Polyacetylenes and polyenes from Echinacea pallida and their anti-inflammatory activity in vitro

Echinacea is among the most popular medicinal plants today and has a long history of use for the treatment of the common cold, upper respiratory infections and inflammatory diseases. Besides Echinacea purpurea and Echinacea angustifolia, also the roots of Echinacea pallida are used medicinally. Polyacetylenes and polyenes are the major lipophilic constituents of Echinacea pallida root extracts. They are natural compounds known for their antifungal and antibacterial activity, and have enzyme inhibitory effects [1]. There is some evidence that they might also exhibit antiallergic as well as anti-inflammatory activities, and recently cytotoxic effects have been found [2].

Fractionation of a supercritical CO₂-extract of Echinacea pallida roots led to the isolation and structure elucidation of seven polyacetylenes and polyenes, namely 8-hydroxy-tetradeca-(9E)-ene-11,13-diyn-2-one, 8-hydroxy-pentadeca-(9E)-ene-11,13-diyn-2-one, tetradeca-8Z-ene-11,13-diyn-2-one, pentadeca-8Z-ene-11,13-diyn-2-one, pentadeca-8Z,13Z-diene-11-yn-2-one, (8Z)-pentadeca-8,11-diene-2-one and (8Z)-pentadeca-8-ene-2-one. The structures of the compounds were determined by UV (DAD-HPLC), NMR (including 1D and 2D NMR experiments) and MS in comparison with data from literature [3,4,5].

The anti-inflammatory activity of various silica gel fractions of the CO₂-extract as well as of the compounds has been evaluated in vitro by using an ELISA assay determining the inhibition of leukotriene B4 formation in human granulocytes. Fractions 6, 7 and 8 showed potent inhibitory activity on LT B4 formation (86.5%±1.17; 67.56%±8.96; 75.34%±0.43, respectively).

References: [1] Binns, S.E. et al. (2000) Planta Med. 66:241–244.

[2] Chicca, A. et al. (2008) Brit. J. Pharmacol. 153:879–885.

[3] Pellati, F. et al. (2006) Phytochemistry 67:1359–1364.

[4] Bauer, R. et al. (1986) Planta Med. 52:424.

[5] Morandi, S. et al. (2008), Org. Biomol. Chem. 6:4333–4339.