1.
The natural product lupeol
1 was isolated from aerial parts of
Vernonia scorpioides with satisfactory yield, which made it viable to be used as starting material in semisynthetic approach. Ten lupeol derivatives
2–11 were prepared by classical procedures. Including, five new esters derivatives
7–11, which were obtained by structural modifications in the isopropylidene fragment. All semisynthetic compounds and lupeol
1–11 were confirmed by
1H NMR,
13C NMR and HRMS. Their antiprotozoal activity was evaluated
in vitro against
L. amazonensis and
T. cruzi. Derivative
6 showed the best antitrypanosomal activity (IC
50 = 12.48 μg/mL) and the lowest cytotoxic derivative (CC
50 = 161.50 μg/mL). The mechanism of action of the most active derivatives (
4, 6 and
11) is not dependent from the enzyme trypanothione reductase.
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