Chemical and biological properties of an arabinogalactan from Phyllanthusniruri

Phyllanthus niruri is a well-known herb widely used medicinally in Asia, Africa, and South America. Aqueous extraction of the intact plant provided an acidic arabinogalactan, which was characterized chemically, and its effects on peritoneal macrophage activation were determined. Methylation analyses and (13)C NMR spectroscopy showed it to have a complex structure with a (1-->4)-linked beta-Galp main chain, substituted by rhamnose, galacturonic acid, arabinose, xylose, galactose, and glucose-containing side chains, with nonreducing end-units of arabinofuranose, xylopyranose, galactopyranose, and glucopyranose. In immunological studies, the arabinogalactan stimulated superoxide anion production, when tested using peritoneal macrophages of mice, but did not interfere with the nitric oxide pathway. Thus, traditional aqueous extraction methods, such as decoction and infusion, provide a major polysaccharide, which stimulates an intense biological response in macrophages: this could represent an interesting approach in phytotherapeutic treatments.