Table 1.

Inhibition of HIV-1 protease activity (IC₅₀) by betulinic acid and derivatives^a.

		IC50		Water solubility
HIV-1 protease inhibitor		μM	μg mL−1
	Pepstatin A	29	44
1	Betulinic acid	60	130	≪ 2x, 0.02 μg mL−1 at 25°C (see ref. 22)
6	[Choline][BA-Gly]	54	86	3x
7	[Bzk][BA-Gly]	28	37 b	2x
8	[Choline][BA]	22	40	> 100x

Note:

^avalues and water In general, the percentage error of IC₅₀ solubility were about 5%;

^bEstimated using the molar mass of main homologue of benzalkonium salt shown in Scheme 3.