Isolation, Purification and Characterization of Cyclomaltooctadecaose (.NU.-Cyclodextrin), Cyclomaltononadecaose (.ZETA.-Cyclodextrin), Cyclomaltoeicosaose (o-Cyclodextrin) and Cyclomaltoheneicosaose (.PI.-Cyclodextrin).

Abstract

Under standard conditions, i.e. use of natural starches as substrates and long reaction times, it has been confirmed that cyclodextrin glucotranferase (CGTase) produces not only conventional α-, β-, and γ-cyclodextrins (CDs) but also large-ring CDs (LR-CDs) composed of 9 to 17 glucopyranose units as minor products. Recently, it was reported that CGTase produced cyclic α-1, 4-glucans with degrees of polymerization ranging from 9 to more than 60 units under different reaction conditions such as the use of synthetic amyloses as substrates and short reaction times. However, the maximum size of LR-CDs which can be produced by CGTase under standard conditions, has not yet been determined. Therefore, in the present study we searched for LR-CDs composed of more than 18 glucopyranose units in commercially available CD powder produced by CGTase from potato starch. We found 4 new kinds of LR-CD, cyclomaltooctadecaose (v-CD), cyclomaltononadecaose (ζ-CD), cyclomaltoeicosaose (o-CD) and cyclomaltoheneicosaose (π-CD), and these were purified by a combination of HPLC and column chromatography. Their molecular weights were determined by FAB-MS, and their α-(1→4)-linked cyclic structures were identified by 1H-NMR and 13C-NMR. The 13C-NMR chemical shifts of these new LR-CDs were elucidated and compared with 9 kinds of previously reported LR-CDs. Their structures were predicted to be similar to those of cyclomaltodecaose (e-CD) and cyclomaltotetradecaose (l-CD). These results indicate that CGTase can produce LR-CDs consisting of up to about 20 glucopyranose units under standard reaction conditions.