The aphorism was to develop new chemical entities as potential anticancer, anti-inflammatory, and analgesic agents. The Leuckart synthetic pathway was utilized in development of novel series of 2-(substituted phenoxy)-N-(1-phenylethyl)acetamide derivatives. The compounds containing 1-phenylethylamine as basic moiety attached to substituted phenols were assessed for their anticancer activity against MCF-7 (breast cancer), SK-N-SH (neuroblastoma), anti-inflammatory activity, and analgesic activity. These investigations revealed that synthesized products
In the past decade, numerous advances have taken place in the understanding of pathogenesis of cancer and its relationship with inflammation. To date the research work on this ground is substantial, but it still lacks clinical accomplishment, with the existing development facade over the clinical exploitation of drugs with dual acting cyclooxygenase-2 (COX-2) inhibition and antiproliferative potency [
Nowadays no data are available concerning the potential use of anticancer agents as COX/LOX inhibitors. Recent molecular targets for the treatment of cancer are the relation between arachidonic acid (AA) and carcinogenesis because of the regulation of AA by two enzymes, cyclooxygenases (COXs) and lipoxygenases (LOXs). Prostaglandin E2 (PGE2), the main product of COX-2, is found in high concentration in tumor cells [
In the present paper a novel and efficient strategy has been developed to synthesize N-(1-(4-chlorophenyl) ethyl)-2-(substituted phenoxy)acetamide derivatives and 2-(substituted phenoxy)-N-(1-(p-tolyl)ethyl)acetamide derivatives with excellent yields. This synthetic pathway was established by the Leuckart reaction. The Leuckart reaction is a process for the reductive amination of aldehydes and ketones by formamide, ammonium formate, or formic acid with formamide [
The commonly used structures (
These compounds were further biologically evaluated for analgesic activity, and few of them showed activity. For the development of novel anticancer agents with lower toxic effect and higher efficiency, we carried out high throughput screening, which resulted in the discovery of titled compounds. Now, we report structure activity relationships and biological assessment of the titled compounds.
All research chemicals were purchased from CDH (Central Drug House P. Ltd., New Delhi, India) and used as such for the reactions. These were used without further purification. Purification of the synthesized compounds was carried out by the recrystallization with appropriate solvent in case of solids but by distillation in case of liquids. Purity of the compounds and completion of reactions were monitored by thin layer chromatography (TLC) using silica gel G as the stationary phase and mobile phases used were n-hexane : ethyl acetate (1 : 1). Spots were visualized by exposure to iodine vapour. Melting points were determined in open capillaries on Thomas Hoover apparatus and are uncorrected. IR spectra were recorded on a Shimadzu IR-435 spectrophotometer using KBr pellets and 1H-NMR spectra were recorded on a Bruker 400 MHz spectrometer (Bruker Corporation, Massachusetts, USA) instrument using tetramethylsilane (TMS) as an internal standard and DMSO-d6 as a solvent. Mass spectra were recorded on Micromass Q-Tof Micro (Waters Corporation Massachusetts, USA). Chemical shifts are given in parts per million (ppm). The anticancer activity was carried out at Tata Memorial Hospital, Mumbai. The anti-inflammatory and analgesic screenings are carried out at pharmacology laboratory of College of Pharmacy IFTM University, Moradabad. The anti-inflammatory activity was carried out using digital plethysmometer (Orchid Scientific, Maharashtra, India). The analgesic activity was carried out by Eddy hot plate method using analgesiometer (Sanghmeshwar International, Ambala, India). All the animal experiments were approved by Institutional Animal Ethical Committee (IAEC).
This procedure of the Leuckart reaction was used for the preparation of amines from ketones. Ammonium carbonate (215 gm, 4 mols) was placed in a 1 litre three-necked round bottom flask, which was fitted with a thermometer, a dropping funnel, and a bent tube attached for distillation to a short condenser. Formic acid (98%, 109 mL) was taken in the dropping funnel and added dropwise. When the reaction subsided, the mixture was heated slowly until the temperature of the reaction increased to about 165°C. The ketone (1 mol) was added in one lot and the temperature was slowly raised to 180–185°C. Ammonia, water, carbon dioxide, and some of the unreacted ketones distilled over. The distilled ketone was separated and returned to the reaction mixture. The mixture which gradually became homogenous was maintained at 180–185°C for 4-5 hours. When the reaction was complete, the mixture was cooled and stirred thoroughly with twice its volume of water. The aqueous layer was separated and the formyl derivative of the amine (nonaqueous layer) so obtained was refluxed with 100–150 mL of concentrated hydrochloric acid for 2-3 hours. After the hydrolysis, the reaction mixture was cooled and extracted with ether to remove any unreacted ketone. The aqueous solution was made strongly alkaline with 30% sodium hydroxide solution and the separated amine was extracted with ether. The ethereal extract was dried over anhydrous sodium sulphate, and after removal of the solvent, the product distilled under reduced pressure.
An ice-cooled aqueous solution of sodium hydroxide (50 mL, 10%) was taken in two different well-corked conical flasks; then, 0.1 mol of synthesized compounds
Phenoxy acetamide derivatives were prepared by reacting (
Wister albino rats of either gender weighing 140–180 g were obtained. The animals were divided into several groups of five animals each. All the animals were housed under standard ambient environment of temperature (25 ± 2°C) and relative humidity of 50 ± 5%. A 12 : 12 hour light : dark cycle was maintained. All the animals were allowed to have free access to water and standard palletized laboratory animal diet 12 hours prior to pharmacological studies. All the experimental procedures and protocols used in this study were reviewed and approved by the Institutional Animal Ethical Committee (IAEC).
Test samples and the reference drugs were prepared as a suspension in 1% tween 80. Control group received 0.1 mL of tween 80 suspension orally. The second group (reference) received a dose of 50 mg/kg suspension of diclofenac sodium. Test groups were treated with a dose of 100 mg/kg of final synthesized compounds.
The acute toxicity study was carried out according to OECD guidelines [
As per above toxicity test, it was observed that at a highest dose of 1000 mg/kg body weight, animals were found to be safe. But few changes were found in the behavioral reaction like touch response, alertness, and restlessness. Therefore, 1/10th of the highest tolerated dose, that is, 100 mg/kg body weight (b.w.), was chosen for the studies.
Compounds
Carrageenan induced rat paw edema method [
Characterization data of N-(1-(4-chlorophenyl)ethyl)-2-(Substituted phenoxy)acetamide derivatives (
Compound | R | Yield (%) | Melting point* (°C) | Rf value# | Molecular formula |
---|---|---|---|---|---|
|
H | 61.4 | 171–173 | 0.37 | C16H16ClNO2 |
|
4-Br | 58.3 | 154–156 | 0.45 | C16H15BrClNO2 |
|
4-NO2 | 59.1 | 165–167 | 0.41 | C16H15ClN2O4 |
|
4-C-(CH3)3 | 62.7 | 205–207 | 0.50 | C20H24ClNO2 |
|
4-OCH3 | 71.0 | 126–128 | 0.38 | C17H18ClNO3 |
|
H | 67.8 | 154–156 | 0.32 | C17H19NO2 |
|
4-Br | 57.2 | 189–191 | 0.46 | C17H18BrNO2 |
|
4-NO2 | 74.5 | 148–150 | 0.51 | C17H18N2O4 |
|
4-C-(CH3)3 | 65.9 | 172–174 | 0.39 | C21H27NO2 |
|
4-OCH3 | 70.4 | 142–144 | 0.47 | C18H21NO3 |
*Recrystallization with ethanol. #Stationary phase: silica gel; mobile phase: n-hexane : ethyl acetate (1 : 1); iodine vapors as visualizing agent.
The compounds exhibited an important analgesic activity as per Eddy’s hot plate method [
The results of anticancer, anti-inflammatory, and analgesic activities are shown in the Tables
Result of anticancer activity.
Compound | % Control growth | Activity | |
---|---|---|---|
MCF-7 (breast) | SK-N-SH (neuroblastoma) | ||
|
88.9 | 88.2 | Inactive |
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30.5 | 67.6 | Active |
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31.6 | 32.3 | Active |
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54.0 | 72.1 | Inactive |
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88.0 | 95.7 | Inactive |
|
71.9 | 32.1 | Active |
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44.4 | 69.1 | Inactive |
|
70.0 | 71.8 | Inactive |
|
58.3 | 73.1 | Inactive |
|
74.0 | 80.1 | Inactive |
*Active against MCF-7 (breast) cell line.
**Active against SK-N-SH (neuroblastoma) cell line.
***Active against both MCF-7 (breast) and SK-N-SH (neuroblastoma) cell lines.
Growth percentages less than 32 are considered as active.
Result of anti-inflammatory activity.
Compound | Mean changes in paw edema (mL) mean ± SEM | % Inhibition | ||||
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30 min | 2 hr | 4 hr | 30 min | 2 hr | 4 hr | |
Control |
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Diclofenac sodium |
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Result of analgesic activity.
Compound | Reaction time (S) after drug administration (mean ± SEM) | % Inhibition | ||||
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30 min | 60 min | 90 min | 30 min | 60 min | 90 min | |
Control |
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Diclofenac sodium |
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A series of titled derivatives N-(1-(4-chlorophenyl)ethyl)-2-(substituted phenoxy)acetamide
General structure of the synthesized compounds.
Synthesis of N-(1-(4-chlorophenyl)ethyl)-2-(substituted phenoxy)acetamide (
Further IR spectrum of compounds (
All compounds
Graphical representation of (% inhibition) of anti-inflammatory activity.
Graphical representation of % increase in reaction time for analgesic activity.
Compounds
From the comprehensive analysis of the results in current studies, we conclude that synthesized compounds have anticancer, anti-inflammatory, and analgesic activities because of the presence of 1-phenylethylamine as basic ring. In analysis of these observations, we conclude that this series (
By comparing the cytotoxic potency of newly synthesized compounds
After carrying out the anti-inflammatory and analgesic screenings of synthesized compounds, the following conclusions are drawn. (i) Presence of Br and NO2 groups at 4 positions in the phenoxy nucleus contributes towards anti-inflammatory activity. (ii) Presence of tert-butyl and methoxy substituent at 4 positions does not contribute towards anti-inflammatory activity. It is also observed that compound
In the series of ten compounds for activity against MCF-7 (breast) cell line, compounds
Out of ten compounds,
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors are grateful to Professor R. M. Dubey, Vice Chancellor of IFTM University, for providing necessary facilities for this research work.