Antiplasmodial Oleanane Triterpenoids from Terminalia albida Root Bark

Phytochemical investigation of the n-BuOH extract of the roots of Terminalia albida Sc. Elliot (Combretaceae) led to the isolation and identification of 10 oleanane triterpenoids (1-10), among which six new compounds, i.e., albidanoside A (2), albidic acid A (4), albidinolic acid (5), albidienic acid (8), albidolic acid (9), and albidiolic acid (10), and two triterpenoid aglycones, i.e., albidic acid B (6) and albidic acid C (7), were isolated here for the first time from a natural source, along with two known compounds. The structures of these constituents were established by means of 1D and 2D NMR spectroscopy and ESI mass spectrometry. The isolated compounds were evaluated for their antiplasmodial and antimicrobial activity against the chloroquine-resistant strain Plasmodium falciparum K1, Candida albicans, and Staphylococcus aureus. Compounds 1-4, 6, 7, and 8 showed moderate antiplasmodial activity with IC₅₀ values between 5 and 15 μM. None of the tested compounds were active against C. albicans or S. aureus. These findings emphasize the potential of T. albida as a source for discovery of new antiplasmodial compounds.