Investigation of the chemical structure and analgesic and anti-inflammatory properties of polysaccharides that constitute the dietary fibers of soursop (Annona muricata) fruit

Soursop fruits are widely used in the folk medicine to treat a variety of health conditions. Once the chemical structure of dietary fibers from fruits is closely related to its biological functions in the human body, we aimed to explore structural features and biological activity of dietary fibers from soursop. Polysaccharides that constitute the soluble and insoluble fibers were extracted and further analyzed using monosaccharide composition, methylation, molecular weight determination and 13C NMR data. Soursop soluble fibers (SWa fraction) were characterized as having type II arabinogalactan and a highly methyl esterified homogalacturonan, while non -cellulosic insoluble fibers (SSKa fraction) were mainly composed by a pectic arabinan, a xylan-xyloglucan complex and a glucuronoxylan. The oral pre-treatment with SWa and SSKa promoted antinociception in mice writhing test, reducing the number of pain-like behaviors (in 84.2 % and 46.9 %, respectively, at 10 mg/kg) and peritoneal leucocyte migration (55.4 % and 59.1 %, at 10 mg/kg), effects possibly associated with the pectins present in fruit pulp extractions. SWa also significantly inhibited the plasmatic extravasation of Evans blue dye in 39.6 % at 10 mg/kg. This paper describes for the first time the structural features of soursop dietary fibers that may be of biological significance in future.