Vitamins in Fleshy Fruits - Fruit Ripening: Physiology, Signalling and Genomics - page 131

8.2.2 Provitamin A in fl eshy fruits are rich in carotenoids and can be

seasonally important sources of provitamin
A in many countries. The fl eshy mesocarp
of palm fruit ( Elaeis guineensis ), the main
oil crop in the world, also represents an
interesting source of provitamin A
(Tranbarger et al. , 2011) as it provides, at
the same time, the provitamin A
carotenoids and the lipids that increase
their bioavailability. Many other fruit

Provitamin A carotenoids ( D - and
E -carotene, E -cryptoxanthin; Fig. 8.1) are
found mostly in yellow and orange fruits,
in which they can accumulate in the
chromoplasts, plastids specialized in
pigment synthesis and storage. Many
widely consumed fl eshy fruits such as
passion fruit, mango and guava (Table 8.1)

Pyruvate + glyceraldehyde-3P

(MEP pathway ∗ )

1-Hydroxy-2-methyl-2-butenyl-4-diphosphate Cytokinins

HDR

Isopentenyl-2P Dimethylallyl-2P

Phylloquinones

IPI

GGPS

Geranylgeranyl-2P Phytyl-2P Tocopherols

PSY

15- cis -Phytoene

Chlorophylls

PDS

Gibberellins (GAs)

9,15,9 -tri- cis - ζ -Carotene

Z-ISO

9,9 -di- cis - ζ -Carotene

ZDS

7,9,7 ,9 -tetra- cis -Lycopene

CRTISO

All- trans -Lycopene

LYCB LYCE

γ -Carotene δ -Carotene

LYCB LYCE

β -Carotene α -Carotene

β -Hydroxylase

Lutein

β -Cryptoxantin

Zeaxantin

Abscisic acid (ABA)

Fig. 8.1. The carotenoid biosynthetic pathway (provitamin A) in plants and related metabolisms: cytokinins,
tocopherols, chlorophyll, phylloquinones (vitamin K), abscissic acid (ABA) and gibberellins (GA). The
corresponding enzymes and metabolites are: HDR, 4-hydroxy-3-methylbut-2-enyl-diphosphate reductase;
IPI, isopentenyl diphosphate isomerase; GGPS, geranylgeranyl pyrophosphate synthase; PSY, phytoene
synthase; PDS, phytoene desaturase; Z-ISO, 15- cis - ] -carotene isomerase; ZDS, ] -carotene desaturase;
CRTISO, carotenoid isomerase; LYCB, lycopene E -cyclase; LYCE, lycopene H -cyclase. *, For the
methylerythritol 4-phosphate (MEP) pathway, see detailed reactions in Fig. 8.2.