3-Methyl-2-phenyl-1-substituted-indole derivatives as indomethacin analogs: design, synthesis and biological evaluation as potential anti-inflammatory and analgesic agents

Figures & data

Figure 1. Chemical structures of some selective cyclooxygenase-2 (COX-2) inhibitor drugs (1–3) and some traditional non-selective NSAIDs (4–6).

Figure 2. Chemical structures of the traditional NSAID indomethacin (6) and the designed indomethacin analogs 10a–f.

Scheme 1. Reagents and conditions: (a) glacial acetic acid, reflux, 10h; (b) benzoyl chloride, 4-chlorobenzoyl chloride or benzyl chloride, NaH, DMF, RT, overnight.

Table 1. In vitro COX-1 and COX-2 inhibition of compounds 10a–f, and reference drug (indomethacin).

	COX Inhibition (IC50 µM)*
Compounds	COX-1	COX-2	Selectivity index†
10a	10.39 ± 1.36	6.54 ± 1.61	1.58
10b	18.72 ± 1.64	8.21 ± 2.10	2.28
10c	7.78 ± 2.01	8.58 ± 2.14	0.90
10d	32.23 ± 2.36	7.98 ± 1.91	13.65
10e	42.36 ± 2.45	1.65 ± 1.02	25.67
10f	17.65 ± 2.79	2.36 ± 1.58	7.47
Indomethacin	0.63 ± 0.02	11.36 ± 1.6	0.055

*Values are expressed as mean ± SEM (n = 3).

†Selectivity index (COX-1 IC₅₀/COX-2 IC₅₀).

Table 2. Anti-inflammatory activities of compounds 10a–f, and reference drug (indomethacin) in carrageenan-induced rat paw edema assay.

	Anti-inflammatory activity (%)
Compounds	1 h	3 h	6 h
10a	26.9	16.2	21.2
10b	17.3	17.4	15.7
10c	5.8	8.8	6.1
10d	73.1	80.1	78.8
10e	73.5	71.8	71.8
10f	67.9	66.8	57.9
Indomethacin	71.2	86.3	88.4

All test compounds (10a–f, indomethacin) were administered (10 mg/kg) 30 min prior to testing. The anti-inflammatory activity % is expressed according to the following equation:

AI (%) = (V_c − V_t/V_c) × 100, where V_c represents the paw volume of control group of animals and V_t represents the paw volume in drug treated animals.

Figure 3. Analgesic effect of test compounds 10a–f compared to indomethacin using acetic acid-induced writhing in mice. Data represent the mean value ± SD of four mice per group. Statistical comparisons between basal and post-drug values were analyzed for statistical significance using the one-way ANOVA followed by Dunnett’s test and denoted by *p < 0.05, #p < 0.01.

Figure 4. Binding of the most active compounds 10d and e inside COX-2 active site. (A) The proposed binding mode inside the active site of COX-2 resulting from docking, the most important amino acids are shown together with their respective numbers. (B) 2D interaction.

Table 3. Molecular modeling data for compounds 10a–f, indomethacin and valdecoxib during docking in the COX-1 (PDB:ID 4COX) and COX-2 (PDB:ID 2AW1) active sites.

	COX-1				COX-2
Compound	Affinity (kcal/mol)	Distance (in Å) from main residue		Functional group	Affinity (kcal/mol)	Distance (in Å) from main residue		Functional group
10a	−5.5167	2.66	Arg120	–CO	−14.5783	2.70	Asn67	–CO
10b	−9.0055	–	–	–	−11.4647	2.76 3.03	Asn67 Asn62	–CO –CO
10c	−12.1998	–	–	–	−15.6805	–	–	–
10d	−5.6238	2.70	Arg120	–CO	−20.8529	2.90 3.05 2.53	His94 Thr199 Thr199	–SO2 –SO2 –SO2
10e	−5.0689	–	–	–	−20.7351	2.93 2.96 2.83	His94 Thr199 Thr199	–SO2 –SO2 –SO2
10f	−4.7538	–	–	–	−21.7493	3.06 2.90	His94 Thr199	–SO2 –SO2
Indomethacin	−17.0967	2.96 2.76	Tyr385 Arg120	–N –CO	–	–	–	–
Valdecoxib	–	–	–	–	−17.0929	3.28 2.73 2.80	His94 Thr199 Thr199	–NH2 –NH2 –SO2