**Preface to "Antioxidant Activity of Polyphenolic Plant Extracts"**

Over the last several years, plant polyphenols have received a grea<sup>t</sup> deal of research interest because of their potential beneficial effects on human health. Within the polyphenols' interesting biological properties, their antioxidant activity is considered as the most important. This book comprises twenty five peer-reviewed papers, including twenty four original research papers and one literature review. The scientific papers present studies on the isolation of individual polyphenols and/or polyphenolic extracts from different plants, evaluation of their antioxidant activity, prevention of oxidative stress-induced diseases and use as food additives. Specifically, some of the included studies provide evidence that polyphenols may be used for the prevention and treatment of diseases such as diabetes mellitus, Alzheimers' disease, cardiovascular and intestinal diseases. Importantly, in several of the studies "green extraction methods" for the isolation of polyphenols have been developed using modern technologies (e.g., ultrasound and microwave assisted extraction and far infrared irradiation), where few or no organic solvents were used, in order to minimize environmental and health impacts. Some of the plants used for the isolation of the polyphenols in these studies were *Prunus dulcis* (almond), *Salvia africana*-*lutea* (beach salvia), *Paeonia officinalis* (common peony), *Rubus idaeus* L. (raspberry), *Cornus stolonifera* Michx. (Red-osier dogwood), *Cornus mas* L. (Cornelian cherry), *Morus alba* and *Morus nigra* (mulberry), *Lavandula stoechas* (French lavender), *Opuntia ficus-indica* (prickly pear), *Dialium indum* (tamarind-plum), *Averrhoa bilimbi* (cucumber tree), *Rosmarinus officinalis* L. (rosemary), *Robiniae pseudoacaciae* (black locust), *Myrtus communis* (common myrtle), *Camellia sinensis* (tea), *Bixa orellana* (annatto) and *Angelica gigas* (Korean angelica). Special interest was also shown for polyphenols derived from olive oil or by-products of the olive oil production process.

As the Guest Editor, I would like to acknowledge the authors of all articles for their valuable contributions. I would also like to thank the publishing team of the *Antioxidants* journal for their professional help in the preparation of this book.

> **Dimitrios Stagos** *Editor*
