Characterization of polysaccharide structure in Citrus reticulate 'Chachi' peel during storage and their bioactivity

The peel of Citrus reticulate 'Chachiennsis' (Chachi) is widely accepted as a functional food. It is generally recognized that its health benefits are dependent on storage time. However, the chemicals responsible for this phenomonon remain unclear. As bioactive polysaccharides are dominant in Chachi, Chachi polysaccharides with various storage times (5-20 years) were prepared. The monosaccharide composition was analyzed by GC-MS. NMR data revealed that Chachi polysaccharides were mainly consisted of arabinogalacturonan and another pectin with side chain of -> 4)-beta-D-Galp-(1 -> . alpha-L-Araf-(1 ->, -> 5)-alpha-L-Araf-(1 ->, -> 4)-alpha-D-GalpA-(1 ->, -> 4)-alpha-D-GalpAMe-(1 ->, -> 4)-beta-D-Galp-(1 -> and -> 4)-beta-D-Glcp-(1 -> were detected. The molecular weight of Chachi polysaccharides decreased along with the extension of storage time. However, the basic structure characteristics remained stable. The immumomodulatory activities of Chachi polysaccharides were improved as the storage time extended. The change of molecular weight was responsible for the improved immunomodulatory activity. The results explained how polysaccharides contributed to the enhanced health benefits of Chachi during storage.