Water-soluble polysaccharides from Piper regnellii (Pariparoba) leaves: Structural characterization and antinociceptive and anti-inflammatory activities

Piper regnellii is a plant popularly known as "Pariparoba" and it is widely used in folk medicine to treat pain, inflammation, among others. This work presents the extraction, purification and characterization of polysaccharides present in the plant leaves and evaluation of their anti-inflammatory and antinociceptive activities. From the crude aqueous extract of P. regnellii leaves, a polysaccharide fraction named PR30R, predominantly constituted of arabinose, galactose and galacturonic acid monosaccharide units, was obtained. Methylation and NMR analysis showed that the main polysaccharides of PR30R are a type II arabinogalactan, formed by a β-D-Galp-(1 → 3) main chain, substituted at O-6 by side chains of β-D-Galp-(1 → 6), which are substituted at O-3 by non-reducing α-L-Araf ends, and a homogalacturonan, formed by →4)-α-D-GalpA-(1→ units. Intraperitoneal administration of the crude polysaccharide fraction PRSF reduced significantly nociception induced by acetic acid in mice at the doses tested, and the PR30R fraction, derived from PRSF, presented antinociceptive and anti-inflammatory effects at a dose of 0.1096 mg/kg (PRSF ED50). These data support the use of the plant leaves in folk medicine as an herbal tea to treat pain and inflammation.