Synthesis,Evaluation of Pharmacological Activities and Quantitative Structure–Activity Relationship Studies of a Novel Group of bis(4‐Nitroaryl‐1,4‐dihyropyridine)

Voltage‐dependent calcium channels are crucial targets for a wide range of clinically active pharmacological agents. From these agents, 1,4‐dihydropyridines constitute a group of small organic compounds are based on a core pyridine structure which can both block and enhance calcium currents. They are considered specific for L‐Type calcium channels; however, other channel types, and in particular certain T‐Type channels, may show sensitivity to dihydropyridine compounds. In this study, we synthesized a novel group of bis‐1,4‐dihydropyridines using the procedure reported by Dagnino that involved the condensation of n‐alkyl diacetoacetate (n = 2–7) with methyl‐3‐aminocrotonate and nitrophenylaldehyde. The synthesis was run under two conditions: (i) reflux and (ii) microwave. Calcium channels antagonist activity were determined in vitro using guinea‐pig ileum longitudinal smooth muscle assay. Synthesis of these compounds was confirmed with 1H‐NMR, IR and mass spectrometry. Then IC₅₀ of them are calculated and compared with Nifedipine. Finally, the result of this pharmacological assay was used in quantitative structure–activity relationship studies utilizing multiple linear regression analysis. Most of these compounds are less active compared with Nifedipine. Decrease in activity is the result of increase in steric hindrance. The quantitative structure–activity relationship study indicates that the activity is related to the electrostatic and topological parameters and the distance between two C5‐esteric groups of 1,4‐dihydropyridine rings.     

Insulinotropic Actions of the Frog Skin Host‐Defense Peptide Alyteserin‐2a: A Structure–Activity Study

Alyteserin‐2a (ILGKLLSTAAGLLSNL.NH₂) stimulated the rate of insulin release from BRIN‐BD11 clonalβ cells at a concentration of 30 nm (p < 0.05) with a response of 296 ± 26% of basal release at 3 μm (p < 0.001). The insulinotropic actions of analogs containing substitutions by l ‐lysine, d ‐lysine, or l ‐tryptophan at sites that maintain amphipathicity were evaluated. The [G11K], [S7k], [S7k,G11k], and [G11k,N15K] analogs were the most potent stimulating insulin release at 0.01 nm (p < 0.05). The [S7K], [G11K], [S14K], [N15K], [G11k], and [S7K,G11K] analogs were the most effective producing an approximately twofold greater (p < 0.001) release of insulin at 3 μm compared with alyteserin‐2a. The [T8W] and [A9W] analogs were less active than alyteserin‐2a. No peptide‐stimulated release of lactate dehydrogenase at concentrations up to 3 μm , indicating that the integrity of the plasma membrane had been preserved. Membrane depolarization and an increase in intracellular Ca²⁺ concentration are involved in the mechanism of action of the peptides. Administration of [G11k]alyteserin‐2a (75 nmol/kg body weight) to high‐fat‐fed mice with obesity and insulin resistance significantly (p < 0.01) enhanced insulin release and improved glucose tolerance during the 60‐min period following an intraperitoneal glucose load.     

Characterization of a Pyrazolo[4,3‐d]pyrimidine Inhibitor of Cyclin‐Dependent Kinases 2 and 5 and Aurora A With Pro‐Apoptotic and Anti‐Angiogenic Activity In Vitro

Selective inhibitors of kinases that regulate the cell cycle, such as cyclin‐dependent kinases (CDKs) and aurora kinases, could potentially become powerful tools for the treatment of cancer. We prepared and studied a series of 3,5,7‐trisubstituted pyrazolo[4,3‐d]pyrimidines, a new CDK inhibitor scaffold, to assess their CDK2 inhibitory and antiproliferative activities. A new compound, 2i , which preferentially inhibits CDK2, CDK5, and aurora A was identified. Both biochemical and cellular assays indicated that treatment with compound 2i caused the downregulation of cyclins A and B, the dephosphorylation of histone H3 at Ser10, and the induction of mitochondrial apoptosis in the HCT‐116 colon cancer cell line. It also reduced migration as well as tube and lamellipodia formation in human endothelial cells. The kinase inhibitory profile of compound 2i suggests that its anti‐angiogenic activity is linked to CDK5 inhibition. This dual mode of action involving apoptosis induction in cancer cells and the blocking of angiogenesis‐like activity in endothelial cells offers possible therapeutic potential.     

Synthesis,in‐vitro Cytotoxicity,and a Preliminary Structure‐Activity Relationship Investigation of Pyrimido[4,5‐c]quinolin‐1(2H)‐ones

As part of our ongoing research effort to develop new antimitotic agents based on the recently reported pyrimido[4,5‐c]quinoline‐1(2H)‐one ring skeleton, we were interested in identifying structural elements that contribute to the cytotoxicity of this class of compounds. The effect of several quinoline‐ring substituents was examined and the new compounds were evaluated in vitro for cytotoxicity against three human cancer cell lines namely, lung fibrosarcoma HT‐1080, colon adenocarcinoma HT‐29, and breast carcinoma MDA‐MB‐231. Most of the compounds showed cytotoxic activity in the low micromolar and sub‐micromolar range. Structure‐activity relationship information revealed that a combination of electronic and steric factors may be involved. Flow cytometric cell cycle analysis performed on HT‐1080 cells revealed that the most cytotoxic compounds 48 , 50 , 54 , 59 , and 63 inhibit the S‐phase and arrest the cells in the G2/M phase of the cell cycle suggesting an antimitotic action of these compounds.     

Structure–Function Relationship of Val/Arg‐rich Peptides: Effects of Net Charge and Pro on Activity

Our previous study reported Val/Arg‐rich peptides, and the relationship was linear between hydrophobicity and antimicrobial potency within a certain range. Here, we further develop a new series of analogs to investigate the effect of net charge and Pro residue on activity. Replacement of Gly with Ala or Pro led to the decrease in antimicrobial activity. The substitution of Gly with Ala retained its hemolytic activity, while the substitution with Pro significantly decreased the toxicity, suggesting positive effect of Pro on hemolytic activity. The increase in net charge from +4 to +6 significantly improved antimicrobial activity and decreased the hemolysis. However, antibacterial and hemolytic activities were not affected by increasing the net charge from +6 to +8, indicating a moderate net positive charge. The peptides produced larger blue shifts in PE/PG than in PC/cholesterol, suggesting a stronger affinity with negatively charged membrane over zwitterionic membrane. Lowering the net charge or insert of Pro led to the lack of α‐helical structure in SDS micelles, which may be correlated with weakened antimicrobial potency. This study indicated that Val/Arg‐rich peptides should have moderate net charge and Pro may play a role in reducing the toxicity against red blood cells.     

An Interactive Human Carbonic Anhydrase‐II (hCA‐II) Receptor – Pharmacophore Molecular Model & Anti‐Convulsant Activity of the Designed and Synthesized 5‐Amino‐1,3,4‐Thiadiazole‐2‐Thiol Conjugated Imine Derivatives

New imines, derived from aromatic aldehyde, chalcones and 5‐amino‐1,3,4‐thiadiazole‐2‐thiol exhibited promising anti‐convulsant activity which is explained through chemo‐biological interactions at receptor site producing the inhibition of human Carbonic Anhydrase‐II enzyme (hCA‐II) through the proposed pharmacophore model at molecular levels as basis for pharmacological activity. The compounds 5‐{1‐(4‐Chlorophenyl)‐3‐[4‐(methoxy‐phenyl)‐prop‐2‐en‐1‐ylidene]amino}‐1,3,4‐thiadiazole‐2‐thiol ( 2b ), 5‐{[1‐(4‐chloro‐phenyl)]‐3‐[4‐(dimethyl‐amino‐phenyl)‐prop‐2‐en‐1‐ylidene]amino}‐1,3,4‐thiadiazole‐2‐thiol ( 2c ) and 5‐{[1‐(4‐chloro‐phenyl)]‐3‐[(4‐amino‐phenyl)‐prop‐2‐en‐1‐ylidene]amino}‐1,3,4‐thiadiazole‐2‐thiol ( 2f ) showed 100% activity in comparison with standard Acetazolamide, a known anti‐convulsant drug. The compounds 2c , 2f also passed the Rotarod and Ethanol Potentiation tests which further confirmed them to be safe in motor coordination activity and safe from generating neurological toxicity.     

Structure‐Activity Relationships for a Series of Compounds that Inhibit Aggregation of the Alzheimer's Peptide,Aβ42

Inhibiting aggregation of the amyloid‐beta (Aβ) peptide may be an effective strategy for combating Alzheimer's disease. As the high‐resolution structure of the toxic Aβ aggregate is unknown, rational design of small molecule inhibitors is not possible, and inhibitors are best isolated by high‐throughput screening. We applied high‐throughput screening to a collection of 65 000 compounds to identify compound D737 as an inhibitor of Aβ aggregation. D737 diminished the formation of oligomers and fibrils, and reduced Aβ42‐induced cytotoxicity. Most importantly, D737 increased the life span and locomotive ability of transgenic flies in a Drosophila melanogaster model of Alzheimer's disease (J Biol Chem, 287, 2012, 38992). To explore the chemical features that make D737 an effective inhibitor of Aβ42 aggregation and toxicity, we tested a small collection of eleven analogues of D737 . Overall, the ability of a compound to inhibit Aβ aggregation was a good predictor of its efficacy in prolonging the life span and locomotive ability of transgenic flies expressing human Aβ42 in the central nervous system. Two compounds ( D744 and D830 ) with fluorine substitutions on an aromatic ring were effective inhibitors of Aβ42 aggregation and increased the longevity of transgenic flies beyond that observed for the parent compound, D737 .     

Multiobjective Optimization on Antiplatelet Effects of Three Components Combination by Quantitative Composition–activity Relationship Modeling and Weighted‐Sum Method

Multicomponent therapeutic has become an increasingly favored strategy for treating complex diseases in recent years. In this study, a multiple objective optimization approach was proposed to design the optimal combination of three components for antiplatelet activity. The platelet aggregation assays induced by three different ways, adenosine diphosphate, arachidonic acid, and collagen, were applied to evaluate the in vitro antiplatelet activities of three active components derived from a traditional Chinese medicine. After analyzing this dataset by quantitative composition–activity relationship modeling, a weighted‐sum optimization method was adopted to calculate the optimal ratio between three components for antiplatelet effects. Further experiments validated our method and showed that better antiplatelet activity was exerted by the optimized combination than the individual component or other combinations. Our findings suggested that the proposed multiobjective optimization approach is a novel method for multicomponent drug design.     

Effects of Hydrophobicity on the Antifungal Activity of α‐Helical Antimicrobial Peptides

We utilized a series of analogs of D‐V13K (a 26‐residue amphipathic α‐helical antimicrobial peptide, denoted D1) to compare and contrast the role of hydrophobicity on antifungal and antibacterial activity to the results obtained previously with Pseudomonas aeruginosa strains. Antifungal activity for zygomycota fungi decreased with increasing hydrophobicity (D‐V13K/A12L/A20L/A23L, denoted D4, the most hydrophobic analog was sixfold less active than D1, the least hydrophobic analog). In contrast, antifungal activity for ascomycota fungi increased with increasing hydrophobicity (D4, the most hydrophobic analog was fivefold more active than D1). Hemolytic activity is dramatically affected by increasing hydrophobicity with peptide D4 being 286‐fold more hemolytic than peptide D1. The therapeutic index for peptide D1 is 1569‐fold and 62‐fold better for zygomycota fungi and ascomycota fungi, respectively, compared with peptide D4. To reduce the hemolytic activity of peptide D4 and improve/maintain the antifungal activity of D4, we substituted another lysine residue in the center of the non‐polar face (V16K) to generate D5 (D‐V13K/V16K/A12L/A20L/A23L). This analog D5 decreased hemolytic activity by 13‐fold, enhanced antifungal activity to zygomycota fungi by 16‐fold and improved the therapeutic index by 201‐fold compared with D4 and represents a unique approach to control specificity while maintaining high hydrophobicity in the two hydrophobic segments on the non‐polar face of D5.     

Effects of increasing hydrophobicity by N‐terminal myristoylation on the antibacterial and hemolytic activities of the C‐terminal cationic segments of human‐β‐defensins 1–3

Analogs of the cationic C‐terminal segments of human‐β‐defensins HBD1‐3, Phd1‐3 with a single disulfide bond, exhibited comparable antimicrobial activity that was salt sensitive. They did not show hemolytic activity. In this study, N‐terminal myristoylation was carried out on Phd1‐3 to examine whether increasing hydrophobicity would result in improved antibacterial activity. The antibacterial activity of the oxidized myristoylated peptides MPhd1‐3 and their reduced forms MPhd1r‐3r was determined. These peptides showed enhanced antibacterial activity as compared to Phd1‐3, on mid‐log phase and stationary phase of Staphylococcus aureus and Escherichia coli, except MPhd1r‐3r that were inactive on stationary‐phase E. coli. In the presence of 150 mm NaCl, MPhd1‐3 showed activity against S. aureus. MPhd1and two exhibited activity against E. coli but MPhd3 was inactive. Zeta potential measurements indicated that MPhd1‐3 were more effective in surface charge neutralization of bacteria as compared to Phd1‐3. MPhd1‐3 exhibited hemolytic activity to varying extents with MPhd1 being most hemolytic. The data indicate that myristoylation enhances antibacterial activity and modulates hemolytic activity to different extents. Apart from hydrophobicity, distribution of cationic residues in MPhd1‐3 plays important roles for these activities.     

Synthesis of nicotinamide derivatives having a hydroxy‐substituted benzene ring and the influence of their structures on the apoptosis‐inducing activity against leukemia cells

With the view of developing novel apoptosis‐inducing agents against malignant cells, nicotinamide derivatives containing substituted O‐benzoyl‐tyrosine, dopamine, and norepinephrine residues were synthesized. Antiproliferative activity measurements using leukemia U937 cells revealed that the benzoyl‐tyrosine derivative having two hydroxys at C‐2 and C‐3 on the benzoyl group, and the one having a hydroxy at C‐2 and a methoxy at C‐4 proved the most potent among the 9 nicotinamide derivatives. The IC₅₀ values of these compounds were 0.87 and 3.15 µM, which indicates their noteworthy activity compared with epigallocatechin gallate, a catechin component in green tea known for its noticeable activity. The cell death process was confirmed to be the result of apoptosis by agarose gel electrophoresis and dye staining, suggesting the high potential of these compounds as apoptosis‐inducing anticancer agents. Drug Dev Res 72: 289–297, 2011. © 2010 Wiley‐Liss, Inc.