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Moisture adsorption-desorption effect on the structure of inclusion complex of 6-chloro-2-pyridylmethyl nitrate and
1Analytical Research Laboratories, Fujisawa Pharmaceutical Co. Ltd, Osaka, Japan.
Abstract:
A new anti-anginal drug, 6-chloro-2-pyridylmethyl nitrate (FR46171), was found to form a complex with beta-cyclodextrin (beta-CyD), molecular ratio 1:1. The FR46171/beta-CyD complex thus prepared showed a moisture adsorption-desorption hysteresis characteristic of hydrophilic polymers. The moisture adsorption-desorption isotherm and differential scanning calorimetry indicated that the moisture adsorbed FR46171/beta-CyD complex includes 13-15 mol of water while the moisture desorbed complex includes 5 mol of water. X-ray diffraction patterns of these samples confirmed their different structures. The scanning electron photomicrographs and the surface areas (BET) suggested that the moisture adsorption-desorption hysteresis observed in FR46171/beta-CyD complex can be attributed to reversible hydrogen bonding between water molecules and hydroxyl groups.