Proanthocyanidins – a final frontier in flavonoid research?

Authors


Author for correspondence: Richard Dixon Tel: +1 580 224 6601 Fax: +1 580 224 6692 Email: radixon@noble.org

Abstract

Contents

  •  Summary 1

  • I. Introduction 1
  • II. Sources and structures of proanthocyanidins 2
  • III. Functions of proanthocyanidins in the plant 4
  • IV. Proanthocyanidins and plant quality traits 5
  • V. Flavanols, proanthocyanidins and human health 6
  • VI. Biosynthesis of proanthocyanidins 8
  • VII. Genetic manipulation of the proanthocyanidin pathway 15
  • VIII. Conclusions and future prospects 16
  •  Acknowledgements 17

  •  References 17

Summary

Proanthocyanidins are oligomeric and polymeric end products of the flavonoid biosynthetic pathway. They are present in the fruits, bark, leaves and seeds of many plants, where they provide protection against predation. At the same time they give flavor and astringency to beverages such as wine, fruit juices and teas, and are increasingly recognized as having beneficial effects on human health. The presence of proanthocyanidins is also a major quality factor for forage crops. The past 2 years have seen important breakthroughs in our understanding of the biosynthesis of the building blocks of proanthocyanidins, the flavan-3-ols (+)-catechin and (–)-epicatechin. However, virtually nothing is known about the ways in which these units are assembled into the corresponding oligomers in vivo. Molecular genetic approaches are leading to an understanding of the regulatory genes that control proanthocyanidin biosynthesis, and this information, together with increased knowledge of the enzymes specific for the pathway, will facilitate the genetic engineering of plants for introduction of value-added nutraceutical and forage quality traits.

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