Isolation,
Structural Modification, and HIV Inhibition
of Pentacyclic Lupane-Type Triterpenoids from <i>Cassine xylocarpa</i> and <i>Maytenus cuzcoina</i>
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Abstract
As a part of our investigation into
new anti-HIV agents, we report
herein the isolation, structure elucidation, and biological activity
of six new (<b>1</b>–<b>6</b>) and 20 known (<b>7</b>–<b>26</b>) pentacyclic lupane-type triterpenoids
from the stem of <i>Cassine xylocarpa</i> and root bark
of <i>Maytenus cuzcoina</i>. 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 <b>27</b>–<b>48</b> 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 IC<sub>50</sub> values in the micromolar range,
highlighting compounds <b>12</b>, <b>38</b>, and <b>42</b> (IC<sub>50</sub> 4.08, 4.18, and 1.70 μM, respectively)
as the most promising anti-HIV agents
