Phenols Flashcards
(31 cards)
What are phenols?
- Phenols are widespread in food and medicinal plants, constituting the largest group of secondary metabolites.
- Phenols have one hydroxyl group attached to a benzene ring.
- Phenols have the hydroxyl group directly connected to the ring, alcohols have a hydroxyl group connected to the main chain. This gives it different properties.
- In phenol it is more acidic and more reactive.
- Polyphenols - many phenols - create complexes such as tannins, anthraquinones, flavonoids and coumarins.
What are Phenolic acids or simple phenols?
Phenolic acids are simple phenols with at least one carboxylic acid group, (phenolic
carboxylic acids).
All green plants have phenolic acids, free or attached to other types of polyphenols. Polyphenols typically exist in a plant as glcysides or aglycones
Phenol is the standard for the disinfecting power of microbial agents.
Let’s look at the simplest form, a phenolic acids. Most phenols are antioxidant, anti-inflammatory, antiseptic and bactericidal.
What is Salicylic acid and what derivatives does it have?
- The most common of the polyphenolic acids is the Salicylic acid
- Is is found in Willow, poplar, meadowsweet and wintergreen.
- It is made by adding the acetyl group: the drug aspirin (acetylsalicylic acid) was made in 1899. ‘A’ stands for acetyl, ‘spir’ from Spiraea ulmaria, a name for meadowsweet.
The phenolic acids are typically glycosides in the plant but are converted to alicylic acid in the body. The most commone glycosides in the plants are methyl salicylate, salicin etc:
- Salicin: Salix alba, Populus spp. and Viburnum opulus.
- Populin: Populus spp.
- Gaultherin: Gaultheria spp.
- Spiraein: Filipendula spp.
- Esters: methyl salicylate, Filipendula and Gaultheria spp and salicyl aldehyde, Filipendula spp.
What actions or properties do salicylates have?
- Antipyretic - increases peripheral blood flow and sweat
- Anti-inflammatory
- Analgesic - pain relief
- Antiseptics as all simple phenols
- Anticlotting action is only found in aspirin! Adding the acetyl group gives it this property. A side effect can be gastic bleeding; salicylatic acids does not have this side effect so sometimes plants are used instead for say gastric ulcers.
Other phenols: What is arbutin?
Some of the other phenols are arbutin
Found in a few plants such as damiana
It has bacteriostatic properties on urine so is often used for urinary infectioons, arbutin is hydrolysed to hydroquinone, a simple phenol, in alkaline urine.
Arctostaphylus uva-ursi
What phenolic essential oils are there?
Phenolic essential oils * Anethole: carminative (aniseed). * Apiole: antispasmodic (parsley). * Cinnamaldehyde: antimicrobial (cinnamon). * Eugenol: antimicrobial (clove).
Other phenolic acids: What is Ellagic acid?
- Part of a bigger compound in tannins.
- Found in grapes, wine, strawberries, black
berries, raspberries, pomegranates and persimmon. - Ellagitannins are slowly hydrolysed in the digestive tract, then releasing ellagic acid.
- This is antioxidant, anti-inflammatory, antimicrobial, antiproliferative (anti cancer), apoptosis and inhibits development of atherosclerosis.
Other phenolic acids: What is Gallic acid?
- Phenolic rings with three hydroxyl groups
- Also found in grapes, wine, walnuts, nuts and berries.
- Catechins, OPCs, tannins broken down to gallic acid.
- Anti-inflammatory, antimicrobial, antioxidant, antimutagenic, antiangiogenic, anticarcinogenic
- Can modulate hepatic detoxification enzymes and is well absorbed and readily bioavailable
What are Phenylpropanoids?
- These are Cinnamic acid derivatives
- They have a phenolic ring with 3- carbon attachment plus carboxyl group – they are a subcategory of the phenolic acids.
Similarly to the phenolic acids, they are
* Antioxidant, antimutagenic, antitumor and antimicrobial to some degree.
* Examples include Caffeic acid, chlorogenic acid, echinacoside, cichoric acid and rosmarinic acid.
Phenolic essential oils include
Anethole: carminative (aniseed).
Apiole: antispasmodic (parsley).
Cinnamaldehyde: antimicrobial (cinnamon).
Eugenol: antimicrobial (clove).
What is Chlorogenic acid
(a phenylpropanoid)?
- Found in lots of herbs such as Artichoke, burdock, coffee beans, tea, wormwood and hawthorn. Pretyy common int plants.
- Similarly to the phenolic acids, it is anti-oxidant, anti-inflammatory, antilipidemic,
antidiabetic, antineurodegenerative and
antihypertensive. - Some research done with metabolic syndrome, found helpful. In vivo:
- Slows intestinal absorption of glucose.
- Lowers post prandial glucose levels.
- Decreases liver glucose output.
- Strengthens the function of beta
cells in pancreas. - We find chlorogenic acid in coffee, which is thought to give the antidiabetic effect when we drink regularly. Not the caffiene here!
What is Caffeic acid ( a phenylpropanoid)?
- Found in red sage etc
- Again its Antioxidant, antiinflammatory, anti-cancer, analgesic, antimicrobial, antiviral activities and cardioprotective.
- Some research shows it may have a beneficial effect on learning.
There is also Caffeic acid phenethyl ester (CAPE) in propolis
* This is a derivative of caffeic acid.
* In vivo research shows it may help: Alzheimers disease, anticarcinogenic, antiinflammatory and immune stimulant properties; anti oxidant, antimicrobial - and has an effect on vascular reactivity and stiffness.
What is Rosmarinic acid
(phenylpropanoid)?
Rosmarinic acid (phenylpropanoid)
* Is found in many plants including; Rosmarinus officinalis, Melissa officinalis, Thymus vulgaris, Salvia officinalis and Borago officinalis.
* It is anti-inflammatory, antiviral, antibacterial, , antiallergic, antidepressant, antioxidant,
anticarcinogenic, neuroprotective.
* In vitro: it is found to be antiviral against herpes simplex and HIV.
* Lemon balm, antiviral effect on herpes viruses. Very effective on the lips in a lip balm - shortens the healing period etc.
What is Echinacoside
(Phenylpropanoid)?
Derived from caffeic acid - similar properties again to caffeic acid. It is again for research shown to be:
* Antioxidant.
* Hepatoprotective.
* Neuroprotective, in vivo.
* Anti-inflammatory.
* Anti-tumour.
* Anti-aging.
* Immunoregulation.
* Improves learning and memory.
Found in Echineacea.
What is Cichoric acid (Phenylpropanoid) ?
Found in chicory - Cichorium intybus - and echinacea (in particular E. purpurea), dandelion leaves, basil and lemon balm.
Found to be:
* Anti-cancer, anti-obesity, antiviral, and anti-diabetic.
* Anti-human immunodeficiency virus (HIV), in vitro.
* Able to modulate macrophage immune responses, in vitro.
* Antiarthritic, anti-inflammatory, in vivo.
Traditionally Echineaea has been used as an anti-arthritic
What are the Rosavins in Rhodiola rosea?
Rosavins in Rhodiola rosea
* The plant contains Phenylpropanoid glycosides rosavin, rosin and rosarin.
* Traditionally the plant has been used to improve memory, mental alertness and
stamina.
* A clinical study found it was anti-fatigue.
What are Coumarins?
Coumarins
* The name comes from the tonka bean = “kumaru”.
* Its a phenolic compound, a phenol propanoid derivative, and its formed by intramolecular reaction between a carboxyl group and a hydroxyl group on the same structure (benzene ring fused to a
lactone ring).
* You can find coumarins in legumes, grasses, and many of foods from the Apiaceae family including carrots, celery and parsnips.
* Often used a flavouring
* Usually in the plant they are in the form of glycosides
Coumarins & glycosides - they are within:
* Melilotoside from Melilotus officinalis.
* Aesculetin, glycoside aesculin from Aesculus
hippocastanum.
* Scopoletin, and the glycoside scopolin in poppies and plants in nightshade family and grapefruit.
* Umbelliferone, and the glycoside skimmin: Apiaceae (Umbelliferae) eg celery
- If a plant is injured, the coumarin and derivatives are released from the glycoside precursors - you can smell them
What is Dicoumarol?
To confuse things a bit there is also a substance called Dicoumarol
* Dicoumarol is formed in mouldy or poorly dried coumarin-rich plants, it is an anti-coagulant.
* Originally derived from sweet clover, Melilotus officinalis, warfarin is a synthetic derivative.
* Dicoumarol is hydroxylated in the 4 position which is essential to give it this antocoagulant property.
* Plant coumarins are not substituted at this position and have no anticoagulant activity - they normally only have coumarin.
Doctors can get confused and say no to coumerins, not knowing they are not actually anti-coagulant.
What are the actions of coumarins?
Coumarin – actions
* Anti-oedema, anti-inflammatory.
* Coumarin-rich plants are traditionally tonic to the venous and lymphatic vessels.
* Antiviral and anti-microbial.
* In vitro, in vivo, ex vivo research shows: antimitotic, immunomodulating, antiviral,
anticancer and cytotoxic agents.
What are Coumarin derivatives?
Coumarin derivatives
* Scopoletin: spasmolytic (is found in Viburnum species such as cramp bark and black haw)
* Scopoletin, umbelliferone: anti-inflammatory
and analgesic in vivo.
* Aesculetin and others: antioxidant in vitro.
* Fraxin: antimetastatic.
* Umbelliferone and scopoletin: antimutagenic in vitro.
* Aesculetin, umbelliferone, scopoletin: cytotoxic in vitro.
* Aesculin, gastroprotective: in vivo.
* Umbelliferone: antiasthmatic in vivo.
* Scopoletin: antithyroid in vivo.
* Umbelliferone: antidiabetic in vivo
What is Troxerutina?
A synthetic drug of coumarin plus rutin derivative. Clinical trials:
* beneficial effects in haemorrhoids, acute pancreatitis, varicose veins
* relieves oedema and subjective symptoms, postoperative treatment of episiotomy and long- standing lymphoedema.
* High-protein oedemas (which you get from burn injury and lymphoedema): it enhances breakdown by macrophages of protein and helps lymphatic drainage.
Where else do we find coumarins? eg aesculus hippocastanum
- Coumarin glycosides, aesculin.
- Plus saponins, they are protective and tonic effect for the venous and lymphatic vessels.
What are furanocoumarins, also called furocoumarin, psoralens?
- These have a coumarin skeleton plus furan ring.
- We find these in Angelica (Angelica archangelica), Rue (Ruta graveolens), Yellow sweet clover (Melilotus officinalis), rutaceae and generally the umbelliferae family.
- We also find it in lime, grapefruit and bergamot - zest and juice as well.
- Furanocoumarins, photosensitizing effect can lead to blistering, as they are activated by UV light.
- An example would be giant hogweed – affects skin.
- Celery creates a lot of furanocoumarin and if it also has a fungus, this can cause blistering
What do I need to know about Psoralen?
- Psoralen makes you more sensitive to sunlight
- Long used in Egypt for loss of pigment for the skin, otherwise known as vitiligo.
- Furanocoumarins plus ultraviolet radiation stimulate melanogenesis (tanning)
- It also has antiproliferative effects (inhibits growth cells)
- However it may initiate phototoxic erythema (inflammation).
- Some people use PUVA (psoralen plus UVA) for treatment of psoriasis: however this is thought to increase risk of skin cancer, and may accelerate cataract formation.
- Furanocoumarin used with UVB sunscreens, have been used to get a quicker tan which is protective against ultraviolet radiation.
- There have been clinical trials run on patients with vitiligo, which uses khellin which comes from the herb the Egyptians used Amni visnaga
- This is taken (orally and topically) and used with ultraviolet A (UVA) irradiation.
- This found that khellin did not lead to phototoxic skin erythema (inflammation) so likely preferable to use.
- The ancient Egyptians also made a decoction of the fruits, spasmolytic, for asthma for kidney stones and angina pectoris.
- Khellin, also found to be a positive inotropic and coronary vasodilator.
What do I need to know about grapefruit?
- Another fruit strong in faranocoumarins is grapefruit
- It contains Bergapten, a furanocoumarin, and the flavonoid naringenin
- These together inhibit a number of enzymes in the cytochrome p-450 family
- The effect is that grapefruit can cause certain medications to stay much longer in the body which can be dangerous eg anti coagulants though it can also help
