Title
ent-Pimarane and ent-Kaurane Diterpenes from Aldama discolor (Asteraceae) and Their Antiprotozoal Activity
Author
Mauro S. Nogueira, Fernando B. Da Costa, Reto Brun, Marcel Kaiser, Thomas J. Schmidt
Year
2016
Journal
Molecules
Abstract
Aldama discolor (syn.Viguiera discolor) is an endemic Asteraceae from the Brazilian “Cerrado”, which has not previously been investigated for its chemical constituents and biological activity. Diterpenes are common secondary metabolites found in Aldama species, some of which have been reported to present potential antiprotozoal and antimicrobial activities. In this study, the known ent-3-α-hydroxy-kaur-16-en-18-ol (1), as well as three new diterpenes, namely, ent-7-oxo-pimara-8,15-diene-18-ol (2), ent-2S,4S-2-19-epoxy-pimara-8(3),15-diene-7β-ol (3) and ent-7-oxo-pimara-8,15-diene-3β-ol (4), were isolated from the dichloromethane extract of A. discolor leaves and identified by means of MS and NMR. The compounds were assayed in vitro against Trypanosoma brucei rhodesiense, T. cruzi and Leishmania donovani, Plasmodium falciparum and also tested for cytotoxicity against mammalian cells (L6 cell line). The ent-kaurane 1showed significant in vitro activity against both P. falciparum (IC = 3.5 μM) and L. donovani (IC = 2.5 μM) and ent-pimarane 2 against P. falciparum (IC = 3.8 μM). Both compounds returned high selectivity indices (SI >10) in comparison with L6 cells, which makes them interesting candidates for in vivo tests. In addition to the diterpenes, the sesquiterpene lactone budlein A (5), which has been reported to possess a strong anti-T. b. rhodesiense activity, was identified as major compound in the A. discolor extract and explains its high activity against this parasite (100% growth inhibition at 2 μg/mL).
Full Article
Instrument
J-815
Keywords
Circular dichroism, Absolute configuration, Natural products, Pharmaceutical