Kumarins

Kumarins, more commonly known in English as coumarins, are a large class of aromatic organic compounds based on the benzopyranone skeleton. The core structure is a benzene ring fused to a lactone (1,2-benzopyran-2-one), and many derivatives are formed by substitutions or by additional ring fusions, such as furanocoumarins or pyranocoumarins. Simple coumarin serves as the parent compound, while numerous natural products and pharmacologically active derivatives arise from it.

Natural occurrence and biosynthesis: Coumarins are widespread in the plant kingdom, especially in Apiaceae (the carrot family) and some Fabaceae species. They contribute to plant aromas and defense. In plants they are generally produced via the phenylpropanoid pathway, beginning from phenylalanine and involving hydroxycinnamates that cyclize to form the lactone ring. Some plants accumulate furanocoumarins, which have an additional furan ring and can be phototoxic.

Diversity and properties: The family includes a spectrum from simple, lightly substituted coumarins to complex fused structures. Simple coumarin is typically colorless and has a vanilla-like odor; many derivatives are colorless crystals with varied biological activities. Coumarins absorb UV light, making some useful as UV absorbers or fluorescence probes. Phototoxic furanocoumarins can induce skin reactions upon light exposure.

Uses and safety: Historically used in perfumes and as flavor agents, with tonka bean coumarin once common in flavorings before safety restrictions limited dietary exposure. In medicine, 4-hydroxycoumarin derivatives underpin several anticoagulants, notably warfarin and related drugs. Regulatory guidance varies by jurisdiction due to risks of liver toxicity from certain kumarins; monitoring and labeling practices reflect these concerns.