Enhanced chartreusin solubility by hydroxybenzoate hydrotropy.

The apparent aqueous solubility of the water-insoluble cytotoxic agent, chartreusin, was increased at neutral pH in the presence of hydroxybenzoates. Water molecules play an important role in the chartreusin conformation. Studies included solubility and spectral examinations. The weakest and strongest interactants with chartreusin were sodium benzoate and sodium trihydroxybenzoate, respectively, while the effect of mono- and dihydroxybenzoates was intermediate. A plane-to-plane orientation of chartreusin and the ligand molecules brought together by electrostatic and hydrophobic interactions is postulated. The dramatic chartreusin aqueous solubility increase relative to its aglycone, chartarin, under similar conditions was best rationalized by micellization.