Preface

Vitamin E was discovered in 1922 by Evans and Bishop as an essential micronutrient for reproduction in rats. Rats fed a diet low in vitamin E had reduced fertility and a high rate of fetal resorption, but supplementation with a lipophilic fraction of lettuce or wheat germ oil resulted in a successful implantation of the embryo, implying an existence of a hitherto unrecognized dietary factor essential for reproduction. The active substance was isolated in 1936 by Evans and was given the name “tocopherol” meaning “to carry a pregnancy” from the Greek words “tokos, birth” and “pherein, to carry”. The ending “-ol” comes from its status as a chemical alcohol. It was named vitamin E according to a consecutive alphabetical order preceded by the discovery of vitamins A–D.

Vitamin E is the generic name of all tocopherols and tocotrienols. Vitamin E encompasses a group of eight isomeric molecules, which are characterized by a 6-hydroxychroman ring structure and a side chain. The tocopherols possess a 4′,8′,12′-trimethyltridecyl phytyl side chain, while the tocotrienols differ by the presence of double bonds at the 3′,7′ and 11′ positions of the side chain. The α-, β-, γ-, and δ-isomers of tocopherol and tocotrienols differ in the number and position of the methyl substituents attached to the chromanol ring.

In 1980, Machlin stated in the preface of his book Vitamin E: A Comprehensive Treatise that “there is more myth and controversy concerning vitamin E than any other single nutrient.” After almost forty years, the situation is still the same, despite the accumulation of much novel scientific information. This reflects that there are many unresolved issues with this vitamin and its metabolites in the fields of chemistry, biochemistry, biology, nutrition, and medicine, which may be ascribed in part to the inherent complexities of the role and action of vitamin E in vivo as well as in vitro.

This book is intended to give an overview of the state-of-the-art chemistry of the properties, actions, functions and nutritional benefits of vitamin E and its metabolites by summarizing what has been demonstrated and what has not, which is essential for understanding the chemical, biological, nutritional and medical effects of vitamin E. Information on the chemistry of the role and action of vitamin E based on sound and solid scientific evidence is essential for understanding the advantages and limits of vitamin E and also for its application in the promotion and maintenance of health and prevention of diseases. This is a timely issue before the centennial anniversary of the discovery of vitamin E.

I would like to express my sincere thanks to all the authors for their contributions and their patience in reacting to editorial demands and to the staff of the Editorial Office of the Royal Society of Chemistry, who encouraged and assisted the publication of this book.

Etsuo Niki

Tokyo, Japan