Editorial [Hot Topic: Xanthone (Dibenzo-γ-Pyrone): An Interesting Framework In Medicinal Chemistry (Guest Editor: Madalena M.M. Pinto)]

The xanthone structure is one of the most interesting frameworks since a large number of the substituents, depending on their chemical nature and position on the aromatic rings, can lead to a myriad of biological activities of its derivatives. As a large number of naturally-occurring and synthetic xanthones with interesting biological and pharmacological activities have been reported in the past years, this group of compounds should deserve special attention. Consequently, this special issue will start with the xanthone derivatives isolated from various sources in the past five years with emphasis on the new structures and some relevant biological activities. Besides natural xanthones with substitution patterns controlled by the biosynthetic pathways, a number of xanthone derivatives, even with more complex structures, have been obtained by classic and biomimetic synthesis. As the synthetic methods for xanthones and related derivatives have been evolved constantly, it is pertinent to examine thoroughly the methodology for the synthesis of these compounds. Equally important are the techniques for structure elucidation of xanthones, especially for the more complex structures. Thus, a variety of modern NMR techniques currently used for structure elucidation of xanthones and their derivatives are also discussed. X-ray crystallography has also found its place in structure elucidation of xanthones; consequently we have included this chapter. Since the ultimate goal of this issue is the potential application of this group of compounds in Medicinal Chemistry, the final chapters are dedicated to the new insights of their biological activities. Finally, it could not be more appropriate to choose a topic emphasizing the recognition of xanthones as potential new antimalarial agents as the closing chapter. I am very optimistic that all the topics in this special issue will arouse the interest of all the readers and that xanthones will find their outstanding place in Medicinal Chemistry in the near future. As a guest editor, I would like to deeply thank all the contributing authors of this issue for their valuable time and effort. My special thanks also go to all the experts who have accepted to act as referees of the articles. Their thorough work and criticism have contributed to a success of this issue.