Chemical and immunological modifications of an arabinogalactan present in tea preparations of Phyllanthus niruri after treatment with gastric fluid.

An arabinogalactan (AG) obtained from tea preparations of Phyllanthus niruri was previously investigated and presented immunological properties when tested with peritoneal mice macrophages. AG was now submitted to acidic and neutral gastric conditions using human gastric fluids and aq. HCl solution. Since the acidic procedures gave rise to the same free monosaccharidic composition, the acid hydrolyzate of AG at pH 2.00 was treated with ethanol to form insoluble (AG-P) and soluble fractions (AG-S). These were analyzed using (13)C NMR, HPSEC, and GC-MS for monosaccharide composition and methylation analyses. The results showed an intense partial degradation, including cleavages of the main chain. AG-S presented the monosaccharides released from the native polymer and some oligosaccharides as shown by methylation data. AG-P contained larger molecular fragments comprising the internal units from AG, which were not attacked by the hydrolysis condition. Both fractions were tested in peritoneal mice macrophages and remained active, promoting an increase of superoxide anion production of 2.0 and 2.3-fold, at 250 microg/mL, for AG-S and AG-P, respectively. When compared to AG, a slight diminished response was observed, revealing a structure-activity relation. The significance of the results is that most plant extracts are orally ingested and will reach the gastrointestinal tract before performing a biological function, so checking these changes is crucial to propose future clinical therapies based on the rational use of phytomedicine.

A polysaccharide from a tea (infusion) of Maytenus ilicifolia leaves with anti-ulcer protective effects.

Maytenus ilicifolia is a medicinal plant used as a tea (infusion) for treatment of stomach ulcers. This tea furnished a polysaccharide after several purification steps, consisting of a freezing-thawing process, Fehling precipitation, ultrafiltration, and dialysis. It consisted of arabinose, galactose, galacturonic acid, 4-O-methylglucuronic acid, rhamnose, and glucose in a 42:41:6:5:4:2 molar ratio. Methylation analysis, controlled Smith degradation, and NMR spectroscopy indicated that it was a type II arabinogalactan containing a (1-->3)-linked beta-d-Galp main chain, substituted at O-6 by (1-->6)-linked beta-d-Galp chains, which were mainly substituted at O-3 by (1-->5)- and (1-->3)-linked alpha-l-Araf chains, and nonreducing end-units of alpha-l-Araf and 4-O-Me-GlcpA. This polysaccharide significantly inhibited ethanol-induced gastric lesions in rats with an ED(50) of 9.3 mg/kg, suggesting that the arabinogalactan liberated from the infusion has a protective anti-ulcer effect.

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.

Xylans from the medicinal herb Phyllanthus niruri.

Phyllanthus niruri is a well-known medicinal herb that is widely used in Asia, Africa, and South America. The characterization of two purified polysaccharides from the whole plant has been investigated. Methylation analysis and (13)C NMR spectroscopy showed the chemical structure of two xylans. A hot 15% aqueous KOH fraction yielded a linear beta-(1-->4)-linked xylan, and 2% aqueous KOH afforded a complex acidic heteroxylan, with a (1-->4)-linked beta-Xylp main chain, substituted by rhamnose, arabinose, and 4-O-methylglucuronic acid side chains. These contained nonreducing end-units of arabinose, xylose, galactose, glucose, and nonmethylated glucuronic acid.

An arabinogalactan isolated from the medicinal plant Maytenus ilicifolia.

An arabinogalactan was obtained from the leaves of Maytenus ilicifolia by hot aqueous 2% KOH extraction, followed by a freezing-thawing process and anion-exchange chromatography. It consisted of arabinose, galactose, galacturonic acid, and rhamnose in a 69:20:6:5 molar ratio. Methylation analysis, partial acid hydrolysis, and (13)C NMR spectroscopy indicated that it was an arabinogalactan containing a (1-->4)-linked beta-Galp main chain, substituted at O-6 with Ara units, which were in turn substituted at O-5 (Araf) and/or O-4 (Arap), O-3, O-3,5, and O-2,5. This arabinogalactan is probably linked to O-4 of some Rhap units of a type I rhamnogalacturonan, formed by repeating (1-->4)-alpha-D-GalpA-(1-->2)-alpha-L-Rhap groups.