Antioxidants and Bioactive Compounds in Fruits - Fruit Ripening: Physiology, Signalling and Genomics - page 111

7.5 Aspects Controlling the
Accumulation of Bioactive Compounds
in Fruits

pounds do not all segregate in the same
fashion; for example, naringenin chalcone
content segregates as a monogenic trait
independently from carotenoids and
chlorophylls in melon (Tadmor et al. ,
2010). Traits linked to fruit nutritional
quality are complex and have polygenic
control and quantitative inheritance. How-
ever, a considerable number of quantitative
trait loci linked to fruit nutritional quality
have recently been characterized in fruits
(Davey et al. , 2006; Fernie et al. , 2006;
Stevens et al. , 2008; Almeida et al. , 2011;
Farre et al. , 2011).

The antioxidant levels of a fruit crop may
be attributed to pre- and postharvest
factors. It has been established that the
accumulation of natural substances with
bioactive and antioxidant activities in fruit
and vegetables is affected by genetic
control (Bramley, 2002; George et al. , 2004;
Leskovar et al. , 2004; Milella et al. , 2011;
Tlili et al. , 2011; Fitzpatrick et al. , 2012),
environmental stimuli (Dumas et al. , 2003;
Atkinson et al. , 2011), and developmental
and ripening infl uences (Perkins-Veazie et
al. , 2001; Bramley, 2002; Serrano et al. ,
2005; Fitzpatrick et al. , 2006, 2012;
Ioannidi et al. , 2009; Martí et al. , 2011;
Tlili et al. , 2011), as well as preharvest and
postharvest conditions (Lee and Kader,
2000; Ioannidi et al. , 2009; Vicente et al. ,
2009; Atkinson et al. , 2011; Vallverdú-
Queralt et al. , 2012). Furthermore, as the
ripening process is thought to involve
oxidative phenomena, a corresponding
antioxidant system is needed to balance
out the subsequent build-up of ROS
(Jimenez et al. , 2002).

7.5.2 Developmental and ripening regulation

The accumulation of phytochemicals with
bioactive properties and the corresponding
total antioxidant activity during fruit
ripening seem to be under developmental
and ethylene control and represent part
of the overall ripening changes consisting
of chlorophyll loss, the appearance of
carotenoids including lycopene and
xanthophylls and the accumulation of
phenylpropanoids, ascorbate, D - and
E -tocopherol and others (Hancock et al. ,
2007; Giorio et al. , 2008; Fraser et al. , 2009;
Ioannidi et al. , 2009; Martí et al. , 2011;
Fitzpatrick et al. , 2012). These changes
occur in all types of fruit, regardless of the
characteristic ripening pattern (climacteric
versus non-climacteric). However, control
of phytochemical accumulation varies
with ripening classifi cation. Although
critical assessment of the developmental
control of fruit ripening and of the main
bioactive compounds can be found in
other chapters, it is thought appropriate to
briefl y mention here the most recent
fi ndings with respect to the afore-
mentioned compounds. Carotenoid in-
crease during ripening is a result of the
coordinated gene expression of the bio-
synthetic genes phytoene synthase (PSY),
especially PSY1 (Bramley, 2002; Giorio et
al. , 2008), and genes encoding desaturases
and isomerases, whereas both lycopene E -
and H -cyclases cease expression resulting in
the rise of lycopene (Galpaz et al. , 2006;

7.5.1 Genetic infl uence

Genetic variability, as depicted by the
plethora of different fruit crop cultivars in
use today, is an important factor in-
fl uencing the accumulation of all bioactive
compounds studied to date, including
vitamins C and E and other compounds
with antioxidant activity such as caroten-
oids ( E -carotene, lycopene and xantho-
phylls), phenylpropanoids, glucosinolates,
polyamines and specifi c amino acids
(arginine and citrulline).
This has been documented in tomatoes
(Abushita et al. , 2000; George et al. , 2004;
Ilahy et al. , 2011), watermelon (Perkins-
Veazie et al. , 2001, 2006; Tlili et al. , 2011),
cherries (Gao and Mazza, 1995; Ferretti et
al. , 2010), strawberries (Olsson et al. , 2004;
Tulipani et al. , 2008) and peppers (Brand
et al. , 2012). Interestingly, these com-