Corosolic Acid Isolated from the Fruit of Crataegus pinnatifida var. psilosa is a Protein Kinase C Inhibitor as well as a Cytotoxic Agent - Ahn, Kyung-Seop; Hahm, Moon Sun; Park, Eun Jin; Lee, Hyeong-Kyu; Kim, Ik-Hwan (Planta Medica, 1998)