Dear Colleagues,

Coumarins are specialized metabolites ubiquitously distributed in the plant kingdom. Their core structure is a 1,2-benzopyrone, which consists of a benzene ring fused to a pyrone ring. Depending on diverse modifications and/or substitutions, they can be classified into two categories: (i) simple coumarins displaying hydroxylations, alkoxylations, alkylations, or glycosylations and (ii) complex coumarins with additional heterocycles leading, notably, to furanocoumarins, pyranocoumarins, or phenylcoumarins.

Coumarins are reported to have many physiological functions. They are involved in defenses against pathogens and insects but also in protection against abiotic stresses. More recently, they were described to play a role in iron uptake and root bacterial community structuratures. In addition, coumarins are considered as bioactive compounds with therapeutic interests in AIDS and several cancers.

Coumarin biosynthesis is mainly a branch of the phenylpropanoid pathway. The molecular characterization of its synthesis has progressed considerably in the last decade. Among the enzymes characterized, several alpha ketoglutarate dependant dioxygenases have been described to mediate the orthohydroxylation of hydroxycinnamoyl-CoA and lead to the synthesis of the coumarin core molecule. Other enzymes such as methyltransferases, prenyltransferases, and cytochrome P450s and, more recently, COSY genes were also reported. Despite these advances, many steps need to be more deeply investigated in order to fully understand the synthesis and chemical diversity of coumarins.

This Special Issue will be dedicated to the study of simple and complex coumarins including chemical structure diversity; characterization of their biosynthetic pathways with transport, regulation, and evolutional aspects; and the elucidation of physiological and biological functions. All works including research papers and reviews related to these items will be considered for publication.

Dr. Romain Larbat
Prof. Alain Hehn
Dr. Alexandre Olry
Dr. Ryosuke Munakata
Guest Editors

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• simple and complex coumarins
• chemical structure diversity
• metabolic pathway
• transport
• molecular evolution
• physiological function
• iron homeostasis
• bioactivity