Abstract

In our search for new antiplasmodial agents, the CH2Cl2/CH3OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2′,6′-dimethoxy-3′,4′-(2′′,2′′-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2′,6′-dimethoxy-3′,4′-(2′′,2′′-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4′′-ethoxy-3′′-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated. The purified compounds were characterized by NMR spectroscopic and mass spectrometric analyses. Compound 1 slowly converts into 2 in solution, and thus the latter may have been enriched, or formed, during the extraction and separation process. The isomeric compounds 1 and 2 were both observed in the crude extract. Some of the isolated constituents showed good to moderate antiplasmodial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.

Highlights

  • Tephrosia is a pantropical genus encompassing more than 350 species, 110 of which are found in Africa, and 30 of these in Kenya [1]

  • UV spectra were recorded on a Specord S600 (Analytik Jena AG, Jena, Germany) spectrophotometer, optical rotations were measured on PerkinElmer 341-LC (PerkinElmer, Wellesley, MA, USA) whereas CD experiments were run on a Jasco J-715 spectropolarimeter (Jasco, Corp., Tokyo, Japan)

  • NMR spectra were acquired on Bruker Advance 600 or a Bruker Advance III HD

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Summary

Introduction

Tephrosia (family Leguminosae) is a pantropical genus encompassing more than 350 species, 110 of which are found in Africa, and 30 of these in Kenya [1]. Some Tephrosia species are traditionally used in herbal medicine, while other members of this genus are known as a fish poison and as insecticides [1,2]. In East Africa, the roots of Tephrosia aequilata are used to cure venereal diseases and to reduce pain [4]. Previous phytochemical investigation of the roots of this plant yielded a new pterocarpan, 3,4:8,9-dimethylene- dioxypterocarpan, and four known chalconoids, namely praecansone A, praecansone B, Z-praecansone A and demethylpraecansone. As Tephrosia aequilata was reported to produce chalconoids [1], we chose to investigate this plant. (2), 400 -ethoxy-300 -hydroxypraecansone methylene-dioxypterocarpene (4), along with seven known compounds (5–11). B (3), and 3,4:8,9-di-methylene-dioxypterocarpene (4), along with seven known compounds (5–11). The characterizationactivities and the of antiplasmodial activities of these compounds are discussed here

Results and Discussion
Compounds
General Experimental Procedures
Plant Material
Extraction and Isolation
Plasmodium Falciparum Culture
Plasmodium falciparum Growth Inhibition Assay
Cytotoxicity Assays
Conclusions

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