Synthesis and biological activity of oxadiazole and triazolothiadiazole derivatives as tyrosinase inhibitors

A series of 16 oxadiazole and triazolothiadiazole derivatives were designed, synthesized and evaluated as mushroom tyrosinase inhibitors. Five derivatives were found to display high inhibition on the tyrosinase activity ranging from 0.87 to 1.49 μM. Compound 5 exhibited highest tyrosinase inhibitory activity with an IC₅₀ value of 0.87 ± 0.16 μM. The in silico protein–ligand docking using autodock 4.1 was successfully performed on compound 5 with significant binding energy value of ?5.58 kcal/mol. The docking results also showed that the tyrosinase inhibition might be due to the metal chelating effect by the presence of thione functionality in compounds 1–5. Further studies revealed that the presence of hydrophobic group such as cycloamine derivatives played a major role in the inhibition. Piperazine moiety in compound 5 appeared to be involved in an extensive hydrophobic contact and a 2.9 Å hydrogen bonding with residue Glu 182 in the active site.     

Design,synthesis and biological evaluation of coumarin derivatives as novel acetylcholinesterase inhibitors that attenuate H2O2-induced apoptosis in SH-SY5Y cells

A novel series of coumarin derivatives were designed, synthesized and investigated for inhibition of cholinesterase, including acetyl cholinesterase (AChE) and butyrylcholinesterase (BuChE). This biological study showed that these compounds containing piperazine ring had significant inhibition activities on AChE rather than BuChE. Further study suggested that 9x, as one of this kind of structure derivative, showed the strongest inhibition activity on AChE with an IC₅₀ value of 34 nM. Moreover, molecular docking, flow cytometry (FCM), and western blot assay suggested that 9x could induce cytoprotective autophagy to attenuate H₂O₂-induced cell death in human neuroblastoma SH-SY5Y cells. These findings highlight a new approach for the development of a novel potential neuroprotective compound targeting AChE with autophagy-inducing activity in future Alzheimer’s disease (AD) therapy.     

Formation of P1, P2-dinucleoside 5′-pyrophosphates under potentially prebiological conditions

Summary Organic pyrophosphates such as UppA and NAD are formed when a solution containing a nucleotide, a nucleoside 5-polyphosphate, Mg²⁺ and imidazole are allowed to dry out. We suggest that this synthesis may have occured concurrently with oligonucleotide formation.Abbreviations Im Imidazole - CDI 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride - EDTA ethylenediaminetetraacetic acid - A adenosine - U uridine - p_nA adenosine 5-poly-phosphate containing n phosphate residues - pU uridine 5-phosphate - AppA P₁,P₂-diadenosine 5-pyrophosphate - UppA P₁-(uridine 5)-P₂-(adenosine 5)-pyrophosphate - ImpA adenosine 5-phosphorimidazolide - NMN nicotinamide mononucleotide - NAD nicotinamide-adenine dinucleotide     

Design, synthesis and evaluation of flavonoid derivatives as potent AChE inhibitors

A new series of flavonoid derivatives have been designed, synthesized and evaluated as potent AChE inhibitors. Most of them showed more potent inhibitory activities to AChE than rivastigmine. The most potent inhibitor isoflavone derivative 10d inhibit AChE with a IC₅₀ of 4 nM and showed high BChE/AChE inhibition ratio (4575-fold), superior to donepezil (IC₅₀ = 12 nM, 389-fold). Molecular docking studies were also performed to explore the detailed interaction with AChE.     

Functionalized thymidine derivatives as carriers for the γ-emitter technetium tricarbonyl moiety

Nuclear medicine imaging of cell proliferation has gained broad interest in clinical oncology. A good tracer to image cell proliferation, possibly associated to tumour progression, should rapidly and specifically be incorporated into growing DNA. Following this idea, we have singled out thymidine as a potential biological carrier for delivery of the organometallic fragment [M(CO)₃]⁺ (M = “cold” Re, γ-emitter ^99mTc) to DNA. In the present paper we report the two-step synthesis of thymidine N-3 derivatives and their coordination complexes. Thymidine could be alkylated without protecting the sugar alcoholic functions. Methyl-2,2′-diaminodiethylamine thymidine derivative was quickly reacted with rhenium and technetium carbonyls in almost quantitative yield. The resulting ^99mTc complex represents a convenient radiopharmaceutical for single photon emission tomography (SPECT).     

Hybrid Pharmacophoric Approach in the Design and Synthesis of Coumarin Linked Pyrazolinyl as Urease Inhibitors,Kinetic Mechanism and Molecular Docking

The current research article reports the synthesis of coumarinyl pyrazolinyl thioamide derivatives and their biological activity as inhibitors of jack bean urease. The coumarinyl pyrazolinyl thioamides were synthesized by reacting thiosemicarbazide with newly synthesized chalcones to afford the products in good yields and the synthesized compounds were purified by recrystallization. Coumarinyl pyrazolinyl thioamide derivatives 5a  –  5q showed significant activity against Urease enzyme and also exhibited good antioxidant potential. The compound 3‐(2‐oxo‐2H‐chromen‐3‐yl)‐5‐phenyl‐4,5‐dihydro‐1H‐pyrazole‐1‐carbothioamide ( 5n ) was found to be superior agent in the series with an IC₅₀ = 0.358 ± 0.017 μm compared to standard thiourea with an IC₅₀ = 4720 ± 174 μm . To undermine the binding mode of inhibition kinetic studies were performed for most potent derivative and it was found that compound 5n inhibits urease enzyme by non‐competitive mode of inhibition. Molecular docking studies were carried out to delineate the binding affinity of the synthesized derivatives.     

Cytochalasin B. VI. Competitive inhibition of nucleoside transport by cultured Novikoff rat hepatoma cells

Cytochalasin B competitively inhibits the transport of uridine and thymidine by Novikoff rat hepatoma cells growing in suspension culture with apparent K_i''s of 2 and 6 µM, respectively, but has no effect on the intracellular phosphorylation of the nucleosides. Choline transport is not affected by cytochalasin B. Results from pulse-chase experiments indicate that cytochalasin B has no direct effect on the synthesis of RNA, DNA, or uridine diphosphate-sugars. The inhibition of uridine and thymidine incorporation into nucleic acids by cytochalasin B is solely the consequence of the inhibition of nucleoside transport.     

Synthesis,molecular docking study and in vitro thymidine phosphorylase inhibitory potential of oxadiazole derivatives

We have synthesized oxadiazole derivatives (1–16), characterized by ¹H NMR, ¹³C NMR and HREI-MS and screened for thymidine phosphorylase inhibitory potential. All derivatives display varied degree of thymidine phosphorylase inhibition in the range of 1.10 ± 0.05 to 49.60 ± 1.30 μM when compared with the standard inhibitor 7-Deazaxanthine having an IC₅₀ value 38.68 ± 1.12 μM. Structure activity relationships (SAR) has been established for all compounds to explore the role of substitution and nature of functional group attached to the phenyl ring which applies imperious effect on thymidine phosphorylase activity. Molecular docking study was performed to understand the binding interaction of the most active derivatives with enzyme active site.     

A simple and efficient synthesis of novel inhibitors of alpha-glucosidase based on benzimidazole skeleton and molecular docking studies

A novel series of benzimidazole derivatives were prepared starting from o-phenylenediamine and 4-nitro-o-phenylenediamine with iminoester hydrochlorides. Acidic proton in benzimidazole was exchanged with ethyl bromoacetate, then ethyl ester group was transformed into hydrazide group. Cyclization using CS₂/KOH leads to the corresponding 1,3,4-oxadiazole derivative, which was treated with phenyl isothiocyanate resulted in carbothioamide group, respectively. As the target compounds, triazole derivative was obtained under basic condition and thiadiazole derivative was obtained under acidic condition from cyclization of carbothioamide group. Most reactions were conducted using both the microwave and conventional methods to compare yields and reaction times. All compounds obtained in this study were investigated for α-glucosidase inhibitor activity. Compounds 6a, 8a, 4b, 5b, 6b and 7b were potent inhibitors with IC₅₀ values ranging from 10.49 to 158.2 μM. This has described a new class of α-glucosidase inhibitors. Molecular docking studies were done for all compounds to identify important binding modes responsible for inhibition activity of α-glucosidase.     

Synthesis and biological evaluation of fatty acyl ester derivatives of 2',3'-didehydro-2',3'-dideoxythymidine

A number of 5′-O-fatty acyl derivatives of 2′,3′-didehydro-2′,3′-dideoxythymidine (stavudine, d4T) were synthesized and evaluated for anti-HIV activities against cell-free and cell-associated virus, cellular cytotoxicity, and cellular uptake studies. The conjugates were found to be more potent than d4T. Among these conjugates, 5′-O-12-azidododecanoyl derivative of d4T (2), displaying EC₅₀ = 3.1-22.4 μM, showed 4- to 9-fold higher activities than d4T against cell-free and cell-associated virus. Cellular uptake studies were conducted on CCRF-CEM cell line using 5(6)-carboxyfluorescein derivatives of d4T attached through β-alanine (9) or 12-aminododecanoic acid (10) as linkers. The fluorescein-substituted analog of d4T with long chain length (10) showed 12- to 15-fold higher cellular uptake profile than the corresponding analog with short chain length (9). These studies reveal that conjugation of fatty acids to d4T enhances the cellular uptake and anti-HIV activity of stavudine.     

Synthesis and cholinesterase inhibition of cativic acid derivatives

Alzheimer’s disease (AD) is a neurodegenerative disorder associated with memory impairment and cognitive deficit. Most of the drugs currently available for the treatment of AD are acetylcholinesterase (AChE) inhibitors. In a preliminary study, significant AChE inhibition was observed for the ethanolic extract of Grindelia ventanensis (IC₅₀ = 0.79 mg/mL). This result prompted us to isolate the active constituent, a normal labdane diterpenoid identified as 17-hydroxycativic acid (1), through a bioassay guided fractionation. Taking into account that 1 showed moderate inhibition of AChE (IC₅₀ = 21.1 μM), selectivity over butyrylcholinesterase (BChE) (IC₅₀ = 171.1 μM) and that it was easily obtained from the plant extract in a very good yield (0.15% w/w), we decided to prepare semisynthetic derivatives of this natural diterpenoid through simple structural modifications. A set of twenty new cativic acid derivatives (3–6) was prepared from 1 through transformations on the carboxylic group at C-15, introducing a C2–C6 linker and a tertiary amine group. They were tested for their inhibitory activity against AChE and BChE and some structure–activity relationships were outlined. The most active derivative was compound 3c, with an IC₅₀ value of 3.2 μM for AChE. Enzyme kinetic studies and docking modeling revealed that this inhibitor targeted both the catalytic active site and the peripheral anionic site of this enzyme. Furthermore, 3c showed significant inhibition of AChE activity in SH-SY5Y human neuroblastoma cells, and was non-cytotoxic.     

3′-Oxo-, amino-, thio- and sulfone-acetic acid modified thymidines: Effect of increased acidity on ribonuclease A inhibition

A family of 3′-functionalized thymidines carrying XCH₂COOH (X = O, NH, S, SO₂) groups has been designed as inhibitors of RNase A. This is because it is possible to manipulate the overall acidity of this new class of nucleic ‘acids’ by changing X from oxygen to the SO₂ group in the series. It is also expected that the acyclic nature of the XCH₂COOH group would provide enough flexibility to the –COOH group to have maximum interactions with the catalytic subsite P₁ of RNase A. As the –SO₂CH₂COOH substituted derivative showed better potency partially because of the increased acidity of the –COOH group, the inhibitory properties of both 5′-substituted and 3′,5′-disubstituted sulfone acetic acid modified thymidines were investigated. Two –SO₂CH₂COOH groups were incorporated with the expectation of targeting two phosphate binding sites simultaneously. Thus, 3′,5′-dideoxy-3′,5′-bis-S-[(carboxymethyl)sulfonyl]thymidine emerged as the best inhibitor in this series with a K_i value of 25 ± 2 μM.     

Benzochalcones bearing pyrazoline moieties show anti-colorectal cancer activities and selective inhibitory effects on aurora kinases

Colorectal cancer is the third and fourth leading cause of cancer in males and females, respectively. Flavonoids, including chalcones, are secondary metabolites in plants that exhibit diverse biological activities, including antibacterial, antimalarial, and antitumor activities. In order to find potent and novel chemotherapy drugs for colorectal cancer, a series of benzochalcone derivatives, in which an α,β-unsaturated carbonyl group was replaced with a pyrazoline, was designed and synthesized. A clonogenic survival assay was performed with each derivative to evaluate antitumor activity. 1-(5-(2,4-Dimethoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl)naphthalen-2-ol (derivative 7) had the most potent inhibitory effect on the long-term clonogenicity of HCT116 human colorectal cancer cells (IC₅₀ = 2.4 μM). The results of Western blot and flow cytometric analyses suggested that derivative 7 could inhibit the proliferation of colorectal cancer cells through inhibition of cell cycle progression and induction of apoptosis. To elucidate its molecular mechanism, in vitro kinase binding assays were carried out, which demonstrated that derivative 7 inhibited aurora kinases A and B selectively. The binding modes between the compound and aurora kinases were interpreted using in silico docking experiments to explain the selective inhibitory effects on aurora kinases A and B. These findings will facilitate the design of potent novel benzochalcones as anticancer agents.     

Growth Inhibition by Purine Derivatives and Its Reversal by Pyrimidine Derivatives in a Mutant of Escherichia coli K12

An adenosine-sensitive mutant was isolated from Escherichia coli K12 derivative strain C600. This mutant (designated as PS100) grew slower than parental strain C600in a minimal medium, and its growth was completely inhibited by addition of all kinds of purine bases, nucleosides and nucleotides tested. On the other hand, this growth inhibitory effect of purine derivatives was reversed by co-addition of uridine to the medium. Other pyrimidine derivatives such as uracil, UMP,cytosine, cytidine, CMP and thymidine were also effective for this reversal. The mutant strain, PS100, showed a lower level (7%) of activity for orotate phosphoribosyltransferase than strain C600 did, and accumulated orotic acid in the growth medium. Lysogenization of strain PS100 with λ transducing phage containing the gene for orotate phosphoribosyltransferase (pyrE) resulted in restoration of the activity for orotate phosphoribosyltransferase and removal of growth inhibition by purine derivatives.     

Oligoadenylates formation on an oligouridylate template in the presence of a lead catalyst

Summary Oligouridylates with more than eight chain units can serve as a template for the template-directed condensation of ImpA catalyzed by Pb²⁺ ion. The templates and the Pb²⁺ ion catalyst facilitate the formation of longer oligoadenylates with five or more units. The ratio of 3–5 linked oligomers to the 2–5 isomers increases with increasing chain length of the oligouridylate template. Short oligouridylates up to a hexamer tend to decrease the yield of oligoadenylates, and do not affect the selectivity of internucleotide linkage.Abbreviations EDTA ethylenediaminetetracetic acid - Tris tris(hydroxymethyl)aminomethane - A adenosine - ImpA adenosine 5-phosphorimidazolide - pA adenosine 5-phosphate - Ap adenosine 2(3)-phosphate - poly A polyadenylic acid - AppA P₁,P₂-diadenosine 5-diphosphate - pAp adenosine 2(3),5-diphosphate - ApA adenylyl adenosine - (pA)_n (n = 2,3,) oligomers of pA - ImpApA 5-phosphorimidazolide of ApA - U uridine - pU uridine 5-phosphate - Up uridine 2(3)-phosphate - poly U polyuridylic acid - pUp uridine 2(3),5-diphosphate - (pU)_n (n = 2,3,) oligomers of pU - (pU)_n – (pA)_m cooligomers composed of (pU)_n and (pA)_m units - AppUpUpUpUp pyrophosphate derived from pA and (pU)₄ - AppUp P₁-(adenosine 5)-P₂-(uridine 2(3)-phosphate 5) -pyrophosphate - BAP bacterial alkaline phosphatase - VPD venom phosphodiesterase - N.P₁ nuclease P₁ - RNase A pancreatic ribonuclease - A^* radioactive adenosine     

Discovery of a novel activator of 5-lipoxygenase from an anacardic acid derived compound collection

Lipoxygenases (LOXs) and cyclooxygenases (COXs) metabolize poly-unsaturated fatty acids into inflammatory signaling molecules. Modulation of the activity of these enzymes may provide new approaches for therapy of inflammatory diseases. In this study, we screened novel anacardic acid derivatives as modulators of human 5-LOX and COX-2 activity. Interestingly, a novel salicylate derivative 23a was identified as a surprisingly potent activator of human 5-LOX. This compound showed both non-competitive activation towards the human 5-LOX activator adenosine triphosphate (ATP) and non-essential mixed type activation against the substrate linoleic acid, while having no effect on the conversion of the substrate arachidonic acid. The kinetic analysis demonstrated a non-essential activation of the linoleic acid conversion with a K_A of 8.65 μM, αK_A of 0.38 μM and a β value of 1.76. It is also of interest that a comparable derivative 23d showed a mixed type inhibition for linoleic acid conversion. These observations indicate the presence of an allosteric binding site in human 5-LOX distinct from the ATP binding site. The activatory and inhibitory behavior of 23a and 23d on the conversion of linoleic compared to arachidonic acid are rationalized by docking studies, which suggest that the activator 23a stabilizes linoleic acid binding, whereas the larger inhibitor 23d blocks the enzyme active site.     

Inhibition of nucleic acid synthesis in leukemia 1210 cells by antimetabolites of coenzyme Q10

Thirteen diversified antimetabolites of coenzyme Q₁₀ which have antitumor activity $\text{in vivo}$ were tested for inhibition of uptake of tritiated thymidine and uridine into DNA and RNA, respectively, of L1210 cells grown in tissue culture. Eight of these antimetabolites have inhibitory activities of the same order of magnitude as the used anticancer drugs, rubidazone and ellipticine. 5-ω-Phenylpropylmercapto-2,3-dimethoxy-1,4-benzoquinone was particularly potent to inhibit nucleic acid synthesis; ED₅₀ for DNA = 2.1 μM and ED₅₀ for RNA = 4.0 μM.     

Design,Synthesis, and Biological Evaluation of Novel Indanone Derivatives as Cholinesterase Inhibitors for Potential Use in Alzheimer's Disease

Indanone derivatives containing meta/para-substituted aminopropoxy benzyl/benzylidene moieties were designed based on the structures of donepezil and ebselen analogs as the cholinesterase inhibitors. The designed compounds were synthesized and their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were measured. Inhibitory potencies (IC₅₀ values) for the synthesized compounds ranged from 0.12 to 11.92 μM and 0.04 to 24.36 μM against AChE and BChE, respectively. Compound 5 c showed the highest AChE inhibitory potency with IC₅₀ value of 0.12 μM, whereas the highest BChE inhibition was achieved by structure 7 b (IC₅₀=0.04 μM). Structure-activity relationship (SAR) analysis revealed that there is no significant difference between meta and para-substituted derivatives in AChE and BChE inhibition. However, the most potent AChE inhibitor 5 c belongs to meta-substituted compounds, while the most active BChE inhibitor is para-substituted derivative 7 b . The order of enzyme inhibition potency based on the substituted amine group is dimethyl amine>piperidine>morpholine. Compounds containing C=C linkage are more potent AChE inhibitors than the corresponding saturated structures. Molecular docking studies indicated that 5 c interacts with AChE in a very similar way to that observed experimentally for donepezil. The introduced indanone-aminopropoxy benzylidenes could be used in drug-discovery against Alzheimer's disease.     

Synthesis,anti-fungal and 1,3-β-d-glucan synthase inhibitory activities of caffeic and quinic acid derivatives

New derivatives of caffeic acid and quinic acid were synthesized and their anti-fungal and inhibitory activities on fungal 1,3-β-glucan synthase were determined in comparison with those of the corresponding chlorogenic acid derivatives. All the chlorogenic, quinic and caffeic acid derivatives that were coupled with an H₂N-orn-4-(octyloxy) aniline group (1, 1b and 1c) displayed potent activities in both anti-fungal and inhibition of 1,3-glucan synthase assays. Compounds 1 and 1c inhibited the fungal membrane enzyme with the potency comparable to that of a known 1,3-β-d-glucan synthase inhibitor, aculeacin A. The results revealed that the anti-fungal activity of the chlorogenic acid derivative with a free amino group was at least partly due to inhibition of the fungal 1,3-β-glucan synthase. These results suggest that further investigation on caffeic acid derivatives may lead to the discovery of novel anti-fungal agents with drug-like properties.     

Synthesis and properties of nucleoside derivatives acylated by chemically stable 2-(trimethylsilyl)benzoyl group

We report the synthesis and properties of nucleoside derivatives acylated by 2-(trimethylsilyl)benzoyl (TMSBz) that proved to be extremely stable under basic conditions when introduced into the 5′-hydroxyl group of thymidine, the 4-amino group of deoxycytidine and the 2′-hydroxyl group of uridine. In particular, 2′-O-TMSBz-uridine could be isolated and was more stable in pyridine, while it isomerized in CH₂Cl₂ in the presence of Et₃N to yield a mixture of the 2′-O- and 3′-O-acylated species.