Thermodynamic study of the ?-cyclodextrin benzyl-2-pyridyl ketone 2-pyridyl hydrazone inclusion process

Hydrophobic interaction chromatography on octyl sepharose--an approach for one-step platform purification of cyclodextrin glucanotransferases

Cyclodextrin glucanotransferase (CGTase) from Bacillus circulans ATCC 21783 was concentrated by ultrafiltration and subsequently purified by hydrophobic interaction chromatography on Octyl Sepharose 4 fast flow. The matrix was able to bind selectively to the enzyme at a very low ammonium sulfate concentration of 0.67 M and enzyme desorption was performed by decreasing gradient of the salt. The overall recovery was 80% with 689-fold purity. CGTases derived from four soil isolates and Toruzyme, the commercial preparation of CGTase, also bound to Octyl Sepharose under similar conditions at 0.67 M and eluted at 0.55-0.5 M of ammonium sulfate. Octyl Sepharose chromatography can thus be used as a platform approach for purification of CGTases from various bacterial sources. Long stretches of sequence predominated by hydrophobic amino acids are reportedly present in the starch binding domains of CGTases. Starch binding experiments indicated the binding of the enzymes to the octyl matrix through these domains.

Complexation and solubility behavior of albendazole with some cyclodextrins

The main purpose of this work was to study the albendazole-cyclodextrins complexation equilibrium and to propose a suitable excipient to improve the solubility behavior and dissolution rate of albendazole. The complexation of albendazole with four cyclodextrins, alpha-CD, beta-CD, gamma-CD, and hydroxypropylated (HP)-beta-CD, has been studied by using electronic absorption spectroscopy and molecular mechanics. The equilibrium was studied at pH 7.5 under various temperature conditions, and at pH 1.8 with HP-beta-CD at 298 K. The albendazole binding constant was the greatest for the HP-beta-CD. Both the un-ionized (Alb) and the ionized species (AlbH+) were shown to interact with HP-beta-CD. The studies at different temperatures suggest that the hydrophobic effect is the most important driving force in these systems. Moreover, the dissolution rate studies with beta- and HP-beta-CDs in the buffered aqueous solution at pH 7.5 have been accomplished and the dissolution rate was observed to increase with the cyclodextrin concentration. The solubility behavior was studied with the Higuchi and Connors method. The phase solubility and direct spectroscopy methods reveal a 1:1 inclusion complex in all of the studied cases. Molecular mechanics data show the most probable structure of the complexes.