Table 2. Residual STS Activity in MCF-7 Cells after Incubation with Compounds 4a–m, 5-Am, COUMATE, and Irosustat at 100, 10, and 1 nM Inhibitor Concentrations.

		residual STS activity [%]a
no.	R	100 nM	10 nM	1 nM	IC50 [nM]
4a	3-Cl	2.4 ± 0.07	28.1 ± 1.12	38.2 ± 1.34	1.90 ± 0.06
4b	3,5-diCl	2.0 ± 0.1	17.8 ± 0.62	63.7 ± 2.55	1.71 ± 0.05
4c	3-Br	2.1 ± 0.07	39.9 ± 2.19	79.4 ± 4.76
4d	3-I	2.0 ± 0.11	31.8 ± 1.59	67.5 ± 3.71
4e	3-CH3	3.1 ± 0.12
4f	3,5-diCH3	10.2 ± 0.61
4g	3-OCH3	6.8 ± 0.24
4h	3,5-diOCH3	34.3 ± 1.88
4i	3-CH2CH3	2.6 ± 0.08
4j	3-CH(CH3)2	2.4 ± 0.12	73.4 ± 4.77
4k	3-NO2	5.9 ± 0.32
4l	3,5-diBr	8.3 ± 0.4
4m	3,5-diI	18.7 ± 0.93
5a	4-F	1.5 ± 0.05	60.2 ± 2.7
5b	H	1.5 ± 0.05	46.6 ± 1.63
5c	2-CF3	5.5 ± 0.3
5d	3,5-diCF3	14.7 ± 0.88
5e	2,3,4-triF	1.0 ± 0.04	24.2 ± 1.45	38.9 ± 1.95	2.95 ± 0.13
5f	3,4-diF	3.0 ± 0.14
5g	3-F	1.0 ± 0.04	1.0 ± 0.05	57.3 ± 3.44	1.69 ± 0.08
5h	2-CF3-4-F	2.4 ± 0.13	48.2 ± 3.37
5i	4-OCF3	1.0 ± 0.03	9.5 ± 0.48	71.8 ± 4.67
5j	4-CF3	2.9 ± 0.15
5k	2-OCF3	15.5 ± 0.93
5l	3,5-diF	1.0 ± 0.05	1.0 ± 0.06	13.6 ± 0.48	0.21 ± 0.01
5m	3-CF3	1.3 ± 0.06	59.9 ± 3.29
COUMATE		51.8 ± 3.36
Irosustat		2.4 ± 0.07	12.9 ± 0.77	16.8 ± 0.5	1.06 ± 0.03

^aSubstrate: [3H]E1S, 3 nM; experiments were carried out in triplicate.