Synthesis of New Hybrid Derivatives from Metronidazole and Eugenol Analogues as Trypanocidal Agents.

BACKGROUND: The search for new drug compounds is always challenging and there are several different strategies that involve the most varied and creative approaches in medicinal chemistry. One of them is the technique of molecular hybridisation: forming a hybrid compound from two or more pharmacophoric subunits. These hybrids may maintain the characteristics of the original compound and preferably show improvements to its pharmacological action, with reduced side effects and lower toxicity when compared to the original components. This study specifically focuses on synthesising hybrid molecules which demonstrate trypanocidal activity against the epimastigote and trypomastigote forms of Trypanosoma cruzi. METHODS: In this context, this study centres on the synthesis of a novel structural scaffold via molecular hybridisation; by using a triazole species to link a metronidazole unit to a eugenol analogue unit, the objective being to combine their therapeutic properties into a new molecular structure. The resulting hybrid molecules were evaluated against T. cruzi which is responsible for high incidences of trypanosomiasis in tropical countries such as Brazil. RESULTS: The results of this study showed an improvement in the anti-parasitic activity of the hybrid compounds with the best result coming from hybrid compounds [8] and [9], which present an activity similar to the control drug benznidazole. The new compounds, utilising a triazole species as a coupling connector, demonstrated promising results and has highlighted the path for planning similar structural patterns to investigate new compounds. CONCLUSIONS: In summary, we can conclude that the synthesised hybrid compounds demonstrate that using a triazole to link metronidazole with natural phenols, produces hybrid molecules that are promising as a new class of compounds of therapeutic interest for further investigation.

Enzymatic Synthesis of Eugenyl Acetate from Essential Oil of Clove Using Lipases in Liquid Formulation as Biocatalyst.

In this research, eugenyl acetate, a compound with flavoring, antioxidant, and antimicrobial properties, was obtained from essential oil of clove (Syzygium aromaticum) via liquid lipase-mediated acetylation. Clove essential oil was extracted by drag water vapor from dry flower buds and its physic-chemical characteristics were analyzed. For the enzymatic synthesis, an extensive evaluation of reaction parameters was accomplished through employment of distinct reaction temperatures, acetic anhydride to eugenol molar ratios, enzyme loads, and three different lipases (a lyophilized enzyme produced by solid-state fermentation of sunflower seed with Penicillium sumatrense microorganism and other two commercial lipases - Lipozyme TL 100L and CALB L). The product eugenyl acetate was confirmed by 1H-NMR, 13C-NMR Distortionless Enhancement by Polarization Transfer (DEPT 135), and Heteronuclear Multiple Bond Correlation (HMBC). Through optimized conditions (55 °C, acetic anhydride to eugenol molar ratio of 1:1, 10 wt% of Lipozyme TL 100L), 91.80% of conversion after 2 h was achieved to the eugenyl acetate production. With the results obtained, it was possible to conclude that the use of lipases in liquid formulation is a promising alternative for the synthesis of essential esters largely applied on food, cosmetic, and pharmaceutical industries.

New Eugenol Derivatives with Enhanced Insecticidal Activity.

Eugenol, the generic name of 4-allyl-2-methoxyphenol, is the major component of clove essential oil, and has demonstrated relevant biological potential with well-known antimicrobial and antioxidant actions. New O-alkylated eugenol derivatives, bearing a propyl chain with terminals like hydrogen, hydroxyl, ester, chlorine, and carboxylic acid, were synthesized in the present work. These compounds were later subjected to epoxidation conditions to give the corresponding oxiranes. All derivatives were evaluated against their effect upon the viability of insect cell line Sf9 (Spodoptera frugiperda), demonstrating that structural changes elicit marked effects in terms of potency. In addition, the most promising molecules were evaluated for their impact in cell morphology, caspase-like activity, and potential toxicity towards human cells. Some molecules stood out in terms of toxicity towards insect cells, with morphological assessment of treated cells showing chromatin condensation and fragmentation, which are compatible with the occurrence of programmed cell death, later confirmed by evaluation of caspase-like activity. These findings point out the potential use of eugenol derivatives as semisynthetic insecticides from plant natural products.

Photoactivatable Odorants for Chemosensory Research.

The chemosensory system of any animal relies on a vast array of detectors tuned to distinct chemical cues. Odorant receptors and the ion channels of the TRP family are all uniquely expressed in olfactory tissues in a species-specific manner. Great effort has been made to characterize the molecular and pharmacological properties of these proteins. Nevertheless, most of the natural ligands are highly hydrophobic molecules that are not amenable to controlled delivery. We sought to develop photoreleasable, biologically inactive odorants that could be delivered to the target receptor or ion channel and effectively activated by a short light pulse. Chemically distinct ligands eugenol, benzaldehyde, 2-phenethylamine, ethanethiol, butane-1-thiol, and 2,2-dimethylethane-1-thiol were modified by covalently attaching the photoremovable protecting group (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ). The CyHQ derivatives were shown to release the active odorant upon illumination with 365 and 405 nm light. We characterized their bioactivity by measuring activation of recombinant TRPV1 and TRPA1 ion channels expressed in HEK 293 cells and the electroolfactogram (EOG) response from intact mouse olfactory epithelium (OE). Illumination with 405 nm light was sufficient to robustly activate TRP channels within milliseconds of the light pulse. Photoactivation of channels was superior to activation by conventional bath application of the ligands. Photolysis of the CyHQ-protected odorants efficiently activated an EOG response in a dose-dependent manner with kinetics similar to that evoked by the vaporized odorant amyl acetate (AAc). We conclude that CyHQ-based, photoreleasable odorants can be successfully implemented in chemosensory research.

Synthesis of Eugenol Derivatives and Evaluation of their Antifungal Activity Against Fusarium solani f. sp. piperis.

BACKGROUND: Fusarium solani f. sp. piperis is a phytopathogen that causes one of the most destructive diseases in black pepper crops, resulting in significant economic and crop production losses. Consequently, the control of this fungal disease is a matter of current and relevant interest in agriculture. OBJECTIVE: The objective was to synthesize eugenol derivatives with antifungal activity. METHODS: In this study, using bimolecular nucleophilic substitution and click chemistry approaches, four new and three known eugenol derivatives were obtained. The eugenol derivatives were characterized and their antifungal and cytotoxic effects were evaluated. RESULTS: Eugenol derivative 4 (2-(4-allyl-2-methoxyphenoxy)-3-chloronaphthalene-1,4-dione) was the most active against F. solani f. sp. piperis and showed acceptable cytotoxicity. Compound 4 was two-fold more effective than tebuconazole in an antifungal assay and presented similar cytotoxicity in macrophages. The in silico study of ß-glucosidase suggests a potential interaction of 4 with amino acid residues by a cation-π interaction with residue Arg177 followed by a hydrogen bond with Glu596, indicating an important role in the interactions with 4, justifying the antifungal action of this compound. In addition, the cytotoxicity after metabolism was evaluated as a mimic assay with the S9 fraction in HepG2 cells. Compound 4 demonstrated maintenance of cytotoxicity, showing IC50 values of 11.18 ± 0.5 and 9.04 ± 0.2 µg mL-1 without and with the S9 fraction, respectively. In contrast, eugenol (257.9 ± 0.4 and 133.5 ± 0.8 µg mL-1), tebuconazole (34.94 ± 0.2 and 26.76 ± 0.17 µg mL-1) and especially carbendazim (251.0 ± 0.30 and 34.7 ± 0.10 µg mL-1) showed greater cytotoxicity after hepatic biotransformation. CONCLUSION: The results suggest that 4 is a potential candidate for use in the design of new and effective compounds that could control this pathogen.

Synthesis of eugenol derivatives and its anti-inflammatory activity against skin inflammation.

Eugenol is a phytochemical present in aromatic plants has generated considerable interest in the pharmaceutical industries mainly in cosmetics. A series of eugenol esters (ST1-ST7) and chloro eugenol (ST8) have been synthesized. The structures of newly synthesized compounds were confirmed by 1H and 13C NMR and mass spectrometry. In an effort to evaluate the pharmacological activity of eugenol derivatives, we explored its anti-inflammatory potential against skin inflammation using in-vitro and in-vivo bioassay. Synthesized derivatives significantly inhibited the production of pro-inflammatory cytokines against LPS-induced inflammation in macrophages. Among all derivatives, ST8 [Chloroeugenol (6-chloro, 2-methoxy-4-(prop-2-en-1-yl)-phenol)] exhibited most potent anti-inflammatory activity without any cytotoxic effect. We have further evaluated the efficacy and safety in in-vivo condition. ST8 exhibited significant anti-inflammatory activity against TPA-induced skin inflammation without any skin irritation effect on experimental animals. These findings suggested that ST8 may be a useful therapeutic candidate for the treatment of skin inflammation.

Novel eugenol bearing oxypropanolamines: Synthesis, characterization, antibacterial, antidiabetic, and anticholinergic potentials.

Five oxypropanol amine derivatives that four of them are novel have been synthesized with high yields and practical methods. in vitro antibacterial susceptibility of Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus strains to synthesized substances were evaluated with agar well-diffusion method by comparison with commercially available drugs. Most of the bacteria were multidrug resistant. It was concluded that these compounds are much more effective than reference drugs. These eugenol bearing oxypropanolamine derivatives were also effective inhibitors against α-glycosidase, cytosolic carbonic anhydrase I and II isoforms (hCA I and II), and acetylcholinesterase (AChE) enzymes with Ki values in the range of 0.80 ±â€¯0.24-3.52 ±â€¯1.01 µM for hCA I, 1.08 ±â€¯0.15-3.64 ±â€¯0.92 µM for hCA II, 5.18 ±â€¯0.84-12.46 ±â€¯2.08 µM for α-glycosidase, and 11.33 ±â€¯2.83-32.81 ±â€¯9.73 µM for AChE, respectively.

Synthesis and leishmanicidal activity of eugenol derivatives bearing 1,2,3-triazole functionalities.

In this paper, it is described the synthesis and the evaluation of the leishmanicidal activity of twenty-six eugenol derivatives bearing 1,2,3-triazole functionalities. The evaluation of the compounds on promastigotes of Leishmania amazonensis (WHOM/BR/75/Josefa) showed that eugenol derivatives present leishmanicidal activities with varying degrees of effectiveness. The most active compound, namely 4-(3-(4-allyl-2-methoxyphenoxy)propyl)-1-(4-methylbenzyl)-1H-1,2,3-triazole (7k) (IC50 = 7.4 ±â€¯0.8 µmol L-1), also targeted Leishmania parasites inside peritoneal macrophages (IC50 = 1.6 µmol L-1) without interfering with cell viability. The cytotoxicity of 7k against macrophage cells presented IC50 of 211.9 µmol L-1 and the selective index was equal to 132.5. Under similar conditions, compound 7k was more effective than glucantime and pentamidine, two drugs currently in the clinic. In addition, theoretical calculations showed that this compound also presents most physicochemical and pharmacokinetic properties within the ranges expected for orally available drugs. It is believed that eugenol bearing 1,2,3-triazole functionalities may represent a scaffold to be explored toward the development of new agents to treat leishmaniasis.

Eugenol derived immunomodulatory molecules against visceral leishmaniasis.

Visceral leishmaniasis (VL) is a life threatening infectious disease caused by Leishmania donovani. It leads to the severe immune suppression in the host defense system. Higher cytotoxicity, rigorous side effects and lower therapeutic indexes (TI) of current antileishmanial drugs have created a necessity to develop new molecules with better antileishmanial activity and high TI value. In this study, we have synthesized 36 derivatives of eugenol and screened them for their activity against promastigote and amastigote forms of L. donovani. Among the synthesized derivatives, comp.35 showed better antileishmanial activity against extra cellular promastigotes (IC50- 20.13 ± 0.91 µM) and intracellular amastigotes (EC50-4.25 ± 0.26 µM). The TI value (82.24 ± 3.77) was found to improve by 10-13 fold compared to Amphotericin B and Miltefosine respectively. Treatment with comp.35 (5 µg/ml) enhanced the nitric oxide (NO) generation, iNOS2 mRNA expression (∼8 folds increase) and decreased the arginase-1 activity (∼4 folds) in L. donovani infected peritoneal macrophages. Comp.35 had also increased the IL-12 (∼6 folds) and decreased the IL-10 (∼3 folds) mRNA expression and release in vitro. Results of in vivo studies revealed that comp.35 treatment at 25 mg/kg body weight efficiently cleared the hepatic and splenic parasite burden with enhanced Th1 response in L. donovani infected BALB/c mice. Hence, this study clearly represents comp.35, as an immunomodulatory molecule, can induce host protective immune response against visceral leishmaniasis through enhanced NO generation and Th1 response, which are essentials against this deadly disease.

In Vitro Incorporation of Radioiodinated Eugenol on Adenocarcinoma Cell Lines (Caco2, MCF7, and PC3).

Recently, the synthesis of radiolabeled plant origin compounds has been increased due to their high uptake on some cancer cell lines. Eugenol (EUG), a phenolic natural compound in the essential oils of different spices such as Syzygium aromaticum (clove), Pimenta racemosa (bay leaves), and Cinnamomum verum (cinnamon leaf), has been exploited for various medicinal applications. EUG has antiviral, antioxidant, and anti-inflammatory functions and several anticancer properties. The objective of this article is to synthesize radioiodinated (131I) EUG and investigate its effect on Caco2, MCF7, and PC3 adenocarcinoma cell lines. It is observed that radioiodinated EUG would have potential on therapy and imaging due to its notable uptakes in studied cells.

Toxicity of clove essential oil and its ester eugenyl acetate against Artemia salina / Toxicidade do óleo essencial de cravo e seu éster acetato de eugenila contra Artemia salina

Abstract The production of compounds via enzymatic esterification has great scientific and technological interest due to the several inconveniences related to acid catalysis, mainly by these systems do not fit to the concept of “green chemistry”. Besides, natural products as clove oil present compounds with excellent biological potential. Bioactives compounds are often toxic at high doses. The evaluation of lethality in a less complex animal organism can be used to a monitoring simple and rapid, helping the identification of compounds with potential insecticide activity against larvae of insect vector of diseases. In this sense, the toxicity against Artemia salina of clove essential oil and its derivative eugenyl acetate obtained by enzymatic esterification using Novozym 435 as biocatalyst was evaluated. The conversion of eugenyl acetate synthesis was 95.6%. The results about the evaluation of toxicity against the microcrustacean Artemia salina demonstrated that both oil (LC50= 0.5993 µg.mL–1) and ester (LC50= 0.1178 µg.mL–1) presented high toxic potential, being the eugenyl acetate almost 5 times more toxic than clove essential oil. The results reported here shows the potential of employing clove oil and eugenyl acetate in insecticide formulations.

Resumo A produção de compostos via esterificação enzimática possui grande interesse científico e tecnológico devido às inúmeras inconveniências relacionadas com a catálise ácida, principalmente por estes sitemas não se adequarem ao atual termo “tecnologias limpas”. Além disso, produtos naturais como o óleo de cravo, apresentam compostos com excelentes potenciais biológicos. Compostos bioativos são quase sempre tóxicos em altas doses. A avaliação da letalidade em um organismo animal menos complexo pode ser usada para um monitoramento simples e rápido, servindo também para a identificação de compostos com potencial atividade inseticida contra larvas de insetos vetores de doenças. Neste sentido, foi determinada a toxicidade frente a Artemia salina do óleo essencial de cravo e do seu derivado acetato de eugenila obtido por esterificação enzimática com lipase Novozym 435. A conversão da reação de síntese de acetato de eugenila foi de 95,6%. Os resultados referentes à avaliação da toxicidade frente ao microcrustáceo Artemia salina demonstraram que tanto o óleo (LC50= 0,5993 µg.mL–1) quanto o éster (LC50= 0,1178 µg.mL–1) apresentam elevado potencial toxicológico, sendo que o éster apresenta aproximadamente 5 vezes mais toxicidade em relação ao óleo. Estes resultados demonstram o potencial emprego do óleo de cravo e de acetato de eugenila em formulações de inseticidas.

Toxicity of clove essential oil and its ester eugenyl acetate against Artemia salina.

The production of compounds via enzymatic esterification has great scientific and technological interest due to the several inconveniences related to acid catalysis, mainly by these systems do not fit to the concept of "green chemistry". Besides, natural products as clove oil present compounds with excellent biological potential. Bioactives compounds are often toxic at high doses. The evaluation of lethality in a less complex animal organism can be used to a monitoring simple and rapid, helping the identification of compounds with potential insecticide activity against larvae of insect vector of diseases. In this sense, the toxicity against Artemia salina of clove essential oil and its derivative eugenyl acetate obtained by enzymatic esterification using Novozym 435 as biocatalyst was evaluated. The conversion of eugenyl acetate synthesis was 95.6%. The results about the evaluation of toxicity against the microcrustacean Artemia salina demonstrated that both oil (LC50= 0.5993 µg.mL-1) and ester (LC50= 0.1178 µg.mL-1) presented high toxic potential, being the eugenyl acetate almost 5 times more toxic than clove essential oil. The results reported here shows the potential of employing clove oil and eugenyl acetate in insecticide formulations.

Novel eugenol derivatives: Potent acetylcholinesterase and carbonic anhydrase inhibitors.

Eugenol was used as starting material to obtain some phenolic compounds. The synthesis of these phenolic compounds was performed in a two-step procedure. The structures of the formed products (novel eugenol derivatives 1-6) have been determined on the basis of NMR spectroscopy and other spectroscopic methods. The compounds were tested in terms of carbonic anhydrase (CA) inhibition potency. Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes, which catalyse the reaction between carbon dioxide (CO2) and water (H2O), to generate bicarbonate (HCO3-) and protons (H+). CO2, HCO3- and H+ are essential molecules and ions for many important physiologic processes occurring in all living organisms. Acetylcholinesterase (AChE, E.C.3.1.1.7) is found in high concentrations in the red blood cells and brain. Novel eugenol derivatives (1-6) were tested for the inhibition of two cytosolic CA isoforms I, and II (hCA I, and II) and AChE. These compounds demonstrated effective inhibitory profiles with Ki values in ranging of 113.48-738.69nM against hCA I, 92.35-530.81nM against hCA II, and 90.10-379.57nM against AChE, respectively. On the other hand, acetazolamide clinically used as CA inhibitor, shoed Ki value of 594.11nM against hCA I, and 120.68nM against hCA II, respectively. Also, AChE was inhibited by tacrine as an AChE inhibitor at the 71.18nM level.

Synthesis and Antileishmanial Activity of Natural Dehydrodieugenol and Its Mono- and Dimethyl Ethers.

The study of chemistry of naturally occurring compounds and the synthesis of their derivatives is fundamentally important for the development of new drugs. In this work, dehydrodieugenol (DHDE) was obtained through oxidative coupling of eugenol, promoted by an aqueous mixture of potassium ferricyanide (K3 [Fe(CN)6 ]) and NH3  · H2 O. The partial methoxylation of DHDE with MeI and K2 CO3 mainly resulted in the molecular-shaped monomethyl ether (DHDE-1MeO) and its dimethyl ether derivative (DHDE-2MeO). The products from the reactions were characterized by (1) H- and (13) C-NMR spectroscopy. Additionally, these studies have reported the antileishmanial activity of DHDE against Leishmania amazonensis (IC50 value of 42.20 µg ml(-1) ) and shown that partial methoxylation of DHDE results in a significant increase in its antiparasitic activity (IC50 value of 13.68 µg ml(-1) ). Based on in vitro bioassays, DHDE-1MeO has shown the highest leishmanicidal activity in promastigota form. Production by direct one-step synthesis of this monomethoxylated compound can be considered to be a cost-effective and environmentally friendly method with a short reaction time.

Influence of plasma-activated compounds on melanogenesis and tyrosinase activity.

Many organic chemists around the world synthesize medicinal compounds or extract multiple compounds from plants in order to increase the activity and quality of medicines. In this work, we synthesized new eugenol derivatives (ED) and then treated them with an N2 feeding gas atmospheric pressure plasma jet (APPJ) to increase their utility. We studied the tyrosinase-inhibition activity (activity test) and structural changes (circular dichroism) of tyrosinase with ED and plasma activated eugenol derivatives (PAED) in a cell-free environment. Later, we used docking studies to determine the possible interaction sites of ED and PAED compounds with tyrosinase enzyme. Moreover, we studied the possible effect of ED and PAED on melanin synthesis and its mechanism in melanoma (B16F10) cells. Additionally, we investigated the structural changes that occurred in activated ED after plasma treatment using nuclear magnetic resonance (NMR). Hence, this study provides a new perspective on PAED for the field of plasma medicine.

A novel synthesis of isoeugenol, [ring-(U)-(14)C].

A novel method for the preparation of isoeugenol, [ring-(U)-(14)C] is presented. Phenols and phenyl esters substituted in the para position with 1-hydroxyethyl or 1-hydroxypropyl acetate esters when treated with 1,8-diazabicyclo[5.4.0]undec-7-ene in dimethylformamide (DMF) eliminate the alkyl carboxylate function to give the unsaturated compound. The reaction fails with unsubstituted or ether substituted phenyl 1-hydroxyacetate esters.

Synthesis and antimicrobial activity of 6-triazolo-6-deoxy eugenol glucosides.

A new series of 1,2,3-triazole eugenol glucosides were synthesized. The new compound structures were confirmed by MS, (1)H NMR and (13)C NMR. All of the synthesized compounds were screened for antimicrobial and cytotoxic activity. Five compounds exerted significant activity against the Gram-negative bacteria Salmonella typhimurium with low IC50 values (49.73-68.53 µΜ), and seven compounds were active against the Gram-positive bacteria Micrococcus luteus (42.89-210.94 µM). In vitro cytotoxicity on mouse spleen cells was also evaluated. One compound bearing a phenyl substituent at the triazole ring showed good activity against Salmonella typhimurium (49.73 µM) and low toxicity to normal cells (CC50=157.83 µM). Thus, the compounds herein can be considered for further modification for improving their antibacterial activity or obtaining novel antibacterial drug candidates.

Lipozyme TL IM as Catalyst for the Synthesis of Eugenyl Acetate in Solvent-Free Acetylation.

The ability of commercial immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM) to catalyze the acetylation of essential clove oil with acetic anhydride in a solvent-free system was studied, and the antimicrobial activity of the ester formed was evaluated as well. Experimental design based on two variables (eugenol to acetic anhydride molar ratio and temperature) was employed to evaluate the experimental conditions of eugenyl acetate ester production. The maximum conversion yield (92.86 %) was obtained using Lipozyme TL IM (5 wt%, based on the total amount of substrates), with eugenol to acetic anhydride molar ratio of 1:5 at 70 °C. The chemical structure of the eugenyl acetate ester obtained at the optimized condition, and purified, was confirmed by the proton nuclear magnetic resonance ((1)H-NMR) analysis. The antimicrobial activity of eugenyl acetate ester was proven effective on Gram-positive and Gram-negative bacteria, with means of 16.62 and 17.55 mm of inhibition halo.

Synthetic modification of hydroxychavicol by Mannich reaction and alkyne-azide cycloaddition derivatives depicting cytotoxic potential.

Here we report the design, synthesis and lead optimization of hydroxychavicol (1) a high yielding metabolite ubiquitously present in the Piper betel leaves with the significant cytotoxic activity. This is the first report to describe the synthetic strategies of two distinct series of hydroxychavicol by Mannich reaction (2-10) and alkyne-azide cycloaddition (11-20). Furthermore, all the synthesized derivatives along with parent compound were evaluated for their in-vitro cytotoxic and antiproliferative potential in several distinct cancers cell lines. Among all, the Mannich reaction derived molecules 6, 8 and 10 displayed more potent cytotoxic activities with IC50 value in a range from 3 to 9 µM, which were 7-10 fold more potent than 1 against five human cancer cell lines viz. HL-60, Mia PaCa-2, MCF-7, HEP G2 and SK-N-SH. Our results describe an efficient synthetic approach used to evaluate the structure activity relationship of 1 and its derivative in search of potential new anticancer agents.

Occupational asthma and dermatitis induced by eugenol in a cleaner

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