Table 1.

Antiproliferative activity of colchicine (1) and its derivatives (2–12) compared with antiproliferative activity of standard anticancer drugs doxorubicin and cisplatin and the calculated values of resistance index (RI) and selectivity index (SI) of tested compounds.

	Cancer Cells									Normal Cells
Compound	A549		MCF-7		LoVo		LoVo/DX			BALB/3T3
	IC50 (μM)	SI	IC50 (μM)	SI	IC50 (μM)	SI	IC50 (μM)	SI	RI	IC50 (μM)
1	0.125 ± 0.013	1.11	0.054 ± 0.028	2.57	0.108 ± 0.025	1.29	1.69 ± 0.28	0.08	15.65	0.139 ± 0.073
2	0.105 ± 0.008	1.35	0.027 ± 0.008	5.26	0.084 ± 0.021	1.69	1.550 ± 0.170	0.09	18.45	0.142 ± 0.073
3	0.010 ± 0.0001	10.3	0.015 ± 0.002	6.87	0.014 ± 0.004	7.36	0.135 ± 0.012	0.76	9.64	0.103 ± 0.089
4	0.115 ± 0.007	8.13	0.178 ± 0.020	7.08	0.125 ± 0.044	10.08	0.700 ± 0.088	1.80	5.60	1.260 ± 0.796
5	0.074 ± 0.009	1.41	0.057 ± 0.011	1.82	0.074 ± 0.019	1.41	1.010 ± 0.020	0.10	13.65	0.104 ± 0.043
6	0.010 ± 0.0001	6.60	0.013 ± 0.002	5.08	0.007 ± 0.002	9.43	0.050 ± 0.010	1.32	7.14	0.066 ± 0.031
7	0.012 ± 0.004	8.50	0.018 ± 0.002	5.67	0.011 ± 0.004	9.27	0.071 ± 0.010	1.44	6.45	0.102 ± 0.063
8	0.030 ± 0.021	4.60	0.055 ± 0.026	2.51	0.018 ± 0.010	7.67	0.074 ± 0.007	1.86	4.11	0.138 ± 0.010
9	0.012 ± 0.004	9.67	0.027 ± 0.007	4.30	0.011 ± 0.0001	10.55	0.072 ± 0.011	1.61	6.55	0.116 ± 0.009
10	0.089 ± 0.020	1.94	0.132 ± 0.017	1.31	0.054 ± 0.017	3.20	0.089 ± 0.026	1.94	1.65	0.173 ± 0.108
11	0.095 ± 0.005	1.54	0.125 ± 0.014	1.17	0.062 ± 0.013	2.35	0.091 ± 0.009	1.60	1.47	0.146 ± 0.014
12	0.093 ± 0.014	2.14	0.125 ± 0.015	1.08	0.281 ± 0.185	0.48	4.240 ± 1.330	0.03	15.09	0.135 ± 0.015
Doxorubicin	0.258 ± 0.044	0.64	0.386 ± 0.118	0.43	0.092 ± 0.018	1.80	4.75 ± 0.99	0.035	51.60	0.166 ± 0.074
Cisplatin	6.367 ± 1.413	0.61	10.70 ± 0.753	0.36	4.37 ± 0.73	0.89	5.70 ± 0.63	0.68	1.3	3.90 ± 1.50

The IC₅₀ value is defined as the concentration of a compound at which 50% growth inhibition is observed. The SI (selectivity index) was calculated for each compound using the formula: SI = IC₅₀ for normal cell line BALB/3T3/IC₅₀ for respective cancerous cell line. A beneficial SI > 1.0 indicates a drug with efficacy against tumor cells greater than the toxicity against normal cells. The RI (resistance index) indicates how many times a resistant subline is chemo-resistant relative to its parental cell line. The RI was calculated for each compound using the formula: RI = IC₅₀ for LoVoDX/IC₅₀ for LoVo cell line. When RI is 0–2, the cells are sensitive to the compound tested, RI in the range 2–10 means that the cell shows moderate sensitivity to the drug tested, RI above 10 indicates strong drug-resistance.