Comparative cytotoxicity of some selenium-containing ligands and complexes and their sulfur-containing analogs (cell lines MCF7 and HEK293; MTT or MTS test).

Compound	CC50, μM		Selectivity Index
	MCF7	HEK293
	2.97 ± 0.15	3.21 ± 0.27	1.3
S-analog of 4d18	15.9 ± 1.4	>100	>6.3
	8.38 ± 2.26	4.26 ± 0.94	0.5
S-analog of 4e18	>100	>100
	4.18 ± 0.65	0.87 ± 0.14	0.2
S-analog of 5c15	0.6 ± 0.0	—	1.3
	0.49 ± 0.07	3.7 ± 0.6	8.5
S-analog of 5d18	3.7 ± 1.6	2.5 ± 0.4	0.7
	1.49 ± 0.38	3.9 ± 0.6	2.6
S-analog of 5e18	7.4 ± 1.4	25.3 ± 1.2	3.4