Phytonutrients Flashcards
Primary metabolites
Are compounds necessary for plant survival such as carbohydrates,
proteins, lipids, enzymes and chlorophyll.
Secondary metabolites:
- Are synthesised by the plant in reaction to its environment an adaptive response.
- Evolve to facilitate the survival of the plant.
- Deter predators and protect from infection.
Roles of secondary
metabolites in plants
- Protection against herbivores, plant pathogens and against other plants.
- Protection against physical stressors such as ultraviolet light.
- Signals for communication and to attract pollinators
Roles of secondary metabolites in the human body
- Function as antioxidants (e.g. quercetin, abundant in red onions)
- Regulate the cell cycle.
- Increase detoxification of carcinogenic and other toxic compounds.
- Reduce DNA damage (e.g. lycopene in tomatoes)
- Mimic or interact with hormones and other body chemistry (e.g. lignans in flaxseeds can support oestrogen levels when low).
Phytonutrient Types
Phenols and polyphenols
Terpenes
Phytosterols
Organosulphur compounds
Alkaloids
Phenol and polyphenol Types
Flavonoids
Phenolic Acids
Lignans
Stilbenes
Quinones
Tannins
Flavonoids
Quercetin, kaempferol, rutin, hesperidin, naringenin, catechins, anthocyanins, isoflavones.
Phenolic acids
Gallic acid (e.g. grapes ),
Caffeic acid (e.g. thyme, sage, sunflower seeds )
Salicylic acid (e.g. in white willow bark)
Lignans
Secoisolariciresinol (e.g. flaxseeds
Stilbenes
Resveratrol (e.g. grapes)
Flavonoids Types
Flavanols or catechins
Flavones
Isoflavones
Flavanones
Anthocyanins
Flavonols
Flavonols
kaempferol in kale, spinach
quercetin in red onions and apples
Flavones
apigenin - parsley, celery, chamomile
Isoflavones
genistein and daidzein - soybeans
Flavanones
Naringin - grapefruit
Anthocyanins
cyanidin - red grapes, blackberry, blueberry
Flavanols or catechins
epicatechin - green tea, cocoa
Flavonoids
Blue, purple, black
Blueberries, blackberries, red cabbage, aubergines, black olives.
Chlrophyll
Green
Kale, spinach, collard, broccoli, brussels sprouts, parsley, lettuce, avocado, watercress, cucumber.
Lycopene
Red, pink
Tomatoes, guava, watermelon.
Carotenoids
Yellow, orange
Carrot, squash, sweet potatoes, orange, papaya, corn, melon, peppers, pumpkin, turmeric.
Sulphur Compounds
White, brown
Garlic, onions, leeks, ginger, white cabbage, mushrooms, parsnips.
Benefits of phytonutrients: Blue, purple, black
Antioxidant to fight free radicals , support heart health, circulation and vision.
Benefits of phytonutrients: Green
High in chlorophyll , provides nutrients, supports liver detoxification, binds with toxins in the gut preventing absorption into the body.
Benefits of phytonutrients: Red
Reduces inflammation, high in vitamin C and supports the prostate.
Benefits of phytonutrients: Orange, Yellow
Improves immune system, vision and joint health.
Benefits of phytonutrients: White, brown
Supports heart, circulation and liver detox
Catechins and epicatechins: Food Sources
- Tea green tea, oolong tea and black tea.
- Cocoa.
- Black grapes, berries,
apples, pears, plums. - Vinegar.
Catechins and epicatechins:Functions
Anti-inflammatory
Neurological health
Cardiovascular health
Joint health
Quercetin
Quercetin is the most abundant of the flavonoids. It is also a building block for other flavonoids (e.g. kaempferol):
* Quercetin has a fast excretion rate so needs to be consumed regularly for therapeutic use.
* Therapeutic dosage range: 150‒1500 mg / day.
Quercetin: Food sources
Onions (especially red),
apples (especially the peel), grapes, capers, asparagus, tomatoes, kale, brassica vegetables and
berries ( blueberries, bilberries, blackberries,
elderberry, cranberry and goji.)
Quercetin: Functions
Cardiovascular health
Anti-cancer
Immune system
Zanthine oxidase
Quercetin: Absorption
Absorption: Only a small percentage of ingested quercetin is absorbed in the blood:
‒ Quercetin occurs in most food as a glycone so it has to split from the sugar portion to be absorbed and become active.
‒ Onion and shallots contain quercetin in its unbound (aglycone) form, which may make absorption easier
‒ Quercetin is hydrophobic, so is best absorbed with fats, emulsifiers or apple pectin.
Quercetin: Interactions
Some antibiotics e.g. fluoroquinolones and some types of chemotherapy e.g. paclitaxel.
Naringin
Naringin belongs to the group of flavanones. It is metabolised to naringenin in the gut by intestinal bacteria
Naringin: Food sources
Citrus fruits (especially in grapefruit, where naringin is responsible for the fruit’s bitter taste). Also found in cooked tomato paste
Naringin: Caution
Grapefruit is contraindicated with numerous medications because naringenin inhibits intestinal CYP3A4 (the pathway used for many pharmaceutical drugs). Its inhibition results
in less metabolism and thus higher circulating levels of drugs.
Naringin: Functions
Cardiovascular health
Anti-cancer
Diabetes
Isoflavonoids
The group includes: Isoflavones, isoflavonones, isoflavans and rotenoids.
Isoflavonoids: Food sources
- Mostly soy, but also other
legumes e.g. lentils, peas,
chickpeas, peanuts. - Alfalfa sprouts.
- Red clover.
- Brussel sprouts.
Isoflavonoids: Metabolism
- In soybeans, isoflavones are present as glycosides
bound to a sugar molecule and need to be split apart to render them active. - Digestion or fermentation of soybeans or soy products results in the release / splitting of the sugar molecule from the isoflavone glycoside, leaving an aglycone.
Isoflavonaoids: Functions
Oestrogenic activity
Cardiovascular health
Osteoporosis
Isoflavonoids: Drug interactions
- High intakes of soy protein may interfere with the efficacy of warfarin.
- Seven studies investigating the effect of soy in combination with tamoxifen have reported
no significant differences with respect to treatment outcomes or rates of adverse effects associated with use of soy among
women who were receiving tamoxifen therapy.
‒ Note that this is usage of soy in its wholefood
form, not as isolated isoflavones.
Isoflavonoids: Safety
- The safety of high intakes of soy isoflavones and other phytoestrogens for breast cancer survivors is an area of considerable debate among scientists and clinicians.
- The Shanghai Breast Cancer Survival Study was
a large, population based cohort study of 5042
female breast cancer survivors in China.
‒ Among women with breast cancer, soy food
consumption was significantly associated
with decreased risk of death and recurrence. - However, all genetically modified sources of soy must be avoided.
Lignans
Lignans can be metabolised by intestinal bacteria to form the phytoestrogen compounds enterodiol and enterolactone:
* They are said to be the ‘Western equivalent’ of phytoestrogens and are a soy alternative.
* It is thought that variations in the intestinal bacteria mean that in Western populations tend to tolerate lignans more than soy.
Lignans: Food Sources
- Flaxseeds (most abundant 1 oz, 85.5mg)
- Sesame seeds (1 oz, 11.2mg), beans and pulses, cruciferous vegetables.
Lignans: Function
Oestrogen Modulation
Anti-cancer
Resveratrol
Resveratrol is the most studied stilbenoid . It is a
powerful antioxidant produced by some plants to protect them against environmental stresses:
Resveratrol: Food Sources
- Red grapes (skins(
- Blueberries, mulberries, raspberries, cranberries.
- Peanuts with red skins on, pistachios.
- Cocoa.
Resveratrol: Functions
Anti-oxidant
Insulin sensitivity
Oestrogen modulation
Resveratrol: Safety
- There is currently no evidence that resveratrol can be toxic or cause adverse effects in humans.
- The safety of resveratrol containing supplements during pregnancy and lactation has not been established.
- Avoid recommending alcohol consumption as a source ofresveratrol red grape juice is just as rich a source!
Resveratrol: Interactions
- High intakes of resveratrol (e.g. supplements) could increase the risk of bleeding when taken with anticoagulant drugs.
- Resveratrol inhibits the activity of cytochrome P450; thus high intakes of resveratrol (e.g. from supplements) could theoretically increase the bioavailability and toxicity of drugs that undergo extensive first pass metabolism by CYP450 (statins, immune suppressants, calcium channel blockers, etc)
Proanthocyanidins
Proanthocyanidins are known as condensed tannins and are formed from building blocks including catechin and epicatechin. They are predominant in the seeds and skin of grapes
Proanthocyanidins: Food sources
- Grapes (skin and seeds(
- Cranberries, blueberries, elderberry, bilberries.
- Cocoa.
- Apples, cinnamon, cashews.
- Maritime pine bark (pycnogenol)
Proanthocyanidins: Functions
Cardiovascular health
Immune modulation
Neurological health
Anti-cancer
Proanthocyanidins: Safety and interactions
- Generally recognised as safe and well tolerated.
- Monitor with antihypertensive medication. Caution with anti-coagulant medications may have additive effects.
Anthocyanins
Anthocyanins and their aglycone ‘anthocyanidins’ are blue, red and purple pigments found in a range of plants. They are protective against UV radiation in plants:
* Found in the tissues of plants including leaves, stems, roots, flowers and fruits.
Anthocyanins: Food sources
Acai berry, blackcurrant, blueberry, bilberry, cherry,
red grape, purple corn.
Anthocyanins: Functions
Cardiovascular health
Type 2 Diabetes
Eye health
Neurological health
Anthocyanins: Interactions
- Many anthocyanins have been identified as inhibitors of BRCP mediated transport, theoretically increasing bioavailability of certain drugs including
– Anticancer agents (mitoxantrone, topotecan,
tyrosine kinase inhibitors) ; antibiotics
(fluoroquinolones); β blockers (prazosin). - High intakes (e.g. from supplements) could increase the risk of bleeding when taken with anticoagulant drugs
Phytosterols
Phytosterols are plant derived lipids that are structurally similar to cholesterol. The two classes of nutritional significance are:
1. Sterols have a double bond in the sterol ring.
The most abundant sterols in plants and the human
diet are β-sitosterol, campesterol and stigmasterol.
2. Stanols which lack a double bond in the sterol ring. Stanols are also present in plants, but only comprise about 10% of total dietary phytosterols.
Phytosterols: Food sources
- Unrefined vegetable oils, nuts, seeds, whole grains and legumes.
Wheat germ: ½ cup (57 g), 197mg
Sesame oil: 1 tbsp (14 g), 118mg
Pistachios: 1 ounce (28 g), 79mg
Phytosterols: Functions
Promotes healthy serum cholesterol
Anti-cancer
Prostate health
Immune health
Phytosterols: Interactions
- Additive effects with cholesterol lowering medication (statins)
- Higher amounts may reduce absorption of dietary carotenoids.
Isothiocyanates
Isothiocyanates (ITCs) are biologically active breakdown products of the sulphur rich compounds, glucosinolates
* Each glucosinolate forms a different ITC when hydrolysed e.g.
– Glucoraphanin forms sulforaphane.
– Sinigrin forms allyl isothiocyanate.
Isothiocyanates - Food Sources
- Cruciferous vegetables (e.g. Brussel sprouts, broccoli, cabbage, kale, ).
- Horseradish.
- Mustard greens.
Isothiocyanates: Functions
Antioxidant / Anti-inflammatory
Liver detoxification
Anti-cancer
Indole-3-Carbinol
Indole-3-carbinol (I3C) is derived from the breakdown of glucobrassicin ; a glucosinolate found in cruciferous vegetables:
* In the acidic environment of the stomach, I3C
forms a number of biologically active indole products, most notably, 3,3’ diindolylmethane (DIM). I3C primarily acts via its major metabolite, DIM
* I3C and DIM have the same physiological effects.
Indole-3-Carbinol: Food sources
- Cruciferous vegs broccoli, kale, cauliflower.
- Broccoli sprouts are between 20 and 50 times
more abundant in I3C than normal broccoli.
Indole-3-Carbinol: Functions
Oestrogen modulation
Cervical intraepithelial neoplasia ( CIN) (Cervical
dysplasia)
Breast and prostate cancer
Carotenoids
Carotenoids belong to the terpene class of phytonutrients, with more than 750 naturally occurring in nature. They are the source of the yellow, orange, and red colours of many plants.
* The most common carotenoids in Western diets are
alpha-carotene, beta-carotene, beta-cryptoxanthin
(pro vitamin A; see ‘Vitamins’ lecture), lutein, zeaxanthin and lycopene
Carotenoids: Food sources
Yellow, orange, and red fruits and
vegetables. Green vegetables.
Lutein and Zeaxanthin: Functions
Eye health
Lutein and Zeaxanthin: Eye Health
- Both collect in the macula of the eye and absorb up to 90% blue light.
- Protect retinal cells from oxidative stress.
- Shown to protect against visual fatigue and improve visual contrast sensitivity.
- Lutein is thought to promote efficient neuronal signalling , improving
- Lutein inhibits NFkB signalling, reducing inflammation associated with eye disorders including uveitis.
Lycopene
Lycopene is a fat-soluble red pigment produced by plants. It is a non-vitamin A carotenoid:
Lycopene: Food sources
- Tomatoes (highest source) more abundant in paste and purée.
- Guava.
- Pink grapefruit.
- Watermelon.
- Papaya.
Lycopene: Functions
Anti-cancer
Prostate health
Cardiovascular health
