Selective inhibition of monoamine oxidase A by purpurin,an anthraquinone

Monoamine oxidase (MAO) catalyzes the oxidation of monoamines that act as neurotransmitters. During a target-based screening of natural products using two isoforms of recombinant human MAO-A and MAO-B, purpurin (an anthraquinone derivative) was found to potently and selectively inhibit MAO-A, with an IC₅₀ value of 2.50 μM, and not to inhibit MAO-B. Alizarin (also an anthraquinone) inhibited MAO-A less potently with an IC₅₀ value of 30.1 μM. Furthermore, purpurin was a reversible and competitive inhibitor of MAO-A with a K_i value of 0.422 μM. A comparison of their chemical structures suggested the 4-hydroxy group of purpurin might play an important role in its inhibition of MAO-A. Molecular docking simulation showed that the binding affinity of purpurin for MAO-A (?40.0 kcal/mol) was higher than its affinity for MAO-B (?33.9 kcal/mol), and that Ile 207 and Gly 443 of MAO-A were key residues for hydrogen bonding with purpurin. The findings of this study suggest purpurin is a potent, selective, reversible inhibitor of MAO-A, and that it be considered a new potential lead compound for development of novel reversible inhibitors of MAO-A (RIMAs).     

Cytotoxic activity,apoptosis induction and structure–activity relationship of 8-OR-2-aryl-3,4-dihydroisoquinolin-2-ium salts as promising anticancer agents

As our continuing research, a series of 2-aryl-8-OR-3,4-dihydroisoquinolin-2-ium bromides were evaluated for cytotoxic activity on cancer cells and apoptosis induction in the present study. SAR was derived also. Among them, 23 compounds showed the higher cytotoxicity on MKN-45 cells with IC₅₀ values of 1.99–11.3 μM than a standard anticancer drug cis-platinum (IC₅₀ = 11.4 μM) or their natural model compound chelerythrine (IC₅₀ = 12.7 μM); 16 compounds possessed the medium to high activity on NB4 cells with IC₅₀ values of 1.67–4.62 μM. SAR analysis showed that both substitution patterns of the N-aromatic ring and the type of 8-OR significantly impact the activity. AO/EB staining and flow cytometry analysis with Annexin V/PI double staining showed that the compounds were able to induce apoptosis in a concentration-dependent manner. The results above suggested that the title compounds are a class of promising compounds for the development of new anti-cancer drugs.     

Synthesis of novel hybrids of pyrazole and coumarin as dual inhibitors of COX-2 and 5-LOX

In our previous study, we designed a series of pyrazole derivatives as novel COX-2 inhibitors. In order to obtain novel dual inhibitors of COX-2 and 5-LOX, herein we designed and synthesized 20 compounds by hybridizing pyrazole with substituted coumarin who was reported to exhibit 5-LOX inhibition to select potent compounds using adequate biological trials sequentially including selective inhibition of COX-2 and 5-LOX, anti-proliferation in vitro, cells apoptosis and cell cycle. Among them, the most potent compound 11g (IC₅₀ = 0.23 ± 0.16 μM for COX-2, IC₅₀ = 0.87 ± 0.07 μM for 5-LOX, IC₅₀ = 4.48 ± 0.57 μM against A549) showed preliminary superiority compared with the positive controls Celecoxib (IC₅₀ = 0.41 ± 0.28 μM for COX-2, IC₅₀ = 7.68 ± 0.55 μM against A549) and Zileuton (IC₅₀ = 1.35 ± 0.24 μM for 5-LOX). Further investigation confirmed that 11g could induce human non-small cell lung cancer A549 cells apoptosis and arrest the cell cycle at G2 phase in a dose-dependent manner. Our study might contribute to COX-2, 5-LOX dual inhibitors thus exploit promising novel cancer prevention agents.     

Synthesis and antiviral evaluation of novel 1,3,4-oxadiazole/thiadiazole-chalcone conjugates

A series of novel 1,3,4-oxadiazole/thiadiazole–chalcone conjugates were synthesized and their in vitro and in vivo antiviral activities were evaluated via microscale thermophoresis method and half-leaf method, respectively. The in vitro results indicated that compounds 7g, 7l, 8h, and 8l displayed good antiviral activity against TMV, with the binding constant values of 5.93, 6.15, 6.02, and 5.04 μM, respectively, which were comparable to that of Ninnanmycin (6.78 μM) and even better than that of Ribavirin (99.25 μM). The in vivo results demonstrated that compounds 7g, 7l, 8h, and 8l exhibited remarkable anti-TMV activity with the EC₅₀ values of 33.66, 33.97, 33.87 and 30.57 µg/mL, respectively, which were comparable to that of Ningnanmycin (36.85 µg/mL) and superior to that of Ribavirin (88.52 µg/mL). Interestingly, the trend of antiviral activity in vivo was consistent with the in vitro results.     

A Single-Domain Llama Antibody Potently Inhibits the Enzymatic Activity of Botulinum Neurotoxin by Binding to the Non-Catalytic α-Exosite Binding Region

Ingestion or inhalation of botulinum neurotoxin (BoNT) results in botulism, a severe and frequently fatal disease. Current treatments rely on antitoxins, which, while effective, cannot reverse symptoms once BoNT has entered the neuron. For treatments that can reverse intoxication, interest has focused on developing inhibitors of the enzymatic BoNT light chain (BoNT Lc). Such inhibitors typically mimic substrate and bind in or around the substrate cleavage pocket. To explore the full range of binding sites for serotype A light chain (BoNT/A Lc) inhibitors, we created a library of non-immune llama single-domain VHH (camelid heavy-chain variable region derived from heavy-chain-only antibody) antibodies displayed on the surface of the yeast Saccharomyces cerevisiae. Library selection on BoNT/A Lc yielded 15 yeast-displayed VHH with equilibrium dissociation constants (K_d) from 230 to 0.03 nM measured by flow cytometry. Eight of 15 VHH inhibited the cleavage of substrate SNAP25 (synaptosome-associated protein of 25,000 Da) by BoNT/A Lc. The most potent VHH (Aa1) had a solution K_d for BoNT/A Lc of 1.47 × 10^− 10 M and an IC₅₀ (50% inhibitory concentration) of 4.7 × 10^− 10 M and was resistant to heat denaturation and reducing conditions. To understand the mechanism by which Aa1 inhibited catalysis, we solved the X-ray crystal structure of the BoNT/A Lc-Aa1 VHH complex at 2.6 Å resolution. The structure reveals that the Aa1 VHH binds in the α-exosite of the BoNT/A Lc, far from the active site for catalysis. The study validates the utility of non-immune llama VHH libraries as a source of enzyme inhibitors and identifies the BoNT/A Lc α-exosite as a target for inhibitor development.     

Design,synthesis and in vitro anti-mycobacterial evaluation of gatifloxacin-1H-1,2,3-triazole-isatin hybrids

A set of novel gatifloxacin-1H-1,2,3-triazole-isatin hybrids 6a-l was designed, synthesized and evaluated for their in vitro anti-mycobacterial activities against M. tuberculosis (MTB) H₃₇Rv and MDR-TB as well as cytotoxicity. The results showed that all the targets (MIC: 0.025–3.12 μg/mL) exhibited excellent inhibitory activity against MTB H₃₇Rv and MDR-TB, but were much more toxic (CC₅₀: 7.8–62.5 μg/mL) than the parent gatifloxacin (GTFX) (CC₅₀: 125 μg/mL). Among them, 61 (MIC: 0.025 μg/mL) was 2–32 times more potent in vitro than the references INH (MIC: 0.05 μg/mL), GTFX (MIC: 0.78 μg/mL) and RIF (MIC: 0.39 μg/mL) against MTB H₃₇Rv. The most active conjugate 6 k (MIC: 0.06 μg/mL) was 16–>2048 times more potent than the three references (MIC: 1.0–>128 μg/mL) against MDR-TB. Both of the two hybrids warrant further investigations.     

Discovery of novel DNA methyltransferase 3A inhibitors via structure-based virtual screening and biological assays

DNA methyltransferases are involved in diverse biological processes and abnormal methylation patterns play essential roles in cancer initiation and progression. DNA methyltransferase 3A (DNMT3A) acting as a de novo DNA methyltransferase, has gained widespread attention especially in haematological diseases. To date, large numbers of DNMTs inhibitors have been discovered, however, the small molecular inhibitors targeting DNMT3A are still in its infancy. In this study, structure-based virtual screening in combination with biological assays was performed to discovery potent novel DNMT3A inhibitors. Compound 40 and 40_3 displayed comparable in vitro inhibitory activity against DNMT3A with IC₅₀ values of 46.5 μM and 41 μM, respectively. Further binding mode analysis suggested these molecules inhibit DNMT3A activity through binding the S-adenosyl-l-methionine (SAM) pocket. Overall, 40 and 40_3 may serve as novel scaffolds for further optimization and small molecular probes for investigating DNMT3A function.     

Synthesis,molecular docking and α-glucosidase inhibition of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylacetamides

A novel series of 2-((5,6-diphenyl-1,2,4-triazin-3-yl)thio)-N-arylacetamides 5a–5q have been synthesized and evaluated for their α-glucosidase inhibitory activity. All newly synthesized compounds exhibited potent α-glucosidase inhibitory activity in the range of IC₅₀ = 12.46 ± 0.13–72.68 ± 0.20 μM, when compared to the standard drug acarbose (IC₅₀ = 817.38 ± 6.27 μM). Among the series, compound 5j (12.46 ± 0.13 μM) with strong electron-withdrawing nitro group on the arylacetamide moiety was identified as the most potent inhibitor of α-glucosidase. Molecular docking study was carried out to explore the binding interactions of these compounds with α-glucosidase. Our study identifies a novel series of potent α-glucosidase inhibitors for further investigation.     

Improved binding affinities of pyrrolidine derivatives as Mcl-1 inhibitors by modifying amino acid side chains

As an important member of anti-apoptotic Bcl-2 protein, myeloid cell leukemia sequence 1 (Mcl-1) protein is an attractive target for cancer therapy. In this study, a new series of pyrrolidine derivatives as Mcl-1 inhibitors were developed by mainly modifying the amino acid side chain of compound 1. Among them, compound 18 (K_i = 0.077 μM) exhibited better potent inhibitory activities towards Mcl-1 protein compared to positive control Gossypol (K_i = 0.18 μM). In addition, compound 40 possessed good antiproliferative activities against PC-3 cells (K_i = 8.45 μM), which was the same as positive control Gossypol (K_i = 7.54 μM).     

Design and synthesis of pregnenolone/2-cyanoacryloyl conjugates with dual NF-κB inhibitory and anti-proliferative activities

Twenty-five novel pregnenolone/2-cyanoacryloyl conjugates (6–30) were designed and prepared, with the aim of developing novel anticancer drugs with dual NF-κB inhibitory and anti-proliferative activities. Compounds 22 and 27–30 showed inhibition against TNF-α-induced NF-κB activation in luciferase assay, which was confirmed by Western blotting. Among them, compound 30 showed potent NF-κB inhibitory activity (IC₅₀ = 2.5 μM) and anti-proliferative against MCF-7, A549, H157, and HL-60 cell lines (IC₅₀ = 6.5–36.2 μM). The present study indicated that pregnenolone/2-cyanoacryloyl conjugate I can server as a novel scaffold for developing NF-κB inhibitors and anti-proliferative agents in cancer chemotherapy.     

Design and synthesis of 4-morpholino-6-(1,2,3,6-tetrahydropyridin-4-yl)-N-(3,4,5-trimethoxyphenyl)-1,3,5-triazin-2-amine analogues as tubulin polymerization inhibitors

A series of thirty-seven 1,3,5-triazine analogues have been synthesized, characterized and evaluated for their antiproliferative activity against a panel of four different human cancer cell lines such as HeLa, HepG2, A549 and MCF-7. Most of the 1,3,5-triazine analogues exhibited promising antiproliferative activity against tested cancer cell lines. Among all the synthesized compounds, 8j showed potent activity against the cancer cell lines such as HeLa, HepG2, A549 and MCF-7 with IC₅₀ 12.3 ± 0.8, 9.6 ± 0.4, 10.5 ± 1.0 and 11.7 ± 0.5 μM respectively. 8j was taken up for elaborate biological studies and the cells in the cell cycle were arrested in G2/M phase. In addition, 8j was examined for its effect on the microtubule system with a tubulin polymerization assay, immunofluorescence. 8j showed remarkable inhibition of tubulin polymerization. Molecular docking studies were also carried out to understand the binding pattern. The studies suggested that 8j has a good binding affinity of ?7.949 towards nocodazole binding site of tubulin while nocodazole has ?7.462.     

Discovery of pyrazolo[1,5-a]pyrimidine-3-carbonitrile derivatives as a new class of histone lysine demethylase 4D (KDM4D) inhibitors

Herein we report the discovery of a series of new small molecule inhibitors of histone lysine demethylase 4D (KDM4D). Molecular docking was first performed to screen for new KDM4D inhibitors from various chemical databases. Two hit compounds were retrieved. Further structural optimization and structure-activity relationship (SAR) analysis were carried out to the more selective one, compound 2, which led to the discovery of several new KDM4D inhibitors. Among them, compound 10r is the most potent one with an IC₅₀ value of 0.41 ± 0.03 μM against KDM4D. Overall, compound 10r could be taken as a good lead compound for further studies.     

Antileishmanial evaluation of clubbed bis(indolyl)-pyridine derivatives: One-pot synthesis,in vitro biological evaluations and in silico ADME prediction

A new series of bis(indolyl)-pyridine derivatives 6(a–m) were synthesized by Chichibabin reaction process and evaluated for antileishmanial and antibacterial activities to establish structure–activity relationship. The synthesis was carried out through one-pot multicomponent reaction of 3-acetylindole, aromatic aldehydes, and ammonium acetate in the presence of camphor-10-sulfonic acid as a catalyst. The compounds 6d (IC₅₀ = 102.47 μM) and 6f (IC₅₀ = 99.49 μM) had shown promising antileishmanial against L. donovani promastigotes when compared with standard sodium stibogluconate (IC₅₀ = 490.00 μM). All the synthesized compounds (MIC range = 41.35–228.69 μg/mL) had shown potent antibacterial activity than standard ampicillin (MIC range = 100.00–250.00 μg/mL) against all the tested bacterial strains. In silico ADME and metabolic site prediction studies were also held out to set an effective lead candidate for the future antileishmanial and antibacterial drug discovery initiatives.     

Anti-diabetic xanthones from the bark of Garcinia xanthochymus

An ethyl acetate extract the bark of Garcinia xanthochymus exhibited strong inhibition towards α-glucosidase and PTP1B with IC₅₀ values of 0.3 ± 0.1 μg/mL and 2.3 ± 0.4 μg/mL, respectively. Chemical constituents of the extract were therefore examined, and two new compounds, xanthochymusxanthones A (1) and B (2), along with ten known xanthones (3–12), were isolated. Their structures were determined using spectroscopic methods, mainly 1D and 2D NMR. Inhibitory activity of the isolated compounds was then tested, and subelliptenone F (12) showed significant effect towards α-glucosidase with IC₅₀ value of 4.1 ± 0.3 μM (compared with acarbose, IC₅₀ = 900.0 ± 3.0 μM) whilst xanthochymusxanthone B (2) exhibited remarkable activity towards PTP1B with IC₅₀ value of 8.0 ± 0.6 μM (compared with RK682, IC₅₀ = 4.4 ± 0.3 μM).     

Natural potential neuroinflammatory inhibitors from Alhagi sparsifolia Shap.

Neuroinflammation is a key contributor to neuronal damage in neurodegenerative diseases. In our previous work on natural effective neuroinflammatory inhibitors, Alhagi sparsifolia Shap. (Leguminosae), a folk medicine widely distributed in Xinjiang, attracted our attention because of its significant anti-neuroinflammatory effect. Therefore, further investigation of the bioactive material basis was carried out. As a result, 33 major components were characterized and identified by chromatographic and spectral methods, respectively. Furthermore, the anti-neuroinflammatory effects of the extract and purified constituents were evaluated in LPS-induced N9 cells in vitro. The results displayed that compounds 1, 2, 3, 5, 6, 8, 11, 15, 16, 17, 22, 23, 25, 26, 28, 30, 33 could exhibit significant inhibitory activities without obvious cytotoxicities at their effective concentrations. Especially, isorhamnetin (1) (IC₅₀ 17.87 μM), quercetin (2) (10.22 μM), 3′,7-dihydroxyl-4′-methoxylisoflavone (5) (17.43 μM), 3′,7-dihydroxyl-4′,6-dimethoxylisoflavone (6) (11.21 μM), syringgaresinol (16) (2.68 μM), bombasinol A (17) (7.61 μM), aurantiamide (23) (14.91 μM) and 1,3,3,4-tetramethyl cyclopentene (33) (2.63 μM) showed much stronger inhibiting effect than that of the positive control minocycline (19.89 μM). Therefore, the effective compositions might be responsible for the significant neuroinflammation inhibitory activities exhibited by the herb. Moreover, compounds 16 and 33 could be good leading compounds for the development of potential therapeutic agents against neurodegenerative diseases.     

Synthesis,potential anti-inflammatory and analgesic activities study of (S)-N-substituted-1-phenyl-3,4-dihydroisoquinoline-2(1H)-carboxamides

A series of (S)-N-substitued-1-phenyl-3,4-dihydroisoquinoline-2(1H)-carboxamide derivatives were designed, synthesized and evaluated for their anti-inflammatory and analgesic effects in vivo. Among the synthesized compounds 2a and 2n showed the best anti-inflammatory activity (inhibition rate: 95% and 92.7%, respectively) and analgesic effect (inhibition rate: 100% and 100%, respectively), which was greater than that or nearly equivalent to that of indomethacin. Compounds 2a and 2n were selected to test their inhibitory effects against ovine COX-1 and COX-2 using the cyclooxygenase inhibition assay in vitro. Compounds 2a and 2n are weak inhibitors of COX-1 isozyme but displayed moderate COX-2 isozyme inhibitory effects (IC₅₀ = 0.47 μM and 1.63 μM, respectively) and COX-2 selectivity indexes (SI = 11.5 and 4.8). Furthermore, compound 2a was more inhibitors of COX-2 isozyme active than the reference drug celecoxib.     

Nitro-substituted tetrahydroindolizines and homologs: Design,kinetics, and mechanism of α-glucosidase inhibition

A series of 1-[(methylsulfonyl)methyl]-2-nitro-5,6,7,8-tetrahydroindolizines and homologs were designed, prepared, and evaluated as non-sugar-type α-glucosidase inhibitors. The inhibitory activity appeared to be related to cyclo homologation with the best congeners being tetrahydroindolizines. The introduction of a methoxycarbonyl group as an additional hydrogen bond acceptor into the exocyclic methylene group was beneficial affording the most potent congener 3e (half maximal inhibitory concentration, IC₅₀ = 8.0 ± 0.1 μM) which displayed 25-fold higher inhibitory activity than 1-deoxynojirimycin (2, IC₅₀ = 203 ± 9 μM)—the reference compound. Kinetic analysis indicated that compound 3e is a mixed inhibitor with preference for the free enzyme over the α-glucosidase–substrate complex (K_i,free = 3.6 μM; K_i,bound = 7.6 μM). Molecular docking experiments were in agreement with kinetic results indicating reliable interactions with both the catalytic cleft and other sites. Circular dichroism spectroscopy studies suggested that the inhibition exerted by 3e may involve changes in the secondary structure of the enzyme. Considering the relatively low molecular weight of 3e together with its high fraction of sp³ hybridized carbon atoms, this nitro-substituted tetrahydroindolizine may be considered as a good starting point towards new leads in the area of α-glucosidase inhibitors.     

Synthesis of triazole Schiff bases: Novel inhibitors of nucleotide pyrophosphatase/phosphodiesterase-1

A series of Schiff base triazoles 1–25 was synthesized and evaluated for their nucleotide pyrophosphatase/phosphodiesterase-1 inhibitory activities. Among twenty-five compounds, three compounds 10 (IC₅₀ = 132.20 ± 2.89 μM), 13 (IC₅₀ = 152.83 ± 2.39 μM), and 22 (IC₅₀ = 251.0 ± 6.64 μM) were identified as potent inhibitors with superior activities than the standard EDTA (IC₅₀ = 277.69 ± 2.52 μM). The newly identified inhibitors may open a new avenue for the development of treatment of phosphodiesterase-I related disorders. These compounds were also evaluated for carbonic anhydrase, acetylcholinesterase and butyrylcholinesterase inhibitory potential and were found to be inactive. The compounds showed non-toxic effect towards PC3 cell lines.     

Novel Toxoplasma gondii inhibitor chemotypes

We profiled three novel T. gondii inhibitors identified from an antimalarial phenotypic high throughput screen (HTS) campaign: styryl 4-oxo-1,3-benzoxazin-4-one KG3, tetrahydrobenzo[b]pyran KG7, and benzoquinone hydrazone KG8. These compounds inhibit T. gondii in vitro with IC₅₀ values ranging from 0.3 to 2 μM, comparable to that of 0.25 to 1.5 μM for the control drug pyrimethamine. KG3 had no measurable cytotoxicity against five mammalian cell lines, whereas KG7 and KG8 inhibited the growth of 2 of 5 cell lines with KG8 being the least selective for T. gondii. None of the compounds were mutagenic in an Ames assay. Experimental gLogD_7.4 and calculated PSA values for the three compounds were well within the ranges predicted to be favorable for good ADME, even though each compound had relatively low aqueous solubility. All three compounds were metabolically unstable, especially KG3 and KG7. Multiple IP doses of 5 mg/kg KG7 and KG8 increased survival in a T. gondii mouse model. Despite their liabilities, we suggest that these compounds are useful starting points for chemical prospecting, scaffold-hopping, and optimization.     

In silico selection and cell-based characterization of selective and bioactive compounds for androgen-dependent prostate cancer cell

Prostate cancer is one of the most prevalent types of cancer in male population. It is a hormone driven disease, especially in its initial phase. Hence, androgen deprivation therapy (ADT) is the major chemotherapeutic effort and novel AR inhibitors with improved pharmacological profiles are needed. In this report, a novel bioactive compound was selected and investigated using in silico and cell-based assays. Neq0502 compound was selective for the testosterone stimulated AR-dependent prostate cancer cell (LNCaP, GI₅₀ = 22.4 μM) when compared with unstimulated LNCaP or AR-insensitive (DU145 and PC-3) cell lines. Cell cycle arrest study provided the same profile for Neq0502 and the reference drug enzalutamide. Moreover, this compound is not cytotoxic for fibroblast Balb/C 3T3 clone A31 cells up to 250 μM, with a good selectivity ratio (SI > 11), which could be used in compound optimization effort to a novel therapeutic alternative.