Cell wall polysaccharides from pulp and peel of cubiu: A pectin-rich fruit

To investigate the polysaccharides of cubiu (Solanum sessiliflorum D.) fruits, pulp and peel were subjected to sequential extractions using different solvents, giving rise to pectins heterogeneous with respect to their structural characteristics, xylan, arabinogalactoxyloglucans and glucomannans. Chemical, physicochemical and spectroscopic analyses were used to characterize the polysaccharides obtained. Pectins with uronic acid content of commercial grade were obtained from the peel of cubiu fruits using water (25 °C and 100 °C) and EDTA and from its pulp using water (100 °C). The fraction with the highest yield (9.6%) and uronic acid content (79.0%) extracted from the peel using water at 100 °C was chemically and structurally characterized. This fraction consists predominantly of a mixture of a homogalacturonan (degree of methyl-esterification 56.9%) and a small amount of rhamnogalacturonan I branched by type I and type II arabinogalactans. The results suggest that cubiu is a promising source of pectins with high uronic acid content extractable by cheaper and environmentally friendly method.