Fennel
Scientific Name(s): Foeniculum vulgare Mill. syn., Foeniculum officinale All., and Anethum foeniculum Family: Apiaceae (carrots)
Common Name(s): Common, sweet, or bitter fennel , carosella , Florence fennel , finocchio , garden fennel , large fennel , wild fennel 1 , 2
Clinical Overview
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Uses of Fennel
Fennel has been used as a flavoring, a scent, an insect repellent, as well as an herbal remedy for poisoning and GI conditions. It has also been used as a stimulant to promote lactation and menstruation. However, there is a lack of clinical evidence to support the use of fennel for any indication.
Fennel Dosing
Fennel seed and fennel seed oil have been used as stimulant and carminative agents in doses of 5 to 7 g and 0.1 to 0.6 mL, respectively.
Contraindications
Contraindications have not been identified.
Pregnancy/Lactation
There are documented adverse reactions and emmenagogue effects. Avoid use.
Fennel Interactions
None well documented.
Fennel Adverse Reactions
Fennel may cause photodermatitis, contact dermatitis, and cross reactions. The oil may induce reactions such as hallucinations and seizures. Poison hemlock may be mistaken for fennel.
Toxicology
Fennel oil is genotoxic in the Bacillus subtilis DNA repair test. Estragole, present in the volatile oil, has been shown to cause tumors in animals.
Botany
Fennel is an herb native to southern Europe and Asia Minor. It is also cultivated in the United States, Great Britain, and temperate areas of Eurasia. All parts of the plant are aromatic. When cultivated, fennel stalks grow to a height of approximately 1 m. Plants have finely divided leaves composed of many linear or awl-shaped segments. Grayish compound umbels bear small, yellowish flowers. The fruits or seeds are oblong ovals about 6 mm long and are greenish or yellowish brown in color with 5 prominent dorsal ridges. The seeds have a taste resembling that of anise. Besides F. vulgare , Foeniculum dulce (carosella) is grown for its stalks, while F. vulgare var azoricum Thell. (finocchio) is grown for its bulbous stalk bases. A number of subspecies have been identified, adding to the potential confusion surrounding the terminology of these plants.
History
According to Greek legend, man received knowledge from Mount Olympus in the form of a fiery coal enclosed in a stalk of fennel. The herb was known to the ancient Chinese, Indian, Egyptian, and Greek civilizations, and the Roman scholar Pliny (AD 61-113) recommended it for improving eyesight. The name foeniculum is from the Latin word for fragrant hay. Fennel was in great demand during the Middle Ages. Wealthy people routinely added the seed to fish and vegetable dishes, while the poor reserved its use for fasting days as an appetite suppressant. The plant was introduced to North America by Spanish priests, and the English brought it to their early settlements in Virginia. 3 All parts of the plant have been used for flavorings, the stalks have been eaten as a vegetable, and the seeds served as a traditional carminative. Fennel has been used to flavor candies, liqueurs, medicines, and food; its use is especially favored for pastries, sweet pickles, and fish. The oil can be used to protect stored fruits and vegetables against growth of toxic fungi. 4 Beekeepers have grown it as a honey plant. 3 It is a purported antidote to poisonous herbs, mushrooms, and snakebites, 5 and is also thought to be useful in treating gastroenteritis and indigestion, in stimulating lactation, as an expectorant, and as an emmenagogue. 1 Tea made from crushed fennel seeds has been used as an eyewash. 3 Powdered fennel is said to drive fleas away from kennels and stables. 4
Chemistry
Fennel seeds contain between 3% and 6% of an essential oil and approximately 20% of a fixed oil composed of petroselinic acid, oleic acid, and tocopherols. The essential oils of sweet and bitter fennel contain up to 90% trans-anethole, up to 20% fenchone and small amounts of limonene, camphor, alpha-pinene, and about 6 additional minor volatile compounds. 6
Sweet fennel contains derivatives of caffeic acid and hydroxybenzoic acid. 7 The fruit (seeds) and leaves contain a number of flavonoid compounds, including quercetin 3-glucuronide, isoquercetin, kaempferol 3-glucuronide, and kaempferol 3-arabinoside. Low concentrations of isorhammetin glycosides are found in the leaves. 8
Fennel Uses and Pharmacology
Stimulant to promote lactation and menstruationAs an herbal medicine, fennel is reputed to increase milk secretion, promote menstruation, facilitate birth, ease the male climacteric, and increase the libido. These supposed properties led to research on fennel for the development of synthetic estrogens during the 1930s. The principal estrogenic component of fennel was originally thought to be anethole, but it is now believed to be a polymer of anethole, such as dianethole or photoanethole. 9
Animal dataAn acetone extract of F. vulgare seeds had estrogenic effects on the genital organs of male and female rats. 10
Clinical dataThere are no clinical data regarding the use of fennel as a stimulant to promote lactation and menstruation.
Acaricidal activityAnimal data
Oil derived from F. vulgare fruit demonstrated acaricidal activity against Dermatophagoides farinae and Dermatophagoides pteronyssinus (house dust mites). The LD 50 value for the oil was 119 and 103 mg/m 2 for D. farinae and D. pteronyssinus , respectively.
Twelve volatile compounds were identified from the oil of Foeniculum fruits. The main constituents were trans-anethole (53.2%), anisaldehyde (0.7%), β-asarone (0.9%), β-caryophyllene (1.1%), p -cymene (3.1%), estragole (12.7%), (+)− fenchone (14.2%), d -limonene (0.7%), 1,5,8- p -menthatriene (0.6%), α-pinene (0.8%), γ-terpinene (0.7%), and thymol (1.4%). The compound most toxic against both species was p -anisaldehyde. Further research is needed to determine any safety issues for the use of F. vulgare in humans. 11
Clinical dataThere are no clinical data regarding the use of fennel for acaricidal activity.
Repellent activityAnimal data
The repellent activity of constituents identified in F. vulgare against hungry female Aedes aegypti mosquitoes was compared with N,N-diethyl-m-toluamide (DEET) using skin and patch tests. With patch testing, responses varied according to the compound and dose. Fenchone caused 94% and 82% repellency at 0.01 and 0.005 mg/cm 2 . ( E )-9-octadecenoic acid gave 91% repellancy at 0.01 mg/cm 2 and 73% repellency at 0.005 mg/cm 2 . At a dose of 0.2 mg/cm 2 , the repellent effects of a fenchone skin test were 100% and 32% with ( E )-9-octadecenoic acid. The efficacy for fenchone was only 30 minutes, compared with more than 1 hour with DEET. 12
Clinical dataThere are no clinical data regarding the use of fennel for mosquito repellent activity.
Anti-inflammatory effectsAnimal data
In mice, a F. vulgare fruit methane extract at a dose of 200 mg/kg caused inhibition of paw edema (69%). Ear edema was also reduced by 70%. These results suggest that F. vulgare fruit methanolic extract may act on the cyclooxygenase and lipoygenase pathways. 13
Clinical dataA study compared the effect and potency of mefenamic acid and an extract of fennel (2% concentration) for the treatment of primary dysmenorrhea in 30 women. Mefenamic acid was more potent than fennel on the second and third days of menstruation ( P ≤ 0.05). However, on the other days, the difference was not significant. With the doses prescribed, no complications were reported in the mefenamic acid treatment cycles (250 mg every 6 hours). However, 5 cases (16.6%) withdrew from the study because of fennel's odor, and one subject reported a mild increase in the amount of her menstrual flow during the fennel treatment cycle. 14
Enhancement of transdermal drug deliveryAnimal data
In animal studies, pretreatment of the skin with several essential oils increased the flux values of trazodone. Pretreatment with a solution containing 10% fennel oil in propylene glycol showed an enhancement ratio of 9.25, compared with the control. The incorporation of fennel in the transdermal device also produced an increase in the flux of trazodone but less of an increase than when the skin was pretreated. 15
Clinical dataThere are no clinical data regarding the use of fennel for enhancement of transdermal drug delivery.
Other usesThe volatile oil of fennel increases the phasic contraction of ileal and tracheal smooth muscle in guinea pigs. The effect was generally greater with ileal muscle. 16 Administration of the volatile oil to rats has exacerbated experimentally induced liver damage. 17
Oil extracted from F. vulgare has shown a protective effect against the toxicity induced by CCl 4 in rat livers. Although the responsible compound has not been identified, d-limonene and β-myrcene have previously been shown to affect the liver. 18
Fennel has demonstrated inhibitory effects on the growth of Bacillus amyloliquefaciens . 19 Bacteriostatic effects against Escherichia coli , Staphylococcus epidermidis , and Saccharomyces cerevisiae have also been demonstrated. 20
Fennel essential oil (FEO) has been shown to inhibit contraction of an isolated uterus that was induced by oxytocin and prostaglandin E 2 . The optimum dose of FEO was 100 mg/mL. FEO may have a mechanism of action similar to that of diclofenac, although the exact mechanism of action of FEO is unknown. 21
F. vulgare fruit methanolic extract may have immunosuppressive properties. Antiallergic activity (type IV) was tested using 2,3-dinitrofluoro-benzene-induced contact hypersensitivity reactions. F. vulgare fruit methanolic extract showed an inhibitory effect. 22
Dosage
Fennel seed and fennel seed oil have been used as stimulant and carminative agents in doses of 5 to 7 g and 0.1 to 0.6 mL, respectively. 22
Pregnancy/Lactation
There are documented adverse reactions and emmenagogue effects. Avoid use. 23 , 24
Interactions
None well documented.
Adverse Reactions
Ingestion of fennel's volatile oil may induce nausea, pulmonary edema, seizures, and vomiting. 25 Laxative and cholagogic properties have also been described. 26 The oil's therapeutic use has occasionally induced epileptiform madness and hallucinations. 4 The principal hazards with fennel itself are photodermatitis and contact dermatitis. Some individuals exhibit cross-reactivity to several species of Apiaceae , characteristic of the celery-carrot-mugwort-condiment cross-reactivity syndrome. 27 Rare allergic reactions have been reported following ingestion of fennel.
A survey of fennel samples in Italy found viable aerobic bacteria, including coliforms, fecal streptococci, and Salmonella species, suggesting the plant may serve as a vector of infectious GI diseases. 28
Toxicology
Fennel oil was found to be genotoxic in the B. subtilis DNA-repair test. 29 Estragole, present in the volatile oil, has been shown to cause tumors in animals. A serious hazard is that poison hemlock can easily be mistaken for fennel. Hemlock contains highly narcotic coniine, and a small amount of hemlock juice can cause vomiting, paralysis, and death. 5
Animal studies have demonstrated toxic effects of fennel essential oil on fetal cells. However, no evidence of teratogenicity was seen. 30
No pathological toxicity was seen in the organs of dead animals, indicating that death may be caused by the effects of metabolite imbalance or a nervous system toxicity. The value of LD 50 was 1,326 mg/kg. 21
Bibliography
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11. Lee HS . Acaricidal activity of constituents identified in Foeniculum vulgare fruit oil against Dermatophagoides spp. (Acari: Pyroglyphidae) . J Agric Food Chem . 2004;52(10):2887-2889.
12. Kim DH , Kim SI , Chang KS , Ahn YJ . Repellent activity of constituents identified in Foeniculum vulgare fruit against Aedes aegypti (Diptera: Culicidae). J Agric Food Chem . 2002;50:6993-6996.
13. Choi EM , Hwang JK . Antiinflammatory, analgesic and antioxidant activities of the fruit of Foeniculum vulgare . Fitoterapia . 2004;75(6):557-565.
14. Namavar Jahromi B , Tartifizadeh A , Khabnadideh S . Comparison of fennel and mefenamic acid for the treatment of primary dysmenorrhea. Intern J Gynaecol Obstet . 2003;80(2):153-157.
15. Das MK , Bhattacharya A , Ghosal SK . Effect of different terpene-containing essential oils on percutaneous absorption of trazodone hydrochloride through mouse epidermis . Drug Deliv . 2006;13(6):425-431.
16. Reiter M , Brandt W . Relaxant effects on tracheal and ileal smooth muscles of the guinea pig. Arzneimittelforschung . 1985;35(1A):408-414.
17. Gershbein LL . Regeneration of rat liver in the presence of essential oils and their components . Food Cosmet Toxicol . 1977;15(3):173-181.
18. Ozbek H , Ugras S , Dulger H , et al. Hepatoprotective effect of Foeniculum vulgare essential oil . Fitoterapia . 2003;74(3):317-319.
19. Ozcan MM , Sagdic O , Ozkan G . Inhibitory effects of spice essential oils on the growth of Bacillus species . J Med Food . 2006;9(3):418-421.
20. Schelz Z , Molnar J , Hohmann J . Antimicrobial and antiplasmid activities of essential oils . Fitoterapia . 2006;77(4):279-285.
2111448553. Ostad SN , Soodi M , Shariffzadeh M , Khorshidi N , Marzban H . The effect of fennel essential oil on uterine contraction as a model for dysmenorrhea, pharmacology and toxicology study . J Ethnopharmacol . 2001;76(3):299-304.
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23. Brinker FJ . Herb Contraindications and Drug Interactions . 2nd ed. Sandy, OR: Eclectic Medical Publications; 1998 .
24. Ernst E . Herbal medicinal products during pregnancy: are they safe? BJOG . 2002;109(3):227-235.
25. Marcus C , Lichtenstein EP . Biologically active components of anise: toxicity and interactions with insecticides in insects. J Agric Food Chem . 1979;27:1217-1223.
26. Cuzzolin L , Zaffani S , Benoni G . Safety implications regarding use of phytomedicines . Eur J Clin Pharmacol . 2006 ;62(1):37-42.
27. Wüthrich B , Hofer T . Food allergy: the celery-mugwort-spice syndrome. Association with mango allergy? [in German] Dtsch Med Wochenschr . 1984;109(25):981-986.
28. Ercolani GL . Bacteriological quality assessment of fresh marketed lettuce and fennel. Appl Environ Microbiol . 1976;31(6):847-852.
29. Sekizawa J , Shibamoto T . Genotoxicity of safrole-related chemicals in microbial test systems. Mutat Res . 1982;101(2):127-140.
30. Ostad SN , Khakinegad B , Sabzevari O . Evaluation of the teratogenicity of fennel essential oil (FEO) on the rat embryo limb buds culture . Toxicol In Vitro . 2004;18(5);623-627.
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