Human neutrophil elastase inhibitory activity of Solanum dulcamara extracts

Dulcamarae stipites, derived from European bittersweet (Solanum dulcamara L., Solanaceae), have a long tradition in European folk medicine as anti-rheumatic and anti-asthmatic remedy. Today, dermatological preparations are used to treat chronic skin diseases, e.g. atopic eczema. As a member of the genus Solanum, S. dulcamara is known to contain steroidal glycoalkaloids, e.g. solasonine as well as steroidal saponins and thus may cause intoxications [1]. Recent studies concerning the anti-inflammatory properties of this plant revealed a COX 1-inhibitory activity and inhibition of the PAF-induced exocytosis [2, 3].

In order to further evaluate possible modes of action of this plant remedy, we evaluated the ability of different extracts to inhibit the serin proteinase human neutrophil elastase, which plays an important role in the inflammatory response of different tissues. A crude methanolic extract exhibited a significant inhibition of 60% at a concentration of 10µg/ml. A subsequent assay conducted on the CH²Cl², EtOAc, and n-Butanol fractions of this extract revealed that most of the activity was concentrated in the CH²Cl² fraction (95% inhibition at 5µg/ml), whereas the n-Butanol fraction was devoid of activity.

Further fractionation of the active extract led to the isolation of different caffeic acid derivatives, e.g. trans-feruloyltyramine.

[1] Hänsel R et al. (Hrsg.): Hagers Handbuch der Pharmazeutischen Praxis, Vol. 6. Berlin, Heidelberg, New York: Springer; 1994.

[2] Tunon H et al.: J Ethnopharmacol. 1995; 48: 61–76.

[3] Jaggi R: Inflamm Res. 2004; 53: 150–157.