Antioxidants and Bioactive Compounds in Fruits - Fruit Ripening: Physiology, Signalling and Genomics - page 110

The main bioactive compounds found
in Prunus species are carotenoids, AsA,
vitamin E and phenolic compounds
(reviewed by Vicente et al. , 2009). Initial
studies that monitored differences in the
phytochemical profi le of peach, nectarine
and plum fruits, either white- or yellow-
fl eshed, have been carried out within the
last 10 years (Tomas-Barberan et al. , 2001;
Gil et al. , 2002). Hydroxycinnamates,
procyanidins, fl avonols and anthocyanins
were quantifi ed in stone fruits using state-
of-the-art techniques (HPLC-DAD-MS-ESI),
which allowed the identifi cation of
procyanidin trimers in plums (Tomas-
Barberan et al. , 2001). A close correlation
between total phenolics and antioxidant
activity was monitored; this was not always
the case in studies with citrus fruits (Goulas
and Manganaris, 2011a). Apparently, dif-
ferent phytochemicals extant in distinct
fruit types differentially affect correlation
with in vitro antioxidant assays. It must be
noted that unmarketable over-ripe fruits
can be utilized as sources of bioactive
compounds (e.g. dietary supplements,
functional foods) (Puerta-Gomez and
Cisneros-Zevallos, 2011).
Extensive studies in terms of their
content have also been carried out in citrus
fruits, mainly in orange, mandarin, lemon,
mandarin, grapefruit and other citrus
species of relatively minor commercial
importance (reviewed by Simonne and
Ritenour, 2011). Carotenoids are the main
pigments reported in citrus fruits, evident
both in the peel and in the juice. Citrus
crops are also characterized by the presence
of naringin and hesperidin fl avanones and
highly oxygenated triterpenoid acids
(limonoids) such as limonin, limonin
glucoside and neoriocitrin (Yu et al. , 2005).
Besides their involvement in the bitter
taste, such compounds have been proved to
possess signifi cant antioxidant capacity.
Tropical fruit seem to possess strong
antioxidant activity (Terry and Thompson,
2011). Within this context, 'Maradol'
papaya fruit exocarp was found to be rich
in phenolic compounds such as ferulic
acid, caffeic acid and rutin, whereas
lycopene, E -cryptoxanthin and E -carotene

were identifi ed in the mesocarp as the
major carotenoids (Rivera-Pastrana et al. ,
2010). Ferulic acid, caffeic acid and rutin
tend to decrease whilst lycopene and
E -cryptoxanthin tend to increase during
papaya postharvest ripening (Rivera-
Pastrana et al. , 2010). Kiwifruit is another
exotic fruit crop with well-advertised
health-promoting properties, with special
reference to its high AsA content. The
bioactive profi le of the most common
kiwifruit cultivar ('Hayward') indicates the
presence of caffeic acid glucosyl derivatives,
coumarin glucosydes, E -sitosterol, stig-
masterol, campesterol and chlorogenic acid,
as well as fl avone and fl avanol molecules
(Fiorentino et al. , 2009). As there can be
wide differences among cultivars of the
same species, such studies are particularly
important where a relatively low number of
fruit cultivars account for the greatest
amount of production worldwide.
Pomegranate is receiving considerable
attention as a 'new' crop owing to its high
bioactive compound content, primarily
anthocyanins (delphinidin, cyanidin and
pelargonidin) (Faria and Calhau, 2011).
Evidence exists describing the anti-
carcinogenic properties of pomegranate
extracts with potential for human cancer
prevention (Lansky and Newman, 2007).
Research is lacking to determine how
the phytochemical profi le of pomegranate
is affected by cultivar variation,
environmental conditions or postharvest
treatments.
In contrast to other fl eshy fruits,
avocado and olive are characterized by
high oil content. The fat content comprises
30-70% of avocado and olive dry mass,
whilst other fl eshy fruits have less than
1%. Avocado fruit cv. 'Hass' showed higher
antioxidant capacity in lipophilic than in
hydrophilic extracts (Villa-Rodriguez et al. ,
2011). Avocado is a rich source of lipo-
philic phytochemicals such as mono-
unsaturated fatty acids, carotenoids,
vitamin E and phytosterols; however,
relatively few studies exist regarding the
changes in phytochemical content of
avocado during maturation or postharvest
ripening (Meyer et al. , 2011).