Fruit and vegetable diversity, secondary metabolites and antioxidants. Flashcards
Why do we eat fruit, veg and nuts
Flavour, alone or complimentary products, variation in out diet, healthy.
What’s healthy about fruit, veg and nuts
Energy source (oil, sugar, starch) protein source (not great) Fibre source minerals phytochemical, pro-vitamins & phytonutrients such as carotenoids, flavonoids, glucosinolates, folate
What are the different pro-vitamins and phytochemical found?
Carotenoids, flavonoids and anthocyanins, glucosinolates & indoles, folate and other vitamins
What colour are carotenoids
soluble in?
red/yellow, orange pigments
non polar= Fat
What colour are Flavonoids and anthocyanins?
solubility?
colourless and purple/ red/ blue pigments
polar = water soluble. (e.g. radishes in water)
What do antioxidants do?
they have the ability to quench oxygen radicals- that would otherwise do damage to our cells.
Do phytonutrients have antioxidant capacity
They do in vitro. but in vivo mechanisms are often more complex or may not be related to antioxidant capacity at all.
> may be absorbed in such small quantities to exert any real antioxidant capacity.
Where does the ‘antioxidant capacity’ of fruits and veg come from
supposedly the phytonutrients and pro-vitamins
What is an antioxidant
It is a molecule with a missing electron from its outer shell.
What are carotenoids?
red/ orange and yellow pigments in fruit and veg.
C40 hydrocarbons
+600 known but only 10-15 found in our diet.
most fruit and veg have predominantly 1-3 major present which determines their colour- depends on genetics.
What dictates what carotenoid is present
genetics- how well the biosynthesis enzyme works. All carotenoids are linked in the same pathway.
What are the primary carotenoids
Lycopene (tomatoes)- RED
beta carotene (Carrots) - ORANGE
alpha carotene (corn) YELLOW
Capsanthin (capsicums)- Red
What are the two major different types of carotenoids
2 enzymes involved.
The alpha and beta carotenes- splits after lycopene. alpha pathway has beta ring on the opposite side.
lycopene B cyclase (LCY-b BATA) forms the beta ring
lycopene epsilon cyclase (LCY-e LCY-b) forms the epsilon ring (Alpha pathway)
Difference between carotenes and Xanthophylls
carotenes have no extra groups attached
Xanthophylls are carotenes + OH group.
Where does vit A come from
formed from B- carotene, Bcyptoxanthin and alpha carotene
where are carotenoids stored in plant cells
In the chloroplasts and chromoplasts
Lycopene is linked to, in terms of health?
Lower incidence of prostate cancer
What are good sources of lutein
Green leafy veg
How are carotenoids stored in the chromoplasts?
either as crystals (trans) or in liquid globules (non-linear- cis and xanthophylls).
Where does uptake of carotenoids usually occur?
In the small intestine
What aids in the absorption of carotenoids?
consuming them in conjunction with fats/oils as they are lipophillic
Avo- ideal matrix- contains lutein and oil
What is lutein
A carotenoid-
associated with AMD
MOREEE
Describe the process of carotenoid absorption in the gut
Mixed micelles release the carotenoids into enterocytes by either passive or active mechanisms.
carotenoids are either cleaved or attached to non-specific transport proteins called chylomicrons and secreted into the lymph system. Chylomicrons are then transported to the liver, and stored or repacked on lipid carrier proteins for distribution.
What does Vitamin A consist of? What are the precursors?
consists of retinol, retinal and retinoic acid. beta carotene, beta cryptoxanthine and alpha carotene are precursors (only in mammals).
What enzyme cleaves pro-vitamins to form Vit A
BCO1= beta carotene oxygenase 1
Humans vary in their ability to cleave beta carotene. What do people who cleave it efficiently have more of? why?
Tend to have more macular carotenoids (lutein/ zeaxanthin)- because intact beta carotene competes with lutein/ zeaxanthin uptake and transport.
What are good food sources of vitamin A
Vitamin A- liver
pro-vit A- many orange fruit and veg: carrot, sweet potato, pumpkin, mango, papaya.
What is the association between night blindness and Vitamin A
In night blindness, there is a limited production of Rhodopsin- responsible for sensing low- light.
Rhodopsin is made up of retinal and opsin, it is located in the rods if the eye.
Vitamin A toxicity includes
Cannot be caused by pro-vit A
Carotenodermia- yellowing of the skin
hypervitaminosis A- over supplementation, pr eating too much liver- may cause birth defects or interfere with liver function.
What two carotenoids accumulate in the macula?
High levels of Zeaxanthin and lutein are associated with reduced incidence and progression of AMD.
where is Lutein accumulated in the macula?
Positioned in the peripheral macula
Where is zeaxanthin positioned in the macula
the central macula
what is more common in the human diet zeaxanthin or lutein?
Lutein (abt 20x more common)
What are good dietary sources of zeaxanthin
sweetcorn (5.28 ug/gFW), persimmons, spinach (raw)
What are good dietary sources of lutein?
Kale (180ug/gFW), turnip greens, spinach, collards, peas
What two carotenoids accumulate in the macula?
High levels of Zeaxanthin and lutein are associated with reduced incidence and progression of AMD.
where is Lutein accumulated in the macula?
Positioned in the peripheral macula
Where is zeaxanthin positioned in the macula
the central macula
what is more common in the human diet zeaxanthin or lutein?
Lutein (abt 20x more common)
What are good dietary sources of zeaxanthin
sweetcorn (5.28 ug/gFW), persimmons, spinach (raw)
What are good dietary sources of lutein?
Kale (180ug/gFW), turnip greens, spinach, collards, peas
What competes with lutein/ zeaxanthin for absorption in the gut?
beta carotene. Same transporter= chylomicrons
what are the three main enzymes that were altered during the biofortification of sweetcorn to increase [zeaxanthine]
- phytoene
- zeta- carotene desaturase
- epsilon cyclase
What in tomatoes has been linked to a lower incidence of prostate cancer
lycopene. - red pigment.
What form is lycopene in the plant cell
crystalline. therefore must be dissolved prior to absorption and cleavage.
Where are flavonoids synthesised in the plant cell?
In the endoplasmic reticulum/ cytosol
How is biofortification of lycopene in tomatoes acheived?
- modified pathway- reducing conversion of lycopene to beta carotene.
- change plant from ‘bush’ to ‘vine’.
- change external appearance- ‘clear epidermis’
What are flavonoids- characterised by?
pigmented polypenols. characterised by phenolic groups (aromatic ring + OH )
Function of polyphenols in plants
herbivore defence
UV light screening
Attractants
- often high [] at fruit surface/ skin rather than in flesh. (genetically determined)
what are the different types of flavonoids
anthocyanins (pigmented), flavone, flavanone, isoflavone, flavonol
Basic structure of flavanoids
Draw
basic 3 ring structure
Where are flavonoids stored in the plant cell
in the plant cell vacuole
Colour range of anthocyanins
red to purple
What are anthocyanins
What pathway are they formed in?
They are a pigmented type of flavonoid
formed in the ‘phenylpropanoid pathway’
what are the commonest anthocyanins in fruit and veg? what determines which is predominant?
cyanidin (purple) and pelargonidin (red)- the presence of a functional F’3H enzyme.
What have flavonoids been shown to do for health?
small [] have been shown to reduce hypertension via vasodilation of blood vessels (via nitric oxide mechanism).
Not all flavanoid groups effective. Anthocyanin appear to be the most strongly inversely associate with hypertension, but some more effective than others.
Where does the majority of flavonoids end up
in the large intestine (only a small []) is absorbed in the small intestine).
What is the most likely antioxidant found in water soluble extracts
anthocyanin
Where are most of the antioxidants in fruits found
the skin
Association between colour of fruit + veg and the antioxidant capacity
The more colourful the fruit and veg the greater the antioxidant capacity
What are some good sources of natural anti-hypertensives
Peonidin- cranberry and purple-fleshed sweet potato
Cyanidin- purple fleshed plums and purple corn & red wine
catechin- cocoa and tea
principle anthocyanin in red plums? what are its potential health benefits
Cyanidin- 3 glucoside
reducing blood P, LDL- cholesterol, and possibly some forms of cancer.
Red fleshed plums have higher levels of anthocyanin then yellow-fleshed plums
