Isolation and characterisation of arabinogalactan-proteins from cell cultures of Pelargonium sidoides DC
Pelargonium sidoides is a traditional medicinal plant from South Africa. An aqueous-ethanolic formulation of the roots is approved for the treatment of acute bronchitis. The main effects could be related to antibacterial activities and the stimulation of the non-specific immune system by the main components of Pelargonium sidoides: coumarins, phenols and tannins . Due to wild harvesting, Pelargonium sidoides is an endangered species. Therefore the propagation of the plant material by cell cultures and the extraction of ingredients are interesting tasks. Calli were established from roots and shoots of germinating seeds and the maintenance of callus and suspension cultures in different media was investigated. In suspension cultures of Echinacea purpurea a secretion of arabinogalactan-proteins (AGPs) with weak immunomodulatory activities has been shown . From suspension cultures of Pelargonium sidoides high amounts of pure AGPs could be isolated by precipitation with β-glucosyl Yariv reagent. To study potential therapeutic benefits the characterisation of these AGPs is necessary. Quantification of neutral sugars by acetylation pointed out arabinose (Ara) and galactose (Gal) as dominating monosaccharides in a ratio of 1: 1.7–1.8. Colourimetric determination of uronic acids revealed an amount of 5–8%. Linkage type analysis showed that the main components are 1,3,6-Gal(p), 1,3-Gal(p) and 1-Ara(f) as well as minor amounts of 1,6-Gal(p), 1,4-Gal(p) and 1,5-Ara(f).
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