Chemical constituents and synthetic methods of bioactive coumarins

Coumarins, with strong fluorescence and aromatic smell, are one of the main active ingredients in medicinal plants. Coumarins are present in free states or glycosides in plants, which are widely distributed in higher plants such as Umbelliferae, Rutaceae, Moraceae, Leguminosae, Oleaceae, and Compositae. Besides, a few coumarins are found in animals and microorganisms. Till now, about 1200 kinds of coumarins have been discovered. These coumarins are the general name of o-hydroxycinnamic acid lactones. The mother nucleus of coumarins is benzo α-pyranone. Other groups are hydroxyl, alkoxy, phenyl and isopentenyl substituents on the rings. The active double bond of isopentenyl and the ortho hydroxyl on the benzene ring can form the structure of furan ring or pyran ring. According to the different positions and characteristics of substituents in the structure of coumarins, they can be divided into simple coumarins, furancoumarins, pyranocoumarins and substituted α-pyranone coumarins. Moreover, coumarins exhibit obvious bioactivities, such as anti-tumor, anti-AIDS, anti-cell proliferation, anti- virus, anti-fungal, anti-bacterial, anti angiosclerosis, anti-oxidation, enhancing human immunity, etc. They are generally used in medicines. Additionally, coumarins show strong optical activity as fluorescent materials, including fluorescent brighteners, fluorescent dyes, laser dyes, organic photosensitive dyes for solar cells, fluorescent probes for biological analysis, etc. In recent years, new technologies, catalysts, and methods have been applied to the synthesis of coumarins. Coumarins are obtained by artificial synthesis or structural modification of coumarin parent nucleus to form new derivatives, and then further screening of the selective activities of these derivatives are evaluated. This has become a hot spot in the development and research of new coumarins as lead compounds. Briefly, coumarins reveal good bioactivities and a wide range of applications in medicines, foods, and materials, which are important and have high application value.