Chilean Plants as a Source of Polyphenols - Natural Antioxidants and Biocides from Wild Medicinal Plants - page 129

conjugates) and 18 anthocyanins were the
most abundant: delphinidin-3,5-dihexoside,
delphinidin-3-rutinoside-5-glucoside, cyani-
din-3,5-dihexoside, petunidin-3,5-dihexoside,
petunidin-3-rutinoside-5-glucoside, peonidin-
3,5-dihexoside, malvidin-3,5-dihexoside,
delphinidin-3-glucoside, delphinidin-3-
rutinoside, malvidin-3-rutinoside-5-glucoside,
cyanidin-3-glucoside, cyanidin-3-rutinoside,
petunidin-3-glucoside, petunidin-3-rutino-
side, peonidin-3-glucoside, peonidin-3-
rutinoside, malvidin-3-glucoside and
malvidin-3-rutinoside. In U. molinae fruit
two anthocyanins were identified: cyani-
din-3-glucoside and peonidin-3-glucoside.

Flavonoids are derived from cinnamic
acid formed by the action of phenylalanine
ammonia-lyase enzyme (PAL) starting from
the amino acid phenylalanine. PAL acts as
the branch point between primary metabo-
lism (shikimic acid metabolic pathway)
and secondary metabolism (phenylpropa-
noid pathway) (Winkel, 2006). Although
polyphenols have structural functions in
plants, many compounds that are constitu-
tive or tissue specific in a species could be
induced in other species or other tissues
under stress conditions (Christie et al. ,
1994). High light/UV, pathogen attack,
low nitrogen, low phosphate, low iron, low
temperature and wounding are some exam-
ples of both abiotic and biotic stress that
could induce polyphenols in plants (Dixon
and Paiva, 1995).
The main factors that affect polyphenol
content in plants may be grouped into geno-
type, environment, storage and processing,
and the stage of harvest (Fig. 8.1).
Genotype refers to the existence of
botanical families (e.g. Labiatae, Rosaceae,
Myrtaceae ) with high polyphenol content
or a particular type of compound. Within a
species there are varieties, selections and
ecotypes that have significantly different
polyphenol content or have a particular
type of such compounds (Fan-Chiang et al .,
2005; Scalzo et al ., 2005; Lohachoompol
et al ., 2008; Speisky et al ., 2008). The cli-
mate, soil and agronomic management
affect the polyphenol content in leaves and
fruits, and some authors postulate that
stressful conditions favour their production
(Häkkinen and Törrönen, 2000; Romero
et al. , 2002; Pedreira dos Santos et al ., 2007;
Servili et al ., 2007; Terry et al ., 2007).
Storage (fresh and frozen) and agro-industrial
processes cause the loss of some types of
polyphenols, as well as the transformation
of certain compounds (hydrolysable tan-
nins) to monomeric forms that would
present a greater bioavailability (Cabrita
et al ., 2000; Zafrilla et al ., 2001; Piljac-
Zegarac et al ., 2009). In relation to the stage
of harvest, leaves and aerial parts of plants
collected in different seasons, and fruits at
different stages of development and matu-
rity, present different concentrations and

8.4 Polyphenols in Chilean Plants:

an Agronomic Perspective

In natural habitats plants are surrounded by
an enormous number of potential enemies.
Nearly all ecosystems contain a wide vari-
ety of bacteria, viruses, fungi, nematodes,
mites, insects, mammals and other herbivo-
rous animals. Owing to their sedentary
nature, plants cannot avoid these herbivores
and pathogens simply by moving away;
they must protect themselves in other ways
(Taiz and Zeiger, 1991).
PNPs are organic compounds that
defend plants against a variety of herbivores
and pathogenic microbes. They also may
serve as structural support (lignin) or pig-
ments (anthocyanins) (Croteu, 2000). PNPs
have no generally recognized, direct roles in
primary metabolism (e.g. photosynthesis,
respiration and solute transport). They also
differ from primary metabolites (amino
acids, nucleotides, sugars and acyl lipids) in
having a restricted distribution in the plant
kingdom. That is, particular secondary
metabolites are often found in only one plant
species or related group of species, whereas
primary metabolites are found throughout
the plant kingdom (Taiz and Zeiger, 1991).
From this point of view, all the plants have
natural products but the relative contents of
these types of compounds in different spe-
cies are related to various factors that will be
described in more detail below.