Table 1. IC₅₀^a Values (μM) of Synthetic Oridonin Nitrogen Mustard Derivatives (16a–f, 17a–c, and 18a–c) against Human Cancer Cell Lines^b.

compd	K562	MCF-7	Bel-7402	MGC-803
oridonin	4.76 ± 0.32	14.60 ± 1.21	7.48 ± 0.53	5.69 ± 0.37
chlorambucil	60.12 ± 5.48	80.54 ± 4.73	49.31 ± 2.87	133.64 ± 11.25
melphalan	33.37 ± 1.16	19.58 ± 1.02	24.76 ± 1.35	36.88 ± 1.21
benzoic acid mustard (15)	142.67 ± 10.23	152.15 ± 8.66	>200	146.20 ± 9.73
16a	9.01 ± 0.78	14.37 ± 1.24	8.35 ± 0.74	9.30 ± 0.18
16b	1.12 ± 0.07c	0.68 ± 0.02c	0.50 ± 0.01c	1.09 ± 0.14c
16c	2.28 ± 0.69c	1.32 ± 0.05c	1.43 ± 0.09c	2.02 ± 0.27c
16d	5.74 ± 0.45	12.90 ± 0.96	7.91 ± 0.85	6.92 ± 0.45
16e	1.41 ± 0.10c	3.22 ± 0.45c	2.36 ± 0.67c	6.72 ± 0.58
16f	7.03 ± 0.34	14.58 ± 0.28	3.84 ± 0.32c	7.10 ± 0.33
17a	1.73 ± 0.09c	3.63 ± 0.15c	2.56 ± 0.51c	4.71 ± 0.16
17b	1.35 ± 0.12c	0.91 ± 0.03c	2.41 ± 0.23c	3.76 ± 0.53c
17c	1.10 ± 0.15c	0.79 ± 0.01c	1.37 ± 0.06c	2.25 ± 0.19c
18a	1.66 ± 0.22c	2.88 ± 0.19c	1.41 ± 0.11c	3.39 ± 0.27c
18b	1.17 ± 0.14c	0.67 ± 0.01c	0.90 ± 0.03c	1.60 ± 0.08c
18c	2.37 ± 0.19c	2.25 ± 0.08c	2.53 ± 0.47c	3.95 ± 0.52c

^aIC₅₀: concentration that inhibits 50% of cell growth.

^bMTT method: drug exposure was for 72 h (means ± SD, n = 3).

^c*p < 0.001 vs oridonin group.