They are found in many plant families. Many alkaloids are used in medicine.
Many alkaloids are toxic.
They often are responsible for the properties of plants poisonous to livestock. Most alkaloids are derived from a few common amino acids. Mmost have physiological activity. Many alkaloids give simple color and precipitation reactions, such as with Dragendorf's reagent, that make it relatively easy to determine their presence or absence in plant material. As a group alkaloids are easily isolated.