Anti-AIDS agents, 18. Sodium and potassium salts of caffeic acid tetramers from Arnebia euchroma as anti-HIV agents.

Monosodium and monopotassium salts [2-4] of isomeric caffeic acid tetramers were isolated from Arnebia euchroma as anti-HIV agents. Mixtures of dipotassium and disodium salts [1] of a caffeic acid tetramer and dipotassium and potassium-sodium salts [5] of a caffeic acid tetramer glucoside were also isolated from the active fraction. The structures of 1-5 were characterized by chemical and spectral evidence. Compounds 2-4 demonstrated potent anti-HIV activity with EC50 values of 2.8, 4.0, and 1.5 micrograms/ml, respectively. Treatment of 1-4 with dilute HCl yielded known caffeic acid tetramers [8 and 9], which were found to be less active, indicating the importance of the sodium and potassium salts to the enhanced anti-HIV activity.