Thiazolidin-2-cyanamides derivatives as novel potent Escherichia coli β-glucuronidase inhibitors and their structure–inhibitory activity relationships

Figures & data

Figure 1. General synthetic procedure for title compounds 1–13. R = 1: 2-Cl; 2: 3-Cl; 3: 4-Cl; 4: 2-F; 5: 4-F; 6: 2,4-di-F; 7: 2,6-di-F; 8: 2-NO₂; 9: 4-NO₂; 10: 4-Br; 11: 4-Me; 12: 4-OMe; 13: H.

Figure 2. Single crystal structure of compound 6.

Table 1. Chemical structures of 13 thiazolidin-2-cyanamide derivatives and the inhibitory activity against EcGUS-mediated PNPG hydrolysis.

No	R	Molecular weight (Da)	Inhibition rate at 10 μM	IC50 (μM)	Ki (μM)	Inbibition type
1	2-Cl	331.77	77.2 ± 0.6%	5.7 ± 0.6	3.5 ± 0.3	Competitive
2	3-Cl	331.77	95.2 ± 0.3%	1.2 ± 0.2	0.7 ± 0.1	Competitive
3	4-Cl	331.77	80.2 ± 1.8%	4.7 ± 0.6	2.0 ± 0.4	Competitive
4	2-F	315.32	61.6 ± 0.6%	11.9 ± 1.5	ND	ND
5	4-F	315.32	66.5 ± 1.2%	7.3 ± 0.7	ND	ND
6	2,4-di-F	333.31	43.9 ± 0.7%	23.1 ± 1.5	ND	ND
7	2,6-di-F	333.31	64.1 ± 1.2%	9.3 ± 1.1	ND	ND
8	2-NO2	342.33	31.4 ± 1.8%	6.1 ± 0.2	ND	ND
9	4-NO2	342.33	40.3 ± 3.2%	22.2 ± 2.5	ND	ND
10	4-Br	376.23	68.7 ± 1.8%	10.8 ± 0.2	ND	ND
11	4-Me	311.36	33.5 ± 2.5%	22.3 ± 2.6	ND	ND
12	4-OMe	327.36	49.6 ± 0.6%	18.5 ± 2.1	ND	ND
13	H	297.33	61.8 ± 1.3%	10.7 ± 0.5	ND	ND
d-Saccharic acid 1,4-lactone		210.14	11.6 ± 0.6%	67.3 ± 0.6	30.9 ± 2.2	ND

ND: not detect.

Figure 3. The dose-dependent inhibition curves of inhibitors on PNPG-hydrolyzing activity of EcGUS. (A) Compounds 1–8; (B) compounds 9–13, and DSL. All data were expressed as mean ± standard deviation of triplicate reactions.

Figure 4. The Lineweaver–Burk plots of (A) compound 1, (B) compound 2, and (C) compound 3 against EcGUS. All data were expressed as mean ± standard deviation of triplicate reactions.

Figure 5. Ligand interactions of (A) PNPG, (B) compound 1, (C) compound 2 and (D) compound 3 with EcGUS. (E) Stereo diagram of PNPG combined with compound 2 in the active site of EcGUS. (F) Binding mode of compound 2 in the active site of EcGUS.