Table 2.

Inhibitory activities against Topo I and cytotoxicities of derivatives of luotonin A on ring A and B.

Compd	R1	R2	R3	R14	Inhibitory activity against Topo I [% (rel. activity)] at 100 μM	IC50 (μM)
						HCT-116	HL-60	H460
1aa	H	H	H	H	33.7 (0.40) [56]	51.11 [56]	>100 [56]	7.7 [58] a)
1d	H	H	F	H	81.1 (0.91) [56]	>100 [56]	56.65 [56]	-
1e	H	OH	H	H	54.1 (0.65) [56]	56.6 [56]	66.29 [56]	-
1f	H	OMe	OMe	H	-	-	-	5.47 [58]
1g	H	-OCH2CH2O-		H	19.2 (0.23) [56]	19.36 [56]	21.78 [56]	81 [58]
1h	H	R c)	H	H	-	-	2 [40]	-
1i	H	R d)	H	H	-	-	2 [40]	-
1j	OH	R e)	H	H	-	-	10 [40]	-
1k	H	H	H	Et	slightly more active b)[41]	-	-	-
1l	H	OH	H	Et	similar to luotonin A [41]	-	-	-
1m	H	H	H	CF3	inhibition at 40 μM [59]	-	-	-
Doxo f)					-	2.31 [56]	4.78 [56]	-
CPT					83.9 (1) [56]	2.17 [56]	5.51 [56]	-

^a) Values obtained from 72 h culture, ^b) no detailed data were available [41], ^c) R = OCH₂CH₂NEt₂, ^d) OCH₂CH₂NMe₂, ^e) CH₂NMe₂, ^f) doxorubicin.