L19 - Phenolics and other compounds

Question 1

What are secondary metabolites ?

Answer 1

organic compounds that do not participate directly in growth and development
(quinine, nicotine, piperine, capsaicine)

Question 2

Primary metabolites

Answer 2

the plants need them to grow (essential)

ex phytosterols, nucleotides, amino acids, organic acids

Question 3

Roles in plants

Answer 3

ecological interactions

• protection against herbivory and microbial infection
• attractants for pollinators and seed dispersing animals
• allopathic agents (plants can compete with each other or co-compete together with other plants)

Question 4

Trichomes

Answer 4

Store metabolites

• defense (attract the predator of the insects)
• quality (ex tomato leaves have a specific recognisable smell)

Question 5

Main chemical families

Answer 5

• Terpenoids/ isoprenes ( from isopentenyldiphosphate (IPP) ) ex. lycopene,menthol,limonene
• alkaloids (more Nitrogen) ( from amino acids)
• phenolic compounds (aromatic molecules) (from the shikimate or the malonate/acetate pathway)

Question 6

What leads to the isoprene unit IPP

Answer 6

- Mevalonate Acetate (MVA) pathway generates
Farnesyl diphosphate (FPP)

-Methyl-erythritol-phosphate (MEP) pathway generates
Geranyl diphosphate (GPP) and geranylgeranyl diphosphate (GGPP)

Difference in the amount of carbon atoms

Question 7

Alkaloids main role

Answer 7

Mainly defense and communication:
• Toxicity, repelling feeding
• Attraction, pollination
• Dispersion
•Warning (i.e.,attracting predators for feeding insects

Question 8

Alkanoid biosynthesis

Answer 8

• Alkaloids are in most cases formed from amino acids (Trp, Tyr, Phe, Lys, Arg)
• Either alone or in combination with a terpenoid-type moiety
• medical purposes (heroin, morphine, opium)

Question 9

Phenolic compounds role

Answer 9

Phenolic compounds were essential for the adaptation of plants to land
• Cell wall structural roles:

Various other roles
• Defending plants
• Wood durability (bark)
• Flower color
• Flavors (taste & odor)

Question 10

Important phenolics

Answer 10

- Flavonoids:
  Anthocyanins 
  (pigments)
  Proanthocyanins
  Isoflavonoids
- Volatile Benzenoids/Phenylopropanoids
- Lignin
- Lignan
- Suberin
- Coumarins, Furanocoumarins, stilbenes

Question 11

Biosynthesis of phenolic compounds

Answer 11

• Derived from Phenylalanine or Tyrosine
• Phenylpropanoids Phenyl ring and Propane (C3)
• All primary derived from
• Phenylpropanoid
• Phenylpropanoid-acetate
• Shikimate Pathway and Aromatic Amino Acid Pathway

Question 12

The Shikimate Pathway

Answer 12

7 steps to Chorismate
• Only in plants and bacteria
• Occurs in the plastids
• EPSP synthase target for Glyphosate (Roundup)

Question 13

Lignin

Answer 13

• Located in secondary cell wall

* Lignin synthesis mostly nonenzymatic process

Question 14

Volatile Benzenoids/Phenylpropanoids (VBPs)

Answer 14

• Pollination syndrome
• Defense and Allopathic compounds
• Volatile Organic Compounds
• Biosynthesis from phenylpropanoids

Question 15

Quality and Postharvest - Secondary motabolites

Answer 15

• Diverse protective roles, protects against oxidative stress
• Synthesis is tightly regulated by stress and environmental factors
• ROS induction by these factors triggers defense system
• Induced production of sec. met. can be desirable for health-, and quality related benefits
• Could also reduce quality, e.g.bitterness, colour loss, etc.

Question 16

Secondary Metabolites. What are they? Function, application

Answer 16

Organic compounds that do not participate directly in growth and development
Often uniquely found in specific taxonomy groups

• Function: pigment / fragrance / defense
• Usefull applications: dyes / medicine / drugs / toxins