Due to their manifold abilities to interact with various plant constituents influencing their solubility, stability and even biological behaviour by complex interaction processes, there is a growing interest to study plant carbohydrates as potential biologically active components. The immunomodulating effects of polysaccharides isolated from Viscum album were described by Büssing, this book, and Schietzel and Stein, this book.
Stems and leaves contain mainly methylester of 1^a4 galacturonic acid (Jordan and Wagner, 1986b). The berries contain rhamnogalacturonanes as basic structures to which individual branched (1^ß6)-D-galactan chains are linked via O-4 of rhamnose residue, while arabinosyl residues or complex arabinan side chains are linked via O-3 group of galactose units. Beside a highly methylated homogalacturonan, a pectin with a molecular weight of 42 kDa (following hydrolysis of ester bonds), minor amounts of an arabinogalactan (110 kDa) were isolated from stems and leaves. In the berries, a high molecular weight rhamnogalacturonan (700 kDa) with arabinogalactan side chains was detected.
In 1999, Edlund and co-workers (Edlund, 1999, Edlund et al., 1999) isolated and characterised polysaccharides from mistletoe berries. The isolated acidic (1,340 kDa) and neutral (30 kDa) oligo- and polysaccharides are composed of a rhamnose-galacturonic acid backbone with highly branched arabinose-galactose side chains (acidic oligosaccharides) and arabinogalactans together with minor amounts of xyloglucan (neutral polysaccharides). Especially the acidic carbohydrates strongly interacts with ML I, as demonstrated by haemagglutination assays, size exclusion chromatography and BIA (Biochemical Interaction Analysis). In contrast to ML I,. the high molecular weight acidic arabinogalactan stimulated the proliferation of CD4+ T helper lymphocytes but not CD8+ T lymphocytes or B lymphocytes (Stein et al., 1999). Thus, also non-lectin components may contribute to the suggested antitumour effects of mistletoe extracts. Interactions between a high molecular weight acidic arabinogalactan and ML I were described by Jordan and Wagner (1986a, b). Further studies are necessary to elucidate biological activities of oligo- and polysaccharides from Viscum album and their manifold possibilities to interact with other active components (see Büssing, this book, and Stein and Schietzel, this book).
Was this article helpful?