**Preface to "Plant Foods and Underutilized Fruits as Source of Functional Food Ingredients: Chemical Composition, Quality Traits, and Biological Properties"**

It is known that specific foods provide additional health benefits to human beings as treatment and/or through the prevention of several diseases. For this reason, people have achieved a better life quality by eating fruits, vegetables, and other foods derived from plants, and using nutraceuticals, dietary supplements, or nutritional phytotherapy following official medicine. Plants produce secondary metabolites (e.g., vitamins, phenolics, terpenes, organic acids) not directly involved in normal organism development, but as defense molecules against biotic and abiotic stresses. These same compounds present specific health-promoting benefits and properties in humans and animals. Neglected and underutilized plants have become essential for the food industry, thanks to their use as an alternative for synthetic nutraceuticals and chemicals, however their potential is still not fully exploited. Studies on these raw materials are of interest to find innovative sources for natural nutraceuticals, antioxidants, and functional foods. This Special Issue provides readers with a good overview of the status and exciting developments in this field. It includes papers focused on modern analytical instrumentation and new methods and biological tests applied to the evaluation of underutilized plants and the phytochemical characterization of innovative natural sources of bioactive compounds and relative health-promoting properties. Guest Editors would like to thank all the colleagues and contributors that published their works in this Special Issue as well as the reviewers that evaluated the submissions assuring a high quality for the published studies. Guest Editors would also like to thank the publisher, MDPI, and the editorial staff of *Foods* for their high-quality, constant, and professional support as well as fortheirinvitation to edit this Special Issue.

> **Dario Donno, Federica Turrini** *Editors*
