Planta Med 2002; 68(12): 1118-1124
DOI: 10.1055/s-2002-36339
Original Paper
Analysis
© Georg Thieme Verlag Stuttgart · New York

Differentiation Between the Complement Modulating Effects of an Arabinogalactan-Protein from Echinacea purpurea and Heparin

Susanne Alban1 , Birgit Classen2 , Gabriele Brunner1 , Wolfgang Blaschek2
  • 1Institute of Pharmacy, University of Regensburg, Regensburg, Germany
  • 2Institute of Pharmacy, University of Kiel, Kiel, Germany
Dedicated to the 65th birthday of Prof. Dr. Gerhard Franz
Further Information

Publication History

Received: March 21, 2002

Accepted: July 13, 2002

Publication Date:
20 December 2002 (online)

Abstract

Due to the important physiological role of the complement system, complement modulation, either inhibition or stimulation, is an interesting target for drug development. Several plant polysaccharides are known to exhibit complement modulating activities. Sometimes these effects are described as complement inhibition, although the basic mechanism is a stimulation of the complement activation. This misinterpretation is due to the observed reduced haemolysis in the widely used haemolytic complement assay, which does not allow to differentiate between complement activators and inhibitors, when it is performed in the classical manner. The aim of the presented study was to demonstrate that by simple modifications of the classical procedure this assay becomes an efficient tool to distinguish between real complement inhibitors and complement activating compounds without performing expensive, molecular mechanistic investigations. As practical examples heparin with proven complement inhibiting activity and AGP, a new arabinogalacatan-protein type II isolated from pressed juice of the aerial parts of Echinacea purpurea, as a potential complement activating compound were included in the study. By means of varying the preincubation time of the test compound with complement, AGP was clearly identified as a stimulator of both the classical and alternative pathway of complement activation. These findings correspond to the results of molecular mechanistic investigations. Selective removal of the arabinose side chains of AGP resulted in considerably reduced activity. Therefore, the three-dimensional structure of the polysaccharide, i. e., a backbone branched by side chains, is supposed to be important for the interactions with the complement system. The complement activating effects of AGP may contribute to the well-established immunostimulating effects of the pressed juice from Echinacea purpurea.

Abbreviations

AGP:arabinogalactan-protein

AGP-hydr.:hydrolysed arabinogalactan-protein

AP-CA:haemolytic complement assay for the alternative
pathway

CP-CA:haemolytic complement assay for the classical
pathway

EGTA-VB:veronal buffered saline containing EGTA and Mg2+

HPS:human pooled serum

RT:room temperature

LPS:lipopolysaccharide

RaE:rabbit erythrocytes

RT:room temperature

ShE(A):(sensitised) sheep erythrocytes

VB:veronal buffered saline containing Ca2+ and Mg2+

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Priv-Doz. Dr. Susanne Alban

Institute of Pharmacy

University of Regensburg

Universitätsstr. 31

93040 Regensburg

Germany

Phone: +49-941-943 4792

Fax: +49-941-943 4762

Email: Susanne.Alban@chemie.uni-regensburg.de