Preface

Selenium, like the moon from which its name has been derived, has different facets. It is a micronutrient for humans and animals. Its deficiency leads to several diseases, while at marginally higher concentration it becomes toxic. It is an important element for the development of semiconductors. The year 2017 is the bicentenary of its discovery by the Swedish scientist J. J. Berzelius. To commemorate this occasion, the publication of this multi-authored volume on “Organoselenium Compounds in Biology and Medicine”, of interest to postgraduate students and researchers in those multidisciplinary areas that have selenium at centre stage, is a fitting tribute.

To date, the majority of books available in the literature on selenium biology are focussed on inorganic selenium compounds. During the past two decades or so there have been significant advances in the design and synthesis of organoselenium compounds exhibiting potential biological activities. Having realized the high toxicity of inorganic forms of selenium (e.g. sodium selenite), which limits the therapeutic window, efforts have been directed to develop a variety of organoselenium compounds that are considerably less toxic. The redox properties, toxicity and specificity of organoselenium compounds can be further tuned by the organic substituents as well as by the presence of non-bonding interactions between selenium and a hetero atom. For example, ebselen, the first synthetic organoselenium compound with glutathione peroxidase-mimicking activity is in clinical trials as an antioxidant drug for heart disease and bipolar disorders, while selenocystine, the 21st amino acid, and its derivatives are very promising compounds in cancer therapy. Several other compounds are in advanced stages of research for therapeutic usage.

The research on selenium has emerged as a multidisciplinary science through the interactions of researchers working in different areas such as organic/inorganic/bio-chemistry, materials science, biology, pharmacology, medicine, agriculture and environmental science. This growing and sustained interest can be witnessed in the publication of several reviews and monographs over the past two or three decades, and the series of international symposia organized globally on a regular basis. These include the International Symposium on Industrial Uses of Selenium and Tellurium, the International Symposium on Selenium in Biology and Medicine, the International Conference on the Chemistry of Selenium and Tellurium (ICCST) and the International Conference on Selenium in the Environment and Human Health. Such events are organized in different countries manifesting the wide geographical distribution of selenium research.

With this background, this volume aims to cover the recent advancements of organoselenium compounds, with emphasis on their biological relevance as antioxidants, antibacterial agents, radioprotectors and anticancer agents, etc. The book, comprising 16 chapters, is therefore representative of the current status of research and developments in the synthesis of organoselenium compounds and their applications in biology and medicine. The first chapter provides an overview of organoselenium chemistry with an obvious bias towards biologically relevant compounds. The remaining 15 chapters have been divided into three sections, each including five chapters. The first section of the book dicusses synthetic advances on bioactive selenium compounds, providing details of the synthetic aspects of biologically relevant novel organoselenium compounds. The second section covers bio-physics and chemistry and effects on oxidative stress of organoselenium compounds, where redox properties of selenium compounds, reactions with reactive oxygen species, non-bonding interactions in glutathione peroxidase mimics and important selenoproteins in maintaining cellular redox balance are discussed. The third section deals with therapeutic applications of organoselenium compounds. In this section, recent advances in the research related to the applications of selenium and organoselenium, in particular in radiotherapy, cancer therapy and cancer prevention, are discussed.

In the preparatory stage of our editorial work, we decided that all chapters should be written in such a way that they covered most of the recent advances in the field and should be easy for the beginners to follow. The selection of chapters should be such that the repetition and overlap of their content could be minimal. As editors we have been fortunate to have worked with authors experienced in their specialized fields from different parts of the world for the individual chapters. Their wholehearted support and co-operation in preparing the chapters is gratefully acknowledged.

We are indebted to all the reviewers for their critical comments and constructive suggestions, which enabled us to improve the content of the chapters. We acknowledge the help of our junior colleague Mr Amey Wadawale with computing during editing. We are thankful to the Royal Society of Chemistry (RSC) for giving us this opportunity. Special thanks to Dr Michelle Carey, senior commissioning editor at the RSC, for many useful suggestions while preparing the book proposal. We thank the authorities of our institute, Bhabha Atomic Research Centre, for encouraging us to take up this project with the RSC. And last, but not least, we appreciate all the efforts of Catriona Clarke and the team at the RSC for the editorial assistance in bringing out the book in time.

Vimal K. Jain and K. Indira Priyadarsini