Isolation, Structural Modification, and HIV Inhibition of Pentacyclic Lupane-Type Triterpenoids from Cassine xylocarpa and Maytenus cuzcoina

As a part of our investigation into new anti-HIV agents, we report herein the isolation, structure elucidation, and biological activity of six new (1-6) and 20 known (7-26) pentacyclic lupane-type triterpenoids from the stem of Cassine xylocarpa and root bark of Maytenus cuzcoina. Their stereostructures were elucidated on the basis of spectroscopic and spectrometric methods, including 1D and 2D NMR techniques. To gain a more complete understanding of the structural requirements for anti-HIV activity, derivatives 27-48 were prepared by chemical modification of the main secondary metabolites. Sixteen compounds from this series displayed inhibitory effects of human immunodeficiency virus type 1 replication with IC50 values in the micromolar range, highlighting compounds 12, 38, and 42 (IC50 4.08, 4.18, and 1.70 μM, respectively) as the most promising anti-HIV agents.