In search of synthetic chemotherapeutic substances capable of inhibiting, retarding, or reversing the process of multi-stage carcinogenesis, we synthesized a series of novel 5-amino pyrazole derivatives 11(a-h) by a nucleophilic substitution reaction and characterized by 1H nuclear magnetic resonance (NMR), liquid chromatography mass spectrometry (LC/MS), Fourier-transform infrared (FTIR), and elemental analysis. These novel compounds were evaluated for their efficacy in inhibiting Ehrlich ascites tumor [EAT] cells in-vivo. In the present study we designed, synthesized, characterized and investigate the anti-angiogenic effects of these compounds, on Ehrlich ascites tumor [EAT] cells in-vivo. The compounds were subsequently tested for their ability to inhibit neovascularisation in chorio allantoin membrane (CAM) model. From the Structure Activity Relationship (SAR) studies, it reveals that, the substitution at N-terminal in pyrazole ring plays key role in the antitumor and anti-angiogenic effects.
Angiogenesis, a physiological process involving the growth of new blood vessels from pre-existing vessels, contributes to the development and progression of various pathological conditions including tumor growth and metastasis, cardiovascular diseases, inflammatory disease and psoriasis. Down-regulation of angiogenesis has been considered to be advantageous for prevention of neoplastic growth and inflammation. Currently, anti-angiogenic strategies are based on inhibition of endothelial cell proliferation, interference with endothelial cell adhesion and migration, and interference with metalloproteinases [
Many researchers have been trying to screen novel anti-angiogenic principles from various natural products. Tumors can make and release many chemicals that can start angiogenesis. Using a drug that targets only one of these chemicals may not have a large effect on the cancer, but combining drugs that attack different targets may prove to be more useful. Synthetic compounds are used to control the advanced stages of malignancies but most of the compounds exhibit normal tissue toxicity with undesirable side effects and development of drug resistance is the major clinical problem.
Indian System of Medicine has many herbal preparations with versatile medicinal properties. In common with many other low-molecular weight phenolic compounds, vanillin displays antimicrobial and antioxidant properties and hence has the potential for use as a food preservative [
In the future, such drugs may blur the line between anti-angiogenesis drugs and other forms of cancer treatment. Researchers are now looking at many different aspects of anti-angiogenesis drugs. Better understanding of these drugs will probably make them a bigger part of cancer treatment in the future. Hence there is a need to discover novel compounds that selectively kill cancer cells. Recently, attention has been toward the drug derived from plant sources which are non-toxic and accessible to common man. Hence attempts are made to synthesize compounds of natural origin.
Unless otherwise mentioned all the chemicals used in the present study were from Sigma–Aldrich, USA. Melting points were determined using SELCO-650 hot stage melting apparatus and were uncorrected. Infrared (IR) spectra were recorded using a Jasco FTIR-4100 series. Nuclear magnetic resonance (1H NMR and 13C NMR) spectra were recorded on Shimadzu AMX 400-Bruker, 400 MHz spectrometer using CDCl3 as solvent and TMS as internal standard (chemical shift in d ppm). Spin multiples are given as br s (broad singlet), d (doublet), t (triplet) and m (multiplet). Mass and purity were recorded on a LC/ MSD-Trap-XCT. Elemental (CHN) analyses were obtained on Vario EL III Elementar. Silica gel column chromatography was performed using Merck 7734 silica gel (60–120 mesh) and Merck made TLC plates. Substituted (E)-1H-pyrazol-5-amine 11(a-h) derivatives were synthesized by the method summarized in
A solution of 4-hydroxy-3-methoxybenzaldehyde (1) (2.0 g, 6.12 mmol) in N, N-dimethyl formamide (20 mL) was taken, anhydrous potassium carbonate (4.2 g, 30.6 mmol) was added and stirred for 20-30 min and then 5-(bromomethyl)-1, 2, 3-trimethoxybenzene (2) (2.69 g, 13.4 mmol) was added. The reaction mixture was stirred for 6 h at room temperature, and monitored by TLC. Upon completion, the solvent was removed under reduced pressure; residue was taken in water and extracted with ethyl acetate. Finally water wash was given to the organic layer and dried with anhydrous sodium sulphate.
The solvent was evaporated to get crude product which
was purified by column chromatography over silica gel (60–120 mesh) using chloroform: methanol (9:1) as an eluent.
Initially mono boc protected 3-methoxy-benzylidene hydrazine (5) was synthesised by the condensation reaction of 3-methoxy-benzaldehyde (3) (1.0 g, 9.84 mmol) with mono boc protected hydrazine (4) (1.0 g, 15.26 mmol). The subsequent double bond reduction was done by using 10% Pd/c in ethanol yielded mono boc protected 3-methoxybenzyl hydrazine (6). The deprotection of amine group was carried out by using HCl in ether gave free amine compound (7). Finally the key intermediate 5-amino pyrazole (9) by the cyclisation of 3-methoxybenzyl hydrazine salt (7) (1.0 g, 5.36 mmol) and 3-cyclopropyl-3-oxopro-panenitrile (8) (0.85 g, 5.36 mmol) were taken in ethanol, and then sodium ethoxide (1.09 g, 16.0 mmol) was added. The reaction mixture was refluxed for 2–3 h. The progress of the reaction was monitored by TLC.
To the solution of intermediate compound 9 (1 eq) in dichloromethane, triethylamine (3 eq) was added and cooled to 0–5 °C in an ice bath. Respective aryl isothiocyanate 10(a-h) (1 eq) were added at cold condition and stirred at room temperature for 6–7 h. The progress of the reaction was monitored by TLC. Upon completion of reaction water was added to reaction mixture and extracted with ethyl acetate. The organic layer was washed with 10% ammonium chloride solution followed by water wash and dried with anhydrous sodium sulphate. The solvent was evaporated and the crude product obtained was purified by column chromatography over silica gel (60–120 mesh) using hexane: ethyl acetate (8:2) as an eluent. Characterization of novel 5-amino pyrazole