Synthesis of glucoconjugates of oleanolic acid as inhibitors of glycogen phosphorylase

Synthesis and biological evaluation of glucoconjugates of oleanolic acid, linked by either a triazole moiety or an ester function, as novel inhibitors of glycogen phosphorylase have been described. Several triterpene-glycoside conjugates exhibited moderate-to-good inhibitory activity against rabbit muscle GPa. Compound 12 showed the best inhibition with an IC₅₀ value of 1.14 μM. Structure-activity relationship (SAR) analysis of these inhibitors is also discussed. Possible binding modes of compound 12 were explored by molecular docking simulations.     

Potent ACE inhibitors from 5-hydroxy indanone derivatives

A novel triazole derivatives(±)-2-(hydroxymethyl)-7,8-dihydro-1H-indeno[5,4-b]furan-6(2H)-one (12a–j) were designed and synthesized by the reaction between racemic azide and terminal acetylenes under click chemistry reaction conditions followed by biological evaluation as angiotensin converting enzyme (ACE) inhibitors. β-Amino alcohol derivatives of 1-indanone (15a–l) were synthesized from 5-hydroxy indanone, it was reacted with epichlorohydrin and followed by oxirane ring opening with various piperazine derivatives. Among the newly synthesized compounds 12b (IC₅₀: 1.388024 µM), 12g (IC₅₀: 1.220696 µM), 12j (IC₅₀: 1.312428 µM) and 15k (IC₅₀: 1.349671 µM) and 15l (IC₅₀: 1.330764 µM) emerged as most active non-carboxylic acid ACE inhibitors with minimal toxicity comparable to clinical drug Lisinopril.     

Synthesis and preliminary evaluation of new ursolic and oleanolic acids derivatives as antileishmanial agents

A series of new ursolic and oleanolic acids derivatives was synthesized via ursolic or oleanolic acids, previously extracted from South American Ilex species. These new compounds were tested for in vitro antiparasitic activity on Leishmania amazonensis and Leishmania infantum strains. Some of these compounds showed activity against the promastigote forms of L. amazonensis or L. infantum, with IC₅₀ ranging from 5 to 12 μM. As expected, most of the compounds showed a significant level of cytotoxicity against monocytes (IC₅₀ = 2-50 μM). From a structure-activity relationships point of view, these pharmacological results enlightened mainly the importance of an acetylation at position 3 of the oleanolic acid skeleton in the activity against the L. amazonensis strain, and of a bis-(3-aminopropyl)piperazine moiety on the carboxylic function of ursolic acid against the L. infantum strain.     

Leishmanicidal Triterpenes from Lantana camara

Two new natural triterpenes, lantaninilic acid and lantoic acid, along with the known triterpenes lantadene A, and oleanolic, ursolic, betulinic, lantanolic, and camaric acid, were obtained from the aerial parts of Lantana camara through bioassay‐guided isolation, monitoring the in vitro antileishmanial activity against promastigotes of Leishmania major. Oleanolic acid ( 3 ), ursolic acid ( 4 ), lantadene A ( 5 ), and lantanilic acid ( 7 ) showed significant leishmanicidal activities with IC₅₀ values of 53.0, 12.4, 20.4, and 21.3 μM , respectively. The IC₅₀ value of ursolic acid ( 4 ; 12.4 μM ) was found to be comparable with that of the standard drugs, pentamidine (IC₅₀ 15.0 μM ) and amphotericin B (IC₅₀ 0.31 μM ). The in vitro activities of L. camara and its constituents against promastigotes of Leishmania major are reported here for the first time.     

Click chemistry based multicomponent approach in the synthesis of spirochromenocarbazole tethered 1,2,3-triazoles as potential anticancer agents

A series of spirochromenocarbazole tethered 1,2,3-triazoles were synthesized via click chemistry based one-pot, five component reaction between N-propargyl isatins, malononitrile, 4-hydroxycarbazole, aralkyl halides and sodium azide using cellulose supported CuI nanoparticles (Cell-CuI NPs) as the heterogeneous catalyst. Antiproliferative activity of all the synthesized compounds was investigated against panel of cancer cell lines such as MCF-7, MDA-MB-231, HeLa, PANC-1, A-549, and THP-1. Many of the synthesized compounds exhibited good anti-proliferative activity against breast (MCF-7 and MDA-MB-231) and cervical (HeLa) cancer cells with IC₅₀ values less than 10 μM. In case of MCF-7 cells, among the nine compounds that showed good anti-proliferative activity, compounds 6f and 6j were found to be highly potent (IC₅₀ = 2.13 μM and 4.80 μM, respectively). In case of MDA-MB-231, three compounds (6k, 6j and 6s) showed antiproliferative activity amongst which 6k was the most potent one (IC₅₀ = 3.78 μM). On the other hand, in cervical cancer HeLa cells, compounds 6b, 6g, 6s and 6u showed excellent antiproliferative activity (IC₅₀ = 4.05, 3.54, 3.83, 3.35 μM, respectively). All the compounds were found to be nontoxic to the human umbilical vein endothelial cells (HUVECs). AO and EtBr staining and fluorescence microscopy studies of the active compounds (IC₅₀ < 5 μM) suggested that these compounds induce cell death by apoptosis.     

Terpenoids. III: Synthesis and biological evaluation of 23-hydroxybetulinic acid derivatives as novel inhibitors of glycogen phosphorylase

A series of 23-hydroxybetulinic acid derivatives were prepared and tested in vitro as a new class of inhibitors of glycogen phosphorylase (GP). Within this series of compounds, 12b (IC₅₀ = 3.5 μM) is the most potent GPa inhibitor. The preliminary SAR results of the 23-hydroxybetulinic acid derivatives are discussed.     

Synthesis and DNase I inhibitory properties of some 4-thiazolidinone derivatives

Twelve new thiazolidinones were synthesized and, together with 41 previously synthesized thiazolidinones, evaluated for inhibitory activity against deoxyribonuclease I (DNase I) in vitro. Ten compounds inhibited commercial bovine pancreatic DNase I with an IC₅₀ below 200 μM and showed to be more potent DNase I inhibitors than crystal violet (IC₅₀ = 365.90 ± 47.33 μM), used as a positive control. Moreover, three compounds were active against DNase I in rat liver homogenate, having an IC₅₀ below 200 μM. (3-Methyl-1,4-dioxothiazolidin-2-ylidene)-N-(2-phenylethyl)ethanamide ( 41 ) exhibited the most potent DNase I inhibition against both commercial and rat liver DNase I with IC₅₀ values of 115.96 ± 11.70 and 151.36 ± 15.85 μM, respectively. Site Finder and molecular docking defined the thiazolidinones interactions with the most important catalytic residues of DNase I, including the H-acceptor interaction with residues His 134 and His 252 and/or H-donor interaction with residues Glu 39 and Asp 168. The three most active compounds against both commercial and rat liver DNase I ( 31 , 38 , and 41 ) exhibited favorable physico-chemical, pharmacokinetic, and toxicological properties. These observations could be utilized to guide the rational design and optimization of novel thiazolidinone inhibitors. Thiazolidinones as novel DNase I inhibitors could have potential therapeutic applications due to the significant involvement of DNase I in the pathophysiology of many disease conditions.     

Synthesis and biological evaluation of 3-(azolylmethyl)-1H-indoles and 3-(α-azolylbenzyl)-1H-indoles as selective aromatase inhibitors

This present study identifies a number of azolyl-substituted indoles as potent inhibitors of aromatase. In the sub-series of 3-(azolylmethyl)-1H-indoles, four imidazole derivatives and their triazole analogues were tested. Imidazole derivatives 11 and 14 in which the benzyl moiety was substituted by 2-chloro and 4-cyano groups, respectively, were the most active, with IC₅₀ values ranging between 0.054 and 0.050 μM. In the other sub-series, eight 3-(α-azolylbenzyl)-1H-indoles were prepared and tested. Compound 30, the N-ethyl imidazole derivative, proved to be an aromatase inhibitor, showing an IC₅₀ value of 0.052 μM. All target compounds were further evaluated against 17α-hydroxylase/C17,20-lyase to determine their selectivity profile.     

Synthesis and Biological Evaluation of Substituted Pyrazole-Fused Oleanolic Acid Derivatives as Novel Selective α-Glucosidase Inhibitors

A series of novel substituted pyrazole-fused oleanolic acid derivative were synthesized and evaluated as selective α-glucosidase inhibitors. Among these analogs, compounds 4a – 4f exhibited more potent inhibitory activities compared with their methyl ester derivatives, and standard drugs acarbose and miglitol as well. Besides, all these analogs exhibited good selectivity towards α-glucosidase over α-amylase. Analog 4d showed potent inhibitory activity against α-glucosidase (IC₅₀=2.64±0.13 μM), and greater selectivity towards α-glucosidase than α-amylase by ∼33-fold. Inhibition kinetics showed that compound 4d was a non-competitive α-glucosidase inhibitor, which was consistent with the result of its simulation molecular docking. Moreover, the in vitro cytotoxicity of compounds 4a – 4f towards hepatic LO2 and HepG2 cells was tested.     

Substrate Specificity of [3H] Muscimol Binding to a Particulate Fraction of a Neuron-enriched Culture of Embryonic Rat Brain

Abstract: The effects of some GABA analogues and some drugs on the binding of [³H]muscimol (3.08 nM) to thoroughly washed subcellular particles prepared from a neuron-enriched culture of embryonic rat brain were examined using Na+-free Tris-citrate medium and a centrifugation method. Competition for [³H]muscimol binding sites by excess(10^?5 M) unlabelled GABA provided estimates of “specific” binding. In accord with in vivo neuropharmacological studies on GABA receptors and with in vitro studies on cerebral membrane preparations, [³H]muscimol binding was potently inhibited by muscimol itself (IC₅₀, 2.5 nM), GABA (1C₅₀, 43 nM), isoguvacine (IC₅₀, 61 nM), and 3-aminopropanesulphonic acid (IC₅₀, 160 nM), and less potently inhibited by the GABA antagonist bicuculline methobromide (IC₅₀, 800 nM). δ- Aminovaleric acid (IC₅₀, 2.6 μM), the glycinelp-alanine antagonist strychnine (IC₅₀, 6.6 μM), and the predominantly glial GABA uptake inhibitors β-alanine (IC₅₀, 23 μM) and p-proline (IC₅₀, 66 μM) also inhibited [³H]muscimol binding. Other inhibitors of Na+-dependent GABA uptake, (±)-nipecotic acid, L- 2,4-diaminobutyric acid, and guvacine, as well as picrotoxinin, were relatively inactive as inhibitors of [³H]muscimol binding (IC₅₀≥ 1 mM). In addition to revealing that GABA receptors are present on neuronal membranes before the formation of most synapses, this binding of [³H]muscimol that occurs to neuronal, but not to glial, membranes might be useful as a “neuronal marker” and for the further characterization and isolation of GABA receptors.     

Design,synthesis and biological evaluation of novel inhibitors against cyanobacterial pyruvate dehydrogenase multienzyme complex E1

Cyanobacterial pyruvate dehydrogenase multienzyme complex E1 (PDHc E1) is a potential target enzyme for finding inhibitors to control harmful cyanobacterial blooms. In this study, a series of novel triazole thiamin diphosphate (ThDP) analogs were designed and synthesized by modifying the substituent group of triazole ring and optimizing triazole-benzene linker as potential cyanobacterial PDHc E1 (Cy-PDHc E1) inhibitors. Their inhibitory activities against Cy-PDHc E1 in vitro and algicide activities in vivo were further examined. Most of these compounds exhibited prominent inhibitory activities against Cy-PDHc E1 (IC₅₀ 1.48–4.48 μM) and good algicide activities against Synechocystis PCC6803 (EC₅₀ 0.84–2.44 µM) and Microcystis aeruginosa FACHB905 (EC₅₀ 0.74–1.77 µM). Especially, compound 8d showed not only the highest inhibitory activity against Cy-PDHc E1 (IC₅₀ 1.48 μM), but also the most powerful inhibitory selectivity between Cy-PDHc E1 (inhibitory rate 98.90%) and porcine PDHc E1 (inhibitory rate only 9.54%). Furthermore, the potential interaction between compound 8d and Cy-PDHc E1 was analyzed by a molecular docking method and site-directed mutagenesis and enzymatic analysis and fluorescence spectral analysis. These results indicated that compound 8d could be used as a hit compound for further optimization and might have potential to be developed as a new algicide.     

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.     

A new ferulic acid ester, a new ellagic acid derivative, and other constituents from pachycentria formosana: effects on neutrophil pro-inflammatory responses

A new ferulic acid ester derivative, tetracosane‐1,24‐diyl di[(Z)‐ferulate] ( 1 ), and a new ellagic acid derivative, 3,4 : 3′,4′‐bis(O,O‐methylene)ellagic acid ( 2 ), have been isolated from leaves and twigs of Pachycentria formosana, together with eight known compounds. Their structures were determined by in‐depth spectroscopic and mass‐spectrometric analyses. Among the isolated compounds, oleanolic acid ( 6 ), ursolic acid acetate ( 7 ), and 3‐epibetulinic acid ( 9 ) exhibited potent inhibition (IC₅₀ values ≤21.8 μM ) of O₂^⋅− generation by human neutrophils in response to N‐formyl‐L ‐methionyl‐L ‐leucyl‐L ‐phenylalanine/cytochalasin B (fMLP/CB). In addition, oleanolic acid ( 6 ), 3‐O‐[(E)‐feruloyl]ursolic acid ( 8 ), 3‐epibetulinic acid ( 9 ), and lawsonic acid ( 10 ) also inhibited fMLP/CB‐induced elastase release with IC₅₀ values ≤18.6 μM .     

Identification of 1,2,4-triazoles as new thymidine phosphorylase inhibitors: Future anti-tumor drugs

Thymidine phosphorylase (TP) is over expressed in several solid tumors and its inhibition can offer unique target suitable for drug discovery in cancer. A series of 1,2,4-triazoles 3a–3l has been synthesized in good yields and subsequently inhibitory potential of synthesized triazoles 3a–3l against thymidine phosphorylase enzyme was evaluated. Out of these twelve analogs five analogues 3b, 3c, 3f, 3l and 3l exhibited a good inhibitory potential against thymidine phosphorylase. Inhibitory potential in term of IC₅₀ values were found in the range of 61.98 ± 0.43 to 273.43 ± 0.96 μM and 7-Deazaxanthine was taken as a standard inhibitor with IC₅₀ = 38.68 ± 4.42 μM. Encouraged by these results, more analogues 1,2,4-triazole-3-mercaptocarboxylic acids 4a–4g were synthesized and their inhibitory potential against thymidine phosphorylase was evaluated. In this series, six analogues 4b–4g exhibited a good inhibitory potential in the range of 43.86 ± 1.11–163.43 ± 2.03 μM. Angiogenic response of 1,2,4-triazole acid 4d was estimated using the chick chorionic allantoic membrane (CAM) assay. In the light of these findings, structure activity relationship and molecular docking studies of selected triazoles to determine the key binding interactions was discussed. Docking studies demonstrate that synthesized analogues interacted with active site residues of thymidine phosphorylase enzyme through π-π stacking, thiolate and hydrogen bonding interactions.     

Triterpenoids as Novel Natural Inhibitors of Human Cathepsin L

Cathepsins L (catL) and B play an important role in tumor progression and have been considered promising therapeutic targets in the development of novel anticancer agents. Using a bioactivity‐guided fractionation, a series of triterpenoids was identified as a new class of competitive inhibitors towards cathepsin L with affinity values in micromolar range. Among the 14 compounds evaluated, the most promising were 3‐epiursolic acid ( 3 ), 3‐(hydroxyimino)oleanolic acid ( 9 ), and 3‐(hydroxyimino)masticadienoic acid ( 13 ) with IC₅₀ values of 6.5, 2.4, and 2.6 μM on catL, respectively. Most of the evaluated triterpenoids do not inhibit cathepsin B. Thus, the evaluated compounds exhibit a great potential to help in the design of new inhibitors with enhanced potency and affinity towards catL. Docking studies were performed in order to gain insight on the binding mode and SAR of these compounds.     

1,3,4-oxadiazole/chalcone hybrids: Design,synthesis, and inhibition of leukemia cell growth and EGFR,Src, IL-6 and STAT3 activities

A new series of 1,3,4-oxadiazole/chalcone hybrids was designed, synthesized, identified with different spectroscopic techniques and biologically evaluated as inhibitors of EGFR, Src, and IL-6. The synthesized compounds showed promising anticancer activity, particularly against leukemia, with 8v being the most potent. The synthesized compounds exhibited strong to moderate cytotoxic activities against K-562, KG-1a, and Jurkat leukemia cell lines in MTT assays. Compound 8v showed the strongest cytotoxic activity with IC₅₀ of 1.95 µM, 2.36 µM and 3.45 µM against K-562, Jurkat and KG-1a leukemia cell lines, respectively. Moreover; the synthesized compounds inhibited EGFR, Src, and IL-6. Compound 8v was most effective at inhibiting EGFR (IC₅₀ = 0.24 μM), Src (IC₅₀ = 0.96 μM), and IL-6 (% of control = 20%). Additionally, most of the compounds decreased STAT3 activation.     

New Halogenated Flavonoids from Adenosma bracteosum and Vitex negundo and Their α-Glucosidase Inhibition

Adenosma bracteosum and Vitex negundo are natural sources of methoxylated flavonoids. Little is known about the α-glucosidase inhibition of multi-methoxylated flavonoid derivatives. Eighteen natural flavonoids were isolated from A. bracteosum and V. negundo. Seven halogenated derivatives were synthesized. Their chemical structures were elucidated by extensive NMR analysis and high-resolution mass spectroscopy as well as comparisons in literature. All compounds were evaluated for their α-glucosidase inhibition. Most compounds showed good activity with IC₅₀ values ranging from 16.7 to 421.8 μM. 6,8-Dibromocatechin was the most active compound with an IC₅₀ value of 16.7 μM. A molecular docking study was conducted, indicating that those compounds are potent α-glucosidase inhibitors.     

Design,Synthesis and Cytotoxicity of New Coumarin-1,2,3-triazole Derivatives: Evaluation of Anticancer Activity and Molecular Docking Studies

A library of new coumarin-1,2,3-triazole hybrids 7a – l were synthesized from 4-(diethylamino)-2-hydroxybenzaldehyde precursor through a series of reactions including Vilsmeier-Haack reaction and condensation reaction to achieve key intermediate oxime and further performed click reaction by using different aromatic azides. We screened all molecules in silico against crystal structure of Serine/threonine-protein kinase 24 (MST3), based on these results all molecules were screened for their cytotoxicity against human breast cancer MCF-7 and lung cancer A-549 cell lines. Compound 7 b (p-bromo) showed best activity against both cell lines MCF-7 and A-549 with IC₅₀ value of 29.32 and 21.03 μM, respectively, in comparison to Doxorubicin corresponding IC₅₀ value of 28.76 and 20.82 μM. Another compound 7 f (o-methoxy) also indicated good activity against both cell lines with IC₅₀ value of 29.26 and 22.41 μM. The toxicity of all compounds tested against normal HEK-293 cell lines have not shown any adverse effects.     

Analogs of arachidonic acid methylated at C-7 and C-10 inhibit leukotriene biosynthesis and phospholipase A2 activity

The ability of (all Z)-7,7-dimethyl-5,8,11,14-eico-satetraenoic acid, (all Z)-7,7-dimethyl-5,8,11-eicosatrienoic acid, (Z,Z)-7,7-dimethyl-5,8-eicosadienoic acid, (all Z)-10,10-dimethyl-5,8,11,14-eicosatetraenoic acid, (all Z)-10,10-dimethyl-5,8,11-eicosatrienoic acid, and rac-(Z,Z)-15-hydroxy-7,7-dimethyl-5,8-eicosadienoic acid to inhibit ionophore-induced slow-reacting substance of anaphylaxis (SRS-A) biosynthesis in rat peritoneal cells was studied. It was thought that compounds such as these might inhibit proton abstractions at the 7 or 10 carbon positions on arachidonic acid which are thought to be important in the mechanism of catalysis of Δ⁵-lipoxygenase(Δ⁵-LO). All compounds were found to be potent inhibitors of SRS-A biosynthesis in the in vitro rat peritoneal cell system (IC₅₀ < 10 μM). In fact they were more potent inhibitors in the test system than standard Δ⁵-LO inhibitors such as NDGA and quercetin. To determine if the mechanism of inhibition of the dimethyl arachidonic acid analogs did involve gD⁵-LO inhibition these compounds were evaluated in an assay system utilizing the Δ⁵-LO from rat basophilic leukemia (RBL^?1_cells. It was found, however, that these compounds were much less potent inhibitors of this enzyme (IC₅₀ ～ 100 μM) than standard compounds such as NDGA (IC₅₀ 0.14 μM) and quercetin (IC₅₀, 0.2 μM). The arachidonic acid analogs were subsequently found to be potent inhibitors of phospholipase A₂ (PLA₂) enzymes with IC₅₀'s between 10–20 μM as inhibitors of a snake venom enzyme. In fact these compounds are among the most potent inhibitors of PLA₂ yet studied, having potencies better than standards such as p-bromophenacyl bromide (IC₅₀, 87 μM) and U-10029A (IC₅₀, 36 μM). These results suggest that the methylated arachidonic acid analogs may inhibit SRS-A biosynthesis through inhibiting PLA₂.