L20 - Pigments

Question 1

Pigments: Role

Answer 1

1. Pigments act as visible signals to attract insects, birds and animals for pollination and seed dispersal
2. They protect plants from damage caused by UV and visible light
3. Important quality features… for commodities
4. Can be a Harvest index
5. Connection of visible pigments to health-related features

Question 2

Types of pigments

Answer 2

1. Chlorophyll
2. Carotenoids
3. Flavonoids
4. Betalains

Question 3

Chlorophylls

Answer 3

• Primary photosynthetic pigments in plants
• Capture light to drive photosynthesis
• Fresh fruits and green vegetables are rich in Chl
• Food additive (green colorant) used in a variety of foods and beverages
• Generally, Chl comprises 0.6% -1.6% on a dry weight basis

Question 4

Ripening and Chlorophyll breakdown

Answer 4

• During ripening of tomato, change in colour through degradation of
chlorophyll and accumulation of carotenoids
• Mutants in this breakdown: green flesh (gf)
• Chlorophyl and carotenoids (lycopene): brownish

Question 5

Chlorophylls

Answer 5

• Cyclic tetrapyrrole ring
• Chl a blue-green Chl b yellow-green
• Both highly susceptible to degradation during processing: food color changes
•
Breakdown is enzymatic process, 2 main pathways:
- Removal of phytate, Mg, and oxidative cleavage
- Oxidative degradation of Chl through hydroperoxide and radical formation by oxidation of lipids

Question 6

Carotenoids

Answer 6

• Yellow, orange and red
pigments – Lipid soluble
• Synthesized in plants, algae and
some photosynthetic bacteria
• 1000 - 750 found in nature

Question 7

Carotenoids role

Answer 7

Plants:

• Photosynthetic system
• Prevent photo oxidative damage
• Plant grow and development (ABA & strigolactones)
• Role in defense mechanisms

Question 8

Carotenoids biosynthesis

Answer 8

• Branches from the plastidialterpenoid pathway
• Biosynthesis in the plastid
• Biosynthesis divided in 2 parts:
  1. early lycopene yielding
  2. α, and β-carotene and xanthophylls

Question 9

Carotenoids regulation

Answer 9

Seems to be connected more to development than to specific regulators for carotenoid biosynthesis
• RIN, NAC1, MYB68, RCP1 (MYB)

Question 10

Carotenoids examples

Answer 10

• Carotenes: Provitamin A function (α-and β-carotene)
Eye and Brain development
• Lycopene: Antioxidant activity
• Lutein, Zeaxanthin: Blue light filtering
• Tocopherol: Vitamin E

Question 11

Carotenoids examples

Answer 11

• Carotenes: Provitamin A function (α-and β-carotene)
Eye and Brain development
• Lycopene: Antioxidant activity
• Lutein, Zeaxanthin: Blue light filtering
• Tocopherol: Vitamin E

Question 12

Flavonoids

Answer 12

• Wide colour range: pale yellow to blue
• Water soluble pigments,
• Stored in the vacuole
• Widely distributed in seed plants

Question 13

Flavonoids

Answer 13

Anthocyanins, Proanthocyanins, Flavonols, Flavones, Chalcones, Aurones

Over 6000 flav. compounds

Question 14

Flavonoids role

Answer 14

Plants:

• Attraction of pollinators and seeds dispersers
• Signalling between plants and soil borne symbiont bacteria
• Defence against microorganisms

Humans:

• Antioxidant, quality and appreciation
• pH indicator: Litmus test

Widely used as natural food colorants

Question 15

Flavonoid structure

Answer 15

Basic structure C6-C3-C6

Question 16

Anthocyanin biosynthesis:

Pigments

Answer 16

• Cyanidin
• Pelargonidin
• Delphinidin

Question 17

Betalains

Answer 17

• Yellow-to-red colors
• Nitrogen-containing
• Water soluble
• Derived from Tyr (Tyrosine)

Question 18

Betalains role

Answer 18

• Plants:
  • Attraction of animal pollinators and dispersers
  • Photoprotection, tolerance to droughts and salinity stress
  • High antioxidant and free radical scavenging activities
• Human:
  • Commercial food colorants and additives
  • Health connection: preventative to several forms of cancer and intermediates are important pharmaceuticals for treatment of Parkinson’s disease (L-DOPA)
  • Substate substrates for other pharmaceutical agents (e.g.dopamine and isoquinolinealkaloids such as morphine)

Question 19

Classes of betalains

Answer 19

1. Betaxanthins:
   Derived from betalamic acid conjuction with amines/amino acids
2. Betacyanins:
   From condensation of
   Betalamic acid with cyclo-DOPA

Question 20

Caryophyllales

Answer 20

Only found in limited number of plants

Does not coincide with anthocyanins in nature

Substitutes ubiquitous anthocyanin pigmentation in those species

Pattern of mutual exclusion between the two pigments types
GMOs can have both