Synthesis, antitumour activities and molecular docking of thiocarboxylic acid ester-based NSAID scaffolds: COX-2 inhibition and mechanistic studies

Figures & data

Figure 1. Reported NSAIDs and celecoxib as anticancer agents (A-E) and the designed compounds.

Scheme 1. Synthesis of the designed thiocarboxylic acid esters of NSAIDs.

Table 1. In vitro antitumor activity of 5-fluorouracil, afatinib, celecoxib, and the tested compounds.

Compd No.	IC50 (μM)^a
	HepG2^b	MCF-7^c	HCT-116^d	Caco-2^e
5-FU	7.91 ± 0.28	5.43 ± 0.20	5.32 ± 0.17	6.85 ± 0.34
Afatinib	5.4 ± 0.25	7.1 ± 0.49	6.2 ± 0.67	7.7 ± 0.57
Celecoxib	25.6 ± 2.3	31.28 ± 2.5	29.54 ± 2.1	42.74 ± 3.1
1a	85.12 ± 4.53	80.41 ± 4.58	89.63 ± 4.68	94.83 ± 4.92
1b	>100	>100	97.56 ± 5.12	>100
2a	59.83 ± 3.55	48.11 ± 3.15	61.29 ± 3.97	72.19 ± 4.06
2b	9.36 ± 0.79	11.86 ± 1.13	18.71 ± 1.50	21.73 ± 1.90
3a	68.75 ± 3.87	63.61 ± 3.62	78.11 ± 4.08	76.52 ± 4.38
3b	10.52 ± 0.98	13.73 ± 1.19	23.76 ± 1.80	26.81 ± 2.17
4a	71.08 ± 4.11	73.65 ± 3.92	85.40 ± 4.57	80.20 ± 4.50
4b	63.62 ± 3.91	46.52 ± 2.84	76.54 ± 4.22	68.75 ± 3.79
5a	36.75 ± 2.70	42.61 ± 2.67	51.17 ± 3.71	63.78 ± 3.58
5b	19.74 ± 1.57	28.90 ± 1.58	39.52 ± 2.61	35.60 ± 2.62
6a	26.76 ± 2.08	6.11 ± 0.31	46.92 ± 3.23	10.16 ± 0.92
6b	>100	95.26 ± 4.96	91.22 ± 4.96	>100
7a	7.86 ± 0.39	9.65 ± 0.96	14.58 ± 1.24	18.13 ± 1.73
7b	14.91 ± 1.38	17.10 ± 1.40	34.05 ± 2.25	29.14 ± 2.45
8a	7.35 ± 0.34	8.62 ± 0.72	9.73 ± 0.85	15.44 ± 1.37
8b	22.30 ± 1.96	34.09 ± 2.07	46.71 ± 2.93	43.79 ± 2.96

^aIC₅₀, compound concentration required to inhibit tumour cell proliferation by 50% (mean ± SD), n = 3.

^bHuman hepato-cellular carcinoma cell line (HepG2).

^cHuman breast adenocarcinoma cell line (MCF-7).

^dHuman colon cancer cell line (HCT-116).

^eHuman colorectal cancer cell line (Caco-2).

IC₅₀, (μM): 1–10 (very strong), 11–25 (strong), 26–50 (moderate), 51–100 (weak), above 100 (non-cytotoxic).

5-FU: 5-Fluorouracil.

Table 2. In vitro COX-1/COX-2 enzyme inhibition assay.

Compd No.	IC50 (μM)^a		SI^b
	COX-1	COX-2
Celecoxib	>50	0.16 ± 0.011	>312.5
2b	>50	0.66 ± 0.052	>75.8
3b	>50	0.69 ± 0.057	>72.5
6a	>50	0.25 ± 0.017	>200.0
7a	>50	0.22 ± 0.019	>227.3
7b	>50	0.49 ± 0.044	>102.0
8a	>50	0.20 ± 0.016	>250.0
8b	>50	0.60 ± 0.055	>83.3

^aIC₅₀ value is the compound concentration required to produce a 50% inhibition of COX-1 or COX-2, calculated as the mean of two determinations using the ovine COX-1/COX-2 assay kit (catalog no. 560101, Cayman Chemicals Inc., USA); the deviation from the mean is <10% of the mean value.

^bSelectivity index (COX-1 IC₅₀/COX-2 IC₅₀).

Table 3. % inhibitory effect of the compounds on kinase activities.

Compd No.	% inhibition of 10 μM
	EGFR	HER2	HER4	cSrc
Staurosporine^a	94	81	100	100
2b	0	1	5	4
3b	0	0	3	3
6a	6	1	5	5
7a	0	0	4	1
7b	1	0	3	3
8a	6	0	10	4

^aStaurosporine used in 1 μM concentration.

Figure 2. The 2D and 3D orientations of the docked compounds 6a (upper panel), 7a (middle panel), and 8a (lower panel) in COX-2 active pocket (H bonds and hydrophobic interactions are shown as dashed green lines or arrows).

Figure 3. The 2D and 3D putative binding complexes of compound 7b (upper panel) and compound 8b (lower panel) within the binding pocket of COX-2 enzyme.