Abstract
Base-catalyzed isomerization of prostaglandin A1 (PGA1) to prostaglandin B1 (PGB1) was significantly accelerated by α-and β-cyclodextrins (α-CyD, β-CyD), where catalytic effect of β-CyD was larger than that of α-CyD. Stability constants and rate constants of PGA1-cyclodextrin (CyD) complexes were kinetically determined on the base of 1 : 1 inclusion complex formation. In order to elucidate the catalytic mechanism of CyDs, effects of variables such as pH, ionic strength, cationic and anionic salts, and solvents on the isomerization rate were studied in the absence and in the presence of CyDs. Furthermore, activation parameters for CyD-catalyzed isomerization were determined. The results indicated that the catalytic effect of CyDs was mainly ascribable to conformational changes of PGA1 molecule within the cavity of CyDs and hydrophobic interaction appeared to be predominant as a binding force.
