Design, synthesis and pharmacological evaluation of novel tetrasubstituted thiophene analogues as anti-inflammatory agents

Figures & data

Scheme 1  Synthesis of compounds 4 & 5. Reagents and conditions: a) ammonia (25%), diethylether, 0–15°C, 1 h; b) ArNCS, diethylether, 0°C-r.t, 5 h; c) 4-substitutedphenacyl bromides, acetonitrile, rt; d) KOH, MeOH, r.t, 1 h.

Scheme 2  Synthesis of compounds 8. Reagents and conditions: a) ArCONCS, diethyl ether, 0°C-r.t, 5 h; b) 4-substitutedphenacyl bromides, acetonitrile, r.t.

Table I.  Chemical structures, anti-inflammatory and analgesic activity of tetrasubstituted thiophenes.

				Anti-inflammatory activity^* Carrageenin-induced rat hind paw oedema % protection			Analgesic activity^*^* Acetic acid induced writhing test % inhibition
Compound no.	R1	R2	Ar	10 mg/kg	20 mg/kg	40 mg/kg	10 mg/kg
4a	H	4-NO2	–	12	17	20	–
4b	CH3	4-NO2	–	10	16	21	–
4c	OCH3	4-NO2	–	34	34	37	24
4d	CH3	3-NO2	–	26	26	30	–
4e	OCH3	3-NO2	–	41	36	38	23
4f	CH3	4-Cl	–	49	52	54	35
5a	H	4-NO2	–	19	15	10	–
5b	CH3	4-NO2	–	23	19	18	–
5c	OCH3	4-NO2	–	24	20	17	–
5d	CH3	3-NO2	–	29	25	31	–
5e	OCH3	3-NO2	–	25	28	30	–
5f	CH3	4-Cl	–	63	50	56	51
8a	4-CH3	–		60	55	51	43
8b	4-OCH3	–		77	69	62	65
8c	4-NO2	–		22	30	47	20
8d	3-NO2	–		25	22	32	17
8e	2,4-diCl	–		65	56	50	40
8f	4-OCH3	–		64	60	50	45
8 g	4-NO2	–		32	35	38	21
8 h	3-NO2	–		22	34	36	18
8i	2,4-diCl	–		68	58	50	47

* Oral administration for all test compounds, P < 0.05, Student's t-test versus controls, the standard drugs, (dose and % protection) were: ibuprofen (20 mg/kg, 33%) and mafanamic acid (100 mg/kg, 39%).

** Intra-peritoneal administration for all test compounds, P < 0.05, Student's t-test versus controls, the standard drug, (dose and % protection) was: ibuprofen (10 mg/kg, 60%).

Table II.  Antioxidant activity of tetrasubstituted thiophenes.

	% Scavenging (Mean ± SEM) of triplicates
Compound no.	5 μg/mL	10 μg/mL	15 μg/mL	20 μg/mL	25 μg/mL	30 μg/mL	35 μg/mL	IC50 μg/mL	r^*^*
4c	20.05 ± 0.001*	22.04 ± 0.002*	23.95 ± 0.002*	24.17 ± 0.001*	26.52 ± 0.001*	28.84 ± 0.003*	30.03 ± 0.001*	na	0.98
4e	10.52 ± 0.003*	11.73 ± 0.002*	14.68 ± 0.001*	15.12 ± 0.001*	15.94 ± 0.003*	17.02 ± 0.001*	18.20 ± 0.003*	na	0.95
4f	3.24 ± 0.001*	4.95 ± 0.001*	6.52 ± 0.002*	8.57 ± 0.001*	10.22 ± 0.001*	12.25 ± 0.003*	14.08 ± 0.003*	na	0.99
5f	21.35 ± 0.002*	22.16 ± 0.001*	25.06 ± 0.001*	26.98 ± 0.002*	28.85 ± 0.001*	31.56 ± 0.001*	33.24 ± 0.001*	na	0.99
8a	–	–	–	–	–	–	–	–	–
8b	20.26 ± 0.001*	26.85 ± 0.003*	29.63 ± 0.001*	35.45 ± 0.002*	37.05 ± 0.001*	40.28 ± 0.001*	45.42 ± 0.003*	na	0.98
8c	–	–	–	–	–	–	–	–	–
8d	–	–	–	–	–	–	–	–	–
8e	22.15 ± 0.003*	24.13 ± 0.003*	25.28 ± 0.002*	26.15 ± 0.001*	29.84 ± 0.001*	30.81 ± 0.001*	33.04 ± 0.002*	na	0.97
8f	18.05 ± 0.002*	21.25 ± 0.002*	24.92 ± 0.002*	29.25 ± 0.002*	34.95 ± 0.003*	39.26 ± 0.002*	44.93 ± 0.003*	na	0.99
8g	00.90 ± 0.002*	01.09 ± 0.001*	01.95 ± 0.001*	02.18 ± 0.003*	02.85 ± 0.001*	03.51 ± 0.003*	04.63 ± 0.002*	na	0.94
8h	–	–	–	–	–-	–	–	–	–
8i	12.23 ± 0.002*	14.42 ± 0.001*	17.75 ± 0.001*	19.24 ± 0.001*	22.84 ± 0.003*	25.93 ± 0.002*	29.81 ± 0.003*	na	0.98
Ascorbic acid	03.45 ± 0.001*	13.28 ± 0.003*	28.26 ± 0.001*	38.96 ± 0.002*	42.28 ± 0.001*	55.97 ± 0.001*	69.05 ± 0.001*	00.86	0.97

*P < 0.001 compared to reagent blank. **Regression analysis, IC₅₀ = 50% Inhibitory concentration, na = IC₅₀>35 μg/mL, - showed no scavenging activity.

^†Ascorbic acid tested at 0.1 μg/mL, 0.2 μg/mL, 0.4 μg/mL, 0.6 μg/mL, 0.8 μg/mL, 1.0 μg/mL, 1.2 μg/mL.