Identification of acridinyl hydrazides as potent aspartic protease inhibitors

We have identified acridinyl derivatives as potent aspartic protease inhibitors by virtual screening of in-house library of synthetic compounds. Enzyme inhibition experiments showed that both compounds inhibit human cathepsin D and Plasmodium falciparum plasmepsin-II in nanomolar ranges. The IC₅₀ values against cathepsin D and plasmepsin-II of compound-Nar103 were found to be 9.0 ± 2.0 and 4.0 ± 1.0 nM and of compound-Nar110 were 0.5 ± 0.05 and 0.13 ± 0.03 nM, respectively. Ligand docking predicted the binding of acridinyl derivatives at the substrate-binding cleft, where hydrazide part of the inhibitors interact with the S1–S1′ subsite residues including catalytic aspartates. The phenyl ring and acridinyl moiety of the inhibitors were predicted to interact with S2/S3 and S2′/S3′ subsite residues.     

Hydrazides of N-blocked amino acids as sole substrates with unique difunctional behavior under papain catalysis

Hydrazides of five N-acylamino acids have been used alone as substrates for papain catalysis to yield N¹,N²-diacylhydrazines. With the exception of N-(benzyloxycarbonyl)(Z)- -alanine hydrazide, they were very effective as both acylating agents of the enzyme and nucleophiles in attacking the enzyme-substrate intermediate. Although Z- -alanine hydrazide was a minimal acylating agent, it was a satisfactory nucleophile. The most favorable reaction involved Z- -alanine hydrazide in producing N¹,N²-bis(Z- -alanyl)hydrazine. When Z- -alanine hydrazide was the substrate, this same chiral diacylhydrazine was formed along with meso N¹-(Z- -alanyl)-N²-(Z- -alanyl)hydrazine. For the acylation step, the enzyme displayed powerful, essentially stereospecific, bias toward the enantiomer. Once the thioester intermediate was formed, little preference was detected for attack by the enantiomers as nucleophiles. The most direct procedure for synthesis of substrates was conversion of Z-amino acids to their esters by means of dry HCl in an absolute alcohol. Treatment with hydrazine produced the hydrazides in excellent yield.     

New Hydrazides and Hydrazide‐Hydrazones of 2,3‐Dihalogen Substituted Propionic Acids: Synthesis and in vitro Antimicrobial Activity Evaluation

The main aim of this research was the synthesis, spectral identification and in vitro antimicrobial evaluation of new hydrazides and hydrazide‐hydrazones of 2,3‐dihalogen substituted propionic acids. New hydrazides were obtained by the substitution reaction of appropriate ethyl esters of 2,3‐dihalogen substituted propionic acids with hydrazine hydrate. Then obtained hydrazides were subjected to condensation reaction with various aldehydes which yielded with new hydrazide‐hydrazone derivatives. All obtained compounds were identified on the basis of spectral methods (¹H‐NMR, ¹³C‐NMR) and in vitro screened against a panel of bacterial and fungal strains according to EUCAST and CLSI guidelines.     

Synthesis and antioxidant activity evaluations of melatonin-based analogue indole-hydrazide/hydrazone derivatives

Melatonin (MLT) is a hormone synthesized from the pineal gland. It is a direct scavenger of free radicals, which is related to its capability to defend cells from oxidative stress. Recently MLT-related compounds are under investigation to establish which exhibit the maximum activity with the lowest side effects. In this study 5-chloroindole hydrazide/hydrazone derivatives were synthesized from 5-chloroindole-3-carboxaldehyde and phenyl hydrazine derivatives. All the compounds characterized and in vitro antioxidant activity was investigated against MLT and BHT. Most of the compounds showed strong inhibitory effect on the superoxide radical scavenging assay at 1?mM concentration (79 to 95%). Almost all the tested compounds possessed strong scavenging activity against the DPPH radical scavenging activity with IC₅₀ values (2 to 60 µM). Lastly, compound 1j revealed stronger inhibitory activity against MLT in the LP inhibitory assay at 0.1mM concentration (51%) while the rest of the compounds showed moderate inhibition.     

Synthesis and antituberculosis activity of derivatives of <Emphasis Type="Italic">Stevia rebaudiana</Emphasis> glycoside steviolbioside and diterpenoid isosteviol containing hydrazone,hydrazide, and pyridinoyl moieties

Conjugates of the antituberculosis drug isoniazid (isonicotinyl hydrazine) and isomeric hydrazides of nicotinic and α-picolinic acid with glycoside steviolbioside from the Stevia rebaudiana plant and the product of its acid hydrolysis, diterpenoid isosteviol, were synthesized. In addition, isosteviol hydrazide and hydrazone derivatives as well as conjugates containing two isosteviol moieties joined by a dihydrazide linker were obtained. The parental compounds and their synthetic derivatives were found to inhibit the in vitro growth of Mycobacterium tuberculosis (H₃₇R_V). The measured minimal concentrations of stevio-side and steviolbioside, at which the growth of M. tuberculosis was inhibited by 100% (MIC), were 7.5 and 3.8 μg/ml, respectively. MIC values for steviolbioside and isosteviol conjugates with hydrazides of pyridine carbonic acid were within the ranges of 5–10 and 10–20 μg/ml, respectively. The maximal inhibitory effect against M. tuberculosis was shown by the isosteviol conjugates with adipic acid dihydrazide (MIC 1.7 and 3.1 μg/ml). Antituberculosis activities of the tested compounds were higher than the activity of antituberculosis drug Pyrizanamide (MIC 20 μg/ml) but lower than that of antituberculosis drug isoniazid (MIC 0.02–0.04 μg/ml).     

Evaluation of sulphonamide derivatives acting as inhibitors of human carbonic anhydrase isoforms I,II and Mycobacterium tuberculosis β-class enzyme Rv3273

A series of novel sulphonamide derivatives was obtained from sulphanilamide which was N4-alkylated with ethyl bromoacetate followed by reaction with hydrazine hydrate. The hydrazide obtained was further reacted with various aromatic aldehydes. The novel sulphonamides were characterised by infrared, mass spectrometry, ¹H- and ¹³C-NMR and purity was determined by high-performance liquid chromatography (HPLC). Human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I and II and Mycobacterium tuberculosis β-CA encoded by the gene Rv3273 (mtCA 3) inhibition activity was investigated with the synthesised compounds which showed promising inhibition. The K_Is were in the range of 54.6?nM–1.8?µM against hCA I, in the range of 32.1?nM–5.5?µM against hCA II and of 127?nM–2.12?µM against mtCA 3.     

Glyconamides as inhibitors of human beta-glucosidases and beta-galactosidases.

d-Gluconamide, d-gluconyl hydrazide, and N-(6-aminohexyl)-d-gluconamide were prepared from d-glucono-1,5-lactone by treatment with ammonia, hydrazine, and 1,6-diaminohexane, respectively. These d-gluconamide derivatives were tested for their inhibitory action on human liver lysosomal glucocerebrosidase and human spleen neutral aryl β-glucosidase. Analogous d-galactonamide derivatives were evaluated for their inhibition of human spleen galactocerebrosidase and G_M1-ganglioside β-galactosidase. d-Gluconyl hydrazide and d-gluconamide were effective inhibitors of the lysosomal glucocerebrosidase, attaining 50% inhibition at 5 and 12 mm, respectively. In contrast, N-(6-aminohexyl)-d-gluconamide did not inhibit the glucocerebrosidase. d-Gluconyl hydrazide was also the most effective inhibitor of human liver and spleen aryl β-glucosidase, 50% inhibition being achieved at 4 mm concentration (competitive inhibition, K_i = 0.4–0.9 mM). d-Galactonamide was the most effective inhibitor of spleen galactocerebrosidase; 4 mm d-galactonamide caused 50% inhibition of the enzyme activity (noncompetitive inhibition). N-(6-Aminohexyl)-d-galactonamide is a potent inhibitor (90% inhibition, 5 mm) of G_M1-ganglioside β-galactosidase but is without effect on galactocerebrosidase. It has, therefore, the potential usefulness in distinguishing between two of the galactosphingolipid β-galactosidases.     

Evaluation of mutagenicity of the antitubercular naphthylglycine hydrazides insalmonella typhimurium

N-(2-naphthyl)glycine hydrazide and N-methyl-N-(2-naphthyl) glycine hydrazide, which inhibitMycobacterium tuberculosis H₃₇ R_V and show activity against experimental tuberculosis, were evaluated for their mutagenic potential inSalmonella typhimurium. Both the compounds at concentration ranges from 0.1 Μgplate to 1000 Μg/plate failed to induce mutations at the histidine locus either directly or after treatment with rat liver homogenate fraction-“S-9”. N-(2-naphthyl)glycine hydrazide and its N-methyl derivative elicited toxicity at concentrations of 500 Μg/plate and 1000 Μg/plate. However, in the presence of the liver homogenate system, reduction in toxicity was noticed probably due to detoxification and/ or conjugation of the compounds. Under the assay conditions employed, standard mutagens like 4-nitroquinoline-N-oxide, 9-aminoacridine and benzo(a)pyrene were positive. The non-mutagenic nature of N-(2-naphthyl)glycine hydrazide and N-methyl-N-(2-naphthyl)glycine hydrazide should enhance their potential for inclusion in treatment protocols for management of tuberculosis     

Studies on the Metabolism of Aspergilli

It was found that either γ-glutamic hydrazide or hydrazine at an appropriate concentration stimulated the formation of glutamic dehydrogenase as well as transaminases. Addition of l-glutamine partially reduced the stimulating effects of analogues.     

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.     

Synthesis,Biological Evaluation and Molecular Docking of Deferasirox and Substituted 1,2,4‐Triazole Derivatives as Novel Potent Urease Inhibitors: Proposing Repositioning Candidate

A series of new deferasirox derivatives were synthesized through the reaction of monosubstituted hydrazides with 2‐(2‐hydroxyphenyl)‐4H‐benzo[e][1,3]oxazin‐4‐one. For the first time, deferasirox and some of its derivatives were evaluated for their in vitro inhibitory activity against Jack bean urease. The potencies of the members of this class of compounds are higher than that of acetohydroxamic acid. Two compounds, bearing tetrazole and hydrazine derivatives (bioisoester of carboxylate group), represented the most potent urease inhibitory activity with IC₅₀ values of 1.268 and 3.254 μm , respectively. In silico docking studies were performed to delineate possible binding modes of the compounds with the enzyme, urease. Docking analysis suggests that the synthesized compounds were anchored well in the catalytic site and extending to the entrance of binding pocket and thus restrict the mobility of the flap by interacting with its crucial amino acid residues, CME592 and His593. The overall results of urease inhibition have shown that these target compounds can be further optimized and developed as a lead skeleton for the discovery of novel urease inhibitors     

The reticulocyte-mediated release of iron and bicarbonate from transferrin: Effect of metabolic inhibitors

The effect of three groups of metabolic inhibitors on the incorporation of Fe and release of bicarbonate from transferrin by rabbit reticulocytes was measured. Inhibitors which affect reticulocyte Fe and transferrin uptake to the same extent (sodium arsenite, N-ethylmaleimide and iodoacetamide); those which inhibit reticulocyte Fe uptake to a greater extent than transferrin uptake (NaN₃, NaF, NaCN, rotenone, oligomycin, 2,4-dinitrophenol and cycloheximide); and compounds which after reticulocyte heme synthesis (CoCl₂, isonicotinic acid hydrazide and hemin) were used. In each case the effect on Fe incorporation and bicarbonate release was the sameThus, additional evidence has been obtained for the idea that the reticulocyte-mediated release of Fe and bicarbonate from transferrin are tightly coupled. The results are consistent with the hypothesis that an enzymatic attack on transferrin-bound bicarbonate is involved in the removal of Fe from transferrin by erythroid cells.     

Synthesis and PreliminaryIn Vitro Evaluation of Antimycobacterial Activity of New Pyrrolo[1,2-a]quinoxaline-carboxylic Acid Hydrazide Derivatives

New pyrrolo[1,2-a]quinoxaline-2- or -4-carboxylic acid hydrazide derivatives were synthesized from nitroaniline or 1,2-phenylenediamine, and evaluated in vitro for their antimycobacterial activity as part of a TAACF TB screening program. Two compounds 7c and 13 showed an interesting activity at 6.25?μg/mL against Mycobacterium tuberculosis H₃₇Rv, with a 94 and 100 percentage inhibition, respectively.     

Novel benzofuran-based sulphonamides as selective carbonic anhydrases IX and XII inhibitors: synthesis and in vitro biological evaluation

Abstract

Pursuing on our efforts toward searching for efficient hCA IX and hCA XII inhibitors, herein we report the design and synthesis of new sets of benzofuran-based sulphonamides (4a,b, 5a,b, 9a–c, and 10a–d), featuring the zinc anchoring benzenesulfonamide moiety linked to a benzofuran tail via a hydrazine or hydrazide linker. All the target benzofurans were examined for their inhibitory activities toward isoforms hCA I, II, IX, and XII. The target tumour-associated hCA IX and XII isoforms were efficiently inhibited with K _Is spanning in ranges 10.0–97.5 and 10.1–71.8?nM, respectively. Interestingly, arylsulfonehydrazones 9 displayed the best selectivity toward hCA IX and XII over hCA I (SIs: 39.4–250.3 and 26.0–149.9, respectively), and over hCA II (SIs: 19.6–57.1 and 13.0–34.2, respectively). Furthermore, the target benzofurans were assessed for their anti-proliferative activity, according to US-NCI protocol, toward a panel of sixty cancer cell lines. Only benzofurans 5b and 10b possessed selective and moderate growth inhibitory activity toward certain cancer cell lines.     

Microbial transformation of isonicotinic acid hydrazide and isonicotinic acid bySarcina sp

Metabolism of isonicotinic acid and isoniazid bySarcina sp. led to the formation of two metabolites which were characterised as 2-hydroxyisonicotinic acid and citrazinic acid. The blue pigment formed during fermentation was shown to be derived from the auto-oxidation of citrazinic acid. 2-Oxo-glutarate accumulated as the major keto acid when isonicotinic acid or isonicotinic acid hydrazide metabolism was inhibited by 1 mM sodium arsenite. Isonicotinic acid, 2-hydroxy-isonicotinic acid and 2-oxo-glutarate were oxidised by isonicotinic acid hydrazide or isonicotinic acid-grown cells; citrazinic acid was, however, not oxidised. Isoniazid hydrazine hydrolase, isonicotinic acid and 2-hydroxyisonicotinic acid hydroxylases were detected in the cell-free extract ofSarcina sp. grown on isonicotinic acid hydrazide or isonicotinic acid. Communication no. 2427from Central Drug Research Institute, Lucknow.     

Synthesis,biological activities,and molecular docking studies of 2-mercaptobenzimidazole based derivatives

A new series of N-acylhydrazone derivatives of 2-mercaptobenzimidazole (2-MBI) has been synthesized through S-alkylation with 1-bromotetradecane and N-alkylation with ethyl-2-chloroacetate. The resulting ester was synthetically modified through hydrazine hydrate to acyl hydrazide which was condensed with aromatic aldehydes to afford the title N-acylhydrazones (4-17). Chemical structures of the newly synthesized compounds have been confirmed through mass, FT-IR and ¹HNMR techniques. In vitro free radical scavenging and α-glucosidase inhibition activities of the compounds were investigated with reference to the standard ascorbic acid and acarbose, respectively. Amongst the target compounds, 13 showed the highest inhibition in DPPH scavenging assay (IC₅₀ = 131.50 µM) and α-glucosidase inhibition potential (IC₅₀ = 352 µg/ml). We extended our investigations to explore the mechanism of enzyme inhibition and conducted docking analysis by using Molecular Operating Environment (MOE 2016.08). A homology model for α-glucosidase was constructed and validated using Ramachandran plot. Docking studies were also carried out on human intestinal α-glucosidases. In view of the importance of the nucleus involved, the synthesized compounds might find extensive medicinal applications as reported in the literature.     

Metabolism of Maleic Hydrazide in Tea, Camellia sinensis

The results obtained with tea plants treated with ¹⁴C-maleic hydrazide indicate that tea plants can metabolize maleic hydrazide to some extent. According to autoradiographic studies, two radioactive spots were found on X-ray films after exposure and development. Based on two-dimensional paper chromatography, possible ring cleavage, and infrared spectroscopic techniques, the possible metabolic products are lactic acid, succinic acid, maleimide and hydrazine. The biological activity of the metabolic products was tested by utilizing the Avena first internode test. Based on this investigation, it was noted that each radioactive area contained compound(s) that possess(es) some growth promoting properties. However, the results obtained with unknown number one (U₁) indicate that it possesses greater growth-promoting properties than unknown two (U₂). finally, the approximate concentrations of U₁ and U₂ were determined by comparison with known concentrations of IAA and in relation to the amount of growth produced during the 19½-hour period of incubation.     

Fluorometric measurement of furfural and 5-hydroxymethylfurfural

Zine(II) forms highly fluorescent chelates with the aroyl hydrazones of furfural and 5-hydroxymethylfurfural, with the latter being more fluorescent than the former. The choice of aromatic acid hydrazide (aroyl hydrazine) as analytical reagents for furfurals was examined; 4-toluenesulfonic acid hydrazine was the most sensitive reagent examined, giving a uv fluorescence 10 times as sensitive as 4-hydroxygenzoic acid hydrazide (PAHBAH). More convenient visible fluorescence was given by PAHBAH and related compounds, and these are capable of detecting less than 500 pmol 5-hydroxymethylfurfural. The condensation reaction is complete in 30 mm ethanolic hydrochloric acid within 2 min at 60°C, and the stable product forms the fluorescent chelate on mixing with a zinc-diethanolamine solution in ethanol.     

Identification and synthesis of N'-(2-oxoindolin-3-ylidene)hydrazide derivatives against c-Met kinase

A series of N′-(2-oxoindolin-3-ylidene)hydrazide derivatives were identified as moderately potent inhibitors against c-Met kinase by pharmacophore-based virtual screening and chemical synthesis methods. The structure-activity relationship (SAR) at various positions of the scaffold was investigated and its binding mode with c-Met kinase was analyzed by molecular modeling studies. In this study, two potent compounds D2 and D25, with IC₅₀ value at 1.3 μM and 2.2 μM against c-Met kinase respectively, were identified. Finally, based on the clues extracted from this study, future development for the optimization of this scaffold was discussed.     

Synthesis of sulfonamide-containing N-hydroxyindole-2-carboxylates as inhibitors of human lactate dehydrogenase-isoform 5

N-Hydroxyindole-2-carboxylates possessing sulfonamide-substituents at either position 5 or 6 were designed and synthesized. The inhibitory activities of these compounds against isoforms 1 and 5 of human lactate dehydrogenase were analysed, and K_i values of the most efficient inhibitors were determined by standard enzyme kinetic studies. Some of these compounds displayed state-of-the-art inhibitory potencies against isoform 5 (K_i values as low as 5.6 μM) and behaved as competitive inhibitors versus both the substrate and the cofactor.