Inhibitory effects of triterpenoids and sterols on human immunodeficiency virus‐1 reverse transcriptase

Abstract Fifty‐five triterpenoids consisting of 19 tetracyclic, 32 pentacyclic, and 4 incompletely cyclized triterpenoids, and 2 sterols, mostly isolated from various plant and fungal materials, were examined for their inhibitory effects on a purified human immunodeficiency virus type 1 (HIV‐1) reverse transcriptase. Twenty triterpenoids and one sterol showed inhibitory effects with 50% inhibition concentration (IC 50 ) values less than 5.0 μM. Among these cycloartenol ferulate (IC 50 =2.2 μM), 24‐methylenecycloartanol ferulate (1.9 μM), lupenone (2.1 μM), betulin diacetate (1.4 μM), and karounidiol 29‐benzoate (2.2 μM) inhibited most effectively. Some of the triterpenoids and sterols may be potential new lead compounds to find still more potent HIV‐1 reverse transcriptase inhibitors.