Synthesis and in‐vitro Cytotoxic Evaluation of Novel Pyridazin‐4‐one Derivatives

A new series of N‐aryl‐4‐oxo‐1,4‐dihydro‐pyridazine‐3‐carboxylic acids has been synthesized by condensation of aryldiazonium with 4‐hydroxy‐6‐methyl‐2‐pyrone. Some of these compounds exhibited in‐vitro cytotoxic activity with moderate to excellent growth inhibition against the murine P815 mastocytoma cell line. Compound 5b showed an important cytotoxic activity against cell line P815 (IC₅₀ = 0.40 μg/mL).     

Substituent Effects on Cytotoxic Activity,Spectroscopic Property,and DNA Binding Property of Naphthalimide Derivatives

A series of novel naphthalimide derivatives NI 1‐5 containing piperazine moieties (N‐(2‐hydroxyethyl)piperazine and 1‐piperazinepropanol) and piperidine moieties (4‐piperidinemethanol, 4‐hydroxypiperidine and 4‐piperidineethanol) have been synthesized and evaluated for their cytotoxic activity, spectroscopic property, and DNA binding behaviors. It was found that substituents at the 4‐position remarkably influence the various activities of this series of compound. Compounds NI 3‐5 modified with piperidines exhibited potent cytotoxic activities against Hela, SGC‐7901, and A549 cells with the IC₅₀ values from 0.73 μm to 6.80 μm , which are better than NI 1‐2 functionalized with piperazines. Compounds NI 1‐2 showed higher binding capacity with Ct‐DNA than compounds NI 3‐5 based on studies of UV–vis, fluorescence and CD spectra. Furthermore, compounds NI 3‐5 , as DNA intercalators, showed fluorescence enhancement upon binding with Ct‐DNA. More interestingly, fluorescence imaging studies of compound NI 4 with A549 cells showed that the fluorescence predominantly appeared in the cytoplasm. These results provided a potential application of NI 3‐5 as anticancer therapeutic and cancer cell imaging agents.     

Synthesis,in‐vitro Antimicrobial and Cytotoxic Studies of Novel Azetidinone Derivatives

Developing novel antimicrobial drugs is increasingly important in the modern pharmaceutical industry. A series of novel 3‐chloro‐4‐[4‐(2‐oxo‐2H‐chromen‐4‐ylmethoxy)phenyl]‐1‐phenylazetidin‐2‐ones 5a–o have been synthesized from 4‐bromomethylcoumarins 1a–e and 4‐aryliminomethyl‐phenols 3a–c . These compounds were screened for their in‐vitro antibacterial activity against two Gram‐positive (Staphylococcus aureus and Vancomycin resistant enteroccoccus) and two Gram‐negative (Escherichia coli and Shigella dysentery) bacterial strains and antifungal activity against Aspergillus fumigatus, Candida albicans, and Penicillium. Results revealed that compounds 5c , 5f , 5h , 5j , and 5m showed excellent activity against a panel of microorganisms. The brine‐shrimp bioassay was also carried out to study their in‐vitro cytotoxic properties and two compounds, 5h and 5m , possessing LD₅₀ = 7.154×10^–4 M and 5.782×10^–4 M, respectively, displayed potent cytotoxic activity against Artemia salina. The presence of a chlorine group in the coumarin moiety, its effect on their antibacterial, antifungal, and cytotoxic activities is discussed. All newly synthesized compounds were characterized by elemental analysis, IR, ¹H‐NMR, ¹³C‐NMR, and MS.     

Synthesis and Structure‐Activity Relationship Studies of Pyrazole‐based Heterocycles as Antitumor Agents

Several 4‐cyano‐1,5‐diphenylpyrazoles attached to different heterocyclic ring systems at position 3 were synthesized starting from ethyl 4‐cyano‐1,5‐diphenyl‐1H‐pyrazole‐3‐carboxylate 1 . The newly synthesized compounds were tested in vivo for their anti‐estrogenic effects and evaluated in vitro for their cytotoxic properties against estrogen‐dependent tumors. 3‐(5‐Mercapto‐1,3,4‐oxadiazole‐2‐yl)‐1,5‐diphenyl‐1H‐pyrazole‐4‐carbonitrile 13 revealed the highest cytotoxic activity with a GI₅₀ value equal to 40 nM against the IGROVI ovarian tumor cell line. It also showed an anti‐estrogen activity 1.6 more effective than the reference drug, in addition to a high tolerable dose. 3‐(5‐(Methylthio)‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1,5‐diphenyl‐1H‐pyrazole‐4‐carbonitrile 7 was found to have the highest anti‐estrogenic activity, while 1,5‐diphenyl‐3‐[5‐(phenylamino)‐1,3,4‐thiadiazol‐2‐yl]‐1H‐pyrazole‐4‐carbonitrile 11 showed the lowest activity. The oral LD₅₀ values revealed that most of the tested compounds are relatively nontoxic.     

Design,Synthesis and Bioevaluation of Novel N‐Substituted‐3,5‐Bis(Arylidene)‐4‐piperidone Derivatives as Cytotoxic and Antitumor Agents with Fluorescent Properties

Ten new N‐substituted‐3,5‐bis(arylidene)‐4‐piperidone derivatives (series 1 and 2 ) were synthesized and subsequently evaluated against human carcinoma cell lines SW1990, MIA PaCa‐2, PG‐BE1, NCI‐H460, and SK‐BR‐3 for cytotoxic activity by the CCK‐8 method, and their fluorescent properties were investigated as well. The compounds were confirmed to display greater cytotoxic activity to the neoplastic cells, and approximately 50% of the IC₅₀ values were lower than 5 μm . In particular, compounds 1a , 1c , 1d, and 1e bearing 3‐bromophenyl groups were revealed as the most active antitumor drug candidates and had the average IC₅₀ values of 1.94, 1.11, 1.16, and 0.817 μm , respectively. Furthermore, their fluorescent properties were interesting and might contribute to the visualization of their distribution in tumor cells. Some possible reasons for the disparity between cytotoxic activity and fluorescent properties in the two series of compounds were explored. This study revealed high potential of these molecules for further development as fluorescent cytotoxic and antitumor agents.     

Synthesis of 13C‐labelled cutin and suberin monomeric dicarboxylic acids of the general formula HO213C‐(CH2)n‐13CO2H (n = 10, 12, 14, 16, 18, 20, 22, 24, 26, 28)

¹³C‐labeled dicarboxylic acids HO₂¹³C‐(CH₂)_n‐¹³CO₂H (n = 10, 12, 14, 16, 18, 20, 22, 24, 26, 28) have been synthesized as internal standards for LC‐MS and GC‐MS analysis of cutin and suberin monomer degradation by soil‐based microorganisms. Different synthetic strategies had to be applied depending on the chain length of the respective synthetic target and because of economic considerations. ¹³C‐labels were introduced by nucleophilic substitution of a suitable leaving group with labelled potassium cyanide and subsequent hydrolysis of the nitriles to produce the corresponding dicarboxylic acids. All new compounds are characterized by GC/MS, IR, and NMR methods as well as by elemental analysis.     

Study of the conformational profile of the cyclohexane analogs of l‐phenylalanine

Abstract: The conformational profile of the conformationally constrained cyclohexane analogs of phenylalanine (1‐amino‐2‐phenylcyclohexanecarboxylic acids, c₆Phe) was assessed using computational methods. For this purpose, the conformational space of the N‐acetyl methylamide derivatives of the stereoisomers (2S,3R)c₆Phe and (2S,3S)c₆Phe was explored by computing their respective Ramachandran maps, and low‐energy minima were characterized at molecular mechanics level by means of the amber program, using the parm94 force field set of parameters. In order to assess the performance of the molecular mechanics calculations, each of the low‐energy conformations was also investigated further at the ab initio level. Accordingly, the molecular mechanics geometries were used as starting conformations to perform full geometry optimizations at the Hartree‐Fock level, using a 6‐31G(d) basis set. Analysis of the results revealed that the cyclohexane structure directly induces some restrictions on the backbone, and constrains the orientation of the aromatic side‐chain to two narrow regions for each stereoisomer. The conformational profile of these amino acids is then explained on the grounds of the interaction between the rigidly held phenyl ring and the main chain NH and CO groups. The results obtained are in good accordance with the experimental observations.     

Structural Factors Affecting Cytotoxic Activity of (E)‐1‐(Benzo[d ][1,3]oxathiol‐6‐yl)‐3‐phenylprop‐2‐en‐1‐one Derivatives

Derivatives of (E)‐1‐(5‐alkoxybenzo[d][1,3]oxathiol‐6‐yl)‐3‐phenylprop‐2‐en‐1‐one 1 demonstrated exceptionally high in vitro cytotoxic activity, with IC₅₀ values of the most active derivatives in the nanomolar range. To identify structural fragments necessary for the activity, several analogs deprived of selected fragments were prepared, and their cytotoxic activity was tested. It was found that the activity depends on combined effects of (i) the heterocyclic ring, (ii) the alkoxy group at position 5 of the benzoxathiole ring, and (iii) the substituents in the phenyl ring B. Replacement of the sulfur atom by oxygen does not influence the activity. None of the listed structural fragments alone assured high cytotoxic activity.     

Synthesis and Cytotoxic Activity of Novel Amidine Analogues of Bis(2‐chloroethyl)amine

Novel nitrogen mustard agents 7 – 12 involving 4‐(N,N‐bis(2‐chloroethyl)aminophenyl)propylamine linked to a 5‐(4‐N‐alkylamidinophenyl)‐2‐furancarboxylic acid moiety by the formation of an amide bond have been synthesized, characterized, and evaluated for their in‐vitro cytotoxic activity against MDA‐MB‐231 and MCF‐7 human breast cancer cells. Evaluation of the cytotoxicity of 7 – 12 employing a MTT assay and inhibition of [³H]thymidine incorporation into DNA demonstrated that these compounds exhibit remarkable cytotoxic effects in comparison with 4‐[bis(2‐chloroethyl)amino]benzenebutanoic acid. Compounds 7 and 9 , which possess a cationic amidine and 4,5‐dihydro‐1H‐imidazol function moiety are approximately ten times more potent than 4‐[bis(2‐chloroethyl)amino]benzenebutanoic acid. The new compounds were evaluated as DNA topoisomerase II inhibitors. The cytotoxicity of the compounds 7 – 12 correlates with their DNA‐binding affinities and their relative potency as topoisomerase II inhibitors.     

Synthesis and Biological Evaluation of New Eugenol Mannich Bases as Promising Antifungal Agents

New Mannich base‐type eugenol derivatives were synthesized and evaluated for their anticandidal activity using a broth microdilution assay. Among the synthesized compounds, 4‐allyl‐2‐methoxy‐6‐(morpholin‐4‐ylmethyl) phenyl benzoate ( 7 ) and 4‐{5‐allyl‐2‐[(4‐chlorobenzoyl)oxy]‐3‐methoxybenzyl}morpholin‐4‐ium chloride ( 8 ) were found to be the most effective antifungal compounds with low IC₅₀ values, some of them well below those of reference drug fluconazole. The most significant IC₅₀ values were those of 7 against C. glabrata (1.23 μm ), C. albicans and C. krusei (both 0.63 μm ). Additionally, the synthesized compounds were evaluated for their in vitro cytotoxic effects on human mononuclear cells. As result, the cytotoxic activity of eugenol in eukaryotic cells decreased with the introduction of the morpholinyl group. Given these findings, we point out compounds 7 and 8 as the most promising derivatives because they showed potency values greater than those of eugenol and fluconazole and they also presented high selectivity indexes.     

Amphipathic control of the 310‐/α‐helix equilibrium in synthetic peptides

Abstract: A series of short, amphipathic peptides incorporating 80% C^α,C^α‐disubstituted glycines has been prepared to investigate amphipathicity as a helix‐stabilizing effect. The peptides were designed to adopt 3₁₀‐ or α‐helices based on amphipathic design of the primary sequence. Characterization by circular dichroism spectroscopy in various media (1 : 1 acetonitrile/water; 9 : 1 acetonitrile/water; 9 : 1 acetonitrile/TFE; 25 mm SDS micelles in water) indicates that the peptides selectively adopt their designed conformation in micellar environments. We speculate that steric effects from ith and ith + 3 residues interactions may destabilize the 3₁₀‐helix in peptides containing amino acids with large side‐chains, as with 1‐aminocyclohexane‐1‐carboxylic acid (Ac₆c). This problem may be overcome by alternating large and small amino acids in the ith and ith + 3 residues, which are staggered in the 3₁₀‐helix.     

Cytotoxic and trypanocidal activities of cinchona alkaloid derivatives

A series of 27 cinchona alkaloid derivatives ( 1f–w , 2a–e and 3a–d ) were investigated for their cytotoxic and trypanocidal activities using seven different cancer cell lines (KB, HeLa, MCF‐7, A‐549, Hep‐G2, U‐87 and HL‐60), two normal cell lines (HDF and CHO) and bloodstream forms of Trypanosoma brucei brucei, respectively. Four compounds ( 1u , 1w , 2e and 3d ) were identified with promising cytotoxic activity with 50% growth inhibition (GI₅₀) values below 10 μM. Two ( 2e and 3d ) of the four compounds also exhibited potent anti‐trypanosomal activity with GI₅₀ values of 0.3–0.4 μM. All four active compounds represented derivatives modified at their C‐9 hydroxy group. With respect to anti‐proliferative activity and selectivity, 2e (epi‐N‐quinidyl‐N′‐bis(3,5‐trifluoromethyl)phenylthiourea) proved to be the most promising derivative for both cancer cells and bloodstream forms of T. b. brucei. The cytotoxic activity of compounds 1u , 1w , 2e and 3d was attributed to their ability to induce apoptosis in cancer cells. The results demonstrate the potential of cinchona alkaloid derivatives as novel anti‐cancer and anti‐trypanosome drug candidates.     

Synthesis and Biological Evaluation of Benzo[d][1,3]Dioxol‐5‐yl Chalcones as Antiproliferating Agents

A series of chalcone derivatives were designed, synthesized, and evaluated for their cytotoxic potential. These molecules have showed promising cytotoxic activity with IC₅₀ values ranging from 5.24 to 63.12 μm . Among them, conjugates 16k , 16m and 16t showed significant antiproliferative activity with IC₅₀ values ranging from 5.24 to 10.39  μ m in MDA‐MB‐231 cell line. These compounds were further investigated for their effect on cell membrane blebbing, chromatin condensation, DNA fragmentation, Hoechst staining, annexin V, and cell cycle arrest (G2/M). The Western blot experiments revealed up regulation of pro‐apoptotic Bax and downregulation of antiapoptotic Bcl‐2. The studies also indicated reduction of mitochondrial membrane potential and increase in the levels of caspase‐3 and caspase‐7.     

Synthesis of deuterium‐labelled 6‐[5‐(4‐amidinophenyl)furan‐2‐yl]nicotinamidine and N‐alkoxy‐6‐{5‐[4‐(N‐alkoxyamidino)phenyl]‐ furan‐2‐yl}‐nicotinamidines

6‐[5‐(4‐Amidinophenyl)furan‐2‐yl]nicotinamidine‐d₄ ( 5 ) was synthesized from 6‐[5‐(4‐cyanophenyl)furan‐2‐yl]nicotinonitrile‐d₄ ( 3 ), through the bis‐O‐acetoxy‐amidoxime followed by hydrogenation. Compound 3 was prepared from 6‐(furan‐2‐yl)‐nicotinonitrile by a Heck coupling reaction with 4‐bromobenzonitrile‐d₄, a product of selective cyanation reaction of 1,4‐dibromobenzene‐d₄ with Cu(1)CN. Deuterium‐labelled N‐methoxy‐6‐{5‐[4‐(N‐methoxy‐amidinophenyl]‐furan‐2‐yl}‐nicotinamidines were prepared via methylation of their respective amidoximes with dimethyl sulfate‐d₆ in aqueous sodium hydroxide in good yields. Copyright © 2004 John Wiley & Sons, Ltd.     

Newly Designed and Synthesized Curcumin Analogs with in vitro Cytotoxicity and Tubulin Polymerization Activity

Novel curcumin analogs with 4‐piperidone ring were designed, synthesized, and evaluated for their cytotoxic activities against five different cancer cell lines. 3,5‐bis(4‐Hydroxy‐3‐methoxybenzylidene)‐4‐oxo‐N‐phenylpiperidine‐1‐carbothioamide (XIIe) exhibited considerable cytotoxic activity with IC₅₀ values in 1–2.5 μm range. In silico and in vitro, studies were also performed to predict the binding affinity of the target compounds to the β‐chain of tubulin receptor (PDB code 1SA1) and their abilities to affect microtubules polymerization cycle. 3,5‐bis(3‐Iodo‐5‐methoxy‐4‐propoxybenzylidene)‐N‐acetylpiperidin‐4‐one (VIIa) was found to exert 93.3% inhibition of tubulin and destabilization of microtubules in vitro compared to vincristine while, 3,5‐bis(3,4,5‐trimethoxybenzylidene)‐N‐benzoylpiperidin‐4‐one (XIIc) showed high potency in a different way where it exerted 94.8% stabilization of microtubules in vitro compared to positive control paclitaxel.     

New Arylpiperazines with Flexible versus Partly Constrained Linker as Serotonin 5‐HT1A/5‐HT7 Receptor Ligands

A series of new long‐chain arylpiperazine (LCAP) derivatives with flexible and partly constrained alkyl linker were synthesized and investigated in vitro as potential serotonin 5‐HT_1A and 5‐HT₇ receptor ligands. The compounds were prepared by a two‐step procedure using naphthalimide and 2H‐1,3‐benzoxazine‐2,4(3H)‐dione as imides, and 1‐(2‐methoxyphenyl)piperazine (o‐OMe‐PhP) and 1,2,3,4‐tetrahydroisoquinoline (THIQ) as amine pharmacophores. Modifications of the spacer structure included introduction of flexible penta‐ and hexamethylene chains as well as partly constrained m‐ and p‐xylyl moieties. In general, the new compounds were more active at the 5‐HT_1A than at the 5‐HT₇ receptor, and the o‐OMe‐PhP derivatives displayed higher affinities than their respective THIQ analogs. The spacer modifications had little effect on the observed in vitro activities. Within the o‐OMe‐PhP series, except for a small binding reduction for ligands containing the m‐xylyl moiety, there was no substantial change in the compounds' potency at both receptors, while for the THIQ derivatives a clear structure–activity relationship was visible only for the interaction of the compounds with the 5‐HT₇ receptor, which strongly favored flexible analogs.     

Rational Evolution of Antimicrobial Peptides Containing Unnatural Amino Acids to Combat Burn Wound Infections

Antimicrobial peptides have long been raised as a promising strategy to combat bacterial infection in burn wounds. Here, we attempted to rationally design small antimicrobial peptides containing unnatural amino acids by integrating in silico analysis and in vitro assay. Predictive quantitative sequence‐activity models were established and validated rigorously based on a large panel of nonamer antimicrobial peptides with known antibacterial activity. The best quantitative sequence‐activity model predictor was employed to guide genetic evolution of a peptide population. In the evolution procedure, a number of unnatural amino acids with desired physicochemical properties were introduced, resulting in a genetic evolution‐improved population, from which seven peptide candidates with top scores, containing 1–3 unnatural amino acids, and having diverse structures were successfully identified, and their antibacterial potencies against two antibiotic‐resistant bacterial strains isolated from infected burn wounds were measured using in vitro susceptibility test. Consequently, four (WL‐Orn‐LARKIV‐NH₂, ARKRWF‐Dab‐FL‐NH₂, KFI‐Hag‐IWR‐Orn‐R‐NH₂ and YW‐Hag‐R‐Cit‐RF‐Orn‐N‐NH₂) of the seven tested peptides were found to be more potent than reference Bac2A, the smallest naturally occurring broad spectrum antimicrobial peptide. Molecular dynamics simulations revealed that the designed peptides can fold into amphipathic helical structure that allows them to interact directly with microbial membranes.     

Ring Expansions of Tetrahydroprotoberberines and Related Dibenzo[c,g]azecines Modulate the Dopamine Receptor Subtype Affinity and Selectivity

The affinities of tetrahydroprotoberberines for dopamine receptors dramatically decrease after cleaving the central C‐N bond to the analogous ten‐membered dibenzo[c,g]azecines [1]. In the present work, we also synthesized eleven‐membered homologues of these heterocycles and measured the affinities of the resulting dibenzazaundecenes and their underlying homoberberines for human dopamine receptors as well as the cytotoxic effects of all target compounds on human glia cells. The tetracyclic iso‐C‐homoberberine‐derivatives revealed to be D₄‐selective antagonists, while all other active compounds showed a significant D₁/D₅ selectivity. Distances in energy‐minimized conformations were measured in order to explain our findings.