The solubility of osthole in a binary system of ethanol and water was measured by UV spectrophotometry from 288.2 to 328.2 K. The solubility of osthole in the system increased with temperature. A synergistic effect appeared at x(2) = 0.5527 (equivalent to 80% ethanol, v/v) binary mixtures. Solubility data correlated with a modified Apelblat equation. The enthalpy and entropy of solution of osthole were evaluated using van't Hoff plots. (c) 2012 Elsevier B.V. All rights reserved.