Extraction, fractionation and characterization of water-soluble polysaccharide fractions from myrtle (Myrtus communis L.) fruit

Abstract

The extraction of polysaccharide fraction (EtOH precipitate) and the fractionation of ethanol-soluble fraction as well as their characterizations were achieved. The EtOH precipitate was extracted from myrtle fruit (Myrtus communis L.), an edible species used for medicinal purposes, after ethanolic treatment and disposal of seeds using a solid/liquid ratio of 1:40 (w/v) at 80 °C for 24 h and precipitation with 70% (v/v) ethanol. The ethanol-soluble fraction was further fractionated by size exclusion chromatography (SEC) using Bio-Gel P2 and then Bio-Gel P4. The yield of EtOH precipitate was 3% (w/w). The 1H NMR spectrum of this fraction indicated characteristic signals for the presence of polysaccharides, which was confirmed by HPAEC carbohydrate analysis. Monosaccharide composition analysis showed that the EtOH precipitate was composed of 12.3% (w/w) neutral sugars (5% arabinose, 3% galactose, 2.2% glucose, 1.6% rhamnose, 0.3% mannose, 0.1% xylose) and 28.8% (w/w) uronic acids (14.4% galacturonic acid and 14.4% glucuronic acid).Analysis of the different ethanol-soluble fractions show the presence of arabinogalactan (AG), cyclitols (and/or alditols), glucose, organic acids, anthocyanins and oligosaccharides. It is interesting to note the high level of free glucose (65–70%) contained in this ethanol-soluble fraction.