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Year : 2016 | Volume : 4 | Issue : 3 | Page : 138 - 141  


Original Articles
Screening of Newly Synthesized Benzofuran [3-2, d] Pyrimidine Derivatives for Anti Inflammatory Activity

Somnath Motgi1, S. Manjunath2

1Professor, Department of Pharmacology, Malla Reddy Institute of Medical Sciences, Suraram, Hyderabad, Telangana 2 Professor, Department of Pharmacology, S.N. Medical College, Bagalkot, Karnataka

Corresponding Author

Dr. Somnath Motgi                                                                                                                             Received: 12-08-2015

Email: motgi.somnath9@gmail.com                                                                                              Accepted: 29-01-2016

                                                                                               

Abstract:

Background: Most of the non steroidal anti-inflammatory drugs are not equally effective in all inflammatory conditions especially in chronic conditions like rheumatoid arthritis, osteoarthritis and ankylosing spondylitis. Hence there is a need for newer and safer non steroidal anti-inflammatory drugs directed against cell adhesion molecules are being studied.

Objective: Evaluation of Newly Synthesized Benzofuran [3-2, d] Pyrimidine Derivatives for Anti Inflammatory Activity

Methods: In the present study some of the newer synthetic compounds like fused benzofuran derivatives, were screened primarily for their anti-inflammatory activity. The results obtained with the newer synthetic compounds were compared with that of standard drug Diclofenac sodium.

Results: Leukotrienes thus contribute towards leukocyte emigration. Since the compounds under study were shown to suppress emigration they might be acting by decreasing leukotrienes also. Depending upon these findings the mechanism by which C3 and C1 were acting as anti-inflammatory agents might be summarized as by inhibiting PG release, by inhibiting production of leukotrienes and by suppressing emigration of leucocytes.

Conclusion: The efficacy of C3 as anti-inflammatory agent seems to be almost similar to that of diclofenac sodium.

Key words: Screening, Anti Inflammatory Activity, knowledge

INTRODUCTION:

 

Unquenchable thirst for knowledge prompts the scientist, to search and to achieve something beneficial for the mankind. This is more relevant in the field of medicine, which has resulted in the search and introduction of newer non-steroidal anti-inflammatory drugs with least toxic effects into the therapeutic armamentarium.

The study of mechanism of inflammation and anti-inflammatory agents, accelerated greatly following initial reports of the remarkable clinical effects of cortisone in 1949, and phenyl butazone in 1952. 1 The first symposium in the field of inflammation was held at Augusta, Michigan in 1967.

Inflammation is defined as the reaction of vascularized living tissue to local injury. 2 Inflammatory changes observed due to any cause are vasodilatation, emigration, chemotaxis and phagocytosis in acute inflammation, and in chronic inflammation, infiltration with mononuclear cells, tissue destruction and repair.

Vane and associate (1971) demonstrated that, low concentration of spirit and indomethacin which are not corticosteroids inhibited prostaglandin synthesis. Aspirin was introduced in 1899, which has analgesic antipyretic and anti-inflammatory actions.

For an ideal anti-inflammatory drug, the criteria to be fulfilled are:

  • Should possess potent anti-inflammatory properties.
  • Should have mild to moderate analgesic and antipyretic action.
  • Should be free from severe toxic effects, if used for prolonged period.
  • Should be non-addicting.

Most of the non-steroidal anti-inflammatory drugs are not equally effective in all inflammatory conditions especially in chronic conditions like rheumatoid arthritis, osteoarthritis and ankylosing spondylitis. Hence there is a need for newer and safer non-steroidal anti-inflammatory drugs directed against cell adhesion molecules are being studied. 3 Several benzofurans were known to possess anti-inflammatory activity. 4, 5, 6

Hence these compounds mentioned below are further subjected to the evaluation of their anti-inflammatory activity in the present work.

  1. 2-Benzyl-4-piperidinobenzofuro [3-2, d] pyrimidine.
  2. 3-Ethyl-4-pipperinobebzofuro [3-2, d] pyrimidine.
  3. 2-Benzyl-4-morpholinobenzofuro [3-2, d] pyrimidine.

The object and scope of present investigation is primarily to get familiar with the concerned available literature in relation to anti-inflammatory drugs, with a view to learn and stabilize, at least some of the techniques of experimental methods used for their screening and to become familiar with research methodology in general and with the drug evaluation for anti-inflammatory activity, in particular.

MATERIAL AND METHODS

 

In the present study some of the newer synthetic compounds like fused benzofuran derivatives, were screened primarily for their anti-inflammatory activity. The results obtained with the newer synthetic compounds were compared with that of standard drug Diclofenac sodium.

MATERIALS:

Diclofenac Sodium (D):

It is an arylacetic acid derivative. The efficacy of diclofenac sodium as an analgesic, antipyretic and anti-inflammatory agent is similar to Ibuprofen. Diclofenac sodium is a white or slightly yellowish crystalline powder, slightly hygroscopic and sparingly soluble in water but soluble in alcohol and freely soluble in methyl alcohol.

Benzofuran Derivatives:

The three new fused benzofuran, derivatives, synthesized in the department of Chemistry, Gulbarga University, Gulbarga are used in the present work to screen for the presence or absence of anti-inflammatory activity. The chemistry of these compounds is given in the following pages.

Nature of the Compounds

Compound 1(C1) is pale yellow plates which is insoluble in water and partially soluble in ethanol.

Compound 2 (C2): it is colorless needles insoluble in water and partially soluble in ethanol and

Compound 3 (C3): it is colorless silky needles insoluble in water and partially soluble in aqueous ethanol.

Acute toxicity study was carried out in mice with test compounds to find out the tolerant dose. Thus the dose of the compounds up to 400 mg / Kg body wt. was found to be tolerant. In the present study the maximum dose used was 300 mg/kg.

Scarcity of the compounds provided did not allow scope for further increase in the dose.

A pilot study employing rat paw edema method, suggested the presence of anti-inflammatory activity in all three compounds C1, C2 and C3. Hence detailed study with these compounds employing rat paw edema was carried out further. The results of the experiment extending beyond 4 hours did not differ significantly from the results obtained at the end of 3 hours. Hence in the present study the final observations were made at the end of 3 hours. 11

The method employed to study rat hind paw edema is based on plethysmographic measurement of edema. This apparatus was introduced by Wilhelmi and Domenjoz (1951) and latter modified by Sisodia and Rao (1966).

The apparatus (Plate I) consists of a vertically placed cylindrical glass tube A, (8 cm in length and 14 mm inside diameter), is attached to another vertical glass tube B (inside diameter 3 mm) by means of horizontal glass tube C (inside diameter 3 mm) to give identical levels of mercury in A and B. the A, B and c are connected to a graduated pipette D (2 ml capacity with 200 equal divisions of 0.01 ml each) by means of pressure tubing. The etched lines are present around tube A and tube B at a distance of 10 mm from the top. The top of the graduated pipette D was connected to an ‘h’ shaped glass tube E, the vertical end of which is provided with a stop cock F, and the other end was connected through pressure tubing to a glass tube G, containing stop cock H. the glass tube G is further connected at other end, to a 20ml syringe I by means of pressure tubing. Mercury is filled into the plethysmograph and levels are adjusted in such a way that the upper meniscus at the etched lines in glass tubes a and B and at the zero mark in D are in the same line.

Leukocyte emigrations in Rat paw edema:

Leukocyte emigration study was also undertaken to see the effects of test compound 3 (C3) in carrageenin induced rat paw edema. The albino rats (Wister Strain) of either sex, weighing between 100-150 gm are used. In total 15 rats are used, which are divided into 3 groups, 5 in each. The second group (normal) is not treated with oral compound or carrageenin. The second (control), and the third group (test) received 4% gum acacia and compound 3 (C3) 100 mg/kg body weight in 4% gum acacia suspension by mouth, respectively. 1 hour after oral feeding, the animals of control and test group are anaesthetized with ether and 0.1 later skin of the plantar region from the normal, control and the test groups of rats are excised aseptically under ether anesthesia and the animals are sacrificed. The whole excised tissue is preserved in 5% formalin for histopathological study to find out leucocytes emigration and suppression.

The results obtained in the different experimental models were subjected to statistical analysis. Standard deviation (S.D), Standard error (S.E), and p values were calculated by using appropriate formulae.

 

RESULTS

 

Results of Test compound in Grinded doses all compounds given orally in % Gumacacia Suspension:

Table 1:- 

Drugs

Diclofenac sodium (D) mg/kg

Test compound I (C1) mg/kg

Dose

4.50

100

200

300

% inhibition of edema at the end of 3 hour

59%

41.2%

46.4%

54.8%

Mean

0.14

0.20

0.18

0.15

SD

0.02

0.02

0.02

0.08

SE

0.01

0.01

0.01

0.03

P value

< 0.001

< 0.01

> 0.05

> 0.10

 

 

 

 Table 2:-

Drugs

Diclofenac sodium (D) mg/kg

Test compound II (C2) mg/kg

Dose

4.50

100

200

300

% inhibition of edema at the end of 3 hour

59%

17.6%

24%

29%

Mean

0.14

0.28

0.26

0.24

SD

0.02

0.04

0.04

0.07

SE

0.01

0.02

0.02

0.02

P value

< 0.001

< 0.001

< 0.02

< 0.001

 

Table 3:-

Drugs

Diclofenac sodium (D) mg/kg

Test compound III (C3) mg/kg

Dose

4.50

100

200

300

% inhibition of edema at the end of 3 hour

59%

44.1%

53.6%

55.3%

Mean

0.14

0.19

0.16

0.15

SD

0.02

0.04

0.05

0.01

SE

0.01

0.02

0.02

0.004

P value

< 0.001

> 0.05

> 0.10

< 0.05

 

DISCUSSION:

 

Several non-steroidal anti-inflammatory drugs are in use to treat number of acute and chronic inflammatory diseases, but many of them do not fulfill all the criteria laid down for an ideal anti-inflammatory drug. So the need of the time is to synthesize more potent well tolerated and least toxic non-steroidal anti-inflammatory drug which is effective in both acute and chronic inflammatory conditions. Hence any chemical or natural product with a potential to reduce inflammation has to be taken seriously. Many benzofurans and its analogues are known to possess anti-inflammatory activity. 5, 7, 8 In the present study such fused benzofuran [3-2, d] pyrimidine compounds obtained from the department of Chemistry, Gulbarga University, Gulbarga, are used.

Inflammation is the protective response to injurious stimuli. Several mediators like histamine, 5 HT, kinins and prostaglandins and events like increased vascular permeability and emigration of leucocytes, take place during the process of inflammation.

Known steroidal and non-steroidal agents exert their anti-inflammatory effect by inhibiting one or more of these mediators and preventing the corresponding vascular and cellular events at one stage or the other. All these mechanisms have already been dealt with in detail in the review of literature.

Many benzofurans and their analogues are known to possess anti-inflammatory activity. 5, 4, 6 It has been reported that some of the benzofurans decrease the adherence of neutrophils to activated endothelial cells by inhibiting the up gradation of the adhesion molecules E-selection and ICAM-1 on the surface of the endothelium. 9 One of the pyrimidine analogues 1, 4, dihydro-1-ehtyl-phenylpyrol (1, 2-a)-pyrimidine-4-one (V33) which possess anti-inflammatory activity has been shown to decrease the production of leukotriene B4 (LTB4) from inflammatory exudates without affecting PGE.2 10

Another pyrimidine analogue thiazole [3-2, a] pyrimidiness has shown considerable reduction in carrageenin induced rat paw edema. 11

In the light of these findings the mechanism by which benzofuran [3-2, d] pyrimidine analogues compound 3 (C3) and compound 1 (C1) act as anti-inflammatory agents can be elucidated thus.

Prostaglandin release was known to be closely associated with emigration of leucocytes into the inflamed site. 12 Since volume of edema was measured at the end of 3 hours which coincides with prostaglandin release, the compounds under study C3 and C1 might be acting at this stage by inhibiting prostaglandin release which in turn might be inhibiting consequent leukocyte emigration. This hypothesis can be supported by the report wherein the collagen induced platelet aggregation was inhibited by benzofuran [3-2., d] pyrimidine analogues. 13 These compounds have also shown to inhibit thrombus formation which is the consequence of platelet aggregation. One more important factor to be considered is the phlogiston agent used in the acute study i.e. carrageenin. Following carrageenin injection maximum edema occurred at 3 hours, when levels of polymorphonuclear leucocytes (PMNs) in the rat hind paw were markedly elevated. 14 In the study with benzofuran [3-2, d] pyrimidine analogues, volume of edema was measured at the end of 3 hours, which coincided with the period of raise in number of PMNS. Leukocyte emigration study carried out revealed very few inflammatory cells in the exudates obtained from rats treated with the compound 3(C3) (Plate -3). This indicates that C3 might be having an inhibitory effect on PMNs emigration and thus inhibiting inflammation.

The role of LTB4 is worth mentioning. It was shown to promote adhesion of neutrophils to vascular endothelial cells. Application of LTB4 to skin promoted the local accumulation of neutrophils. 15 It was also detected in the inflammatory exudates from carrageenin sponges implanted in rats. 16 They are also known to increase vascular permeability. Thus they play an important role as mediators of inflammation.

Leukotrienes thus contribute towards leukocyte emigration. Since the compounds under study were shown to suppress emigration they might be acting by decreasing leukotrienes also. Depending upon these findings the mechanism by which C3 and C1 were acting as anti-inflammatory agents might be summarized as by inhibiting PG release, by inhibiting production of leukotrienes and by suppressing emigration of leucocytes.                         

 

CONCLUSION:

The efficacy of C3 as anti-inflammatory agent seems to be almost similar to that of diclofenac sodium. Potency of C1 as an anti-inflammatory agent seems to be lesser than that of C3 on dose basis. Compound 2 (C3) seems to be least effective as anti-inflammatory agent. Further pharmacological studies are required to throw light on the therapeutic potential of these synthetic compounds.

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  2. Cotran RS, Kumar V, Robbins SL. Inflammation and repair of disease. In: Robbins SC, Kotran RS, Kumar V, editors. Robbins Pathologic basis of disease, 4th Philadelphia, Saunders;1989.p. 39-89.
  3. Kavanaugh AF, Davis LS, Nicholas LA. Treatment of refractory rheumatoid arthritis with a monoclonal antibody to intercellular adhesion molecule 1. Arthritis Rheum 1994;37(7):992-9.
  4. Saxena PN, Beg MMA, Singhal KC et al. Prostaglandin like activity in the cerebrospinal fluid of febrile patients. Indian J Med Res 1979;70:495-8.
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  8. Connicola M, Donnoli D, Stella L. Research on heterocyclic compounds, Anti-inflammatory activity of some immidazo (1, 2-C) pyrimidine derivatives. Pharmacol Res 1990;22,Suppl 3:80-1.
  9. Boschelli DH, Karmer JB, Khatana SS et al. Inhibition of E-Selection, ICAM-1 and VCAM-1 mediated cell adhesion by Benzo[b], thiophene-benzofuran-indole- naphthalene-2-carboxamides identification of P.D, 144795 as anti-inflammatory agent. J Med Chem 1995;38(22):4597-614.
  10. Evangelista S, Pirisino R, Pierretti F et al. A pharmacological properties 1, 4-dihydro-1-ethyl-7-phenylpyroll [1, 2-a] - pyrimidine-4-one (V 33). Drugs Exp Clinic Res 1987;13(8):5018.
  11. Passorotti CM, Valenti M, Marini M. In search for new anti-inflammatory drugs, synthesis and anti-inflammatory activity of some Thiazolo [3-2, a] pyrimidine derivatives. Boll Chim Farm 1995;134:639-43.
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