Antiplasmodial activity and identification of a new iridoid triacetate from Heinsia crinata

Malaria is a serious public health challenge and one of the biggest impediments to global development. Investigations were conducted on Heinsia crinata (Afz) G. Taylor (Rubiaceae) which is a shrub with woody stems and branches, collected from DRC's Botanical Gardens, on July and September 2013. The aim of this work was the evaluation of the in vitro and in vivo antiplasmodial activity of the stem bark extracts, investigation of the antioxidant activity of methanolic extracts, and finally the bioguided fractionation. Culture of P. Falciparum chloroquine-sensitive (3D7) was maintained as described by Frédérich et al. [1]. The inhibition of the parasite growth was evaluated by colorimetric method (p-LDH assay) [2]. Ethanolic extract was tested in vivo at the concentration of 300 mg/Kg per os, using a protocol based on the 4-day suppressive test [3]. ABTS assay based on the method reported by Franck et al. [4] and DPPH radical scavenging capacity according to the method developed by Brand-Williams et al. [5], were assessed. The results confirmed the antiplasmodial potential of the extracts with IC₅₀ value of 29.2 ± 1.39 µg/mL. The plant exhibited a moderate in vivo antiplasmodial activity in Plasmodium berghei-infected mice with 48.5% of inhibition of the parasite growth, a good antioxidant activity with IC₅₀ values of 66.22 ± 2.68 µg/mL in ABTS assay and 234.9 ± 41.46 µg/mL in DPPH assay. Finally, an in vitro bioguided fractionation using preparative HPLC and TLC techniques, allowed the identification of the new iridoid, Lamiridoside triacetate by mean of UV, MS, and NMR spectroscopic analysis. This compound exhibited a moderate in vitro antiplasmodial activity, with an IC₅₀ value of 16.39 ± 0.43 µg/mL.

Acknowledgements: The University of Liege, laboratory of Pharmacognosy.

Keywords: Malaria, antiplasmodial, Heinsia crinata, lamiridoside tri-acetate.

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