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Senna is a very strong plant that treats constipation temporarily

Senna

Senna alexandrina Fabaceae

The senna plant has been used for thousands of years to ease constipation. Senna offers a stimulating and efficient cathartic action, containing a range of chemical constituents including anthraquinones which give senna its reliable laxative effect.

Sustainability Status

Sustainability status

At risk from overharvesting and habitat loss. Commonly sourced from the wild though may also be in cultivation. Only source cultivated supplies or from certified sustainable wild collection. Read more about our sustainability guide.

Key benefits
  • Cathartic for digestive complaints
  • Strong antioxidant
  • Antimicrobial
  • Anti-infectious properties
  • Diaphoretic
  • Vermifuge

  • How does it feel?

    The experience of Senna is dose dependent. The lighter dose offers a herbal tea that is: light, soft, almost tasteless but a gentle, soothing experience. The mucilage is faint but offers a light, sunny, almost creamy taste. A heavier dose may cause cramp-like discomfort, uncomfortable diarrhoea, and nausea.

    The leaves are stronger in action although most commonly used for their therapeutic potential are the Senna pods. Dried pods are often found in Afro-Caribbean food shops and are used as a decoction, for a bedtime drink, and is considered a liver detox (short term use only). This results in a bowel movement, up to ten hours after the dose has been taken.

    Senna Alexandrina
    senna pods
    senna seed pods

  • What can I use it for?

    It can be used for a short-term requirement, in an otherwise healthy person when a soft stool is desirable for example if one has an anal fissure, or haemorrhoids (8). It is helpful to employ the additional use of aromatic herbs to counteract any unwanted side effects. The leaves irritate the digestive tract and encourage peristalsis, so are helpful for short term relief of constipation.

    However long term habitual use should be avoided so as to avoid weakening the digestive tract and causing dependency, and if there is inflammation in the gut (for example with Crohn’s or IBS) it should be avoided.

  • Into the heart of senna

    Senna AlexandrinaSenna is a powerful herb which has been used for centuries as a potent laxative across the globe. In Sanskrit the whole plant is known as rajavriksha– “king of trees”. Because of its potency, when using senna in herbal blends it is best to start with small doses of the pods as they are milder than the strongly purgative leaves. Senna is commonly sold in pharmacies as an over the counter medicine. 

    It has bitter, sweet and cooling properties and is used in Chinese medicine to drain downward, and guide out stagnation and for constipation due to heat accumulation in the intestines. The literal translation of “fan xie ye” (the Chinese name for Senna) is “purgative leaf of the foreigners”. 

  • Traditional uses

    senna flowerOur earliest records of its use is by 9th century Arabian physicians, early Chinese medicine and Ayurvedic texts. Traditionally the leaves of Senna are used for a laxative effect, prepared with complementary dried figs, plums and honey(10). Senna will reduce lactation (11).

    Traditionally, it was used to treat ringworm infections and other intestinal worms in combination with other known herbal protocols. It was once considered useful in the treatment of halitosis (bad breath) and biliousness (marked by suffering disorder in the liver)(12).

    According to Culpepper (1649) ‘the leaf heats in the second degree and dries in the first, it carries downwards both choller, phlegm, and melancholy, it cleanseth the brain, heart, liver, spleen, it cheers the senses, opens obstructions, takes away dullness of sight, preserves youth, helps deafness (if purging will help it) helps melancholy and madness’ (13).

    Used traditionally to cleanse the digestive system during fasting and is useful for all fevers. It was used for catarrhal complaints, jaundice, obesity, faulty menstruation, worms and smallpox(15). According to Levy (1974) Senna was used to tone and restore the digestive system and to thoroughly cleanse the system. Using 8-10 large pods in ž pint of cold water, soaked for 7 hours taken with a pinch of powdered ginger per cupful. 

  • Traditional actions

    Western Actions

    Ayurvedic Actions

    Chinese Actions

  • Traditional energetic actions

    Herbal energetics are the descriptions Herbalists have given to plants, mushrooms, lichens, foods, and some minerals based on the direct experience of how they taste, feel, and work in the body. All traditional health systems use these principles to explain how the environment we live in and absorb, impacts our health. Find out more about traditional energetic actions in our article “An introduction to herbal energetics“.

  • What practitioners say

    senna plantEnergetically, senna is considered bitter, cooling and pungent. Working therapeutically on the digestive, excretory and circulatory systems. It can have a strong purgative action and should be taken with care, adhering strictly to the recommended doses. The patient’s constitution should be strongly considered to avoid incorrect usage.

    The addition of ginger or crushed fennel seeds will reduce any unwanted griping, pain and nausea particularly when senna is administered acutely in larger doses or given to sensitive individuals. After consuming senna, urine may temporarily show a reddish hue, which is considered transient and harmless. However, any suspected blood in the stool or urine should be followed up immediately by a physician.

    Modern practitioners may use senna for strong, otherwise healthy patients. It is better to manage constipation on a longer-term basis with mucilaginous herbs (like slippery elm and marshmallow), moistening & hydration therapies as well as stress management and gut health support. They are also likely to encourage increased consumption of fresh organic fruits and vegetables and outdoor physical exercise. All of these areas are focused on and improved before or alongside administering other medicinal herbal therapeutic treatments. 

    Rhubarb (Rheum palmatum), dandelion root (Taraxacum officinalis, radix) and licorice root (Glycyrrhiza glabra, radix) are generally considered preferable to senna, with fewer side effects and smoother, milder action. However, modern research may indicate a wider spectrum of usage for Senna particularly for the effective treatment of modern diseases (16).

    Sennosides are compounds in senna that irritate the lining of the large intestine causing the muscles to contract strongly creating the bowel movement. The sennosides are broken down in the bacterial flora of the colon and prevent the reabsorption of fluid, this helps to maintain a softness and motionability to the stool. The World Health Organisation (WHO) has approved senna’s use in occasional short term constipation.

    From a Chinese medicine perspective Senna Angustifolia (fan xie ye) will ‘clear heat’ and ‘purge fire’ with a nature that is sweet, bitter and very cold. Dosage used: laxative (0.5g – 1g), cathartic (1-3g), purgative (4-8g) (17).

  • Research

    senna podsModern research supports the traditional knowledge of senna as a plant medicine that offers ‘Health-promoting effects’. It has shown that all parts of the plant have a therapeutic potential: the root, stem, leaf and flower are all rich in numerous phytochemicals offering a diverse beneficial effect for treatment of metabolic syndromes (18).

    The antioxidant activity found in Senna genus was correlated with the contained polyphenols and the phenolic and flavonoid content. We could profit from this antioxidant activity particularly in our modern treatment of diseases that are on the increase: cardiovascular disease (CVD), Diabetes (T2DB), Parkinson’s disease and neurodegenerative dysfunction (19). Modern research may support the broader spectrum of use for senna particularly in the treatment of skin conditions and infectious disorders.

    A randomised controlled trial was conducted to compare the efficacy of senna versus Poly Ethylene Glycol (PEG) for colon preparation for colon cleansing. 

    Two groups who were going to undergo an elective colonoscopy were split into those taking senna (152 patients) and PEG (170 patients). The group taking senna were advised to take 24 tablets in divided doses (the first twelve at 2pm and the other twelve at 10pm). They were also advised to drink lots of clear liquid, and each senna tablet contained 9-11 mg of Sennoside A and B.

    senna seed pods

    In the PEG group patients received 4 sachets in 4 litres of water the day before the procedure, and were asked to drink 250ml every 15 minutes from 5pm the evening before. They were also asked to drink clear liquid on the morning of the colonoscopy and fast after midnight. 

    The Aronchick scoring scale was used to evaluate the quality of the colon cleansing, and compliance, tolerance and adverse events were also evaluated. 

    Overall results showed that the treatments were equal when it came to quality of colon cleansing, tolerance and compliance as well as incidences of adverse effects. There was more abdominal pain in the senna group, and more nausea and vomiting in the PEG group. Overall it was concluded that senna has the same efficacy as PEG for colon cleansing and could be prescribed as an alternative for bowel preparation. This study shows that senna works well for relieving constipation (35).

  • Did you know?

    The genus name Senna derives from the Arabic word ‘sana’ used to describe plants that have leaves and pods with cathartic, laxative properties (20). 

    Nowadays, senna tablets are prescribed on the NHS alongside other medication as a bowel preparation formulation prior to a colonoscopy (21). 

    Senna has been used in the Southern Hemisphere for a wide range of cultural uses. From rituals to nutrition, house building decoration to poisons and medicine. In both East and West Africa a decoction was used during ceremonial tribal incisions and tattoos were performed. Probably as an anti-infective. The crude pounded bark was interestingly used as a fish poison and an addition to curries and chillies (9).

Additional information

  • Botanical description

    Senna is native to Northern Egypt, it belongs to a large genus of attractive flowering plants presently found throughout the tropics with up to 350 species recognised worldwide (3). Commonly used species in Herbal Medicine are Cassia senna and Cassia acutifolia also known as Alexandrian Senna. Cassia angustolia is also used, and is known as Indian Senna. For both plants the medicinal parts are the leaf and pods. As for Rhamnus purshianus or Cascara sagrada the bark of the tree is used. Both contain natural compounds known as anthraquinones.

    The Senna plant is a legume, a recognizable member of the pea family previously known as the Leguminosae, now called the Fabaceae. Senna is a shrub of approximately one meter in height with a straight woody stem and a soft, appealing appearance. It has attractive yellow inflorescences best described as pretty ‘pea-type family’ flowers.  The lance-shaped leaves are arranged either side of a central stem. The dried fruits (seed pods) are flat and papery each containing about 6-8 seeds (4,5).   

    With a high adaptability in terms of soil and climate, the senna plant can easily be propagated from these seeds that will remain viable for several years (6). 

  • Safety

    Senna is generally considered safe and well tolerated, but it can cause adverse events when used in high doses or for a longer time than is recommended. These events usually require dosage reduction and are generally mild and uncomfortable but transient in nature. Most unfortunate clinical events are linked to the overuse of laxative medication. This approach may be taken by the individual for weight management, stress management and metabolic disorders.

    Do not prescribe in pregnancy or during lactation without medical supervision because of potential genotoxicity (25). Not to be administered to children under the age of 12 without medical attention. The European Medical Agency (EMA) does not recommend Senna for breastfeeding or pregnant mothers and other vulnerable people.

    Do not use Senna products for more than 10 days at a time, as this may lead to the weakening of the large bowel muscles (27). Senna is generally considered useful for the occasional bout of constipation but if you are still constipated after taking Senna for three consecutive days, we advise that you contact a herbalist (28). You can find a herbalist in our resources section here.

    Senna use can lead to the intensification of menstrual bleeding.

    Remember persistent constipation should always be thoroughly investigated and seeing a herbalist is advised.

    Avoid using the Senna bark fresh or inadequately prepared because this is likely to result in severe vomiting and intestinal spasm (29). For constipation it is the leaves and pods that are used.

  • Interactions

    Senna should not be used with diuretic medication, antiarrhythmic drugs or corticoadrenal steroid tablets because herb/drug interactions lead to increased and unwanted potassium loss. This will increase the likelihood of heart arrhythmias so avoid simultaneous use with all antiarrhythmic drugs. This includes digoxin, lanoxin, and any other heart medication (24).

    As senna increases the speed of bowel movements, it can decrease how long any medication is in the body and therefore decrease efficacy of oral medications.

    In cases of excessive use, Senna can cause a disturbance in fluid and electrolyte balance. Regular and long-term use is likely to lead to dependency and may reduce a person’s natural capacity for an unassisted, natural, regular bowel movement.

  • Contraindications

    Do not use it in cases of intestinal obstruction, or with abdominal pain of unknown origin.

    Avoid use in cases of diarrhoea, or during any intestinal inflammation such as Crohn’s disease, ulcerative colitis, appendicitis, as it is likely to accelerate the inflammatory process (23).

  • Preparation

    • Fresh herb tea
    • Dried herb tea
    • Tincture
    • Tablet
    • Capsule
    • Granular form
    • Anal suppository 
    • Syrup

  • Dosage

    A wide range of dosage procedures have been recorded from traditional to modern use. With each individual reacting uniquely to this form of plant medicine.  However, typical dosage forms for adult consumption range from

    • 1.5g to 6g/day of dried leaf
    • 0.5g to 2g/day of dried pods
    • 1.5ml to 6ml/day of a 1:2 liquid extract or equivalent in tablet form (30). 
    • Senna is best used with other common aromatic herbs to mitigate uncomfortable side effects. Traditionally ginger was used but mint, rosemary, lemon balm, coriander, lavender would all prove beneficial.

  • Plant parts used

    Pods and leaves

  • Constituents

    • Anthraquinones 
    • Sennosides (rhein-dianthrone diglucosides)
    • Aglycones
    • Monoanthraquinone glycosides
    • Dianthrone diglucosides
    • Flavonoids

    The antioxidant activity of the Senna genus is correlated with phenolic and flavonoid content which includes the following chemical compounds: 

    • Cassine 
    • Chysophanol
    • Aloe-emodin
    • Epicarechin
    • Physcion 
    • Proanocyanidins 
    • Quercimeritin
    • Rhein
    • Rutin
    • Scutellarein
    • Stigmasterol (32)

  • Habitat

    Senna is native to tropical Africa and is distributed throughout the tropics

    The senna shrub has a high adaptability in terms of soil and climate; the senna genus is found to thrive in a wide range of natural habitats, from forests, to deserts, to rock outcrops with a wide geographical distribution. Senna is found primarily in the tropical regions of South America, Africa, Australia, to South-East Asia and the Pacific Islands. It can be found at altitudes up to 1000-1400 meters. (33). Within the UK, some ornamental species are commonly used in landscape gardening because the Senna species is a very attractive garden plant.

  • Sustainability

    Wild Senna is currently endangered (34). 

    Habitat loss and over harvesting from the wild are two of the biggest threats faced by medicinal plant species. There are an increasing number of well-known herbal medicines at risk of extinction. We must therefore ensure that we source our medicines with sustainability in mind.

    The herb supplement industry is growing at a rapid rate and until recent years a vast majority of medicinal plant products in global trade were of unknown origin. There are some very real and urgent issues surrounding sustainability in the herb industry. These include environmental factors that affect the medicinal viability of herbs, the safety of the habitats that they are taken from, as well as the welfare of workers in the trade.

    The botanical supply chain efforts for improved visibility (transparency and traceability) into verifiably sustainable production sites around the world is now certificated through the emergence of credible international voluntary sustainability standards (VSS). Read our article on Herbal quality and safety: what to know before you buy to learn more about what to look for and questions to ask suppliers about sustainability.

  • Quality control

    The active compounds commonly regarded as quality markers of senna are sennosides. 

    Herbal Medicines are often extremely safe to take, however it is important to buy herbal medicines from a reputed supplier. Sometimes herbs bought from unreputable sources are contaminated, adulterated or substituted with incorrect plant matter.

    Some important markers for quality to look for would be to look for certified organic labelling, ensuring that the correct scientific/botanical name is used and that suppliers can provide information about the source of ingredients used in the product.

    A supplier should be able to tell you where the herbs have come from. There is more space for contamination and adulteration when the supply chain is unknown.

  • How to grow

    Senna can be grown from seed in a greenhouse in the spring or from cuttings in the early summer. This plant requires plenty of sun.

    Leaves can be harvested before or whilst the plant is in flower. Seed pods are to be collected when they are ripe, in the autumn.

  • Recipe

    Traditionally in Egypt and in other Arabian countries, medicinal herbs and spices were commonly disguised in sweet honey and tamarind and taken as required as a post-meal condiment.  Senna was often mixed with honey, raisins, figs, prunes and other laxative dried fruits. Here is a simple Fig & Senna Syrup Recipe for you to try at home. This recipe can easily be made within the hour, by a beginner medicine maker. 

    Fig and senna syrup recipe

    Ingredients: 

    • 18g Senna pods & 2 Tbsp of freshly ground fennel seeds and 100 ml of boiling water
    • 8 or 9 fresh or soaked but drained figs
    • 1 Tbsp each of powdered rose hips and rose petals 
    • 100g of sugar & pinch of cinnamon powder 
    • Juice of ½-1 large lemon plus grated rind

    Method:

    Place pods, seeds, hips, lemon rind & petals in a glass bowl. Add boiling water and leave covered for 3-4 hours. Strain (keep the remaining juice) and then add the figs and blend using the previously saved juice to get a nice liquid consistency. Pour all the ingredients (including sugar/mixed well) into a saucepan gently bring to the boil and then reduce the heat, stirring occasionally. After approximately you should have a smooth, thick, glossy syrup. Remove from the heat and add a pinch of cinnamon powder and lemon juice to maintain the consistency required. Stir well. Remove from heat and pour into sterilized 150ml bottles. It should be kept refrigerated for 3-4 weeks. Shake well before use.

    Dosage:

    2 teaspoons to be taken on an empty stomach before bed. Please do not exceed dose and do not use more than 2-3 days at a time. This should be a medicine used occasionally for mild adult constipation. Please seek professional advice if symptoms persist for longer than 3 days.

  • References

    1. Flora of Australia [FOA] (2020). Senna Mill. [online] Available at: https://profiles.ala.org.au/opus/foa/profile/Senna [Accessed 07 January 2023].
    2. UK Government: Medicines & Healthcare products Regulatory Agency: Drug Safety Update. [GOV.UK] (2020). Stimulant laxatives (bisacodyl, senna & sennosides, sodium picosulfate) available over the counter: new measures to support use.[online] Available at: https://www.gov.uk/drug-safety-update/stimulant-laxatives-bisacodyl-senna-and-sennosides-sodium-picosulfate-available-over-the-counter-new-measures-to-support-safe-use#:~:text=Medicines% [Accessed 08 January 2023].
    3. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    4. Chevallier, A. FNIMH (2016). Encyclopedia of herbal medicine: 550 herbs and remedies for common ailments. Great Britain: Dorling Kindersley.
    5. Marazzi, B. & Endress, P. (2008). Patterns of floral asymmetry in Senna (leguminosae, Cassinae). American Journal of Botany, 95(1), pp. 1-8. https://pubmed.ncbi.nlm.nih.gov/21632312/
    6. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    7. Bone, K. (2003). A clinical guide to blending liquid herbs: herbal formulations for the individual patient. Missouri: Churchill Livingstone.
    8. Mills, S. & Bone, K. (2005). The essential guide to herbal safety. UK: Elsevier, 2010.
    9. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    10. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    11. Bartram, T. (1998). Bartram’s encyclopedia of herbal medicine. London: Constable & Robinson.
    12. Kloss, J. (1939). Back to eden: the classic guide to herbal medicine, natural foods, and home remedies since 1939. California: Back to Eden Publishing, 1994.
    13. Knowles, J., et al. (2018). The illustrated college herbal: plants from the pharmacopoea londinensis Londinensis of 1618. London: Gutenberg Press.
    14. Cunningham, S. (2007). The magical power of herbs. India: New Age Books.
    15. De Bairacli Levy, J. (1974). Common herbs for natural health. London: Faber & Faber, 1997. 
    16. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    17. Reid, D. (1987). Chinese herbal medicine. Wellingborough: Thorsons Publishing Group.
    18. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    19. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    20. Flora of Australia [FOA] (2020). Senna Mill. [online] Available at: https://profiles.ala.org.au/opus/foa/profile/Senna [Accessed 07 January 2023].
    21. Kingston Hospital Day Surgery Unit. (2022). Instructions for Bowel Preparation for Colonoscopy. [pdf] Available at:https://kingstonhospital.nhs.uk/wp-content/uploads/2019/12/bowel-preparation-for-colonoscopy.pdf. [Accessed 08 January 2023].
    22. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    23. Mills, S. & Bone, K. (2005). The essential guide to herbal safety. UK: Elsevier, 2010.
    24. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    25. Budzynska, et al. (2012). Systematic Review of Breastfeeding & Herbs. Breastfeeding Medicine. Vol 7(6): pp.489-503. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3523241/
    26. National Library of Medicine (NIH), (2020). Senna. https://www.ncbi.nlm.nih.gov/books/NBK547922/
    27. UK Government: Medicines & Healthcare products Regulatory Agency: Drug Safety Update. [GOV.UK] (2020). Stimulant laxatives (bisacodyl, senna & sennosides, sodium picosulfate) available over the counter: new measures to support use.[online] Available at: https://www.gov.uk/drug-safety-update/stimulant-laxatives-bisacodyl-senna-and-sennosides-sodium-picosulfate-available-over-the-counter-new-measures-to-support-safe-use#:~:text=Medicines% [Accessed 08 January 2023].
    28. Mills, S. & Bone, K. (2005). The essential guide to herbal safety. UK: Elsevier, 2010.
    29. Bone, K. (2003). A clinical guide to blending liquid herbs: herbal formulations for the individual patient. Missouri: Churchill Livingston
    30. Mills, S. & Bone, K. (2005). The essential guide to herbal safety. UK: Elsevier, 2010.
    31. Bone, K. (2003). A clinical guide to blending liquid herbs: herbal formulations for the individual patient. Missouri: Churchill Livingstone.
    32. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/
    33. Alshehri, M. et al. (2022). A Review of Recent Studies on the Antioxidant and Anti-infectious Properties of Senna Plants. Oxidative Medicine and Cellular Longevity: pp. 6025900. https://pubmed.ncbi.nlm.nih.gov/35154569/ 
    34. Flora of Australia [FOA] (2020). Senna Mill. [online] Available at: https://profiles.ala.org.au/opus/foa/profile/Senna [Accessed 07 January 2023].
    35. Shavakhi A. High dose Senna or Poly Ethylene Glycol (PEG) for elective colonoscopy preparation: a prospective randomized investigator-blinded clinical trial. PubMed Central (PMC). Published February 1, 2011. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3214296/

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Aromatic
An ‘aromatic’ remedy, high in volatile essential oils, was most often associated with calming and sometimes ‘warming’ the digestion. Most kitchen spices and herbs have this quality: they were used both as flavouring and to ease the digestion of sometimes challenging pre-industrial foods. Many aromatics are classed as ‘carminatives’ and are used to reduce colic, bloating and agitated digestion. They also often feature in respiratory remedies for colds, chest and other airway infections. They are also classic calming inhalants and massage oils, and are the basis of aromatherapy for their mental benefits.
Astringent taste
The puckering taste you get with many plants (the most familiar is black tea after being stewed too long, or some red wines) is produced by complex polyphenols such as tannins. Tannins are used in concentrated form (eg from oak bark) to make leather from animal skins. The process of ‘tanning’ involves the coagulation of relatively fluid proteins in living tissues into tight clotted fibres (similar to the process of boiling an egg). Tannins in effect turn exposed surfaces on the body into leather. In the case of the lining of mouth and upper digestive tract this is only temporary as new mucosa are replenished, but in the meantime can calm inflamed or irritated surfaces. In the case of open wounds tannins can be a life-saver – when strong (as in the bark of broadleaved trees) they can seal a damaged surface. One group of tannins, the reddish-brown ‘condensed tannins’ are procyanidins, which can reduce inflammation and oxidative damage.
Bitter
Bitters are a very complex group of phytochemicals that stimulate the bitter receptors in the mouth. They were some of the most valuable remedies in ancient medicine. They were experienced as stimulating appetite and switching on a wide range of key digestive functions, including increasing bile clearance from the liver (as bile is a key factor in bowel health this can be translated into improving bowel functions and the microbiome). Many of these reputations are being supported by new research on the role of bitter receptors in the mouth and elsewhere round the body. Bitters were also seen as ‘cooling’ reducing the intensity of some fevers and inflammatory diseases.
Blue-purple colouring
Any fruits with a blue-purple colouring contain high levels of the polyphenols known as anthocyanins. These work 1) on the walls of small blood vessels, helping to maintain capillary structure to reduce a key stage in inflammation, and improving the microcirculation to the tissues; 2) to improve retinal function and vision; 3) to support connective tissue repair around the body.
Cooling
Traditional ‘cold’ or cooling’ remedies often contain bitter phytonutrients such a iridoids (gentian), sesiquterpenes (chamomile), anthraquinones (rhubarb root), mucilages (marshmallow), some alkaloids and flavonoids. They tend to influence the digestive system, liver and kidneys. Cooling herbs do just that; they diffuse, drain and clear heat from areas of inflammation, redness and irritation. Sweet, bitter and astringent herbs tend to be cooling.
Hot
Traditional ‘hot’ or ‘heating’ remedies, often containing spice ingredients like capsaicin, the gingerols (ginger), piperine (black or long pepper), curcumin (turmeric) or the sulfurous isothiocyanates from mustard, horseradich or wasabi, generate warmth when taken. In modern times this might translate as thermogenic and circulatory stimulant effects. There is evidence of improved tissue blood flow with such remedies: this would lead to a reduction in build-up of metabolites and tissue damage. Heating remedies were used to counter the impact of cold, reducing any symptoms made worse in the cold. .
Mucilaginous
Mucilages are complex carbohydrate based plant constituents with a slimy or ‘unctuous’ feel especially when chewed or macerated in water. Their effect is due simply to their physical coating exposed surfaces. From prehistory they were most often used as wound remedies for their soothing and healing effects on damaged tissues. Nowadays they are used more for these effects on the digestive lining, from the throat to the stomach, where they can relieve irritation and inflammation such as pharyngitis and gastritis. Some of the prominent mucilaginous remedies like slippery elm, aloe vera and the seaweeds can be used as physical buffers to reduce the harm and pain caused by reflux of excess stomach acid. Mucilages are also widely used to reduce dry coughing. Here the effect seems to be by reflex through embryonic nerve connections: reduced signals from the upper digestive wall appear to translate as reduced activity of airway muscles and increased activity of airway mucus cells. Some seed mucilages, such as in psyllium seed, flaxseed (linseed) or guar bean survive digestion to provide bulking laxative effects in the bowel. These can also reduce rate of absorption of sugar and cholesterol. .
New-mown hay aroma
The familiar country odour of haymaking, of drying grass and other plants, is largely produced by coumarins (originally isolated from tonka beans – in French coumarou) and widely used in perfumery. They are chemically categorised as benzopyrone lactones and are important phytochemicals, with strong antioxidant activity in the laboratory and likely effects in modulating inflammation. They were most often associated with the calming effect linked to their use in stuffing mattresses and pillows and plants, high In coumarins were commonly used for these properties.
Resinous
Resins are most familiar as tacky discharges from pine trees (and as the substance in amber, and rosin for violin bows). They were most valued however as the basis of ancient commodities like frankincense and myrrh (two of the three gifts of the Three Wise Men to the baby Jesus) and getting access to their source was one benefit to Solomon for marrying the Queen of Sheba (now Ethiopia). Resins were the original antiseptic remedies, ground and applied as powders or pastes to wounds or inflamed tissues, and were also used for mummification. With alcohol distillation it was found that they could be dissolved in 90% alcohol and in this form they remain a most powerful mouthwash and gargle, for infected sore throats and gum disease. They never attracted much early research interest because they permanently coat expensive glassware! For use in the mouth, gums and throat hey are best combined with concentrated licorice extracts to keep the resins in suspension and add extra soothing properties. It appears that they work both as local antiseptics and by stimulating white blood cell activity under the mucosal surface. They feel extremely effective!
Salty
The salty flavour is immediately distinctive. A grain dropped onto the tongue is instantly moistening and a sprinkle on food enkindles digestion. This easily recognisable flavour has its receptors right at the front of the tongue. The salty flavor creates moisture and heat, a sinking and heavy effect which is very grounding for the nervous system and encourages stability. People who are solid and reliable become known as ‘the salt of the earth'.
Sharpness
The sharp taste of some fruits, and almost all unripe fruits, as well as vinegar and fermented foods, is produced by weak acids (the taste is generated by H+ ions from acids stimulating the sour taste buds). Sour taste buds are hard-wired to generate immediate reflex responses elsewhere in the body. Anyone who likes the refreshing taste of lemon or other citrus in the morning will know that one reflex effect is increased saliva production. Other effects are subjective rather than confirmed by research but there is a consistent view that they include increased digestive activity and contraction of the gallbladder.
Sweet
In the days when most people never tasted sugar, ‘sweetness’ was associated with the taste of basic foods: that of cooked vegetables, cereals and meat. In other words sweet was the quality of nourishment, and ‘tonic’ remedies. Describing a remedy as sweet generally led to that remedy being used in convalescence or recovery from illness. Interestingly, the plant constituents most often found in classic tonics like licorice, ginseng are plant steroids including saponins, which also have a sweet taste.

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