Phenols

Phenols are a broad class of aromatic organic compounds manufactured by plants that can be strong systemic poisons for organisms including animals, bacteria, fungi, parasites and viruses. Phenolic compounds are stored in the tissues of plants to deter plant browsers and are released when plant material decomposes or is damaged. They are also involved in defence against attacks by pathogens and ultraviolet radiation.

Polyphenols

Poly means many, which refers to the large number of groupings of the basic phenol rings. There are over 4,000 polyphenol compounds. Many are powerful antioxidants and can neutralise free radicals, reduce inflammation and slow the growth of tumours.

Various polyphenols provide the colours of ripe plums and berries and the intense colours of geraniums and delphiniums.

A polyphenol antioxidant is a type of antioxidant containing a polyphenolic or natural phenol substructure. Anthocyanins, flavonoids, tannins, resveratrol (found in grapes and cocoa) and catechins (such as epigallocatechin gallate (found in green tea) are all polyphenol compounds. Consuming foods rich in polyphenols can be beneficial to those suffering with diabetes or infections.

Polyphenols are reducing agents and together with other dietary reducing agents, such as carotenoids, vitamins C and vitamin E, referred to as antioxidants, protect the human body’s tissues against oxidative stress and associated pathologies such as cancers, coronary heart disease and inflammation.

Polyphenols are the most abundant antioxidants in the diet, and the main classes of polyphenols are phenolic acids, mainly caffeic acid and flavonoids.

Examples of polyphenols

• Capsaicin in chilli and paprika.
• Cinnamic acid in cinnamon.
• Ferulic acid in cereal grains,
• Punicalagins in pomegranates.
• Resveratrol in red wine.
• Rosmarinic acid found in rosemary, thyme, oregano, sage and peppermint.
• Thymol in thyme.

Highest sources of polyphenols in milligrams per 100 grams

NOTE: Some foods high in polyphenols are also high in harmful lectins, such as foods in the nightshade family and various beans. See>> Lectin intolerance.

Detailed structure of polyphenols

Polyphenols are divided into four primary groups:

1. Flavonoids
2. Lignans
3. Phenolic acids
4. Stilbenes

Flavonoids (first primary polyphenol group)

Flavonoids are divided in six groups

1. Anthocyanins
2. Flavanols
3. Flavonols
4. Flavanones
5. Flavones
6. Isoflavones

NOTE: Flavanols and flavonols are different subclasses of flavonoids, distinguished by their oxidation state and structure.

Anthocyanidins are associated with heart health, antioxidant effects and helping with obesity and diabetes prevention. For more details and highest natural sources see>> Anthocyanins

2. Flavanols

Types of flavanols

• Dimers (proanthocyanidins)
• Monomers (catechins)
• Polymers (proanthocyanidins)
• Theaflavins
• Thearubigins

Highest sources of flavanols in alphabetical order

• Apple skins (red)
• Apricots
• Berries
• Broccoli
• Grapes (red)
• Kale
• Onions
• Scallions
• Teas (black, green, oolong and white)

Dimers and polymers (proanthocyanidins)

Richest sources of proanthocyanidins

• Apple skins (red)
• Berries
• Cocoa beans
• Grape skins (red)
• Wine (red)

Molymers (catechins) can reduce chronic fatigue syndrome symptoms and are also associated with cardiovascular and neurological health.

Highest sources of catechins in alphabetical order

• Apples
• Apricots (richest source)
• Berries
• Cacao beans
• Grapes
• Teas (green, oolong and white)

Theaflavins and thearubigins are found in black tea.

3. Flavonols

Quercetin is a flavonol which is an antihistamine associated with helping to relieve hay fever and hives. It is also known for its anti-inflammatory benefits.

Kaempferol, and other flavanols, are associated with powerful anti-inflammatory and antioxidant activities leading to chronic disease prevention.

Types of flavonols

• Isorhamnetin
• Kaempferol
• Myricetin
• Quercetin

Highest sources of flavonols in alphabetical order

• Apples
• Berries
• Cocoa beans
• Grapes
• Teas (green, oolong and white)

4. Flavanones

Flavanones are associated with anti-inflammatory activity and antioxidant, cardiovascular health and relaxation.

Types of flavanones

• Eriodictyol
• Heridictyol
• Hesperidin
• Hesperitin
• Isosakuratenin
• Naringin
• Naringenin
• Narirutin
• Neohesperidin
• Neoeriocitrin

Highest sources of flavanones on alphabetical order

• Grapefruit
• Lemon
• Lime
• Oranges
• Pomelo
• Tangerines

5. Flavones

Flavones are associated with antioxidant benefits and delaying the metabolising of drugs.

Types of flavones

• Apigenin
• Baicalein
• Chrysin
• Luteolin

Highest sources of flavones in alphabetical order

• Celery
• Parsley
• Peppers (hot)
• Thyme

6. Isoflavones

Isoflavones are phyto-oestrogens, meaning that they are chemicals that act like the hormone oestrogen. They may be useful for treating some hormonal issues in women, but they may cause issues with the thyroid glands and therefore should be consumed in moderation.

Types of isoflavones

• Biochanin A
• Daidzein
• Formononetin
• Genistein
• Glycitein

Highest sources of isoflavones in alphabetical order

• Legumes
• Soya products

Lignans (second primary polyphenol group)

Lignans consist of enterolactone, sesamin and enterodiol and can protect against breast cancer in women. The body converts lignans into chemicals with some oestrogen-like effects. Sesamin is a lignan which can help to reduce fat. Lignans also have anticancer, antibacterial and antiviral activity.

Natural sources of lignans in alphabetical order

• Algae
• Asparagus
• Bamboo shoots
• Barley
• Berries
• Bran
• Broccoli
• Carrots
• Cashew nuts
• Fagara
• Flaxseeds and oil (richest source)
• Garlic
• Kale
• Lentils
• Nutmeg
• Pears
• Prunes
• Sesame seeds and oil
• Sunflower seeds
• Triticale (hybrid of wheat and rye)
• Wheat

Phenolic acid (third primary polyphenol group)

Phenolic acid, either alone or in combination with vitamins, such as carotenoids, vitamin E, and vitamin C, act as antioxidants to protect various tissues in the human body from oxidative stress.

Highest sources of phenolic acid in alphabetical order

• Blueberries
• Coffee beans
• Kiwi fruits
• Onions (red)
• Radishes (black)
• Tea

Two classes of phenolic acids can be distinguished:

1. Hydroxybenzoic acid
2. Hydroxycinnamic acid

Components of hydroxybenzoic acid

• Ellagitannins in fruits such as blackberries, raspberries and strawberries
• Gallic acid in tea leaves
• Gallotannins in mangoes

Components of hydroxycinnamic acid

• Caffeic acid
• Coumaric acid
• Ferulic acid
• Quinic acid
• Shikimic acid
• Sinapic acid
• Tartaric acid

Caffeic acid health benefits

Caffeic acid is found in all plants because it is a key intermediate in the biosynthesis of lignin. It possesses cancer preventing and anti-tumour properties and reduces body weight, lipid metabolism and obesity-related hormone levels.  It can also boost athletic performance, reduce exercise-related fatigue and help with the treatment of herpes, HIV/AIDS and other virus infections.

Highest sources of caffeic acid in alphabetical order

• Apples
• Artichoke
• Barley
• Berries
• Chia seeds
• Cucumber
• Eyebright
• Figwort
• Honey
• Mesima mushrooms
• Pears
• Potatoes
• Propolis
• Wine

Chlorogenic acid benefits

Chlorogenic acid has powerful antioxidant and anti-inflammatory effects, which can protect against diabetes and cardiovascular disease by improving blood sugar and blood pressure levels. It also shows potential for neuroprotective effects by reducing inflammation and oxidative stress in the brain which could provide anticancer and anti-aging benefits. It can also help with losing weight so is useful dietary addition for people with obesity.

Caffeic and quinic acid combine to form chlorogenic acid, which is found in many types of fruit and in high concentrations in green coffee beans. Roasting coffee beans reduces the levels significantly.

Highest sources of chlorogenic acid in alphabetical order

• Apples
• Artichokes
• Aubergines
• Bay leaf
• Chicory
• Coffee beans (green)
• Honeysuckle
• Prunes
• Rocket (arugula)
• Tea (black)

Stilbenes (fourth primary polyphenol group)

Stilbenes are found in only low quantities in the human diet. One of these, resveratrol, for which anti-carcinogenic effects have been shown during screening of medicinal plants and which has been extensively studied, is found in low quantities in red wine.

However, because resveratrol is found in such small quantities in the diet, any protective effect of this molecule is unlikely at normal nutritional intakes.

Highest sources of resveratrol in alphabetical order

• Bilberries
• Blueberries
• Cocoa
• Cranberries
• Grape skins (red or black)
• Mulberries
• Peanut skins
• Pistachio nuts
• Raspberries
• Red wine

Pterostilbene

Pterostilbene is a powerful antioxidant found in certain berries and nuts that is similar to resveratrol but more potent.

Highest sources of pterostilbene

• Almond skins
• Blackberries
• Blueberries
• Cranberries
• Grapes skins (red or black)
• Lingonberries
• Mulberries
• Peanut skins

NOTE: Blue berries may interact with diabetic and blood thinning medication so should be consumed with caution.

Phenol intolerance

Many synthetic food additives are now derived from petroleum or crude oil such as

• Butylated hydroxyanisole (BHA) E321
• Butylated hydroxytoluene (BHT) E392
• Tertiary butylhydroquinone (TBHQ) E320

Tertiary butylhydroquinone (TBHQ) is an aromatic organic compound which is a type of phenol used as a food preservative which is a form of butane. It is also used in the stabilisation process of explosive compounds. It can be found as an additive in the following products:

• Cosmetic skincare products for adults and babies.
• Crackers
• Crisps
• Fast foods
• Lacquers
• Pet foods
• Resins
• Varnish

Consuming high doses (1-4 g) of tertiary butylhydroquinone can cause the following symptoms:

• Asthma
• Collapse
• Delirium
• Dermatitis
• Hyperactivity in children
• Nausea and vomiting
• Restlessness
• Rhinitis (inflammation inside the nose)
• Tinnitus (ringing in the ears)

It may also aggravate attention deficit hyperactivity disorder (ADHD symptoms). It can also affect oestrogen levels in women.

Phenolic compounds are regularly found throughout the environment in thousands of items including most foods, pollen and chemicals. Many forms of asthma are caused by allergic reactions from both airborne phenolic compounds and those found in foods. It is difficult to avoid phenols as one of them, gallic acid, occurs in about 70% of the foods humans consume.

NOTE: If there is no improvement to symptoms through the elimination of phenols, then check that the intolerance is not to the other food allergens listed here>> Allergies

Related subjects

• A-Z of natural foods and remedies
• A-Z of nutrients
• Allergies
• Cancer
• Dementia
• Diabetes
• Heart disorders
• High blood pressure
• Obesity
• Respiratory disorders

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