Table 1.

Relative inhibition potencies (rp), inhibition potencies on valency-corrected basis (rp/n) for tetra-tacrines 3a–6a and inhibitory potencies (IC₅₀ [nM]) against Electrophorus electricus AChE by 3a–6a and 3b–6b.

Inhibitor	AChE IC50a	AChE rpb	AChE rp/nc
3a	43.7 ± 7.3 nM	12.9	3.2
3b	565 ± 79 nM	—	—
4a	60.2 ± 5.5 nM	5.8	1.5
4b	348 ± 23 nM	—	—
5a	12.5 ± 3.3 nM	1.0	0.25
5b	12.6 ± 2.4 nM	—	—
6a	232 ± 21 nM	0.03	0.008
6b	7.1 ± 1.0 nM	—	—
Tacrine	53.4 ± 1.1 nM	—	—
Methyl α-D-glucopyranoside	N.I.d	—	—

^a[S] = 121 μM (S = substrate).

^brp = IC₅₀ (mono-tacrine)/IC₅₀ (tetra-tacrine).

^crp/n = rp/number of tacrine rings.

^dTested at 100 μM inhibitor concentration.