Structure identification of a polysaccharide purified from litchi (Litchi chinensis Sonn.) pulp

As a health-beneficial fruit, litchi is widely accepted by people in subtropical and tropical regions. However, the critical chemicals responsible for the health benefits are not clear yet. As a large amount of polysaccharides are present in litchi, they might play an important role in the health benefits. In this work, the main water-soluble polysaccharide (LPPBa) was purified from litchi pulp. The chemical structure was characterized as arabinogalactan by gas chromatography and nuclear magnetic resonance spectrometry (NMR). NMR data revealed the glycosidic linkages and their locations in backbone and branches. The precise structure was putatively identified as below, and it was different to those commonly occurred arabinogalactans. The molecular weight was determined to be 2.4 × 10(6)Da by gel permeation chromatography.