oa Editorial [Hot Topic Flavonoid (Guest Editor: Meng-Xia Xie)]

Flavonoids, the secondary metabolites of plants, are widely distributed in the plant kingdom. Now, over 8000 compounds have been known, and which can mainly divided into flavans, flavanones, flavones, flavanonols, flavonols, catechins, anthocyanidins and isoflavone, etc. Flavonoids have received considerable attention due to their broad-spectrum pharmacological activities and extensive biological effects, which characteristics place the flavonoids among the most attractive natural substances. This hot topic issue includes six reviews which cover on the recent development for the six main aspects of flavonoids. The first review summarizes the anticancer properties of synthetic flavonoid derivatives obtained through medicinal chemistry with a special focus on recent preclinical and clinical development as anticancer agents. The second review shows the antioxidative properties of flavonoids, and presents the progress on the different pathways that the flavonoids functioned. In the third review, the main approaches for investigating the interaction of flavonoids with biomacromolecules in recent years are provided and some important parameters including their binding constants, the number of binding site, and the position of the flavonoids on the protein have been summarized. The fourth review discusses the structure-activity relationships of flavonoids from four aspects, phytoestrogens, antioxidants, whitening agents and protein regulators. The novel flavonoids isolated from plants or herbs and the developed analytical methods for separation, identification and quantification of compounds are summarized in fifth review. The last review presents the progress in the synthesis of new drugs based on the structural skeleton of flavonoids. In summary, the hot topic issue provided the recent progress on the therapeutic and pharmacological activities, identification and quantification, and novel synthetic derivatives of flavonoids. It might represent a significant contribution of this field, and we hope to attract the attention of a broad audience. Finally, I am grateful for the Editor-in-Chief of Current Organic Chemistry and his coworker for invitation to act as a Guest Editor of this hot topic Issue and continuing support to complete the challenging task. I also want to express my thanks to all the authors for their valuable and interesting contributions, and to all the referees for their help and valuable comments.