Synthesis and Pharmacological Evaluation of Some Phenylpyrazolo Indoquinoxaline Derivatives

Indoloquinoxalin was fused with 2,3 diphenyl quinoxaline by a methylene bridge which was then allowed for acetylation. The acetylated product was made to react with different aromatic aldehydes to give chalcones. Chalcones refluxed with substituted acid hydrazides to afford different indoloquinoxaline pyrazolines. The structure of chalcones and indoloquinoxaline pyrazolines were confirmed by M.P, TLC and spectral data. All the synthesized compounds were screened for their antioxidant, antiinflammatory and antihistamic activities.


Introduction
Quinoxaline derivatives have been reported to possess a wide variety of biological activities [1][2][3] .Notable among these are antioxidant, anti-inflammatory antimicrobial, anticancer and antihistamic activities.Drugs having pyrazoline ring system [4][5][6] are well known for their anti-inflammatory, antioxidant, antihistamic, antimicrobial, antidepressant, hypoglycemic, hypotensive, anticarcinogenic activities etc.In view of the above facts, we report here in the synthesis of some indoloquinaxoline pyrazoline derivatives by condensing indoloquinoxaline chalcones with different aromatic acid hydrazides.All the synthesized compounds (IQVI 1-IQVI 15) were screened for their antioxidant, anti-inflammatory and antihistamic activities.The structure of chalcones and indoloqunoxaline pyrazolines were confirmed by M.P, TLC, Spectral data (Table 1 & 2).

Experimental
The melting point of the compounds was determined on a Thoshniwal electric melting point apparatus and the values were uncorrected.I.R spectra of the compounds were recorded on a Thermo Nicolet Nexus 670-FTIR, IICT, Hyderabad using KBr disc method. 1 H NMR spectra were recorded on Avance-300, IICT, Hyderabad using CDCl 3 as solvent.Mass spectra were recorded on GCMS-Auto tuning-EI at IICT, Hyderabad.All the solvents used were of analytical grade.

General procedure for
and chloro acetone (0.01 M) were taken into 250 mL round bottom flask.150 mL of dry acetone and 30 g of anhydrous potassium carbonate was added to it and the reaction mixture was refluxed for 6 h at 75 o C. Filtrate obtained was concentrated under vacuum.The purity of the compound (IQ IV) was checked by TLC and melting point.

Pharmacological evaluation
Antioxidant activity 11
Reaction mixture was allowed for 20 min.UV absorbance was measured at 517 nm.The percentage of scavenging has been calculated by the equation given below.Ascorbic acid was used as standard drug (Table 3).

Carrageenan induced rat hind paw edema method
The method of Winter et al. 12 was used with modification.The apparatus used for the measurement of rat paw volume was phlethismograph.The animals were divided into eight groups of six animals each.One group served as a standard (Ibuprofen) and another group served as control (1% CMC) and rest of the groups were used for the test drugs.Food was withdrawn overnight with adequate water before the experiment.The drugs were given orally.After 1 h, a sub plantar injection of 0.05 mL of 1% carrageenan was administered.The volume of the injected paw was measured with a plethysmograph immediately.The paw volume was again measured after 3 h.The average paw volume in a group of drug treated rats was compared with that of a group with vehicle (control group) and the percentage inhibition of oedema was calculated using the formula (Table 4).
% Inhibition = (1-Vt / Vc) x 100 Vt = Mean volume of the test drug, Vc = Mean volume of the control.Anti-histaminic activity 13

Histamine chamber method
In this method thirty two healthy adult guinea pigs of either sex divided into 8 group of 2 animals each weighing around 400 g, fasted overnight, were kept in histamine chamber and exposed to histamine aerosol (0.5% aqueous solution of histamine acid phosphate in a Nebulizer) until they collapse.Those that collapse within 2 minutes were revived with fresh air and used for this test.Twelve hours later, the animals were given an oral dose of test compound suspended in 1% acacia solution and after 1 h for absorption, the guinea pigs were again exposed to the same concentration of histamine aerosol.Those that do not collapse within 6 minutes are deemed protected.Percentage protection has been measured by calculating the time of onset of convulsions (Table 5).

Conclusion
Indoquinoxaline and diphenylquinoxaline both these quinoxalines were connected with methylene bridge, which is then allowed for acetylation.The acetylated product (IQ IV) is made to react with different aromatic aldehydes to give chalcones (IQV 1-IQV 5).

Table 1 .
Physical data of phenylpyrazolo indoloquinoxaline derivatives

Table 3 .
Antioxidant activity of phenylpyrazolo indoloquinoxaline derivativesOne-way ANOVA followed by Dunnett's post HOC test; The numbers given in the brackets were the % scavenging.