Bioactivities and Mode of Actions of Dibutyl Phthalates and Nocardamine from Streptomyces sp. H11809.

Dibutyl phthalate (DBP) produced by Streptomyces sp. H11809 exerted inhibitory activity against human GSK-3ß (Hs GSK-3ß) and Plasmodiumfalciparum 3D7 (Pf 3D7) malaria parasites. The current study aimed to determine DBP's plausible mode of action against Hs GSK-3ß and Pf 3D7. Molecular docking analysis indicated that DBP has a higher binding affinity to the substrate-binding site (pocket 2; -6.9 kcal/mol) than the ATP-binding site (pocket 1; -6.1 kcal/mol) of Hs GSK-3ß. It was suggested that the esters of DBP play a pivotal role in the inhibition of Hs GSK-3ß through the formation of hydrogen bonds with Arg96/Glu97 amino acid residues in pocket 2. Subsequently, an in vitro Hs GSK-3ß enzymatic assay revealed that DBP inhibits the activity of Hs GSK-3ß via mixed inhibition inhibitory mechanisms, with a moderate IC50 of 2.0 µM. Furthermore, the decrease in Km value with an increasing DBP concentration suggested that DBP favors binding on free Hs GSK-3ß over its substrate-bound state. However, the antimalarial mode of action of DBP remains unknown since the generation of a Pf 3D7 DBP-resistant clone was not successful. Thus, the molecular target of DBP might be indispensable for Pf survival. We also identified nocardamine as another active compound from Streptomyces sp. H11809 chloroform extract. It showed potent antimalarial activity with an IC50 of 1.5 µM, which is ~10-fold more potent than DBP, but with no effect on Hs GSK-3ß. The addition of ≥12.5 µM ferric ions into the Pf culture reduced nocardamine antimalarial activity by 90% under in vitro settings. Hence, the iron-chelating ability of nocardamine was shown to starve the parasites from their iron source, eventually inhibiting their growth.

Synthesis, Characterization and Biological Evaluation of New 3,5-Disubstituted-Pyrazoline Derivatives as Potential Anti-Mycobacterium tuberculosis H37Ra Compounds.

A total of fourteen pyrazoline derivatives were synthesized through cyclo-condensation reactions by chalcone derivatives with different types of semicarbazide. These compounds were characterized by IR, 1D-NMR (1H, 13C and Distortionless Enhancement by Polarization Transfer - DEPT-135) and 2D-NMR (COSY, HSQC and HMBC) as well as mass spectroscopy analysis (HRMS). The synthesized compounds were tested for their antituberculosis activity against Mycobacterium tuberculosis H37Ra in vitro. Based on this activity, compound 4a showed the most potent inhibitory activity, with a minimum inhibitory concentration (MIC) value of 17 µM. In addition, six other synthesized compounds, 5a and 5c-5g, exhibited moderate activity, with MIC ranges between 60 µM to 140 µM. Compound 4a showed good bactericidal activity with a minimum bactericidal concentration (MBC) value of 34 µM against Mycobacterium tuberculosis H37Ra. Molecular docking studies for compound 4a on alpha-sterol demethylase was done to understand and explore ligand-receptor interactions, and to hypothesize potential refinements for the compound.

The Synthesis, Characterization, Cytotoxic Activity Assessment and Structure-Activity Relationship of 4-Aryl-6-(2,5-dichlorothiophen-3-yl)-2-methoxypyridine-3-carbonitriles.

A series of 2-methoxypyridine-3-carbonitrile (5a-i)-bearing aryl substituents were successfully synthesized in good yields by the condensation of chalcones (4a-i) with malononitrile in basic medium. The condensation process, in most cases, offers a route to a variety of methoxypyridine derivatives (6a-g) as side products in poor yields. All new compounds were fully characterized using different spectroscopic methods. Mass ESI-HMRS measurements were also performed. Furthermore, these compounds were screened for their in vitro cytotoxicity activities against three cancer cell lines; namely, those of the liver (line HepG2), prostate (line DU145) and breast (line MBA-MB-231). The cytotoxicity assessment revealed that compounds 5d, 5g, 5h and 5i exhibit promising antiproliferative effects (IC50 1-5 µM) against those three cancer cell lines.

Synthesis of Fluorescent 1-(3-Amino-4-(4-(tert-butyl)phenyl)-6-(p-tolyl)furo[2,3-b]pyridin-2-yl)ethan-1-one: Crystal Structure, Fluorescence Behavior, Antimicrobial and Antioxidant Studies.

Furopyridine III, namely 1-(3-amino-4-(4-(tert-butyl)phenyl)-6-(p-tolyl)furo[2,3-b]pyridin-2-yl)ethan-1-one, synthesized from 4-(4-(tert-butyl)phenyl)-2-oxo-6-(p-tolyl)-1,2-dihydropyridine-3-carbonitrile I in two steps. The title compound is characterized by NMR, MS and its X-ray structure. The molecular structure consists of planar furopyridine ring with both phenyl rings being inclined from the furopyridine scaffold to a significant different extent. There are three intramolecular hydrogen bonds within the structure. The lattice is stabilized by N-H…O, H2C-H …π and π…π intermolecular interactions leading to three-dimensional network. Compound III exhibits fluorescent properties, which are investigated. Antimicrobial potential and antioxidant activity screening studies for the title compound III and the heterocyclic derivatives, I and II, show no activity towards neither bacterial nor fungal strains, while they exhibited weak to moderate antioxidant activity compared to reference.

Antituberculosis activity, phytochemical identification of Costus speciosus (J. Koenig) Sm., Cymbopogon citratus (DC. Ex Nees) Stapf., and Tabernaemontana coronaria (L.) Willd. and their effects on the growth kinetics and cellular integrity of Mycobacterium tuberculosis H37Rv.

BACKGROUND: Costus speciosus, Cymbopogon citratus, and Tabernaemontana coronaria are herbal plants traditionally used as remedies for symptoms of tuberculosis (TB) including cough. The aims of the present study were to evaluate the in vitro anti-TB activity of different solvent partitions of these plants, to identify the phytochemical compounds, and to assess the effects of the most active partitions on the growth kinetics and cellular integrity of the tubercle organism. METHODS: The in vitro anti-TB activity of different solvent partitions of the plant materials was determined against M. tuberculosis H37Rv using a tetrazolium colorimetric microdilution assay. The phytochemical compounds in the most active partition of each plant were identified using gas chromatography-mass spectrometry (GC-MS) analysis. The effects of these partitions on the growth kinetics of the mycobacteria were evaluated over 7-day treatment period in a batch culture system. Their effects on the mycobacterial cellular integrity were observed under a scanning electron microscope (SEM). RESULTS: The respective n-hexane partition of C. speciosus, C. citratus, and T. coronaria exhibited the highest anti-TB activity with minimum inhibitory concentrations (MICs) of 100-200 µg/mL and minimum bactericidal concentration (MBC) of 200 µg/mL. GC-MS phytochemical analysis of these active partitions revealed that majority of the identified compounds belonged to lipophilic fatty acid groups. The active partitions of C. speciosus and T. coronaria exhibited high cidal activity in relation to time, killing more than 99% of the cell population. SEM observations showed that these active plant partitions caused multiple structural changes indicating massive cellular damages. CONCLUSIONS: The n-hexane partition of the plant materials exhibited promising in vitro anti-TB activity against M. tuberculosis H37Rv. Their anti-TB activity was supported by their destructive effects on the integrity of the mycobacterial cellular structure.

The Effects of 4-Hydroxybenzoic Acid Identified from Bamboo (Dendrocalamus asper) Shoots on Kv1.4 Channel.

BACKGROUND: Bamboo shoot has been used as a treatment for epilepsy in traditional Chinese medicine for generations to treat neuronal disorders such as convulsive, dizziness and headaches. 4-hydroxybenzoic acid (4-hba) is a non-flavonoid phenol found abundantly in Dendrocalamus asper shoots (bamboo), fruits (strawberries and apples) and flowers. Kv1.4 is a rapidly inactivating Shaker-related member of the voltage-gated potassium channels with two inactivation mechanisms; the fast N-type and slow C-type. It plays vital roles in repolarisation, hyperpolarisation and signaling the restoration of resting membrane potential through the regulation of the movement of K+ across the cellular membrane. METHODS: Chemical compounds from Dendrocalamus asper bamboo shoots were purified and identified as major palmitic acids mixed with other minor fatty acids, palmitic acid, 4-hydroxybenzaldehyde, lauric acid, 4-hydroxybenzoic acid and cholest-4-ene-3-one. The response of synthetic 4-hydroxybenzoic acid was tested on Kv1.4 potassium channel which was injected into viable oocytes that was extracted from Xenopus laevis. The current were detected by the two-microelectrode voltage clamp, holding potential starting from -80 mV with 20 mV step-up until +80 mV. Readings of treatments with 0.1% DMSO, 4-hba concentrations and K channel blockers were taken at +60 mV. The ratio of tail/peak amplitude is the index of the activity of the Kv1.4 channels with n ≥ 6 (number of oocytes tested). The decreases of the ratios of five different concentrations (1 µM, 10 µM, 100 µM, 1 mM and 2.5 mM) were compared with 0.1% DMSO as the control. RESULTS: All concentration showed statistically significant results with P < 0.05 except for 100 µM. The normalised current of the 4-hba concentrations were compared with potassium channel blockers (TEA and 4-AP) and all groups showed statistically significant results. This study also showed that time taken for each concentration to affect Kv1.4 does not play any significant roles. CONCLUSION: 4-hydroxybenzoic acid was found to be able to enhance the inactivation of Kv1.4 by lowering the membrane potential so that the abnormal neuronal firing can be inhibited. With IC50 slightly higher than 10 µM, increasing concentrations (100 µM, 1 mM and 2.5 mM) had shown to exhibit toxicity effects. The best concentration from this study is 10 µM with Hill slope of 0.1799.

One-pot microwave assisted stereoselective synthesis of novel dihydro-2'H-spiro[indene-2,1'-pyrrolo-[3,4-c]pyrrole]-tetraones and evaluation of their antimycobacterial activity and inhibition of AChE.

An efficient one-pot microwave assisted stereoselective synthesis of novel dihydro-2'H-spiro[indene-2,1'-pyrrolo[3,4-c]pyrrole]-tetraone derivatives through three-component 1,3-dipolar cycloaddition of azomethine ylides generated in situ from ninhydrin and sarcosine with a series of 1-aryl-1H-pyrrole-2,5-diones is described. The synthesised compounds were screened for their antimycobacterial and AChE inhibition activities. Compound 4b (IC50 1.30µM) has been found to display twelve fold antimycobacterial activity compared to cycloserine and it is thirty seven times more active than pyrimethamine. Compound 4h displays maximum AchE inhibitory activity with IC50 value of 0.78±0.01µmol/L.

Ethyl nitrobenzoate: A novel scaffold for cholinesterase inhibition.

A series of novel cholinesterase inhibitors containing nitrobenzoate core structure were synthesized by a facile and efficient method. The structure of the novel compounds were fully characterized and confirmed by analytical as well as spectroscopic methods. Compound indicated as 2f was found to possess the best cholinesterase inhibitory activities of all the evaluated compounds. Results suggest that 2f is a selective acetylcholinesterase inhibitor, although it also inhibits butyrylcholinesterase at higher concentration. Kinetics inhibition result suggest that 2f is a mixed-mode inhibitor of acetylcholinesterase. In addition, it was found to have low cytotoxicity. Molecular docking on compound 2f was carried out to rationalize the observed in vitro enzymatic assay results. Most importantly, the potential of nitrobenzoate derivatives as cholinesterase inhibitor was shown through this study. In summary, we discovered nitrobenzoates as a new scaffold that may eventually yield useful compounds in treatment of Alzheimer's disease.

The Effect of 4-hydroxybenzaldehyde on the γ-aminobutyric Acid Type A Receptor.

The α1ß2γ2 subtype of GABAA receptors is the most commonly found GABAA receptor subtype in the mammalian cortex and hippocampus. It is expressed heterologously in the Xenopus laevis oocyte as a α1ß2γ2S/L subtype for application as an in vitro model for the screening of compounds that modulate receptor activities. In fact, 4-hydroxybenzaldehyde (4-HB) has been identified as one of the major components in Dendrocalamus asper bamboo shoots in our previous study, and the current study showed that at 101.7 µM, 4-HB significantly reduced the GABA-induced chloride current of GABAA receptors expressed on Xenopus oocytes, indicating a possible GABAergic antagonistic effect at high concentrations.

A facile stereoselective synthesis of dispiro-indeno pyrrolidine/pyrrolothiazole-thiochroman hybrids and evaluation of their antimycobacterial, anticancer and AchE inhibitory activities.

A facile stereoselective synthesis of novel dispiro indeno pyrrolidine/pyrrolothiazole-thiochroman hybrids has been achieved by 1,3-dipolar cycloaddition of azomethine ylides, generated in situ from ninhydrin and sarcosine/thiaproline, on a series of 3-benzylidenethiochroman-4-ones. The synthesised compounds were screened for their antimycobacterial, anticancer and AchE inhibition activities. Compound 4l (IC50 1.07µM) has been found to exhibit the most potent antimycobacterial activity compared to cycloserine (12 times), pyrimethamine (37 times) and ethambutol (IC50 <1.56µM) and 6l (IC50=2.87µM) is more active than both cycloserine (4 times) and pyrimethamine (12 times). Three compounds, 4a, 6b and 6i, display good anticancer activity against CCRF-CEM cell lines. Compounds 6g and 4g display maximum AchE inhibitory activity with IC50 values of 1.10 and 1.16µmol/L respectively.

A Sustainable Approach to the Stereoselective Synthesis of Diazaheptacyclic Cage Systems Based on a Multicomponent Strategy in an Ionic Liquid.

The microwave-assisted three-component reactions of 3,5-bis(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones, acenaphthenequinone and cyclic α-amino acids in an ionic liquid, 1-butyl-3-methylimidazolium bromide, occurred through a domino sequence affording structurally intriguing diazaheptacyclic cage-like compounds in excellent yields.

Cholinesterase inhibitory triterpenoids from the bark of Garcinia hombroniana.

UNLABELLED: Context: Garcinia hombroniana Pierre, known as manggis hutan in Malaysia is a rich source of xanthones and benzophenones. OBJECTIVES: This study was aimed to isolate and characterize potential cholinesterase inhibitors from the extracts of G. hombroniana bark and investigate their interactions with the enzymes. MATERIALS AND METHODS: The dichloromethane extract afforded five triterpenoids which were characterized by NMR and mass spectral techniques. Cholinesterase inhibitory assay and molecular docking were performed to get insight of the inhibitory activity and molecular interactions of the compounds. The compounds were also tested for their antioxidant capacity. RESULTS: The isolated triterpenoids were identified as: 2ß-hydroxy-3α-O-caffeoyltaraxar-14-en-28-oic acid (1), taraxerol (2), taraxerone (3), betulin (4) and betulinic acid (5). Compound 1 was the most active dual inhibitor of both AChE and BChE. Compound 1 also showed good antioxidant activities. CONCLUSION: Compound 1 had dual and moderate inhibitory activity on AChE and BChE worthy for further investigations.

Synthesis and discovery of highly functionalized mono- and bis-spiro-pyrrolidines as potent cholinesterase enzyme inhibitors.

Novel mono and bis spiropyrrolidine derivatives were synthesized via an efficient ionic liquid mediated, 1,3-dipolar cycloaddition methodology and evaluated in vitro for their AChE and BChE inhibitory activities in search for potent cholinesterase enzyme inhibitors. Most of the synthesized compounds displayed remarkable AChE inhibitory activities with IC50 values ranging from 1.68 to 21.85 µM, wherein compounds 8d and 8j were found to be most active inhibitors against AChE and BChE with IC50 values of 1.68 and 2.75 µM, respectively. Molecular modeling simulation on Torpedo californica AChE and human BChE receptors, showed good correlation between IC50 values and binding interaction template of the most active inhibitors docked into the active site of their relevant enzymes.

Ionic liquid mediated synthesis of mono- and bis-spirooxindole-hexahydropyrrolidines as cholinesterase inhibitors and their molecular docking studies.

One pot, three-component reaction of 1-acryloyl-3,5-bisarylmethylidenepiperidin-4-ones with isatin and sarcosine in molar ratios of 1:1:1 and 1:2:2 furnished to mono- and bis-spiropyrrolidine heterocyclic hybrids comprising functionalized piperidine, pyrrolidine and oxindole structural motifs. Both mono and bis-spiropyrrolidines displayed good inhibitory activity against acetylcholinesterase (AChE) with IC50 values of 2.36-9.43 µM. For butyrylcholinesterase (BChE), mono-cycloadducts in series 8 with IC50 values of lower than 10 µM displayed better inhibitory activities than their bis-cycloadduct analogs in series 9 with IC50 values of 7.44-19.12 µM. The cycloadducts 9j and 8e were found to be the most potent AChE and BChE inhibitors with IC50 values of 2.35 and 3.21 µM, respectively. Compound 9j was found to be competitive inhibitor of AChE while compound 8e was a mixed-mode inhibitor of BChE with calculated Ki values of 2.01 and 6.76 µM, respectively. Molecular docking on Torpedo californica AChE and human BChE showed good correlation between IC50 values and free binding energy values of the synthesized compounds docked into the active site of the enzymes.

Cholinesterase inhibitory activity versus aromatic core multiplicity: a facile green synthesis and molecular docking study of novel piperidone embedded thiazolopyrimidines.

Novel thiazolopyrimidine derivatives have been synthesized via microwave assisted, domino cascade methodology in ionic liquid and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Among the newly synthesized compounds 6d, 6a, 6e and 6b displayed higher AChE inhibitory activity than standard drug, galanthamine, with IC50 values of 0.53, 1.47, 1.62 and 2.05µM, respectively. Interestingly, all the compounds except for 6m-r and 6x displayed higher BChE inhibitory potentials than galanthamine with IC50 values ranging from 1.09 to 18.56µM. Molecular docking simulations for 6d possessing the most potent AChE and BChE inhibitory activities, disclosed its binding interactions at the active site gorge of AChE and BChE enzymes.

Synthesis and evaluation of novel benzimidazole derivatives as sirtuin inhibitors with antitumor activities.

A total of 15 novel benzimidazole derivatives were designed, synthesized and evaluated for their SIRT1 and SIRT2 inhibitory activity. All compounds showed better inhibition on SIRT2 as compared to SIRT1. Among these, compound 5j displayed the best inhibitory activity for SIRT1 (IC50=58.43µM) as well as for SIRT2 (IC50=45.12µM). Cell cytotoxicity assays also showed that compound 5j possesses good antitumor activity against two different cancer cell lines derived from breast cancer (MCF-7 and MDA-MB-468). A simple structure-activity-relationship (SAR) study of the newly synthesized benzimidazole derivatives was also discussed.

Ionic liquid mediated synthesis and molecular docking study of novel aromatic embedded Schiff bases as potent cholinesterase inhibitors.

Novel aromatic embedded Schiff bases have been synthesized in ionic liquid [bmim]Br and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes inhibitory activities. Among the newly synthesized compounds, 5f, 5h and 7j displayed higher AChE enzyme inhibitory activities than standard drug, galanthamine, with IC50 values of 1.88, 2.05 and 2.03µM, respectively. Interestingly, all the compounds except for compound 5c displayed higher BChE inhibitories than standard with IC50 values ranging from 3.49 to 19.86µM. Molecular docking analysis for 5f and 7j possessing the most potent AChE and BChE inhibitory activities, disclosed their binding interaction templates to the active site of AChE and BChE enzymes, respectively.

Cytotoxic benzophenone and triterpene from Garcinia hombroniana.

Garcinia hombroniana (seashore mangosteen) in Malaysia is used to treat itching and as a protective medicine after child birth. This study was aimed to investigate the bioactive chemical constituents of the bark of G. hombroniana. Ethyl acetate and dichloromethane extracts of G. hombroniana yielded two new (1, 9) and thirteen known compounds which were characterized by the spectral techniques of NMR, UV, IR and EI/ESI-MS, and identified as; 2,3',4,5'-tetrahydroxy-6-methoxybenzophenone(1), 2,3',4,4'-tetrahydroxy-6-methoxybenzophenone (2), 2,3',4,6-tetrahydroxybenzophenone (3), 1,3,6,7-tetrahydroxyxanthone (4), 3,3',4',5,7-pentahydroxyflavone (5),3,3',5,5',7-pentahydroxyflavanone (6), 3,3',4',5,5',7-hexahydroxyflavone (7), 4',5,7-trihydroxyflavanone-7-rutinoside (8), 18(13→17)-abeo-3ß-acetoxy-9α,13ß-lanost-24E-en-26-oic acid (9), garcihombronane B (10), garcihombronane D (11), friedelan-3-one (12), lupeol (13), stigmasterol (14) and stigmasterol glucoside (15). In the in vitro cytotoxicity against MCF-7, DBTRG, U2OS and PC-3 cell lines, compounds 1 and 9 displayed good cytotoxic effects against DBTRG cancer cell lines. Compounds 1-8 were also found to possess significant antioxidant activities. Owing to these properties, this study can be further extended to explore more significant bioactive components of this plant.

Facile, regio- and diastereoselective synthesis of spiro-pyrrolidine and pyrrolizine derivatives and evaluation of their antiproliferative activities.

A number of novel spiro-pyrrolidines/pyrrolizines derivatives were synthesized through [3+2]-cycloaddition of azomethine ylides with 3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones 2a-n. Azomethine ylides were generated in situ from the reaction of 1H-indole-2,3-dione (isatin, 3) with N-methylglycine (sarcosine), phenylglycine, or proline. All compounds (50 µM) were evaluated for their antiproliferative activity against human breast carcinoma (MDA-MB-231), leukemia lymphoblastic (CCRF-CEM), and ovarian carcinoma (SK-OV-3) cells. N-α-Phenyl substituted spiro-pyrrolidine derivatives (5a-n) showed higher antiproliferative activity in MDA-MB-231 than other cancer cell lines. Among spiro-pyrrolizines 6a-n, a number of derivatives including 6a-c and 6i-m showed a comparable activity with doxorubicin in all three cell lines. Among all compounds in three classes, 6a, 6b, and 6m, were found to be the most potent derivatives showing 64%, 87%, and 74% antiproliferative activity in MDA-MB-231, SK-OV-3, and CCRF-CEM cells, respectively. Compound 6b showed an IC50 value of 3.6 mM in CCRF-CEM cells. These data suggest the potential antiproliferative activity of spiro-pyrrolidines/pyrrolizines.

Evaluation of the Cytotoxicity of Levodopa and its Complex with Hydroxypropyl-ß-Cyclodextrin (HP-ß-CD) to an Astrocyte Cell Line.

A simple, reliable a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium, (MTS) assay was conducted to evaluate the potential cytotoxic effects of levodopa, a "gold standard therapy" for Parkinsonism, and its complex with Hydroxypropyl-ß-Cyclodextrin (HP-ß-CD) on an astrocyte cell line. The cells were incubated in a range of concentrations from 4.69 to 300 µg/mL levodopa, HP-ß-CD or the complex for up to 72 hours. At every 24-hour interval, the optical density (OD), which reflects the number of viable cells, was recorded. In general, linear dose-dependent cytotoxicity profiles were observed for the cells subjected to levodopa or the complex, whereas a slightly triphasic response was observed for the cells exposed to HP-ß-CD. A significant difference (P < 0.05) in cytotoxicity was detected between the HP-ß-CD-treated group and the levodopa-treated group. In particular, we observed that the cells treated with the complex, even at the highest concentrations (> 200 µg/mL), exhibited improved tolerability in a time-dependent manner, which may indicate the potential ability of HP-ß-CD to mask the toxic effects of levodopa via complexation.