Design,synthesis and evaluation of carbamate-modified (−)-N1-phenethylnorphysostigmine derivatives as selective butyrylcholinesterase inhibitors

We synthesized carbamate-modified (?)-N¹-phenethylnorphysostigmine derivatives 3a–u and evaluated their anti-cholinesterase activities. In vitro evaluation showed that cyclohexylmethylcarbamate derivative 3u potently and selectively inhibits butyrylcholinesterase.     

Design,synthesis, evaluation and QSAR analysis of N1-substituted norcymserine derivatives as selective butyrylcholinesterase inhibitors

We synthesized a series of N¹-substituted norcymserine derivatives 7a–p and evaluated their anti-cholinesterase activities. In vitro evaluation showed that the pyridinylethyl derivatives 7m–o and the piperidinylethyl derivative 7p improved the anti-butyrylcholinesterase activity by approximately threefold compared to N¹-phenethylnorcymserine (PEC, 2). A quantitative structure-activity relationship (QSAR) study indicated that logS might be a key feature of the improved compounds.     

Chlorinated tacrine analogs: Design,synthesis and biological evaluation of their anti-cholinesterase activity as potential treatment for Alzheimer’s disease

In search of potent acetyl cholinesterase inhibitors with low hepatotoxicity for the treatment of Alzheimer’s disease, introduction of a chloro substitution to tacrine and some of its analogs has proven to be beneficial in maintaining or potentiating the cholinesterase inhibitory activity. Furthermore, it was found to be able to reduce the hepatotoxicity of the synthesized compounds, which is the main target of the study. Accordingly, a series of new 4-(chlorophenyl)tetrahydroquinoline derivatives, was synthesized and characterized. The synthesized compounds were evaluated for their in vitro and in vivo anti-cholinesterase activity using tacrine as a reference standard. Furthermore, they were investigated for their hepatotoxicity compared to tacrine. The obtained biological results revealed that all synthesized compounds displayed equivalent or significantly higher anti-cholinesterase activity and lower hepatotoxicity in comparison to tacrine. In addition, in silico drug-likeness of the synthesized compounds were predicted and their practical logP were assessed indicating that all synthesized compounds can be considered as promising hits/leads. Furthermore, docking study of the compound showing the highest in vitro anticholinesterase activity was performed and its binding mode was compared to that of tacrine.     

Survey of Phytochemical Composition and Biological Effects of Three Extracts from a Wild Plant (Cotoneaster nummularia Fisch. et Mey.): A Potential Source for Functional Food Ingredients and Drug Formulations

This study was focused on the analysis of the phenolic content, antioxidant, antibacterial, anti-cholinesterase, anti-tyrosinase, anti-amylase and anti-glucosidase activity of three solvent extracts from Cotoneaster nummularia. Moreover, water extract was tested in terms of mutagenic/anti-mutagenic effects. The antioxidant activities of these extracts were evaluated by DPPH, ABTS, O₂, metal chelating, phosphomolybdenum, β-carotene/linoleic acid, ferric and cupric reducing power assays. Enzyme inhibitory activities were also examined with colorimetric methods. Generally, methanol and water extracts exhibited excellent biological activities. These extracts were rich in phenolic and flavonoid content. Furthermore, Cotoneaster extracts indicated appreciable antibacterial properties against human pathogen strains. HPLC analysis showed that ferulic acid, chlorogenic acid, (-) – epicatechin and (+)-catechin were the major phenolics in extracts tested. These data offer that these extracts from C. nummularia may be considered as a potential source of biological agents for developing functional foods or drug formulations.     

Structure-activity relationships of the saponins dioscin and dioscinin

Hemolytic and antifungal activities of partial acid hydrolysates of dioscin and dioscinin were compared. In general, these activities were proportional to the number of sugar residues and those derivatives having branched sugar chains showed higher activities than those with straight chains. The 17-hydroxyl group of the dioscinin derivatives reduced both biological activities.     

Development and evaluation of multifunctional agents for potential treatment of Alzheimer's disease: application to a pyrimidine-2,4-diamine template

We investigated a group of 2-benzylpiperidin-N-benzylpyrimidin-4-amines with various electron-withdrawing or electron-donating groups (EWGs or EDGs, respectively) as multi-targeted Alzheimer's disease (AD) therapeutics. The synthesized derivatives were screened for anti-cholinesterase (AChE and BuChE), anti-Aβ-aggregation (AChE- and self-induced) and anti-β-secretase (BACE-1) activities in an effort to identify lead, multifunctional candidates as part of our multi-targeted approach to treat AD. Biological assessment revealed that the nature of the substituent on the C-4 benzylamine group (e.g., halogen vs methoxy-based) greatly affected the biological profile. In vitro screening identified N(2)-(1-benzylpiperidin-4-yl)-N(4)-(3,4-dimethoxybenzyl)pyrimidine-2,4-diamine (7h) as the lead candidate with a dual ChE (AChE IC(50)=9.9 μM; BuChE IC(50)=11.4 μM), Aβ-aggregation (AChE-induced=59.3%; self-induced=17.4% at 100 μM) and BACE-1 (34% inhibition at 10 μM) inhibitory profile along with good cell viability (% neuroblastoma cell viability at 40 μM=81.0%). Molecular modeling studies indicate that a central pyrimidine-2,4-diamine ring serves as a suitable template to develop novel small molecule candidates to target multiple pathological routes in AD.     

A potential role of alkaloid extracts from Salsola species (Chenopodiaceae) in the treatment of Alzheimer's disease

From the aerial parts of Salsola oppositofolia, S. soda and S. tragus an alkaloid extract was obtained and tested to evaluate antioxidant and anti-cholinesterase activities. The in vitro study of the antioxidant activity by the DPPH method revealed a significant activity of Salsola alkaloid extracts with IC(50) values ranging from 16.30 microg/mL for S. oppositifolia to 26.17 microg/mL for S. tragus. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were evaluated. S. tragus alkaloid extract exerted the highest inhibitory activity against AChE (IC(50) of 30.2 microg/mL) and BChE (IC(50) of 26.5 microg/mL). Interestingly, S. soda and S. oppositifolia exhibited a selective inhibitory activity against BChE with IC(50) values of 34.3 microg/mL and 32.7 microg/mL, respectively. Tetrahydroisoquinoline alkaloids were identified and quantified by GC/MS analysis.     

Preparation and in vitro antioxidant activity of kappa-carrageenan oligosaccharides and their oversulfated, acetylated, and phosphorylated derivatives

In order to study the relationship between chemical structure and properties of modified carrageenans versus antioxidant activity in vitro, kappa-carrageenan oligosaccharides were prepared through mild hydrochloric acid hydrolysis of the polysaccharide, and these were used as starting materials for the partial synthesis of their oversulfated, acetylated, and phosphorylated derivatives. The structure and substitution pattern of the oligosaccharides and their derivatives were studied using FTIR and (13)C NMR spectroscopy, and their in vitro antioxidant activities were investigated. Certain derivatives of the carrageenan oligosaccharides exhibited higher antioxidant activity than the polysaccharides and oligosaccharides in certain antioxidant systems. The oversulfated and acetylated derivatives, which scavenge superoxide radicals, the phosphorylated and low-DS acetylated derivatives, which scavenge hydroxyl radicals, and the phosphorylated derivatives, which scavenge DPPH radicals, all exhibited significant antioxidant activities in the systems examined. The effect of the molecular weight of the carrageenan on antioxidant activities, however, is not obvious from these studies.     

Synthesis and pharmacological activities of xanthone derivatives as alpha-glucosidase inhibitors

Considerable interest has been attracted in xanthone and its derivatives because of their large variety of pharmacological activities. In this project, a series of hydroxylxanthones and their acetoxy and alkoxy derivatives were synthesized and evaluated as alpha-glucosidase inhibitors, aimed at clarifying the structure-activity correlation. The results indicated that these xanthone derivatives were capable of inhibiting in vitro alpha-glucosidase with moderate to good activities. Among them, polyhydroxylxanthones exhibited the highest activities and thus may be exploitable as a lead compound for the development of potent alpha-glucosidase inhibitors.     

Determination of binary pesticide mixtures by an acetylcholinesterase-choline oxidase biosensor

In this study, acetylcholinesterase (AChE) and choline oxidase (ChO) were co-immobilized on poly(2-hydroxyethyl methacrylate) (pHEMA) membranes to construct a biosensor for the detection of anti-cholinesterase compounds. pHEMA membranes were prepared with the addition of SnCl(4) to achieve the desired porosity. Immobilization of the enzymes was done by surface attachment via epichlorohydrin (Epi) and Cibacron Blue F3G-A (CB) activation. Enzyme immobilized membrane was used in the detection of anti-cholinesterase activity of aldicarb (AS), carbofuran (CF) and carbaryl (CL), as well as two mixtures, (AS+CF) and (AS+CL). The total anti-cholinesterase activity of binary pesticide mixtures was found to be lower than the sum of the individual inhibition values.     

Synthesis of phenanthroindolizidine alkaloids and evaluation of their antitumor activities and toxicities

We previously reported that phenanthroindolizidine alkaloid 3 and its derivatives had markedly potent in vitro cytotoxicity. However, they had low in vivo antitumor activities and high in vivo toxicities, which was a serious problem. To address this problem, new phenanthroindolizidine derivatives were synthesized and their antitumor activities and toxicities were evaluated. This study describes the relationship between the chemical structures, antitumor activities, and toxicities of these phenanthroindolizidine derivatives. Based on its properties, compound 8 was found to be the most suitable potential antitumor agent.     

Synthesis and insecticidal evaluation of novel N'-tert-butyl-N'-substitutedbenzoyl-N-5-chloro-6-chromanecarbohydrazide derivatives

A series of novel N'-tert-butyl- N'-substitutedbenzoyl-N-5-chloro-6-chromanecarbohydrazide derivatives were synthesized, and their larvicidal activities against Oriental armyworm were evaluated. The results of bioassays indicated that most of these title compounds exhibit higher larvicidal activities than RH-5849, and several of them somewhat lower than the commercial insecticide tebufenozide. The larvicidal activities are strongly associated with the types and patterns of substitution on the benzene, and 3,5-dimethyl, 2-nitro-4-chloro and 3-methyl derivatives are most prominent in increasing activity. Toxicity assays indicated that these derivatives could induce a premature, abnormal, and lethal larval moult.     

Trypsin-resistant forms of human growth hormone have diabetogenic and insulin-like activities

Although diabetogenic and insulin-like activities are intrinsic properties of the growth hormone (GH) molecule, it has been frequently suggested that the hormone must be proteolytically processed for these activities to be expressed. If this is correct, then derivatives of GH having resistance to appropriate proteolytic attack might not have diabetogenic and/or insulin-like activity. The purpose of the present study was to prepare derivatives of human GH that are resistant to digestion by trypsin and to determine whether they possess diabetogenic or insulin-like activity. Three derivatives were prepared from purified native human GH in which lysine residues were modified with methyl acetimidate, citraconic anhydride or S-ethyl-thioltrifluoroacetate, and one in which arginine residues were modified with camphorquinone-10-sulfonic acid. Comparisons of peptide maps of tryptic digests of these derivatives with that of unmodified human GH indicated that all four were resistant to proteolysis by trypsin. All of these trypsin-resistant forms of human GH were found to possess significant growth-promoting, diabetogenic and insulin-like activities, although all activities were attenuated to some extent in each derivative. The relative potencies of the human GH derivatives in a radioimmunoassay for human GH were somewhat similar to their order of potency in the growth-promoting and diabetogenic assays. These results suggest that if proteolytic processing of the GH molecule is involved in the expression of one or more of its biological activities, such processing probably does not involve a trypsin-like proteinase.     

Parallel measurement of brain acetylcholinesterase and the muscarinic cholinergic receptor in the diagnosis of acute, lethal poisoning by anti-cholinesterase pesticides

The activity of acetylcholinesterase (AChE) and the density of muscarinic cholinergic binding receptors (mCBR) were measured in brains from normal Japanese quail (Coturnix coturnix japonica) and from quail after lethal intoxication with diazinon. These were measured in brains from whole heads held at 25 C for 0 to 8 days after death. The maximum relative loss of activity due to post mortem decomposition alone during 8 days was 13% and 10% for AChE and mCBR, respectively. During post mortem decomposition, the ratio of AChE: mCBR activities remained constant at approximately 1.3:1 in normal brains while it was always less than or equal to 0.5:1 after intoxication with diazinon. Normal AChE activity could be estimated from mCBR density. Parallel measurement of AChE and mCBR may assist in the post mortem diagnosis of death due to acute poisoning with anti-cholinesterase pesticides when control specimens are not available.     

Synthesis, acute toxicities, and antitumor effects of novel 9-substituted beta-carboline derivatives

A series of novel 9-substituted beta-carboline derivatives was synthesized from harmine and l-tryptophan, respectively. Cytotoxic activities of these compounds in vitro were investigated. The results showed that most compounds of 9-substituted beta-carboline derivatives had more remarkable cytotoxic activities in vitro than their corresponding parent compounds. Acute toxicities and antitumor effects of the selected beta-carboline derivatives in mice were also examined. The results demonstrated that a short alkyl or benzyl substituent at position-9 increased the antitumor activities significantly and a ethoxycarbonyl or carboxyl substituent at position-3 reduced the acute toxicity and neurotoxicity of these beta-carboline derivatives dramatically. Moreover the compounds both with an alkoxycarbonyl or carboxyl substituent at position-3 and a short alkyl or benzyl substituent at positon-9 exhibited more significant antitumor activities and lower acute toxicities and neurotoxicities than the other compounds. The compound 8c, having an n-butyl and a carboxyl substituent at position-9 and 3, respectively, was found to have the highest antitumor effect and the lowest acute toxicity and neurotoxicity. These data suggested that (1) appropriate substituents at both position-9 and 3 of beta-carboline derivatives might play a crucial role in determining their enhanced antitumor activities and decreased acute toxicities and neurotoxic effects; (2) the beta-carboline derivatives have the potential to be used as antitumor drug leads.     

Design,synthesis, and antibacterial activity of 2,5-dihydropyrrole formyl hydroxyamino derivatives as novel peptide deformylase inhibitors

The synthesis and antibacterial activity of 2,5-dihydropyrrole formyl hydroxyamino derivatives are reported. The antibacterial activities of these derivatives were evaluated, and some of these derivatives showed better in vitro antibacterial activity than existing drugs, including penicillin, ciprofloxacin, vancomycin, and linezolid.     

Stereoselective synthesis of 15- and 16-substituted isosteviol derivatives and their cytotoxic activities

By means of functional interconversions in ring D of the tetracyclic diterpene isosteviol (ent-16-ketobeyeran-19-oic acid 1), various 15- and 16-substituted isosteviol derivatives were stereoselectively prepared. The cytotoxic activities in vitro of these new isosteviol derivatives were investigated, and some of them showed noteworthy activities against B16-F10 melanoma cells.     

Synthesis and structure–activity relationships of sinenxan A derivatives as multidrug resistance reversal agents

Two types of sinenxan A derivatives with different side chains at C-5 were synthesized and evaluated for their in vitro multidrug resistant reversal activities. Several derivatives exhibited better activities than the positive control verapamil. The structure–activity relationships of these derivatives suggested that a carbonyl group at C-13 and the length of side chain at C-5 are important for the activity.     

Effects of backbone structures and stereospecificities of lipid A-subunit analogues on their biological activities

Among chemically synthesized analogues corresponding to the nonreducing sugar part of lipid A, we have found an analogue (GLA-27) which exhibits Limulus, mitogenic, polyclonal B cell activation (PBA), interferon-inducing, and tumor necrosis factor (TNF)-inducing activities but not pyrogenic activity. The structure of GLA-27 comprises 4-O-phosphono-D-glucosamine with tetradecanoyl and 3-tetradecanoyloxytetradecanoyl (C14-O-(C14] groups as the 3-O- and 2-N-acyl substituents, respectively. Derivatives of GLA-27 with different backbone structures, such as the 1-deoxy, 3-epimeric, 3-amino, and 1-deoxy-3-epimeric derivatives of glucosamine, were chemically synthesized, and their mediator-inducing activities such as interferon- and TNF-inducing activities were investigated in comparison with their B cell activation activities including mitogenic and PBA activities. Among these derivatives, a derivative with a 1-deoxyglucosamine backbone (GLA-40) exhibited stronger B cell activation activities than those of GLA-27 while the mediator-inducing activities of GLA-40 were weaker than those of GLA-27. In addition to these derivatives, stereoisomers of GLA-27 which possess the (R) and (S) forms of C14-O-(C14) as the 2-N-acyl substituent were also synthesized and their biological activities compared. The (S) isomer exhibited much stronger mediator-inducing activities than the (R) isomer. On the other hand, B cell activation activities of the (R) isomer were strong and those of the (S) isomer weak. These results clearly demonstrate that mediator-inducing activities and B cell activation activities can be selectively expressed by modifying the structures of lipid A analogues.     

Immunogenicity and bioactivity of glucagon, modified at methionine-27.

Porcine glucagon was modified at methionine-27 by methylation or oxidation. Antisera against the glucagon derivatives were obtained. One of these antisera showed a high affinity for glucagon, with no cross-reactivity with gut-GLI 1. Biological activities of these derivatives were assessed on rat hepatocytes. Both derivatives had the same maximal glucose-mobilising activity as native glucagon, but a decrease potency, suggesting a crucial role of methionine in the binding of glucagon to its hepatic receptor.