Polyphenols - Fruit Ripening: Physiology, Signalling and Genomics - page 159

9 Polyphenols

Agnès Ageorges, Véronique Cheynier* and Nancy Terrier
INRA, Montpellier cedex, France

9.1 Introduction

while others are restricted to certain
botanical families. Phenolic profi les are
genetically determined and commonly
used for taxonomic studies, providing
evidence of phylogenic proximities and
markers in varietal authentication. For
instance, the relative abundance of antho-
cyanin diglucosides distinguishes berries
(and wines) of non- vinifera or hybrid grape
varieties from those of Vitis vinifera
cultivars. Polyphenols are also differently
distributed within the plant, in both time
and space, in relation to their particular
roles.
Fruit polyphenol composition has been
studied extensively, in particular with
respect to food quality and nutrition
issues. Indeed, polyphenols contribute to
major organoleptic properties of fruits,
including colour, sensitivity to enzymatic
browning and taste properties such as
bitterness and astringency. They also
attract considerable interest for their
potential role in the health benefi cial
effects associated with dietary con-
sumption of fruits and vegetables.
After reviewing the structures and
properties of major fruit polyphenols, this
chapter will discuss fruit polyphenol com-
position and sources of variations, and
highlight some of the biosynthetic and
regulatory processes.

Polyphenols are a large class of plant
secondary metabolites, ubiquitous in
plants and structurally diverse. The earlier
defi nition of polyphenols, proposed by
Bate-Smith and Swain (1962), implied the
ability to precipitate alkaloids and proteins
from solution, while many recent papers
refer to all phenolic compounds as
polyphenols. In fact, the term polyphenols
should be restricted to plant phenolic
compounds 'derived exclusively from the
shikimate derived phenylpropanoid and/or
the polyketide pathway(s), featuring more
than one phenolic ring and being devoid of
any nitrogen-based functional group in
their most basic structural expression', as
stated recently by Quideau et al. (2011).
This defi nition covers several groups,
including fl avonoids, hydroxystilbenes,
lignans and benzoic acid derivatives such
as gallotannins and ellagitannins. Wide
structural diversity is encountered within
each group, and especially the fl avonoid
family, comprising over 8000 molecules
(Andersen and Markham, 2006).
Phenolic compounds are found through-
out the plant kingdom, but polyphenols are
represented mostly in vascular plants, as
reviewed recently (Lattanzio et al. , 2012).
Some polyphenols are rather common,