Alkamides from Anacyclus pyrethrum L. and Their in Vitro Antiprotozoal Activity

Abstract

In our ongoing study to evaluate the antiprotozoal activity of alkamides from Asteraceae, a dichloromethane extract from the roots of Anacycluspyrethrum L. showed a moderate in vitro activity against the NF54 strain of Plasmodium falciparum and against Leishmaniadonovani (amastigotes, MHOM/ET/67/L82 strain). Seven pure alkamides and a mixture of two further alkamides were isolated by column chromatography followed by preparative high performance liquid chromatography. The alkamides were identified by mass- and NMR-spectroscopic methods as tetradeca-2E,4E-dien-8,10-diynoic acid isobutylamide (anacycline, 1), deca-2E,4E-dienoic acid isobutylamide (pellitorine, 2), deca-2E,4E,9-trienoic acid isobutylamide (3), deca-2E,4E-dienoic acid 2-phenylethylamide (4), undeca-2E,4E-dien-8,10-diynoic acid isopentylamide (5), tetradeca-2E,4E,12Z-trien-8,10-diynoic acid isobutylamide (6), and dodeca-2E,4E-dien acid 4-hydroxy-2-phenylethylamide (7). Two compounds-undeca-2E,4E-dien-8,10-diynoic acid 2-phenylethylamide (8) and deca-2E,4E-dienoic acid 4-hydroxy-2-phenylethylamide (9)-were isolated as an inseparable mixture (1:4). Compounds 3, 4, and 5 were isolated from Anacycluspyrethrum L. for the first time. While compounds 4 and 5 were previously known from the genus Achillea, compound 3 is a new natural product, to the best of our knowledge. All isolated alkamides were tested in vitro for antiprotozoal activity against Plasmodium falciparum, Trypanosomabruceirhodesiense, Trypanosomacruzi, and Leishmaniadonovani and for cytotoxicity against L6 rat skeletal myoblasts.

Keywords: Anacyclus pyrethrum L.; Leishmania donovani; Plasmodium falciparum; Trypanosoma brucei rhodesiense; Trypanosoma cruzi; alkamide; antiprotozoal activity.

Figure 1

UHPLC/+ESI QqTOF MS-MS chromatograms of the CH₂Cl₂-extract of Anacyclus pyrethrum L. (A) c = 10 mg/mL and the selected fractions (B–E) c = 5 mg/mL. (B) fraction XV, (C) fraction XIX, (D) fraction XX, and (E) fraction XXII. All peaks are labelled with the measured m/z values and compound numbers. Blue represents base peak chromatogram m/z 100–500, and magenta represents base peak UV-chromatogram at 260 nm.

Figure 2

Structures of the isolated alkamides from A. pyrethrum. Deca-2E,4E,9-trienoic acid isobutylamide (9,10-dehydropellitorine; compound 3) is a new natural product.