Hydroxypropyl cyclic ß-(1 → 2)-D-glucans and epichlorohydrin ß-cyclodextrin dimers as effective carbohydrate-solubilizers for polycyclic aromatic hydrocarbons.

The removal of polycyclic aromatic hydrocarbons by soil washing using water is extremely difficult due to their intrinsic hydrophobic nature. In this study, the effective aqueous solubility enhancements of seven polycyclic aromatic hydrocarbons by chemically modified hydroxypropyl rhizobial cyclic ß-(1 → 2)-D-glucans and epichlorohydrin ß-cyclodextrin dimer have been investigated for the first time. In the presence of hydroxypropyl cyclic ß-(1 → 2)-D-glucans, the solubility of benzo[a]pyrene is increased up to 38 fold of its native solubility. The solubility of pyrene and phenanthrene dramatically increased up to 160 and 359. Coronene, chrysene, perylene, and fluoranthene also show an increase of 11, 23, 23, and 97 fold, respectively, of enhanced solubility by complexation with synthetic epichlorohydrin ß-cyclodextrin dimer. The physicochemical properties of the complex are characterized by Fourier-transform infrared spectra and differential scanning calorimetry. Utilizing a scanning electron microscopy, the morphological structures of native benzo[a]pyrene, pyrene, phenanthrene, coronene, chrysene, perylene, fluoranthene and their complex with novel carbohydrate-solubilizers are studied. These results elucidate that polycyclic aromatic hydrocarbons are able to form an efficient complex with hydroxypropyl cyclic ß-(1 → 2)-D-glucans and ß-cyclodextrin dimer, suggesting the potential usage of chemically modified novel carbohydrate-solubilizers.

Solubility enhancement of α-naphthoflavone by synthesized hydroxypropyl cyclic-(1→2)-ß-D-glucans (cyclosophoroases).

Rhizobium leguminosarum produces unbranched cyclic ß-1,2-glucans, cyclosophoraoses (Cys). In the present study, Cys were modified with hydroxypropyl groups via a one step chemical derivatization and the complexation ability and solubility enhancement of hydroxypropyl cyclosophoraoses (HP Cys) with α-naphthoflavone (α-NF) were investigated. In the presence of HP Cys, the aqueous solubility of α-NF greatly increased up to 257-fold. Complex formation of HP Cys and α-NF was confirmed by nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). Furthermore, the morphological structure of α-NF with HP Cys was examined using scanning electron microscopy (SEM). A hypothetical model was proposed based on molecular dynamics (MD) simulations and a docking study of α-NF with HP Cys. Our results suggest that HP Cys form complexes with α-NF and can be utilized as a promising solubilizer. This is the first study to identify carbohydrates that can enhance the solubility of α-NF.