Design,Synthesis, and Antifungal Activities of Novel Carboxamides Derivatives Bearing a Chalcone Scaffold as Potential SDHIs

In search for SDHIs fungicides, twenty-five novel carboxamides containing a chalcone scaffold were designed, synthesized, and evaluated for antifungal activities against five pathogenic fungi. The results showed that compound 5 k exhibited outstanding antifungal activity against R. solani with an EC₅₀ value of 0.20 μg/mL, which was much better than that of commercial SDHIs Boscalid (EC₅₀=0.74 μg/mL). Moreover, compound 5 k also displayed promising antifungal activities against S. sclerotiorum, B. cinerea, and A. alternate (IC₅₀=2.53–4.06 μg/mL), indicating that 5 k had broad-spectrum antifungal activity. Additionally, in vivo antifungal activities results showed that 5 k could significantly inhibit the growth of R. solani in rice leaves with good protective efficacy (57.78 %) and curative efficacy (58.45 %) at 100 μg/mL, both of which were much better than those of Boscalid, indicating a promising application prospect. Moreover, SEM analysis showed that compound 5 k could remarkably disrupt the typical structure and morphology of R. solani hyphae. Further SDH enzyme inhibition assay and molecular docking study revealed that lead compound 5 k had a similar mechanism of action as commercial SDHI Boscalid. These results indicated that compound 5 k showed potential as a SDHIs fungicide and deserved further investigation.     

Simplified Derivatives of Dibenzylbutyrolactone Lignans from Hydrocotyle bonariensis as Antitrypanosomal Candidates

The search for the pharmacophore of a bioactive compound, crucial for drug discovery studies, involves the adequate arrangement of different atoms in the molecule. As part of a continuous work aiming discovery of new drug candidates against the protozoan parasite Trypanosoma cruzi, the hexane extract of Hydrocotyle bonariensis was subjected to a bioactivity-guided fractionation to afford two chemically related dibenzylbutyrolactone lignans – hinokinin ( 1 ) and hibalactone ( 2 ). Compounds 1 and 2 showed activity against trypomastigote with EC₅₀ values of 17.0 and 69.4 μM, respectively. Compound 1 was also active against the clinically relevant form of the parasite, amastigotes, displaying an EC₅₀ value of 34.4 μM. The structure-activity relationship (SAR) indicated that the absence of the double bond at C-7 is a crucial feature for the increment of the antiparasitic activity. The lethal action of the most potent compound 1 was investigated in the trypomastigotes. The fluorescent-based assay with SYTOX Green demonstrated a significant alteration of the plasma membrane permeability of the parasite. Additionally, compound 1 demonstrated no significant hemolytic activity in mice erythrocytes at 200 μM. To search the pharmacophore, three different simplified compounds – 3,4-methylenedioxydihydrocinnamic acid ( 3 ), 3,4-methylenedioxydihydrocinnamic alcohol ( 4 ) and 3,4-methylenedioxycinnamic acid ( 5 ) – were prepared and tested against T. cruzi. These derivatives displayed EC₅₀ values of 37.2 ( 3 ), 25.8 ( 4 ) and 73.5 ( 5 ) μM against trypomastigotes, and 41.3 ( 3 ) and 48.2 ( 4 ) μM against amastigotes, whereas compound 5 was inactive. Except for compound 2 , which resulted in a CC₅₀ value of 114.5 μM, all compounds showed no mammalian cytotoxicity at 200 μM. An in silico ADMET study was performed and predicted values demonstrated an acceptable drug-likeness profile for compounds 1 – 5 . Despite the minor reduction in the potency, the simplified derivatives retained the antitrypanosomal activity against the intracellular amastigotes, even with 95 % reduction of their molecular weight. Additionally, in silico studies suggested them as more soluble compounds, making these simplified structures promising scaffolds for optimization studies in Chagas disease.     

Synthesis,Antifungal Activity,DFT Study and Molecular Dynamics Simulation of Novel 4-(1,2,4-Oxadiazol-3-yl)-N-(4-phenoxyphenyl)benzamide Derivatives

In order to find novel potential antifungal agrochemicals, a series of new 4-(1,2,4-oxadiazol-3-yl)-N-(4-phenoxyphenyl)benzamide derivatives 3a – j were designed, synthesized and characterized by their ¹H - , ¹³C-NMR and HRMS spectra. The preliminary antifungal assay in vitro revealed that compounds 3a – j exhibited moderate to good antifungal activity against five plant pathogenic fungi. Especially, compound 3e presented significant antifungal activity against Alternaria solani, Botrytis cinerea and Sclerotinia sclerotiorum, superior to positive control boscalid. In the in vivo antifungal assay on tomato plants and cucumber leaves, compound 3e presented good inhibition rate against B. cinerea at 200 mg/L. Molecular dynamics simulation revealed that compound 3e could bind with the active site of class II histone deacetylase (HDAC).     

Synthesis and Antifungal Activity of Curcumol Derivatives

To discover novel and effective antifungal candidates, a series of new curcumol derivatives were designed, synthesized, and evaluated their antifungal activity against five phytopathogenic fungi by the mycelium growth rate method. Derivatives c4 , c22 and c23 exhibited excellent antifungal activity against Phomopsis sp. with EC₅₀ values of 3.06, 3.07, and 3.16 μM, respectively. Specifically, compound c4 exhibited the strongest antifungal activity against Phomopsis sp., which was 44 times that of pyrimethanil (EC₅₀=134.37 μM). The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that compound c4 could cause cell senescence and death of Phomopsis sp. by changing the normal hyphal morphology and disrupting the normal metabolism of hyphal cells. Moreover, compound c4 showed excellent curative effect against Phomopsis sp. on kiwifruit. These findings confirmed that compound c4 has great potential as a potent antifungal agent.     

Quinoline Alkaloids from the Roots of Orixa japonica with the Anti-Pathogenic Fungi Activities

A new quinoline alkaloid, 5-hydroxy-6-methoxy-N-methyl-2-phenylquinoline-4-one ( 1 ), and seventeen known quinoline alkaloids ( 2 – 18 ) were isolated from the roots of Orixa japonica. The structure of 1 was determined by analysis of spectroscopic data. Among them, compounds 2 , 3 , and 13 were isolated from this plant for the first time. All isolates were screened for the anti-pathogenic fungi activities, including Rhizoctonia solani, Magnaporthe oryzae, and Phomopsis sp. The results showed that five compounds ( 4 , 8 , 10 , 11 , and 12 ) exhibited significant anti-pathogenic fungi effects at 50.0 μg/mL. In special, compound 10 exhibited the best antifungal activities toward R. solani and M. oryzae with the IC₅₀ values of 37.86 and 44.72 μM, respectively, better than that of the positive control, hymexazol (IC₅₀ 121.21 and 1518.18 μM, respectively). Moreover, eleven new quinoline alkaloids derivatives ( 12a–12k ) were designed and synthesized to investigate the structure−activity relationships (SARs). The SARs analysis indicated that the furo[2,3-b]quinoline skeleton and the methoxy at C-7 (compounds 8 , 11 , and 12 ) played a key role for improving the antifungal activities.     

Synthesis and Antifungal Activity of Novel L-Menthol Hydrazide Derivatives as Potential Laccase Inhibitors

To discover novel laccase inhibitors as potential fungicides, twenty-six novel L-menthol hydrazide derivatives were designed and synthesized. In the in vitro antifungal assay, most of the target compounds displayed pronounced antifungal activity against Sclerotinia sclerotiorum, Fusarium graminearum, and Botryosphaeria dothidea. Especially, the EC₅₀ of compounds 3 b and 3 q against B. dothidea was 0.465 and 0.622 mg/L, which was close to the positive compound fluxapyroxad (EC₅₀=0.322 mg/L). Scanning electron microscopy (SEM) analysis showed that compound 3 b could significantly damage the mycelial morphology of B. dothidea. In vivo antifungal experiments on apple fruits showed that 3 b exhibited excellent protective and curative effects. Furthermore, in the in vitro laccase inhibition assay, 3 b showed outstanding inhibitory activity with the IC₅₀ value of 2.08 μM, which is much stronger than positive control cysteine and PMDD-5Y. These results indicated that this class of L-menthol derivatives could be promising leads for the discovery of laccase-targeting fungicides.     

Occurrence of Antimicrobial Serin-Proteinases in Sunflower Seeds

Using an experimental approach directed to the isolation of antimicrobial proteins, we have detected the presence of a trypsin inhibitor (TI) with associated antifungal activity in sunflower seeds. Purification of the isolated protein by affinity chromatography on a trypsin‐agarose matrix confirmed that a trypsin inhibitor was responsible for the inhibition of spore germination of the fungal pathogen Sclerotinia sclerotiorum. The protein is a potent antifungal compound as it can completely inhibit the germination of S. sclerotiorum ascospores at a concentration of 14 μg/ml. The putative contribution of this TI to control fungal invasion is discussed.     

Synthesis and Evaluation of Novel Metacetamol Derivatives with Hydrazone Moiety as Anticancer and Antimicrobial Agents

By exploiting the wide biological potential of the hydrazone scaffold, a series of hydrazone derivatives were synthesized, starting from N-(3-hydroxyphenyl)acetamide (metacetamol). The structures of the compounds were determined using IR, ¹H and ¹³C-NMR, and mass spectroscopic methods. The obtained molecules ( 3 a – j ) were evaluated for their anticancer potential against MDA-MB-231 and MCF-7 breast cancer cell lines. According to the CCK-8 assay, all tested compounds showed moderate to potent anticancer activity. Among them, N-(3-(2-(2-(4-nitrobenzylidene)hydrazinyl)-2-oxoethoxy)phenyl)acetamide ( 3 e ) was found to be the most effective derivative with an IC₅₀ value of 9.89 μM against MDA-MB-231 cell lines. This compound was further tested for its potential effects on the apoptotic pathway. Molecular docking studies was also carried out for 3 e in the colchicine binding pocket of tubulin. Additionally, compound 3 e also demonstrated effective antifungal activity, particularly against Candida krusei (MIC=8 μg/ml), indicating that nitro group at the 4^th position of the phenyl ring was the most preferable substituent for both cytotoxic and antimicrobial activity. Our preliminary findings suggest that compound 3 e could be exploited as a leading structure for further anticancer and antifungal drug development.     

Influence of Chirality of Benzimidazole Amine Hybrids on Inhibition of Human Erythrocytes Carbonic Anhydrase I,II and Acetylcholinesterase

Novel chiral benzimidazole amine hybrids ( 4a – 4d ) were synthesized from commercially available amine [(R)- (+)-phenylethylamine, (−) (S)-(-)-phenylethylamine, (−) (R)-(-)-cyclohexylethylamine, (S)-(+)-cyclohexylethylamine] and 2-(chloromethyl)-N-tosyl-1H-benzimidazole. The synthesized compounds ( 4a – 4d ) were characterized by IR, NMR, and LC/MS analysis. The inhibitory effect of 4a – 4d on human erythrocytes carbonic anhydrase I (hCA-I), II (hCA-II), and acetylcholinesterase (AChE) activity was investigated. For hCA-I, the IC₅₀ values of 4a – 4d were found to be 4.895 μM, 1.750 μM, 0.173 μM, and 0.620 μM, respectively, and for hCA-II, the IC₅₀ values of 4a – 4d were found to be 0.469 μM, 0.380 μM, 0.233 μM, 0.635 μM, respectively. Furthermore, IC₅₀ values of 4a – 4d on AChE were found as 87.5 nM, 100 nM, 26.92 nM, and 100 nM, respectively. In addition, molecular docking analysis was performed to evaluate the affinity of 4a – 4d against hCA-I, hCA-II, and AChE and explain their binding interactions.     

Design,Synthesis, and Evaluation of Chalcone Derivatives as Multifunctional Agents against Alzheimer's Disease

Fifteen chalcone derivatives 3a – 3o were synthesized, and evaluated as multifunctional agents against Alzheimer's disease. In vitro studies revealed that these compounds inhibited self-induced Aβ_1-42 aggregation effectively ranged from 45.9–94.5 % at 20 μM, and acted as potential antioxidants. Their structure-activity relationships were summarized. In particular, (2E)-3-[4-(dimethylamino)phenyl]-1-(pyridin-2-yl)prop-2-en-1-one ( 3g ) exhibited an excellent inhibitory activity of 94.5 % at 20 μM, and it could disassemble the self-induced Aβ_1-42 aggregation fibrils with ratio of 57.1 % at 20 μM concentration. In addition, compound 3g displayed good chelating ability for Cu²⁺, and could effectively inhibit and disaggregate Cu²⁺-induced Aβ aggregation. Moreover, compound 3g exerted low cytotoxicity, significantly reversed Aβ_1-42-induced SH-SY5Y cell damage. More importantly, compound 3g remarkably ameliorated scopolamine-induced memory impairment in mice. In summary, all the results revealed compound 3g was a potential multifunctional agent for AD therapy.     

Four New Stilbene Derivatives Isolated from Gnetum latifolium var. funiculare Markgr. and Their Inhibition of NO Production in LPS-activated RAW264.7 Cells

Gnetum latifolium var. funiculare Markgr. is a medicinal plant and widely distributed in mountainous areas of Vietnam. Phytochemical investigation on the trunks of this plant afforded eight stilbene derivatives ( 1 – 8 ) including for new compounds ( 1 – 4 ). Their structures were determined based on extensive analyses of HR-ESI-MS, 1D and 2D NMR spectra. Among the isolates, compounds 1 – 3 showed moderate NO production inhibition in LPS-activated RAW264.7 cells with the IC₅₀ values ranging from 46.81 to 68.10 μM, compounds 4 and 6 showed weak effects with the IC₅₀ values of 96.57 and 79.46 μM, respectively, compared to that of the positive control compound, dexamethasone (IC₅₀ 14.20 μM).     

Four New Flavonoid C-Glycosides Isolated from Achyranthes aspera and Their Nitric Oxide Production Inhibitory Activities

A chemical study of the methanol extract of the aerial parts of Achyranthes aspera led to the isolation of four new flavonoid C-glycosides ( 1 – 4 ) along with eight known analogs ( 5 – 12 ). Their structures were elucidated by a combination of spectroscopic data analysis, HR-ESI-MS, 1D and 2D NMR spectra. All the isolates were evaluated their NO production inhibitory activity in LPS-activated RAW264.7 cells. Compounds 2 , 4 , and 8 – 11 showed significant inhibition with IC₅₀ values ranging from 25.06 to 45.25 μM, compared to that of the positive control compound, L-NMMA, IC₅₀ value of 32.24 μM, whereas the remaining compounds were weak inhibitory activity with IC₅₀ values over 100 μM. This is the first report of 7 from Amaranthaceae family, and 11 from the genus Achyranthes.     

Elsholblanosides A−D,Four New Oleuropeic Acid Derivatives Isolated from Elsholtzia blanda and Their Inhibition of NO Production in LPS-activated RAW264.7 Cells

Phytochemical investigation on the aerial parts of Elsholtzia blanda Benth. afforded four new oleuropeic acid derivatives ( 1 – 4 ), named as elsholblanosides A−D, respectively, together with 11 known compounds ( 5 – 15 ). Their structures were determined based on extensive analyses of HR-ESI-MS, 1D and 2D NMR, and ECD spectra. Compounds 1 – 4 and 14 showed moderate NO production inhibition in LPS-activated RAW264.7 cells with their IC₅₀ values ranging from 23.2 to 86.33 μM, compared to that of the positive control compound, dexamethasone, IC₅₀ value of 16.9 μM.     

Membrane damage as first and DNA as the secondary target for anti‐candidal activity of antimicrobial peptide P7 derived from cell‐penetrating peptide ppTG20 against Candida albicans

P7, a peptide analogue derived from cell‐penetrating peptide ppTG20, possesses antibacterial and antitumor activities without significant hemolytic activity. In this study, we investigated the antifungal effect of P7 and its anti‐Candida acting mode in Candida albicans. P7 displayed antifungal activity against the reference C. albicans (MIC = 4 μM), Aspergilla niger (MIC = 32 μM), Aspergillus flavus (MIC = 8 μM), and Trichopyton rubrum (MIC = 16 μM). The effect of P7 on the C. albicans cell membrane was examined by investigating the calcein leakage from fungal membrane models made of egg yolk l ‐phosphatidylcholine/ergosterol (10 : 1, w/w) liposomes. P7 showed potent leakage effects against fungal liposomes similar to Melittin‐treated cells. C. albicans protoplast regeneration assay demonstrated that P7 interacted with the C. albicans plasma membrane. Flow cytometry of the plasma membrane potential and integrity of C. albicans showed that P7 caused 60.9 ± 1.8% depolarization of the membrane potential of intact C. albicans cells and caused 58.1 ± 3.2% C. albicans cell membrane damage. Confocal laser scanning microscopy demonstrated that part of FITC‐P7 accumulated in the cytoplasm. DNA retardation analysis was also performed, which showed that P7 interacted with C. albicans genomic DNA after penetrating the cell membrane, completely inhibiting the migration of genomic DNA above the weight ratio (peptide : DNA) of 6. Our results indicated that the plasma membrane was the primary target, and DNA was the secondary intracellular target of the mode of action of P7 against C. albicans. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Phytoconstituents of Selaginella effusa Alston and Their α-Glucosidase as well as Urease Inhibitory Activities

Three new compounds ( 1 – 2 , 14 ), as well as 22 known compounds ( 3 – 13 , 15 – 25 ), were extracted for the first time from the Selaginella effusa Alston (S. effusa). For the unknown compounds, the planar configurations were determined via NMR and by high-resolution mass spectrometry, while their absolute configurations were determined by calculated electronic circular dichroism (ECD), and the configuration of the stereogenic center of biflavones 4 – 5 were established for the first time. The pure compounds ( 1 – 25 ) were tested in vitro to determine the inhibitory activity of the enzyme-catalyzed reactions. Compounds 1 – 9 inhibited α-glucosidase with IC₅₀ values ranging from 0.30±0.02 to 4.65±0.04 μM and kinetic analysis of enzyme inhibition indicated that biflavones 1 – 3 were mixed-type α-glucosidase inhibitors. Compounds 12 – 13 showed excellent inhibitory activity against urease, with compound 12 (IC₅₀=4.38±0.31 μM) showing better inhibitory activity than the positive control drug AHA (IC₅₀13.52±0.61 μM). In addition, molecular docking techniques were used to simulate inhibitor-enzyme binding and to estimate the binding posture of the α-glucosidase and urease catalytic sites.     

Design,Synthesis, Docking Study of Pyrazolohydrazinopyrimidin-4-one Derivatives and Their Application as Antimicrobials

New series of pyrazoles 4a – c and pyrazolopyrimidines 5a – f had been constructed. The newly synthesized compounds were assessed for their antimicrobial activity towards E. coli and P. aeruginosa (gram –ve bacteria), B. subtilis and S. aureus (gram +ve bacteria) and A. flavus and C. albicans (representative of fungi). The pyrazolylpyrimidine-2,4-dione derivative 5b is the most active candidate against B. subtilis (MIC=60 μg/mL) and P. aeruginosa (MIC=45 μg/mL). Regarding antifungal potential, compound 5f was the most effective against A. flavus (MIC=33 μg/mL). Similarly, compound 5c displayed strong antifungal activity towards C. Albicans (MIC=36 μg/mL) in reference to amphotericin B (MIC=60 μg/mL). Finally, the novel compounds had been docked inside dihydropteroate synthase (DHPS) to suggest the binding mode of these compounds.     

Docosahexaenoic acid supplementation of primary rat hippocampal neurons attenuates the neurotoxicity induced by aggregated amyloid beta protein42 and up-regulates cytoskeletal protein expression

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by extracellular deposits of fibrillar aggregates of amyloid-β peptide (Aβ). Levels of docosahexaenoic acid (DHA, 22:6n-3), the major fatty acid component of the neuronal membrane, are reduced in the AD hippocampus. We hypothesized that hippocampal neurons with reduced DHA levels would be more susceptible to aggregated Aβ-induced death and that this might be overcome by increasing hippocampal neuronal DHA levels. Embryonic Day 18 rat hippocampal cells were cultured in neurobasal medium with B27 supplemented with 0–100 μM DHA for 8 days, then were treated with 5 μM aggregated Aβ₄₂ for 1 day. We found that supplementation with 5–10 μM DHA, which resulted in hippocampal neuron DHA levels of 12–16% of total fatty acids, was optimal for primary hippocampal neuronal survival, whereas supplementation with 5 or 25 μM DHA attenuated aggregated Aβ₄₂-induced neurotoxicity and protected hippocampal neurons, with 25 μM DHA being more effective. DHA supplementation also resulted in significant up-regulation of expression of tyrosine tubulin and acetylated tubulin. We suggest that hippocampal neuronal DHA levels may be critical for AD prevention by attenuating the neurotoxicity induced by Aβ and in maintaining hippocampal neuron survival.     

Design,Synthesis, and Antimycobacterial Evaluation of Novel Tetrahydroisoquinoline Hydrazide Analogs

A series of novel 2-substituted-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbohydrazide were designed, synthesized and structures were confirmed by analytical methods, viz., ¹H-NMR, ¹³C-NMR and Mass spectrometry. Synthesized derivatives were evaluated for their anti-mycobacterial activity against Mycobacterium tuberculosis (Mtb) H37Ra. Among all the evaluated compounds, 10A25 containing biphenyl moiety exhibited significant inhibition with IC₅₀ 4.7 μM. 10A19 , with an electron-withdrawing Iodo group in the ortho position of the phenyl exhibited significant anti-tubercular activity with IC₅₀ 8.8 μM. IC₅₀ values of the remaining compounds ranged from 9.2 to 73.6 μM. Molecular docking study of the significantly active compound 10A25 was performed to determine the putative binding position of the test ligand at the active site of the selected target proteins Mycobacterium tuberculosis enoyl reductase (InhA) PDB – 4TZK and peptide deformylase PDB – 3E3U. A suitable single crystal for one of the active compounds, 10A12 , was generated and analysed to further confirm the structure of the compounds.