Food Phenolics

Question 1

What are primary metabolites

Answer 1

the molecules involved in major metabolic pathways such as growth and energy production (sugars and amino acids etc.)

Question 2

what are plant secondary metabolites

Answer 2

the building blocks and enzymes derived from primary metabolic processes which produce a large number of secondary compounds

Question 3

what are the 3 main groups of plant secondary metabolites

Answer 3

1. Terpenes and terpenoids.
2. alkaloids (from aromatic and aliphatic amino acids
3. phenolic compounds (from amino acids such as phenylanaline and tyrosine, via the shikmic or malonic acid pathways.

Question 4

what is the role of plant phenolics

Answer 4

they are plant stress response metabolites.

Question 5

what are some of the main groups of Phenolics

Answer 5

simple phenols (phenolic acids and counarins) and polyphenols (flavonoids and non-flavonoids)

Question 6

What are phenolic acids? (classification, what foods found in, and chemical structures)

Answer 6

C1-C6, or C3-C6. They are simple phenols which can further be divided into hydroxybenzoic acids and hydroxycinnamic acids. Found mostly in fruits and vegetables, but in the bound form in grains and seeds. They can only be freed by acid or alkaline hydrolysis, or by enzymes. for chemistry, look for simple acids, with a. benzene ring.

Question 7

What are stilbenes? What structure, and what foods?

Answer 7

C6-C2-C6 backbone (2 benzene rings joined by 2 double bonded carbons. Mostly found in grapes and peanuts. Non Flavonoid

Question 8

What are lignans

Answer 8

Non Flavonoid. made of 2 C6-C3 units. Flaxseed is a rich source.

Question 9

What are flavonoids and their structure?

Answer 9

have a C6-C3-C6 backbone (benzene connected to ring with O which forms another Benzene.). The oxidation state on the C ring (O bound heterocyclic ring) determines the groups of flavonoids.

Question 10

what are the 6 subgroups of Flavanoids and identify key structural differences.

Answer 10

Flavones, Flavonols, Flavan-3-ols (catechins), flavanones, Anthocyanidins, and isoflavonoids.

Question 11

What is Glycosylation of flavonoids

Answer 11

It is when sugars are added to the hydroxy groups (usually glucose), enhancing their water solubility. it can also make the compounds less absorbable, as it can’t get through the lipid bilayer.

Question 12

what is the difference between hydrolysable and non-hydrolysable tannins.

Answer 12

Hydrolysable tannins are a non-flavonoid phenolic which is esterified to a sugar’s hydroxyl group. This weak ester bond allows for hydrolysis in acidic conditions, splitting into sugars and phenolic carboxylic acids. Non-hydrolysable tannins do not contain this sugar, meaning that they are not degraded in acidic conditions.

Question 13

what are some of the polyphenols found in tomato

Answer 13

tomato peel and seeds are rich in gallic acid, hydroxycinnamic acids, and quercetin.

Question 14

what are some of the polyphenols found in mixed salads

Answer 14

fennel contains flavonols; quercetin glycosides, kaempferol glycosides and isorgamnetin glycosides. lettucs contains quercetin and kaempferol derivatives. Apples contains the flavonol quercetin, and flavan-3-ols epicatechin and catechin.

Question 15

what are some food industry by-products which are rich in polyphenols

Answer 15

apple pommace, olive waste, sugarcane bagasse, citrus peel, coffee waste, grape seeds and skin, avocado seeds.

Question 16

what are some benefits of using food industry by-products which are rich in polyphenols

Answer 16

value-adding to growers, sustainability, can be used as purified supplements.

Question 17

what are the stages of polyphenols analysis?

Answer 17

Sample preparation, extraction, clean-up - isolation. then quantification (total phenolics and antioxidant activities), characterisation (liquid chromatography and mass spectrometry for example) bioactivity studies, bio-accessibility studies (gastric, small intestinal digestion, colonic fermentation).

Question 18

what is the bioactivity of a food substance

Answer 18

the effect that the substance has on living organisms or biological systems. This can be broken down into biological effects (how it effects the biological processes themselves) and therapeutic potential (potential to treat disease)

Question 19

what are the three main processes which underly health promoting aspects of phenolics?

Answer 19

1. antioxidant activity
2. metal chelation
3. enzyme inhibitory activity

(all are dependant on structural properties of phenolics)

Question 20

How does antioxidant function promote health

Answer 20

They reduce the oxidative stress (free radicals overwhelming the antioxidant defence). Oxidative stress can lead to cell damage and tissue not functioning properly

Question 21

How does metal chelation promote health

Answer 21

it can lower the redox potential of the metals which is making them redox inactive. this means chelation is also an important antioxidant activity.

Question 22

How does enzyme inhibition promote health

Answer 22

Some phenolics inhibit oxidative enzymes which produce free radicals. This reduces oxidative stress, promoting health by preventing cell and tissue damage. they are also important in inhibiting starch digestion enzymes, controlling the blood sugar spike, important in diabetic, and pre-diabetic individuals.

Question 23

what is the bioaccessibility vs bioavailability

Answer 23

Bioaccessibility is the fraction of the substance (phenolic) which is released from its matrix in the GI tract and becomes available for absorption (how much isn’t trapped in the food. e.g. ~60% is trapped in apple fiber material. Bioavailability is the proportion that enters the bloodstream and is available for use or storage by the body (dependant on a lot of things, but also bioaccessibility)

Question 24

why is bioaccessibility important to phenolics health benefits

Answer 24

it is not about how much you ingest, if it is not being available to absorption. Also, bioavailability is not always accurate, as phenolics are very helpful to the GI tract, meaning that if they don’t reach the bloodstream, they can still be very useful. Also, they can be metabolised by the colonic bacteria, providing other localised colonic health benefits.

Question 25

how does colonic fermentation occur with phenolics

Answer 25

colonic bacteria break phenolics into smaller organic compounds, which can be absorbed or further degraded.

Question 26

what is catechin an example of

Answer 26

a flavanol