Design, synthesis, characterization and in vitro and in vivo anti-inflammatory evaluation of novel pyrazole-based chalcones

Figures & data

Figure 1. Structures of some known pyrazole NSAIDs and compound 10i.

Scheme 1. Reagents and conditions: (a) Ac₂O, BF₃.OEt₂, 0 °C -rt, N₂, 3 h; (b) NaOH, EtOH, rt, 24 h.

Scheme 2. Reagents and conditions: (a) CH₃COCl, AlCl₃ (anhydrous), Et₂O, N₂, 0 °C - rt; (b) Me₂SO_4, K₂CO₃, acetone, reflux, 12 h; (c) HCOOEt, NaH, THF, N₂, rt; (d) NH₂NH₂.H₂O, rt; (e) MeI, NaH, DMF, N₂, 0 °C.

Figure 2. HMBC (H to C) and ¹H–¹H COSY correlations.

Figure 3. HMBC spectrum of compound 6 represents correlation between H-13 and 3C.

Figure 4. HMBC spectrum of compound 7 represents correlation between H-13 and 1C.

Table 1. ¹H, ¹³C NMR and 135-DEPT spectral data and ¹H-¹H COSY, HSQC and HMBC correlations in compound 6.

				Correlations
Position	^1H NMR (ppm)	^13C NMR (ppm)	DEPT	COSY	HSQC	HMBC
1	7.55 (1H, d)	137.90	CH	2H	1C	3C
2	6.20 (3H, m)	107.44	CH	1H	2C	3C, 4C
3	–	135.51	C	–	–	–
4	–	100.68	C	–	–	–
5, 9	–	159.32	C	–	–	–
6, 8	6.20 (3H, m)	90.54	CH	–	6C, 8C	4C, 5C, 6C, 7C, 8C, 9C
7	–	162.25	C	–	–	–
10, 12	3.75 (6H, s)	55.74	CH3	–	10C, 12C	5C, 9C
11	3.87 (3H, s)	55.39	CH3	–	11C	7C
13	3.65 (3H, s)	36.65	CH3	–	13C	3C

Table 2. ¹H, ¹³C NMR and 135-DEPT spectral data and ¹H-¹H COSY, HSQC and HMBC correlations in compound 7.

				Correlations
Position	^1H NMR (ppm)	^13C NMR (ppm)	DEPT	COSY	HSQC	HMBC
1	7.41 (1H, d)	130.12	CH	2H	1C	2C, 3C, 13C
2	6.31 (1H, d)	107.82	CH	1H	2C	1C, 3C, 4C
3	–	144.42	C	–	–	–
4	–	104.42	C	–	–	–
5, 9	–	159.38	C	–	–	–
6, 8	6.20 (2H, s)	90.92	CH	–	6C, 8C	4C, 5C, 6C, 7C, 8C, 9C
7	–	161.08	C	–	–	–
10, 12	3.76 (6H, s)	55.92	CH3	–	10C, 12C	5C, 9C
11	3.85 (3H, s)	55.25	CH3	–	11C	7C
13	3.97 (3H, s)	38.94	CH3	–	13C	1C

Table 3. In vitro COX-1 and COX-2 enzyme inhibitory activities of pyrazole containing chalcones (10a–n).

	% inhibition of COX (100 μM)*
Compound	COX-1	COX-2
10a	52.42	35.43
10b	58.31	40.17
10c	37.30	35.96
10d	10.05	39.64
10e	25.53	36.54
10f	48.26	50.59
10g	29.73	38.59
10h	10.41	39.01
10i	41.50	52.27
10j	05.86	18.06
10k	06.50	12.65
10l	40.66	37.01
10m	39.82	19.64
10n	16.29	10.80
Indomethacin	70.07	43.33

*The determination was performed in duplicate for two independent experiments.

Table 4. Anti-inflammatory activity of the target compounds against the carrageenan-induced paw edema in rats with different time intervals.

		Paw volume (ml)
Compound	Dose (mg/kg.p.o.)	1 h	3 h	6 h
Normal group	–	0.40 ± 0.04	0.35 ± 0.04	0.38 ± 0.06
Control	–	0.94 ± 0.05#	1.17 ± 0.1#	1.69 ± 0.08##
Standard*	100	0.84 ± 0.05	0.98 ± 0.07**	0.73 ± 0.05**
10a	100	0.52 ± 0.04	1.40 ± 0.2	1.79 ± 0.3
10b	100	0.51 ± 0.03	1.58 ± 0.3	1.72 ± 0.5
10c	100	0.68 ± 0.2	1.82 ± 0.07	1.92 ± 0.4
10d	100	0.53 ± 0.06	1.42 ± 0.05	1.68 ± 0.1
10e	100	0.86 ± 0.17	1.02 ± 0.03*	1.11 ± 0.1*
10f	100	0.76 ± 0.1	1.05 ± 0.2*	1.12 ± 0.1*
10g	100	0.75 ± 0.2	1.82 ± 0.1	1.98 ± 0.3
10h	100	0.88 ± 0.1	0.98 ± 0.1*	1.19 ± 0.1*
10i	100	0.75 ± 0.04	0.98 ± 0.03*	1.13 ± 0.2*
10j	100	0.68 ± 0.04	1.54 ± 0.03	1.55 ± 0.09

*Standard: Indomethacin, each value is the mean ± SEM for six rats.

#p < 0.05, ##p < 0.01 when compared with normal control group.

**p < 0.01, *p < 0.05 when compared with carrageenan control group.

Table 5. Effects of test compounds on cotton pellet induced granuloma in rats.

Treatment and dose	Weight (mg) Mean ± SEM
(100 mg/kg., p.o.)	Wet	Dry
Vehicle control	256 ± 11.2	153 ± 9.9
Standard^a	148 ± 11.5**	76 ± 4.9**
10e	189 ± 12.1*	91 ± 6.3*
10f	182 ± 8.2*	79 ± 2.3*
10h	190 ± 11.8*	92 ± 4.5*
10i	178 ± 10.8*	88 ± 8.4*

^aStandard: Indomethacin.

**p < 0.01, *p < 0.05 when compared with normal control group.