RCM-kappa-CN) is a milk-derived amyloidogenic protein that readily undergoes nucleation-dependent aggregation and amyloid fibril formation via a similar pathway to disease-specific amyloidogenic peptides like amyloid beta (Abeta), which is associated with Alzheimer's disease. In this study, a series of flavonoids, many known to be inhibitors of Abeta fibril formation, were screened for their ability to inhibit RCM-kappa-CN fibrilisation, and the results were compared with literature data on Abeta inhibition. Flavonoids that had a high degree of hydroxylation and molecular planarity gave good inhibition of RCM-kappa-CN fibril formation. IC(50) values were between 10- and 200-fold higher with RCM-kappa-CN than literature results for Abeta fibril inhibition, however, with few exceptions, they showed a similar trend in potency. The convenience and reproducibility of the RCM-kappa-CN assay make it an economic alternative first screen for Abeta inhibitory activity, especially for use with large compound libraries.

Omega-conotoxin GVIA mimetics based on an anthranilamide core: effect of variation in ammonium side chain lengths and incorporation of fluorine.

A number of omega-conotoxin GVIA mimetics based on an anthranilamide core were prepared and tested for their affinity for rat brain Ca(v)2.2 channels. Features such as the presence of hydroxyl and fluoro substituents on the tyrosine side chain mimic, the length of the chains on the lysine/arginine side chain mimics and the use of diguanidino and diamino substituents rather than mono-guanidine/mono-amine substitution were examined. The diguanidinylated compounds proved to be the most active and deletion of the hydroxyl substituent had a limited influence on activity. The SAR associated with variation in the lysine/arginine side chain mimics was not strong. The introduction of a fluoro substituent into the tyrosine mimic produced the most active compound prepared in this study (2g), with an EC(50) at rat brain Ca(v)2.2 channels of 6 microM.

Discovery of CYT997: a structurally novel orally active microtubule targeting agent.

CYT997 was discovered as a potent tubulin polymerization inhibitor possessing potent cytotoxic activity against a range of cancer cells. Details of SAR studies, pharmacokinetic investigations and synthesis of compounds leading to the discovery of CYT997 are reported.

Ring expansion reactions of 4-amino-1,1-dioxo-[1,2,3,5]-thiatriazoles.

An unusual ring-expansion reaction of 4-amino-1,1-dioxo-[1,2,3,5]-thiatriazoles has been identified that produces the relatively rare 5-amino-1,1-dioxo-[1,2,4,6]-thiatriazines and. Initial alkylation of the thiatriazole with alpha-halo-esters at N-3 produces alpha-substituted esters which, under basic reaction conditions, undergo opening of the thiatriazole ring and re-closure to a thiatriazine ring. Similar alkylations of with diethyl chloromalonate and ethyl dichloroacetate lead to the loss of SO2 and the production of triazine and triazole, apparently by an initial alkylation at N-5. The reaction of with phenacyl bromides or a phenacyl dibromide forms fully unsaturated 5-amino-1,1-dioxo-[1,2,4,6]-thiatriazines.

2-Amino-3-aroyl-4,5-alkylthiophenes: agonist allosteric enhancers at human A(1) adenosine receptors.

2-Amino-3-benzoylthiophenes are allosteric enhancers (AE) of agonist activity at the A(1) adenosine receptor. The present report describes syntheses and assays of the AE activity at the human A(1)AR (hA(1)AR) of a panel of compounds consisting of nine 2-amino-3-aroylthiophenes (3a-i), eight 2-amino-3-benzoyl-4,5-dimethylthiophenes (12a-h), three 3-aroyl-2-carboxy-4,5-dimethylthiophenes (15a-c), 10 2-amino-3-benzoyl-5,6-dihydro-4H-cyclopenta[b]thiophenes (17a-j), 14 2-amino-3-benzoyl-4,5,6,7-tetrahydrobenzo[b]thiophenes (18a-n), and 15 2-amino-3-benzoyl-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophenes (19a-o). An in vitro assay employing the A(1)AR agonist [(125)I]ABA and membranes from CHO-K1 cells stably expressing the hA(1)AR measured, as an index of AE activity, the ability of a candidate AE to stabilize the agonist-A(1)AR-G protein ternary complex. Compounds 3a-i had little or no AE activity, and compounds 12a-h had only modest activity, evidence that AE activity depended absolutely on the presence of at least a methyl group at C-4 and C-5. Compounds 17a-c lacked AE activity, suggesting the 2-amino group is essential. Polymethylene bridges linked thiophene C-4 and C-5 of compounds 17a-j, 18a-n, and 19a-o. AE activity increased with the size of the -(CH(2))(n)()- bridge, n = 3 < n = 4 < n = 5. The 3-carbethoxy substituents of 17a, 18a, and 19a did not support AE activity, but a 3-aroyl group did. Bulky (or hydrophobic) substituents at the meta and para positions of the 3-benzoyl group and also 3-naphthoyl groups greatly enhanced activity. Thus, the hA(1)AR contains an allosteric binding site able to accommodate 3-aroyl substituents that are bulky and/or hydrophobic but not necessarily planar. A second region in the allosteric binding site interacts constructively with alkyl substituents at thiophene C-4 and/or C-5.