Drugs have been used to treat and prevent malaria for centuries. Bark from the cinchona tree, which contained an array of alkaloids with antimalarial properties, appeared in Western therapeutics in the 17th century. One of the alkaloids, quinine, was isolated in 1820 and became the drug of choice for treating malaria until World War II, when supplies of the drug for much of the world were cut off by the Japanese occupation of cinchona-growing regions in Southeast Asia. Efforts to create alternatives to quinine led to the search for synthetic antimalarial drugs. Chloroquine, first developed in the 1930s, became the most widely used synthetic antimalarial during the 1960s and 1970s.