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.     

Syntheses of benzophenone-xanthone hybrid polyketides and their antibacterial activities

Muchimangins are benzophenone-xanthone hybrid polyketides produced by Securidaca longepedunculata. However, their biological activities have not been fully investigated, since they are minor constituents in this plant. To evaluate the possibility of muchimangins as antibacterial agent candidates, five muchimangin analogs were synthesized from 2,4,5-trimethoxydiphenyl methanol and the corresponding xanthones, by utilizing p-toluenesulfonic acid monohydrate for the Brønsted acid-catalysis. The antibacterial assays against Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis, and Gram-negative bacteria, Klebsiella pneumoniae and Escherichia coli, revealed that the muchimangin analogs (±)-1,3,6,8-tetrahydroxy-4-(phenyl-(2′,4′,5′-trimethoxyphenyl)methyl)-xanthone (1), (±)-1,3,6-trihydroxy-4-(phenyl-(2′,4′,5′-trimethoxyphenyl)methyl)-xanthone (2), and (±)-1,3-dihydroxy-4-(phenyl-(2′,4′,5′-trimethoxyphenyl)methyl)-xanthone (3) showed significant activities against S. aureus, with MIC values of 10.0, 10.0, and 25.0 μM, respectively. Analogs (±)-1 and (±)-2 also exhibited antibacterial activities against B. subtilis, with MIC values of 50.0 and 12.5 μM, respectively. Furthermore, (+)-3 enhanced the antibacterial activity against S. aureus, with a MIC value of 10 μM.     

Strategy for designing selective α-l-rhamnosidase inhibitors: Synthesis and biological evaluation of l-DMDP cyclic isothioureas

This study shows that the cyclization of l-DMDP thioureas to bicyclic l-DMDP isothioureas improved α-l-rhamnosidase inhibition which was further enhanced by increasing the length of the alkyl chain. The addition of a long alkyl chain, such as decyl or dodecyl, to the nitrogen led to the production of highly potent inhibitors of α-l-rhamnosidase; it also caused broad inhibition spectrum against β-glucosidase and β-galactosidase. In contrast, the corresponding N-benzyl-l-DMDP cyclic isothioureas display selective inhibition of α-l-rhamnosidase; 3′,4′-dichlorobenzyl-l-DMDP cyclic isothiourea (3r) was found to display the most potent and selective inhibition of α-l-rhamnosidase, with IC₅₀ value of 0.22 μM, about 46-fold better than the positive control 5-epi-deoxyrhamnojirimycin (5-epi-DRJ; IC₅₀ = 10 μM) and occupied the active-site of this enzyme (K_i = 0.11 μM). Bicyclic isothioureas of ido-l-DMDP did not inhibit α-l-rhamnosidase. These new mimics of l-rhamnose may affect other enzymes associated with the biochemistry of rhamnose including enzymes involved in progression of tuberculosis.     

Synthesis,evaluation of anti-HIV-1 and anti-HCV activity of novel 2′,3′-dideoxy-2′,2′-difluoro-4′-azanucleosides

A series of 2′,3′-dideoxy-2′,2′-difluoro-4′-azanucleosides of both pyrimidine and purine nucleobases were synthesized in an efficient manner starting from commercially available L-pyroglutamic acid via glycosylation of difluorinated pyrrolidine derivative 15. Several 4′-azanucleosides were prepared as a separable mixture of α- and β-anomers. The 6-chloropurine analogue was obtained as a mixture of N⁷ and N⁹ regioisomers and their structures were identified based on NOESY and HMBC spectral data. Among the 4′-azanucleosides tested as HIV-1 inhibitors in primary human lymphocytes, four compounds showed modest activity and the 5-fluorouracil analogue (18d) was found to be the most active compound (EC₅₀ = 36.9 μM) in this series. None of the compounds synthesized in this study demonstrated anti-HCV activity.     

Novel oxazolinyl derivatives of pregna-5,17(20)-diene as 17α-hydroxylase/17,20-lyase (CYP17A1) inhibitors

New oxazolinyl derivatives of [17(20)E]-pregna-5,17(20)-diene: 2′-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4′,5′-dihydro-1′,3′-oxazole 1 and 2′-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4′,4′-dimethyl-4′,5′-dihydro-1′,3′-oxazole 2 were evaluated as potential CYP17A1 inhibitors in comparison with 17-(pyridin-3-yl)androsta-5,16-dien-3β-ol 3 (abiraterone). Differential absorption spectra of human recombinant CYP17A1 in the presence of compound 1 (λ_max = 422 nm, λ_min = 386 nm) and compound 2 (λ_max = 416 nm) indicated significant differences in enzyme/inhibitors complexes. CYP17A1 activity was measured using electrochemical methods. Inhibitory activity of compound 1 was comparable with abiraterone 3 (IC₅₀ = 0.9 ± 0.1 μM, and IC₅₀ = 1.3 ± 0.1 μM, for compounds 1 and 3, respectively), while compound 2 was found to be weaker inhibitor (IC₅₀ = 13 ± 1 μM). Docking of aforementioned compounds to CYP17A1 revealed that steroid fragments of compound 1 and abiraterone 3 occupied close positions; oxazoline cycle of compound 1 was coordinated with heme iron similarly to pyridine cycle of abiraterone 3. Configuration of substituents at 17(20) double bond in preferred docked position corresponded to Z-isomers of compounds 1 and 2. Presence of 4′-substituents in oxazoline ring of compound 2 prevents coordination of oxazoline nitrogen with heme iron and worsens its docking score in comparison with compound 1. These data indicate that oxazolinyl derivative of [17(20)E]-pregna-5,17(20)-diene 1 (rather than 4′,4′-dimethyl derivative 2) may be considered as potential CYP17A1 inhibitor and template for development of new compounds affecting growth and proliferation of prostate cancer cells.     

Study of antileishmanial activity of 2-aminobenzoyl amino acid hydrazides and their quinazoline derivatives

A new small library of 2-aminobenzoyl amino acid hydrazide derivatives and quinazolinones derivatives was synthesized and fully characterized by IR, NMR, and elemental analysis. The activity of the prepared compounds on the growth of Leishmania aethiopica promastigotes was evaluated. 2-Benzoyl amino acid hydrazide showed higher inhibitory effect than the quinazoline counterpart. The in vitro antipromastigote activity demonstrated that compounds 2a, 2b, 2f and 4a had IC₅₀ better than standard drug miltefosine and comparable activity to amphotericin B deoxycholate, which indicates their high antileishmanial activity against Leishmania. aethiopica. Among the prepared compounds; 2-amino-N-(6-hydrazinyl-6-oxohexyl)benzamide 2f (IC₅₀ = 0.051 μM) has the best activity, 154 folds more active than reference standard drug miltefosine (IC₅₀ = 7.832 μM), and half fold the activity of amphotericin B (IC₅₀ = 0.035 μM). In addition, this compound was safe and well tolerated by experimental animals orally up to 250 mg/kg and parenterally up to 100 mg/kg.     

Sialidase inhibitory activity of diarylnonanoid and neolignan compounds extracted from the seeds of Myristica fragrans

Sialidases are key virulence factors that remove sialic acid from host cell surface glycans, thus unmasking receptors to facilitate bacterial adherence and colonization. In this study, we report the isolation and characterization of novel inhibitors of the Streptococcus pneumoniae sialidases NanA, NanB, and NanC from Myristica fragrans seeds. Of the isolated compounds (1–12), malabaricone C showed the most pneumococcal sialidases inhibition (IC₅₀ of 0.3 μM for NanA, 3.6 μM for NanB, and 2.9 μM for NanC). These results suggested that malabaricone C and neolignans could be potential agents for combating S. pneumoniae infection agents.     

Synthesis,anticancer, and docking studies of salicyl-hydrazone analogues: A novel series of small potent tropomyosin receptor kinase A inhibitors

A series of novel salicyl-hydrazone analogues were synthesized and evaluated for their in vitro cytotoxic activities in five human cancer cell lines, namely, lung cancer (A549), ovarian cancer (SK-OV-3), skin cancer (SK-MEL-2), colon cancer (HCT15) and pancreatic cancer (MIA-PaCa-2) cells, and for their in vitro tropomyosin receptor kinase A (TrkA) inhibitory activities. Each of the compounds showed significant cytotoxicity against all cancer cells. Compound 3i was found to be most potent against all cancer cell lines with IC₅₀ values of 2.46 (A549), 0.87 (SK-OV-3), 1.43 (SK-MEL-2), 0.89 (HCT15), and 0.48 μM (MIA-PaCa-2), followed by compound 3l. Cytotoxicity of 3i was similar to that of doxorubicin (0.87 μM) against HCT15 cells. Compounds 3i and 3l also showed highest TrkA inhibitory activities with IC₅₀ values of 0.231 and 0.380 μM, respectively. A SAR study of the series revealed that compounds with hydroxyl groups showed better cytotoxicity and TrkA inhibitory potency (in the following order 2,4-OH > 2,3,4-OH > 3,4-OH > 4-OH) than compounds possessing electron donating or withdrawing groups on the benzylidenephenyl ring. Docking studies of compounds 3i and 3l conducted on the crystal structure of TrkA receptor (a promising target for anticancer agents) showed both had a high docking score and similar order of experimental TrkA inhibitory activities. The formation of several hydrogen bonds involving N and O containing moieties contributed most significantly to ligand binding and stabilization at the active site of the receptor. In addition, ligand-receptor complexes were further stabilized by π-cation, π-anion, amide-π stacked, and van der Waal’s interactions. Conformational analyses showed ligand molecules adopted similar conformations at the receptor active site during interactions, but that the low energy optimized conformations of compounds 3i and 3l differed.     

New antiprotozoal agents: Synthesis and biological evaluation of different 4-(7-chloroquinolin-4-yl) piperazin-1-yl)pyrrolidin-2-yl)methanone derivatives

In an endeavor to develop efficacious antiprotozoal agents 4-(7-chloroquinolin-4-yl) piperazin-1-yl)pyrrolidin-2-yl)methanone derivatives (5–14) were synthesized, characterized and biologically evaluated for antiprotozoal activity. The compounds were screened in vitro against the HM1: IMSS strain of Entamoeba histolytica and NF54 chloroquine-sensitive strain of Plasmodium falciparum. Among the synthesized compounds six exhibited promising antiamoebic activity with IC₅₀ values (0.14–1.26 μM) lower than the standard drug metronidazole (IC₅₀ 1.80 μM). All nine compounds exhibited antimalarial activity (IC₅₀ range: 1.42–19.62 μM), while maintaining a favorable safety profile to host red blood cells. All the compounds were less effective as an antimalarial and more toxic (IC₅₀ range: 14.67–81.24 μM) than quinine (IC₅₀: 275.6 ± 16.46 μM) against the human kidney epithelial cells. None of the compounds exhibited any inhibitory effect on the viability of Anopheles arabiensis mosquito larvae.     

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 of novel nicotinamides as potent and selective monoamine oxidase a inhibitors

A series of N-(2-morpholinoethyl)nicotinamide (1–13) and N-(3-morpholinopropyl)nicotinamide derivatives (14–26) have been designed, synthesized and evaluated in vitro for their monoamine oxidase (MAO) A and B inhibitory activity and selectivity. Most of these synthesized compounds proved to be potent, and selective inhibitors of MAO-A rather than of MAO-B. 5-Chloro-6-hydroxy-N-(2-morpholinoethyl)nicotinamide (13) displayed the highest MAO-A inhibitory potency (IC₅₀ = 0.045 μM) and a good selectivity. 2-Bromo-N-(2-morpholinoethyl)nicotinamide (3) was the most potent MAO-B inhibitor with the IC₅₀ value of 0.32 μM, but it was not selective. Molecular dockings of compound 13 were performed in order to give structural insights regarding the MAO-A selectivity.     

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.     

Optimization and bioevaluation of Cdc37-derived peptides: An insight into Hsp90-Cdc37 protein-protein interaction modulators

Targeting Hsp90-Cdc37 protein-protein interaction (PPI) is becoming an alternative approach for future anti-cancer drug development. We previously reported the discovery of an eleven-residue peptide (Pep-1) with micromolar activity for the disruption of Hsp90-Cdc37 PPI. Efforts to improve upon the Pep-1 led to the discovery of more potent modulators for Hsp90-Cdc37 PPI. Through the analysis of peptides binding patterns, more peptides were designed for further verification which resulted in Pep-5, the shortest peptide targeting Hsp90-Cdc37, exerting the optimal structure and the most efficient binding mode. Subsequent MD simulation analysis also confirmed that Pep-5 could perform more stable binding ability and better ligand properties than Pep-1. Under the premise of retentive binding capacity, Pep-5 exhibited lower molecular weight and higher ligand efficiency with a K_d value of 5.99 μM (Pep-1 K_d = 6.90 μM) in both direct binding determination and biological evaluation. The optimal and shortest Pep-5 might provide a breakthrough and a better model for the future design of small molecule inhibitors targeting Hsp90-Cdc37 PPI.     

Synthesis of isothiazol-3-one derivatives as inhibitors of histone acetyltransferases (HATs)

High-throughput screening led to the identification of isothiazolones 1 and 2 as inhibitors of histone acetyltransferase (HAT) with IC50s of 3 μM and 5 μM, respectively. Analogues of these hit compounds with variations of the N-phenyl group, and with variety of substituents at C-4, C-5 of the thiazolone ring, were prepared and assayed for inhibition of the HAT enzyme PCAF. Potency is modestly favoured when the N-aryl group is electron deficient (4-pyridyl derivative 10 has IC₅₀ = 1.5 μM); alkyl substitution at C-4 has little effect, whilst similar substitution at C-5 causes a significant drop in potency. The ring–fused compound 38 has activity (IC₅₀ = 6.1 μM) to encourage further exploration of this bicyclic structure. The foregoing SAR is consistent with an inhibitory mechanism involving cleavage of the S–N bond of the isothiazolone ring by a catalytically important thiol residue.     

Antimycobacterial activity of novel hydrazide-hydrazone derivatives with 2H-chromene and coumarin scaffold

This study reports the synthesis of new 2H-chromene or coumarin based acylhydrazones, which were evaluated for their in vitro antimycobacterial activity against reference strain Mycobacterium tuberculosis H37Rv and compared to the first-line antituberculosis drugs, isoniazid (INH) and ethambutol (EMB). The most active compounds 7m (MIC 0.13 μM), 7o (MIC 0.15 μM) and 7k (MIC 0.17 μM) demonstrated antimycobacterial activity at submicromolar concentration level and remarkably minimal associated cytotoxicity in the human embryonic kidney cell line HEK-293T. Structure-activity relationship for this class of compounds has been established.     

Discovery of a cobalt complex with high MEK1 binding affinity

A series of Schiff base ligands (L¹–L⁵) and their cobalt(II) complexes (1–5) were designed and synthesized for MEK1 binding experiment. The biological evaluation results showed that Bis(N,N′-disalicylidene)-3,4-phenylenediamine-cobalt(II) 1 and Bis(N,N′-disalicylidene)-1,2-cyclohexanediamine-cobalt(II) 2 are much more effective than the parent Schiff bases (L¹ and L²). Importantly, 2 exhibited MEK1 binding affinity with IC₅₀71 nM, which is so far the best result for metal complexes and more potent than U0126 (7.02 μM) and AZD6244 (2.20 μM). Docking study was used to elucidate the binding modes of complex 2 with MEK1. Thus cobalt(II) complex 2 may be further developed as a novel MEK1 inhibitor.     

SAR studies of differently functionalized chalcones based hydrazones and their cyclized derivatives as inhibitors of mammalian cathepsin B and cathepsin H

Cathepsins have emerged as potential drug targets for melanoma therapy and engrossed attention of researchers for development and evaluation of cysteine cathepsin inhibitors as cancer therapeutics. In this direction, we have designed, synthesized, and assayed in vitro a small library of 30 low molecular weight functionalized analogs of chalcone hydrazones for evaluating structure–activity relationship aspects and inhibitory potency against cathepsin B and H. The maximum inhibitory effect was exerted by chalcone hydrazones, which are open chain analogues followed by their cyclized derivatives, pyrazolines and pyrazoles. All the synthesized compounds were established as reversible inhibitors of these enzymes. Cathepsin B was selectively inhibited by the compounds in each series. Compounds 1d, 2d and 4d were recognized as most potent inhibitors of cathepsin B in this study with K_i values of 0.042 μM, 0.053 μM and 0.131 μM whereas 1b (K_i = 1.111 μM), 2b (K_i = 1.174 μM) and 4b (K_i = 1.562 μM) inhibited cathepsin H activity effectively. And, preeminent cathepsin B inhibitors were –NO₂ functionalized however, –Cl substituted moieties were the most persuasive inhibitors for cathepsin H among all the designed compounds. Molecular docking studies performed using iGemdock provided valuable insights.     

Three new benzophenone glycosides with MAO-A inhibitory activity from Hypericum thasium Griseb.

Purification of n-BuOH fraction from 80% ethanol extract of Hypericum thasium Griseb. resulted in the isolation of three new compounds 3′,4,5′-trihydroxy-6-methoxy-2-O-α-l-arabinosylbenzophenone (1), 3′,4,5′,6-tetrahydroxy-2-O-α-l-arabinosylbenzophenone (2), and 3′,4-dihydroxy-5′-methoxy-2-O-α-l-arabinosyl-6-O-β-d-xylosylbenzophenone (3) along with a known flavonoid glycoside quercetin-3-O-α-l-arabinofuranoside (4). The structures of the new compounds were elucidated by 1D and 2D NMR analysis as well as HRESIMS. The isolated compounds (1–4), as well as quercetin, and kaempferol previously isolated from EtOAc fraction were screened against MAO-A inhibitory activity. When tested against the MAO-A quercetin and kaempferol displayed IC₅₀ values of 19.6, and 17.5 μM, respectively. The IC₅₀ values for MAO-A inhibition by compounds (1–4) were 310.3, 111.2, 726.0, and 534.1 μM, respectively. Standard inhibitor (clorgyline) exhibited MAO-A inhibition with an IC₅₀ value of 0.5 μM.     

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.