Synthesis of 2-Substituted Pyrimidines and Evaluation of Its Pharmacological Activities

 

R Murugan*, R Arjunan, M Austin, J Belsen, P Vijin and S Tom

Annamalai University, Annamalai Nagar, Chidambaram (India).

*Corresponding Author E-mail:  muruganpharma@yahoo.co.in

 

ABSTRACT:

It is the continuation of our search for new substituted pyrimidines based on analgesic, CNS depressant sedative and hypnotic activity. A mixture of acetanilide, aromatic aldehyde in ethanol, Sodium hydroxide to give (Compound-I) N-phenyl 3- phenyl-2-propenamide. Compound-I on reaction with ethanol, Sodium hydroxide, urea to give (Compound-II) 6-phenyl amino-4phenyl-2-hydroxy pyrimidine. The compound-I react with Sodium hydroxide, thiourea, ethanol to give (Compound-III) 6-phenyl amino 4-phenyl- 2-mercapto pyrimidine. The synthesized compounds were evaluated for their analgesic and depressant activities compared to Diclofenac and Diazepam as positive control. Detailed synthesis, spectroscopic and toxicity data were studied and reported.

 

KEYWORDS: Pyrimidine Derivatives, Synthesis, Analgesic, Depressant.

 


 

INTRODUCTION:

The biological significance of the pyrimidine derivatives has led us to the synthesis of the substituted pyrimidine1. As pyrimidine is a basic nucleus in DNA and RNA, it has been found to be associated with diverse biological activities. The synthesis of substituted pyrimidine and many detailed reviews have been appeared 2-5.

 

Nitrogen, oxygen, and sulphur containing heterocyclic compounds have received considerable attention due to their wide range of pharmacological activities6-12. Pyrimidine based heterocyclic compounds are potentially bio active molecules and exhibit analgesic13, antihypertensive14, antipyretic15, antiviral16, and anti-inflammatory activities17. These are also associated with nucleic acid, antibiotic, anti malarial and anticancer drugs18. Many of pyrimidine derivatives are reported to possess potential CNS depressant properties19. Hence it was thought of interest to synthesize new derivatives of 2- substituted pyrimidines by simple method and investigate them for pharmacological activities. The structures of newly synthesized compounds have been established by elemental analysis and spectral studies20. In addition they have been screened for analgesic and depressant activities compared to Diclofenac potassium and Diazepam as positive control.

 

MATERIAL AND METHODS:

Melting points were recorded in open capillaries and are uncorrected. The IR spectra (kbr) are recorded on a shimadzu FT-IR spectrometer. Purity of the compounds was checked by TLC. For analgesic studies, adult, healthy albino rats 100-200g were used. For depressant activity studies, mice weighing 20-25g were used. All the animals were maintained under standard conditions and have access to pelleted animal feed and water. The study protocols were approved by the institutional animal ethics committee.

 

Experimental:

Preparation of 3- n-phenyl phenyl-2-propenamide (compound-I)

To a mixture of acetanilide (0.01 mol) and aromatic aldehyde (benzaldehyde) (0.01 mol) in ethanol (20ml) was stirred together for 24 hrs in 10% Sodium hydroxide solution (8ml). It was then diluted with water (100ml) and acidified with Conc.Hcl and the product obtained was filtered, washed with water crystallized from ethanol to give Compound-I

 

Preparation of 6-phenyl amino-4phenyl-2-hydroxy pyrimidine (compound-II)

Compound-I (0.01mol) and urea (0.01mol) in ethanol (50ml) was refluxed for 6 hrs in aqueous Sodium hydroxide solution (0.01mol). The product obtained was filtered washed with water and re crystallized from ethanol.

 

Preparation 6-phenyl amino 4-phenyl- 2-mercapto pyrimidine (compound-III)

Compound -I (0.01mol) and thiourea (0.01mol) in ethanol (50ml) was refluxed for 6 hrs in aqueous Sodium hydroxide solution (0.01mol) into 250 ml water. The product obtained was filtered, washed with water and re crystallized from ethanol.


TABLE-I: Study of analgesic effects in rats by tail immersion method

 

S.

No

Drug

Weight of

the animal

Volume of drug

Basal reaction time after drug administration in  seconds

0 min

5 min

10 min

15 min

30 min

35 min

45 min

 

1

 

Normal saline

120 gms

130 gms

150 gms

1.8 ml

2 ml

2.3 ml

3

4

3

3

4

3

3

4

3

3

4

3

3

4

3

3

4

3

3

4

3

 

2

Diclofenac

Sodium

160 gms

140 gms

140 gms

2.4 ml

2.1 ml

2.1 ml

3

3

3

4

5

4

5

6

5

6

7

7

6

7

7

5

5

6

4

3

4

 

3

Thio urea

Derivative

150 gms

140 gms

140 gms

2.3 ml

2.1 ml

2.1ml

3

3

3

3

3

3

4

3

5

5

4

5

6

5

6

5

5

5

5

4

4

 

4

Urea derivative

150 gms

140 gms

140 gms

2.3 ml

2.1 ml

2.1 ml

3

3

3

3

3

3

3

3

3

3

3

3

5

4

5

5

5

5

4

5

3

TABLE: 2 Study of CNS Depressant Activity in Mice by Actophotometer

Body

Weight

Treatment

Dose

Mg/Kg

Locomotor Activity

Scores in Min % Change in activity =

T-C/C x 100

Average

Before Treatment

After Treatment

24 gm

23 gm

25 gm

 

Diazepam

Std

0.24ml

0.23 ml

0.25 ml

652

502

465

151

196

225

76.85

60.95

51.61

 

63.13%

25gm

24 gm

27 gm

 

Thiourea

Derivative

0.25 ml

0.24 ml

0.27 ml

520

652

530

180

180

225

65.38

72.39

57.54

 

65.10%

24 gm

23gm

27 gm

Urea

Derivative

0.24 ml

0.23 ml

0.27 ml

585

542

576

178

220

195

69.14

59.40

66.14

65.03

 

Scheme of work chat and characterization graph

 


COMPOUND – I


 

COMPOUND – II

 

COMPOUND - III

 

 


Evaluation of analgesic activity:

The analgesic activity was evaluated on albino rats using tail immersion method21. Rats of either sex weighed between 100-200g divided in to four batches, each containing three animals. Batch 1 served as control and received normal saline orally. The second group received 50 micro gm/kg body weight of Diclofenac sodium (0.1%, 5ml) in distilled water orally and served as standard. The group of 3-4 received orally the test compounds 2 and 3 at the dose of 50 micro gm/kg body weights (0.1%, 5 ml). Each group of animal was taken basal reaction time to radiant heat by placing the tip of the tail to 1-3 cm in hot water. The tail withdrawal from the water is taken as the end point. Normally a rat withdraws its tail within 3 – 4 sec. Any animal failing to do so is rejected from the study. The doses are given to the rats and the reaction is observed in 0, 5, 10, 15, 30, 35, 45 minutes after the administration. As the reaction time reaches 10 sec, it is considered as maximum analgesia. The readings are tabulated in TABLE-1.

 

Evaluation of depressant activity:

The central nervous system depressant activity was evaluated on mice by using actophotometer. Mice of either sex weighed between 20-25g divided in to three groups. Each groups containing three animals. Group one received a Dose of 3mg/kg IP {Make a stock solution containing 0.3 mg/ml of the standard drug (Diazepam) and inject 1ml/100g to the body weight of mouse} and administered subcutaneously and served as standard. The group 2-3 is given test compounds 2 and 3 (Dose: 3mg/kg: test solution containing 0.3 mg/ml of the drug and inject 1 ml/100g to body weight of mice) and administered subcutaneously and served as test sample. Animals are weighed and numbered them. Turn on the  Actophotometer equipment (check and make sure that all the photocells are working for accurate recording) and place individually each mouse in the activity cage for 10 min. Note the basal activity score of all the animals. Inject Drug sample (1ml/100gm) and re-test each mouse for activity scores for 10 min. Note the difference in the activity, before and after drug sample. The readings are tabulated in TABLE-2

 

RESULTS AND DISCUSSION:

The structures of newly synthesized compounds were elucidated by IR and elemental analysis and thin layer chromatography. The IR spectrum of compound I exhibited the absorption bands at I.R (KBr) cm1 C=C (1342.36), N-H (1755.1), C-H (2823.59), and C=O (1710.74). Compound 2 exhibited the absorption band at N-H (1755.1), C-H (2291.28), C-O (1764.75), C=N (1726.17), and C=C (1342.36). Compound 3 exhibited the absorption bands at N-H (1755.1), C-H (2291.28), S-H (2559), and C=C (1338.58).

 

Analgesic activity:

In the newly synthesized compounds, both compound II and compound III shows almost equivalent analgesic effect in comparison with the standard drug Diclofenac sodium as per TABLE-1

 

Central nervous system depressant activity:

Both compound-II and compound-III were made to undergo CNS depressant activity by using actophotometer. Both the urea derivative compound-II and thiourea derivative compound-III were found to produce effects slightly greater than the standard drug diazepam.

 

CONCLUSION:

Newly synthesized 2-substituted pyrimidines urea derivative: phenyl amino-4phenyl-2-hydroxy pyrimidine (compound-II) and thio urea derivative preparation: 6-phenyl amino 4-phenyl- 2-mercapto pyrimidine (compound-III) has proven that 2-substituted pyrimidines are essential for analgesic and CNS depressant activities. The above activities are quite interesting and further studies in the molecule are essential.

 

Thus from the above discussion it may be concluded that it is worthwhile to pursue further investigation by manipulating the above novel of 2-substituted pyrimidine derivatives.

 

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Received on 18.08.2009          Modified on 15.10.2009

Accepted on 12.11.2009         © RJPT All right reserved

Research J. Pharm. and Tech. 3(1): Jan. - Mar. 2010; Page 161-164