Synthesis and Screening of Biphenyl ether derivatives for their Anti-inflammatory and Analgesic activity

 

HG Akkamma^*, BS Vikram^, T Srinivas Rao and D Baggiya Selvi

Karnataka College of Pharmacy, # 33\2, Thirumenahalli, Hegde Nagar Main Road, Yelahanka Hobli, Jakkur Post, Bangalore-560064

ABSTRACT:

Nimesulide (Biphenyl Ether) derivatives were synthesized by four steps, Step-1- Ulmaan ether synthesis, Step-2- Reduction of NO_2, Step-3- Condensation reaction, Step-4- Nitration and evaluated for their anti-inflammatory and analgesic activities.

The compounds have been characterized on the basis of preliminary methods, spectral data and tested for anti- inflammatory activity and compared with standard drug as per the standard drug rat hind paw edema method by using Plethesimograph and analgesic activity by Eddies-hotplate method. Among the derivatives prepared, few showed the moderate activity and few showed decreased activity.

 

 

 

INTRODUCTION:

Nimesulide is a sulfanilide, containing Biphenyl ether moiety and belongs to class of Non steroidal anti inflammatory drugs (NSAIDS) and was one of the first compounds to be known to have cyclo-oxygenase-2 (COX-2) selectivity. However the importance of the cox-2 has gained tremendous value in last few years, especially after the introduction of newer cox-2 inhibitors such as Celecoxib   and Rofecoxib.

 

Nimesulide was originally discovered   and patented in 1974 by Mooreand Harrington and subsequently assigned to M/s Riker² Nimesulide.

 

Traditionally NSAIDS act by blocking the production of a family of chemicals that courses inflammation known as prostaglandins.

 

Two enzymes appear to be crucial for the production of these prostaglandins namely cox-1and cox-2.NSAIDS inhibit both cox-1andcox-2.Unfortunately, these non selective inhibition of both cox-1and cox-2 inhibits prostaglandins involve in some of the house keeping functions of the body such as helping blood to clot and protecting our stomach from ulcers.

 

This non selective inhibition of both cox-1and cox-2 leads to bleeding and stomach ulceration. So cox-2 inhibitor holds the advantage of inhibiting the enzyme involved in inflammation and leaves our physiologic housekeeping functions alone.

 

Motivated by the fore mentioned findings and as a concentration of our ongoing program in the field of biphenyl ether as anti-inflammatory and anti-microbial agents it was designed to synthesize novel series of biphenyl ether derivatives.

 

PROCEDURE FOR THE SYNTHESIS OF NIMESULIDE and ITS DERIVATIVES:-

STEP-1:-

ULMANN ETHER SYNTHESIS:-

Compounds-I (0.03 mole) was made to react  with IIa (0.03mole) in presence of DMF and K₂co_, by refluxing for 8 hrs with continuous stirring, completion of the reaction monitored by the TLC (Hexane: Methylene  chloride, 3:1) where by IIIa is distilled water (235⁰c)

 

STEP-2:-

REDUCTION OF NO₂ GROUP:

0.1 mol of IIIa was treated with iron in presence of ethanol and reflexed for one hour, during reflexing dilute HCl (10ml of 50%w/w in ethanol ) was added slowly drop wise. Then the reaction mixture was cooled and 15%KOH in ethanol was added, filtered and concentrated the mother liquor, cooled in ice and filtered the crystals IVa (44⁰c) and re crystallized from hexane. So formed compound IVa was subjected for sulfonation  with sulfonyl chloride by adding drop wise with heating for about 100^o c for one hour, reaction was mixture by TLC (Hexane: ethyl acetate 9:1) and the reaction mixture was cooled 0^o c and filtered (Va) washed with cold tolune , dried and re crystallized from ethanol.

 

GENERAL PROCEDURE FOR THE SYNTHESIS OF  VIb TO VIe:-

0.2 mol of ortho chloro Nitro benzene was made to react with equal moles of chloro substituted phenols (IIb, IIc) in presence of DMF andK₂CO₃ by  refluxing for 8 hrs with constant stirring, completion of the reaction was mixture  by TLC.(Hexane:Methylene:Chloride,3:1) whereby respective IIIb and IIIc were obtained ,those on reduction with Fe (0.1 mol)   in presence of EtOH, dil. HCL (10ml of 50%w/w in EtOH) added drop wise with stirring for 1 hr, during refluxing after the completion of the reaction, washed with 15% KOH in EtOH (to remove the acid content) then concentrated the mother liquor, cooled in ice to get the compounds IVa-IVc. So obtained amines were dissolved in toluene and equal moles of pyridine and alkyl sulfonyl chlorides were added drop wise with stirring for 1hr.After the completion of reaction, the products Vb and Vc were washed with cold water and then re crystallized from methanol.

 

Finally VIb and VIc were achieved by nitration using HNO₃ / Glacial acetic acid compound Via was characterized on the  basis of MP,IR,NMR.

 

IR spectrum showed the characteristic bonds at 3290,1600,1540,1340and1160 authenticating presence of –NH stretching, -NH bonding,C-NO₂,-C-SO₂and C-O-C-NH groups respectively.

 

The H-NMR showed the signal in the form of singlet near σ3.2 for CH₃ proton s at position 1, another singlet was obtained at about σ 7.8 for –NHCH and doublet at σ8,for CH2-CH,CH₂ CH₂ and at σ7.5 CH₂-CH, CH₂-CH respectively. Singlet at σ7.4 for CH₂-CH, CH₂ – C₂H₅ compounds VIb- VIe were having the same basic moiety or nucleus as that of VIa were also characterized as follows,

IR spectrum showed the characteristic bonds

VIb -NH –strech (3230), NH bending (1600) C-NO₂(1540),C-SO₂ (1350),  C-O-C(1150),C-Cl (680)

VIc-NH -strech(3240),NH-bending(1590),C-NO₂(1510),C-SO₂(1340),C-O-C(1160),C-Cl(680)

VId-NH -strech(3260),NH-bending(1600),C-NO₂(1540),C-SO₂(1340),C-O-C(1155),C-Cl(770)

VIe-NH – strech (3260), NH-bending (1590),C-NO₂ (1540), C-SO₂(1340),C-O-C(1160),C-Cl(720)

 

ANALGESIC ACTIVITY:-

Test for analgesic activity was performed according to the tail flick technique, using the mouse as test animal. Totally 42 animals were used for this study. They were divided into 7 groups. Test compounds (VIa-VIe), Nimesulide and Diclofenac sodium were administered orally at a dose of 15mg/kg as an aqueous suspension (tween80), while the control group was fed with the same volume of tween 80 suspension.

 

The reaction time was recorded at 1, 2, 3 Hrs after the treatment. The %of Analgesic activity was calculated by the formula

%Analgesic Activity = T₂/T₁ x 100

T_1- Reaction time before treatment

T₂-Reaction time after treatment

 

Table no: 1   PHYSICAL DATA OF THE COMPOUNDS.

COMPOUND	MOLECULAR               FORMULA	MP/BP in 0c	% Yield
IIIa	C12H9NO3	B.P- 235	70
IIIb	C12H8 NO3Cl	M.P-46	84
IIIc	C12H8 NO3Cl	M.P-58	72
IVa	C12 H11NO	M.P-44	81
Ivb	C12H10NOSCl	M.P-70	80
Ivc	C12H13NOCl	M.P-93	75
Va	C12H13NO3S	M.P-127	58
Vb	C12H 12NO3SCl	M.P-110	79
Vc	C12H12NO3SCl	M.P-112	70
Via	C13H12N2O5SCl	M.P-145.5-146	82
Vib	C13H11N2O5SCl	M.P-132	81
Vic	C18H13N2O5SCl	M.P-146	90
Vid	C18H13N2O5SCl	B.P-343	89
Vie	C18H13N2O5SCl	B.P-404	55

 

TABLE:2  ANALGESIC ACTIVITY.

COMPOUNDS	1ST HOUR	2ND HOUR	3RD HOUR
CONTROL	5.56 +2.16	3.128 ±1.08	3.84 ±1.21
STANDARD	331.6 ±3.11	260.32 ±1.75	222.12 ±1.70
VIa	311.0 ±1.81	233.48 ±2.32	201.13 ±1.41
VIb	260.22 ±2.5	206.35 ±1.62	141.17 ±3.23
VIc	291.44 ±2.72	224.10 ±3.17	180 ±1.67
VId	303.15 ±2.20	226.61 ±2.20	194.33 ±1.68
VIe	264.11 ±3.12	200.27 ±3.32	161.41 ±1.44

 

Anti-inflammatory activity:-

Anti-inflammatory activity performed by carragennan induced paw oedema test in rats was done by following the procedure of winter et al. The rats were divided into three groups (control, drugs, standard drugs) of six animals each.

 

A freshly prepared suspension of carrageenan (1% in 0.9 % saline), 0.05ml was injected under the plantar aponeurosis of the right hind paw of each rat.

 

The compounds and standard drugs were administered orally to the animals of drug treated groups and std drugs group, respectively 1hr, before the carragenan injection. The paw volume of each rat was measured before1hr and after 3hr of carrageenan treatment with the help of a plethesmometer. The percent of anti inflammatory activity was calculated accordingly to the formula given below as in table.

 

 

 

ANTI- INFLAMMATORY ACTIVITY:-

DRUGS	DOSE (ORAL ROUTE)	%DECREASE IN PAW OEDEMA
Phenobarbitone (std)	50mg/kg	36.90
Nimesulide	50mg/kg	36.25
Via	50mg/kg	26.68
VIb	50mg/kg	27.24
Vic	50mg/kg	25.23
VId	50mg/kg	21.35
VIe	50mg/kg	20.98

 

Percentage inhibition of oedema =  1  - Vt/Vc X 100

Where, V_t and V_C are paw volume of rats of the treated and control group respectively. Results obtained were statically analyzed.

 

RESULT AND DISCUSSION:-

All the tested compounds VIb to VIe exhibited analgesic activity (table2) but none were found to be equipotent to the standard drug only compound Vd show improved potency. It was previously shown that presence of N – methyl group in Nimesulide enhanced the analgesic activity [^..^. CH₃ smaller group than C₆H₅] and one more thing is that introduction of aromatic nucleus increases the stability of the molecule but decreases the activity.

 

All newly synthesized compounds (VIa-VIe) have shown anti-inflammatory activity of varying degree from 12 to36 % and results were shown in table.

 

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Received on 20.10.2009        Modified on 08.12.2009

Accepted on 30.12.2009        © AJRC All right reserved