Joseph Caventou. Portrait of Joseph Bienaime Caventou (1795-1842), French chemist. From 1809 he and P.J. Pelletier began extracting chemicals from plants by using mild solvents rather than the traditional method of destructive distillation. In 1817 they isolated chlorophyll, the green chemical used by plants in photosynthesis. They also discovered a number of useful 'vegetable bases' (alkaloids). These included strychnine (a poison), caffeine (a stimulant), quinine (malaria treatment), cinchonine (fever treatment) and veratrine.