Prickly Ash Uses and Plant Monograph
Prickly Ash, Zanthoxylum spp., is an impressive shrub or tree belonging to the rutaceae (citrus) genus with over 549 species worldwide with each region using the species native to the area for medicinal purposes.
Prickly Ash Uses & Plant Profile Summary:
- Botanical Name: Zanthoxylum americanum, Zanthoxylum clava-herculis
- Other Common Names: Z. americanum: Northern prickly ash, toothache tree, yellow wood, xanthoxylum, clavalier, suterberry, wild Szechuan peppercorn; Z. clava-herculis: Southern prickly ash, toothache tree, yellow wood, xanthoxylum, hercules’ club
- Family: Rutaceae
- Parts Used: Stem and root bark, fruit
- Energetics: Warming, drying
- Taste: Fruit: astringent, sour; bark: pungent, acrid, bitter
- Plant Properties: circulatory stimulant, antirheumatic, anti-inflammatory, antifungal, tonic, diaphoretic, alterative, emmenagogue, sialagogue, carminative, bitter, analgesic, immunomodulator
- Plant Uses: dental pain, osteoarthritis, rheumatoid arthritis, Raynaud’s syndrome, peripheral vascular disease, varicose veins, sciatica, intermittent claudication, endometriosis, gastric complaints, infections, fever, hypotension, skin disorders, pulmonary issues
- Plant Preparations: decoction, tincture, topical
If you’ve tried Sichuan cuisine from China, you may be familiar with the distinguished numbing and citrusy flavor made using Sichuan pepper, which belongs to the Zanthoxylum family. This plant is not only medicinal and a tasty food additive, it is also the host plant for the giant swallowtail butterfly, Papilio cresphontes.1
Zanthoxylum also goes by the common name toothache tree, owing its name to the numbing and tingling effect it has in the mouth when the berries or bark are chewed. At the first herbal taste testing class I attended, we were made to close our eyes and try to experience tasting different herbs with all of our senses and the most memorable herb I tried that day was prickly ash with its lemony, astringent and numbing flavor and sensations.
This unique numbness-inducing trait makes it helpful in relieving dental pain and can be used to address other dental issues such as gum disease, periodontitis, canker sores, and gingivitis. Its action as a sialagogue, which promotes saliva production and flow, also helps with xerostomia (dry mouth).2
In North America, the two species commonly used interchangeably are Zanthoxylum Americanum, distributed in Southern Canada (Quebec and Ontario), and Northern, Central, and Western U.S., and Zanthoxylum clava-herculis, found in Central and Southern U.S. such as mid-Florida, Southern Virginia then west to Texas and Oklahoma.3,4,5 The word ‘zanthoxylum’ originates from the Greek language, where ‘xanthos’ means ‘yellow’, and ‘xylon’ means ‘wood’. The species name ‘clava-herculis’ refers to Hercules’ club, which was Hercules’ favored mythological wooden weapon.6
Circulatory stimulant
One of the best circulatory stimulants to add to a formula, prickly ash encourages increased blood flow to the joints and muscles of the body. It’s more specifically a peripheral circulatory stimulant, meaning it would not strain the heart to distribute blood throughout the body.7 This blood flow stimulation has the benefit of improved oxygenation throughout the musculoskeletal system and enhanced distribution of nutrients that can support tissue repair. It also functions to remove metabolic waste products more efficiently and reduce the impact of free radical damage.
For this very reason, when decreased circulation results from cold conditions, Zanthoxylum can aid in arthritic conditions such as osteoarthritis and rheumatoid arthritis. It can support the healing of damaged tissues and reduce pain, swelling, stiffness, and tenderness.
It is used for circulatory issues such as cold extremities and cramping and for related conditions such as Raynaud’s syndrome, peripheral vascular disease (such as arterial diseases and varicose veins), and intermittent claudication, all of which have a reduction of blood flow to the extremities resulting in pain, cramping, color and/or skin changes. It may also be used in cases of carpal tunnel syndrome where paresthesia, also known as pins-and-needles, are felt symptomatically.
When it comes to working with prickly ash for circulatory issues, one of my favorite ways is to make an ointment by incorporating an olive-oil extract of prickly ash with beeswax and some shea butter. I’ve made this ointment for a person who had reached out to me about struggling with the early stages of diabetic foot, a complication of diabetes that is characterized by nerve and blood vessel damage that can result in ulcers and infections. It can similarly be applied topically to areas of the body that are affected by reduced circulation to support with improved circulation and healing.
Endometriosis
This circulatory stimulant action supports the use of prickly ash in cases of endometriosis where increased blood flow can improve sluggish circulation, relieving pelvic congestion. It may also help to apply the herb as a liniment for chronic pelvic inflammatory disease. My preference is to make an extract of the berry and bark in witch hazel extract and to apply it warmed topically around the pelvic region.
Digestive Support
As a circulatory stimulant, other body systems are impacted such as the digestive tract where mucosal secretions may be increased, and motility is regulated in cases where there is sluggish digestion. This in turn may support symptoms of dyspepsia, diarrhea, constipation, catarrhal gastritis, ulcers, and stomach distention owing to its dual action as a carminative. In 1849, it had been used as a treatment during the cholera epidemic by the eclectic physician John King.8
Fever Support
This increased blood flow may also induce sweating through a diaphoretic action, which Samuel Thompson used to use in the 19th century in order to support the body’s fever mechanism when it came to infections.9
Systemic Tonic
Prickly ash has a role as a herbal tonic due to its ability to bring the different affected organ systems into balance and maintain nourishment in tissues that may need the added support. One way it does this is by regulating hypersecretion or not enough secretions in the mucous membranes of the gastrointestinal tract. It is a heart tonic that improves capillary circulation and has been indicated for cases of hypotension due to the compound nitidine contained in Zanthoxylum.10 It is also a tonic of the nervous system and can bring both nourishment and pain relief to injured nerves such as in sciatica. Prickly ash can be made into an enjoyable lemony tea that could pair well with added lemon and a sweetener to gain its benefits as a tonifying herb.
Antimicrobial Effects
Prickly ash has potential as an antimicrobial agent against strains of fungi, viruses and a resistant strain of bacteria, which is significant in terms of its relevance to plant-based antibiotics that may be able to replace the conventional antibiotics the bacteria has developed resistance to.
A study was conducted to determine the antifungal effect of all parts (bark, root, leaf, fruit, stem) of the Zanthoxylum americanum plant on 11 different strains of fungi using a disk diffusion assay. It was determined that all parts of the plant displayed a broad spectrum of antifungal activity and inhibited 8 out of 11 fungi, with the leaf and fruit extract being the most antifungal. This was observed to have been due to the higher furanocoumarin content found in the fruit and leaf compared to the other parts of the prickly ash plant.11
The bark extract of southern prickly ash, Zanthoxylum clava-herculis, has shown antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), a bacterium that has developed resistance to a number of conventional antibiotics that can result in an infection that may be life-threatening for some. This antibacterial activity is due to the alkaloid chelerythrine, which displayed significant effects compared to the antibiotics tetracycline, erythromycin, and norfloxacin. The results of this study have added to the ongoing studies on the potential of using plant extracts as a broad-spectrum antibiotic, especially in the case of growing bacterial resistance.12
Coumarins and lignans contained in prickly ash have been reported to include effects as an antiviral agent.13 Furanocoumarins extracted from other plants such as Ferula sumbul have inhibited HIV replication and ribonucleoproteins on influenza A and B viruses as shown in in-vitro studies.14
Cytotoxicity
An in-vitro assay (an analysis of a sample in a tube) was conducted on human leukemia cells (HL-60) using the abovementioned coumarin and lignan extracts from Zanthoxylum americanum and found that they all displayed inhibitory effects towards DNA synthesis occurring in the cells. These observations support the theory that prickly ash contains constituents that have cytotoxic (causing damage to abnormal cells such as cancer cells) and anticancer activity.15
Skin Conditions
In a study done on plant extracts that could prevent or manage the formation of skin cellulite, a 90% ethyl alcohol extraction of Zanthoxylum clava-herculis bark was found to increase microcirculation, which is the circulation of blood in small blood vessels of the body. This increased blood flow may improve skin elasticity, impacting the appearance of cellulite.16
Magnoflorine is an alkaloid found in the bark of prickly ash and this compound was found to inhibit NF-kB, a protein involved in promoting inflammation in the body.
This alkaloid may reduce inflammation and has a role in the relaxing of smooth muscles and improving vasodilation of the blood vessels, and in turn increasing microcirculation.17,18
Another relevant compound found in prickly ash for skin health is the compound 8-methoxypsoralen, which is a furanocoumarin that was used to treat skin disorders such as vitiligo (the absence of melanocytes in areas of the skin) as it increases melanin pigment with UV light exposure.19
Indigenous Ethnomedicine
The use of the different parts of the Zanthoxylum americanum internally and externally is traditionally an important ethnomedicine for Indigenous communities in what is now known as North America. The Chippewa used an infusion of the bark in the form of a tea for coughs, and pulmonary issues, and decocted the root to gargle for an ulcerated throat. The Ojibwa used an infusion of ripe berries to spray on the chest for bronchial congestion and to drink for throat ulcers.20
The Menominee sprayed an infusion of berries on skin wounds and on the throat externally for bronchial issues. The Comanche would pulverize the root to apply topically to burns and the Meskwaki would make a syrup of the decocted bark and berries for coughs. The Alabama would decoct the bark or infuse the inner bark to apply on itchy skin.21 The Houma were said to have grated the Z. clava-herculis root into whiskey to apply topically for swelling.22
J. T. Garrett, a member of the Eastern Band of Cherokee from North Carolina, shared in his book “The Cherokee Herbal” that an elder had expressed that Z. americanum is used “to stimulate the circulatory system and for fever that comes with being sickly and having no energy”.23
Constituents
The active constituents contained in both Zanthoxylum species are similar though some differ in proportions and generally include alkaloids, coumarins, lignans, alkylamides, volatile oils, resins, and tannins.24,25 While some sources have attributed Z. clava-herculis as being the more potent of the two, Ellingwood has expressed that both species are interchangeable medicinally.26,27,28
The compounds found in the bark of Z. clava-herculis are the aporphine alkaloids magnoflorine, benzo-phenanthridine alkaloids, coumarins, lignan, essential oils, and long-chain amides.29 In Z. Americanum, the coumarins include depetaline, xanthyletin, alloxanthoxyletin, and xanthoxyletin in the bark.30 The berries in Z. americanum contain higher amounts of xanthotoxin, psoralen, volatile oil, and furanocoumarins, the latter of which has a role in its antimicrobial activity.31,32,33 The major alkaloids in Z. Americanum are laurifoline and nitidine, whereas in Z. clava-herculis it is chereythrine and magnoflorine.34
The essential oils found in the leaf of Z. clava-herculis are methane monoterpenoids, limonene, and 1,8-cineole whereas in the bark are sabinene, limonene, and terpinene-4-ol.35,36
The isobutylamide, neoherculin, is an alkamide in Z. clava-herculis that acts as an insecticide, which has been reported to act as an insecticidal agent toward body lice eggs and houseflies.37,38,39 The compounds hydroxyl-alpha-sanshool and neoherculin are responsible for the numbing and tingling effect on the nerves.40,41 For this reason, prickly ash is a herb I reach for whenever I experience dental pain by either lightly chewing on the dried bark or making a gargle out of the decocted bark.
Botanically speaking
Z. americanum and Z. clava-herculis are deciduous trees or shrubs with alternate branches and gray-brown bark that contains conical prickles that are irregularly dispersed. The leaves are deeply lobed and the leaf stalk is round with a prickly underside. The flowers are small, green-yellow in color found in terminal umbels on branches, forming on the previous year’s twig before the leaves in the spring. They contain 5 petals, 5 stamens, and up to 5 pistils, flowering between April and May in the U.S. The berries are shiny blackish-blue surrounded by a red shell found in clusters on branch tops. The root system is shallow and spreads by suckers to form dense thickets of the plant. When the leaves, berries, and twigs are crushed, they give off a citrus aroma whereas the bark is pungent.
In Z. americanum, the tree or shrub can be found growing in moist soil and shade on the edges of forests in woodlands.42,43 It can grow up to 3 meters tall and consists of ovate acute leaves with 5-11 leaflets with a terminal leaflet.
In Z. clava-herculis, the tree or shrub grows in light to medium well-draining and sandy soil and can grow up to 10 meters high.44,45 The leaves are oval shaped with a pointed tip and small rounded teeth margins and have 5–17 leaflets. The bark consists of corky knobs that are triangular in appearance and also have larger prickles on the branches and petioles.46
Harvesting Tips
The bark is harvested in the Spring while it is still dormant by being careful to avoid the large thorns and by peeling off small areas of the bark or branches, being mindful to harvest ethically and keep the plant alive. The berries start to form in the late summer between August and October in the United States and can be harvested once they turn red and develop the black seed on the inside, with the red shell being the part harvested. As the berries may be surrounded by thorns, harvesting can be done with a gloved hand keeping to the rule of not harvesting more than 1/3 of berries on each plant in order to leave wildlife to feed. The bark and berries can be laid out to dry in a dark, well-ventilated area until shriveled and fully dried.
Preparation
- Tincture: 2–4 ml of dried berries or bark (1:5 in 60%) taken 3 times a day.47
- Tea decoction: 1–2 tsp of dried berries or bark in 1 cup of water, boiled then simmered covered for 10–15 minutes. Taken 3 times a day.48
- Topical: a liniment of dried berries or bark in rubbing alcohol or witch hazel extract can be prepared and applied topically on skin ulcers (that have not broken through the skin) and areas experiencing rheumatic pain and fibrositis.
The dried berries and bark can also be chewed in order to relieve dental pain.
Special Considerations
The use of Z. americanum and Z. clava-herculis is contraindicated during pregnancy as they have actions as an emmenagogue. While there have been no studies established on the safety of using Zanthoxylum spp. during lactation, the use of the herb should be avoided. The consumption of these species has resulted in toxic reactions in cattle and fish.49
Caution is advised for people taking antihypertensive drugs and muscle relaxants such as scopolamine as the Zanthoxylum species may potentiate the effect of the drug. An alcohol extract of zanthoxylum may result in a disulfran or disulfram-like reaction when taking disulfram or metronidazole drugs. Taking iron supplements with prickly ash may decrease iron absorption. It is also contraindicated for those on anticoagulant therapy.50 Overdose may lead to increased blood pressure, cardiac function, and salivation.51
Summary
While the information on prickly ash is limited in terms of more recent research, it is traditionally and clinically relevant as a strong circulatory stimulant supporting bringing blood flow to areas of the musculoskeletal and circulatory system that need nourishment and repair. It is tonifying to support the balance of body functions in terms of nerve health and the gastrointestinal system and the tingling sensation makes for an effective analgesic.
Footnotes
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