Antiplasmodial properties of kaempferol-3- O-rhamnoside isolated from the leaves of Schima wallichii against chloroquine-resistant Plasmodium falciparum

Abstract

Previous intervention studies have shown that the most effective agents used in the treatment of malaria were isolated from natural sources. Plants consumed by non-human primates serve as potential drug sources for human disease management due to the similarities in anatomy, physiology and disease characteristics. The present study investigated the antiplasmodial properties of the primate-consumed plant, Schima wallichii (S. wallichii) Korth. (family Theaceae), which has already been reported to have several biological activities. The ethanol extract of S. wallichii was fractionated based on polarity using n-hexane, ethyl acetate and water. The antiplasmodial activity was tested in vitro against chloroquine-resistant Plasmodium falciparum (P. falciparum) at 100 μg/ml for 72 h. The major compound of the most active ethyl acetate fraction was subsequently isolated using column chromatography and identified by nuclear magnetic resonance. The characterized compound was also tested against chloroquine-resistant P. falciparum in culture to evaluate its antiplasmodial activity. The ethanol extract of S. wallichii at 100 μg/ml exhibited a significant parasite shrinkage after 24 h of treatment. The ethyl acetate fraction at 100 μg/ml was the most active fraction against chloroquine-resistant P. falciparum. Based on the structural characterization, the major compound isolated from the ethyl acetate fraction was kaempferol-3-O-rhamnoside, which showed promising antiplasmodial activity against chloroquine-resistant P. falciparum with an IC₅₀ of 106 μM after 24 h of treatment. The present study has provided a basis for the further investigation of kaempferol-3-O-rhamnoside as an active compound for potential antimalarial therapeutics.

Keywords: antiplasmodial; malaria; medicinal plant; natural product; primates.

Figure 1

Plasmodium falciparum morphology after 24 h of incubation with the Schima wallichii (S. wallichii) Korth. extract. (A) No change was observed without treatment or control (arrow), while changes were detected following incubation with (B) 10 or (C) 100 μg/ml extract as indicated by the arrows. The treatment with 100 μg/ml S. wallichii Korth. extract caused shrinkage and pyknotic bodies in the parasite morphology.

Figure 2

Growth inhibitory effect against Plasmodium falciparum (P. falciparum) following treatment with the Schima wallichii (S. wallichii) Korth. extract and fractions for 24–72 h (100 μg/ml each). The ethyl acetate fraction of S. wallichii Korth. showed the strongest inhibitory effect on the P. falciparum growth rate. Data are the mean of three independent experiments.

Figure 3

Structure of kaempferol-3-O-rhamnoside (or 3,4′,5,7-tetrahydroxyflavone-3-O-rhamnoside) isolated from Schima wallichii Korth. leaves.

Figure 4

Antiplasmodial activity of kaempferol-3-O-rhamnoside against Plasmodium falciparum. Treatment with 250 μM kaempferol-3-O-rhamnoside showed strong antiplasmodial activity. Data are the mean of three independent experiments. ^*P<0.05 compared to control.

Figure 5

Various concentrations of kaempferol-3-O-rhamnoside determining the IC₅₀ value against Plasmodium falciparum after incubation for 24 h. The IC₅₀ value of kaempferol-3-O-rhamnoside was 106 μM. Data are the mean of three independent experiments.