Synthesis, characterization, and comparative analysis of amylose-guest complexes prepared by microwave irradiation

The preparation and characterization of amylose-small molecule complexes is a heavily researched area. There are few reports, however, that compare complexation efficiencies across a matrix of different amylose hosts and guests. We present herein a detailed account of using microwave irradiation to prepare amylose-small molecule complexes in water. Microwave heating reduced the time required to prepare these amylose complexes from hours to minutes. We characterized not only the quantity of complex for each amylose-guest pairing but also the loading of small molecule guest in that complex. Amylose-1-naphthol complexes were found to have the highest loading density compared with other hydrophobic guests studied; in the case of 1-naphthol, there was a linear dependence of guest loading on amylose molecular weight. In addition, complexes featuring 1-naphthol were the most ordered as judged by powder X-ray diffraction (XRD) and differential scanning calorimetry. Further, powder XRD analysis of the microwave-prepared complexes revealed that many contained mixtures of V-form (single helix) and B-form (double helical) amylose. Lastly, untreated Hylon VII complexed the widest variety of small molecules with the overall greatest efficiency.