Secondary metabolites of the leaves of Tricalysia atherura N. Hallé (Rubiaceae) and their potential antiplasmodial activity

Abstract

One monoterpene indole alkaloid, atheruramine (1) bearing an ether bridge linking, one hydrobenzoin derivative, tricalydioloside (2) and two ursane-type triterpenes, atherurosides (A and B) (3 and 4) were isolated from the leaves of Tricalysia atherura, together with eight known compounds. The structures of these new compounds were elucidated on the basis of the results of spectroscopic analysis, and the relative configurations of compounds 1–3 were established by NOE difference. Four of the metabolites were screened in vitro against both chloroquine (CQ)-sensitive (3D7) and -resistant (Dd2) strains of Plasmodium falciparum; they were found to exhibit moderate activity against chloroquine-resistant (Dd2) (IC₅₀ 64.99–92.29 μg/mL). Meanwhile, crude extract possesses high antiplasmodial activity against both 3D7 and Dd2 strains of P. falciparum (IC₅₀ 4.39–7.54 μg/mL) and high selectivity indices values (SI > 10) and was found to be safe.

Graphical Abstract

Keywords:

• Tricalysia atherura
• Rubiaceae
• indole alkaloid
• atheruramine
• hydrobenzoin derivative
• pentacyclic triterpenes
• antiplasmodial
• cytotoxic activities

Acknowledgments

The authors thank Mr. Victor Nana (National Herbarium of Cameroon) for his assistance in the collection and identification of the plant material. The authors also acknowledge the laboratory for Phytobiochemistry and Medicinal Plant Studies, Antimicrobial and Biocontrol Agents Unit, at the Department of biochemistry of the University of Yaounde I in Cameroon for antiparasite and cytotoxic activities.

Disclosure statement

The authors report no declarations of interest.

Additional information

Funding

TThe authors acknowledge The World Academy of Science (TWAS) and the International Center for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi, Pakistan for the Postgraduate Fellowship number: 3240311210 granted to Djikam Sime Gwladys.