Chemotaxonomy (from chemistry and taxonomy), also called chemosystematics, is the attempt to classify and identify organisms (originally plants), according to demonstrable differences and similarities in their biochemical compositions. The compounds studied in most of the cases are mostly proteins, amino acids and peptides. Examples of chemotaxonomic markers are phospholipid-derived fatty acids and enzymes.
E.G. Family Rutaceae can be distinguished by the presence of oil glands; Families Aschepiadaceae and Apocyanaceae can be differentiated based on the presence of latex.
Chemosystematics can be viewed as a hybrid science that complements available morphological data to improve plant systematics.
John Griffith Vaughan was one of the pioneers of chemotaxonomy.