Table 3. IC₅₀ Values Obtained with the MTT Assay following 72 h Treatment with DOX and Ciprofloxacin (Cip)/Norfloxacin (Nor) Derivatives.

	IC50 (μM) ± ESa				IC50 (μM) ± ESa
Compd	MCF7	MCF7/ADR	R.I.	Compd	MCF7	MCF7/ADR	R.I.
1a	8.80 ± 1.59	8.72 ± 1.25	1.0	1b	5.24b ± 0.70	5.63b ± 0.07	1.1
3a	15.45 ± 1.20	19.55 ± 3.20	1.3	3b	11.68 ± 1.40	15.04 ± 2.10	1.3
6a	16.84 ± 2.40	15.12 ± 2.30	0.9	6c	15.04 ± 0.10	17.15 ± 1.00	1.1
6b	12.12 ± 1.10	18.76 ± 0.10	1.5	6d	10.53 ± 1.20	28.04 ± 1.10	2.7
7a	3.12 ± 0.62	14.69 ± 4.20	4.7	7c	2.27b ± 0.31	18.31 ± 1.40	8.1
7b	5.23 ± 0.82	23.55 ± 3.60	4.5	7d	5.83 ± 0.82	20.02 ± 0.30	3.4
Cip	8.85 ± 0.09	19.12 ± 0.50	2.2	Nor	19.37 ± 0.70	20.06 ± 1.40	1.0
DOX	0.031 ± 0.001	66.90 ± 2.56	22

^aMean ± ES 4/5 independent experiments.

^bp < 0.05 vs reference compound.