Cycloisomaltooligosaccharides Contained in the Kokuto Produced in Okinawa Prefecture

Abstract

Kokuto samples that have been traditionally produced in Okinawa Prefecture were dissolved in water and insoluble contaminants were removed by centrifugation. Water-soluble oligosaccharides contained in the supernatant fraction were subjected to charcoal and HP-20 columns to analyze the contained oligosaccharides. There were several oligosaccharides which were not digested by highly branched dextran glucodextranase, indicating that cyclic oligosaccharides are present in Kokuto. These oligosaccharides eluted at the same retention times as those of isomaltooligosaccharides composed of glucose units of 7, 8 and 9 (CI-7, CI-8 and CI-9) by HPLC analysis. These oligosaccharides were not digested by an α-amylase or by an α-1,3-glucanase but digested by an endodextranase. Mass spectrometry analysis also indicated that the molecular mass of these oligosaccharides was the same as those of CI-7, CI-8 and CI-9. We assumed that cyclic isomaltooligosaccharides exist in Kokuto, which human beings have been eating for long time.