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Fennel

Botanical name

(Bitter) Fennel - Foeniculum vulgare Mill. ssp. vulgare var. vulgare

Family

Umbelliferous plants (Apiaceae)

Common name

Common fennel, Garden fennel, Wild fennel

Useful information about the plant

The common fennel (Foeniculum vulgare Mill) is native to the Mediterranean and it comes in two varieties. The subspecies piperitum (Pepper or Bulgarian fennel or donkey) grows wild on dry, rocky soils, the subspecies vulgare (Garden fennel) is mostly in a two-year-old farmed form that is cultivated throughout Europe and other temperate zones and is also found wild. Three variants of this have developed over time: var vulgare, the Bitter fennel, with its bitter-sweet and slightly pungent fruit; var dulce, the Sweet or Roman Fennel with pleasant sweet-tasting fruits, var. azoricum is the vegetable and onion-fennel, the leaf sheaths at the base of the stem are fleshy and are popular as a vegetable. The Latin genus name Foeniculum comes from the Latin "fenum" = hay, which is used here in the diminutive form. The blue-green, bluish frosted plant grows up to 120cm and blooms in July / August with numerous small golden yellow flowers, 12 to 25 are arranged in the double-rayed umbels. The aromatic leaves are scented with conspicuous leaf sheaths in a pithy stem. They are 3 to 4 times pinnate with very narrow, almost thread-like leaves. When ripe they are greenish-brown fruits 3 to 12mm long with 5 light, angular protruding ribs. Like all Umbelliferae it has "double achenes" which easily disintegrate even before they come apart into the two fruits (achenes).

Medicinally used plant parts (drug)

The ripe fruit, with its typical smell of fennel, which is clearly notable when rubbed, is created by the essential oil contained in the fruit. The commercially available drug comes from imports from China, Egypt, Bulgaria, Hungary and Romania.

Ingredients of the drug

Fennel fruits contain an essential oil ("Bitter fennel oil") with sweet-tasting trans-anethole (main component) and the bitter fenchone that gives the Bitter fennel its slightly bitter taste. The essential oil of Sweet fennel (var. dulce) contains significantly less fenchone, so the flavour of the fruit is dominated by the sweet trans-anethole. The fennel fruit also contains a fatty oil.

Descriptions of the quality

The quality of the following drugs or drug preparations is specified in the European Pharmacopoeia (Ph. Eur.):

  • Bitter fennel (Foeniculi amari fructus)
  • Sweet fennel (Foeniculi dulcis fructus)
  • Bitter fennel oil (Foeniculi amari fructus aetheroleum)
  • Bitter fennel herb oil (Foeniculi amari herbae aetheroleum)

Medical Application

Recognised medical use

Internally for dyspeptic complaints such as mild, spasmodic gastric-intestinal complaints, bloating, flatulence, internally and externally for catarrhs of the respiratory tract (Commission E, ESCOP). The HMPC has classified fennel and fennel oil as traditional herbal medicinal products (see "traditional use").

Traditional use

The HMPC has classified fennel as a traditional herbal medicine (§ 39a AMG). Based on many years of experience, fennel can be used for mild spasms and cramps in the stomach-intestinal tract (flatulence) and light menstrual cramps as well as a decongestant in coughs associated with a cold. Traditionally used to support the digestive function and to stimulate the appetite (traditional use according to § 109a).

Medicinal herbal preparations in finished drug products

  • Crushed fennel fruit for teas, in tea bags
  • Alcoholic extracts (tincture) in drops
  • Dried extract in tablets
  • Bitter fennel oil in pastilles
Often combined with other similarly acting drugs. Savoury preparations such as fennel syrup and fennel honey can be used for colds, especially with children.

Dosage

Prepared drugs: see package insert;
Tea infusion: drink 1 cup of warm fennel tea several times a day (even in mixtures with other drugs as a gastrointestinal tea, cough-and bronchial tea).
Fennel oil: Take 3-5 drops on a lump of sugar several times daily.

Preparation of a tea infusion

Pour 1 litre of hot (not boiling!) water over 1 heaped teaspoon (1.5 - 2.5g) of freshly chopped fennel, let it stand for 15 minutes then strain. To enhance the effectiveness, the fennel should be crushed or coarsely powdered before the tea is prepared so that the essential oil can get into the tea.

Advice

Fennel preparations must be avoided in cases where there is an existing allergy to Apiaceae (fennel, caraway, celery, cilantro or dill) or to anethole. There is currently no experience on the harmlessness of the use of fennel during pregnancy, breast-feeding or in children under the age of 4. As a precautionary measure, children and adolescents under the age of 18 should not take the essential oil (bitter fennel oil), and children under the age of 4 should also not take the fennel fruit because of missing data and because of the estragole content.
Fennel oil should not be applied for longer than 2 weeks because of the levels of trans-anethole and estragole. This advice is based on the finding that "Photoanethol" with estrogenic properties could form from anethole during exposure to light during storage. Furthermore, in animal studies (mice) over 12 months with pure estragole (methyl chavicol) liver tumours could be observed. These results cannot however be transferred to the administration of fennel fruit and fennel oil.

Side effects

Occasionally, allergies to the skin and respiratory tracts

Interactions

None known

References

Drug monographs

HMPC, Commission E, ESCOP, WHO Vol. 3

Further reading

Wichtl: Teedrogen und Phytopharmaka, pg. 265
Schilcher: Leitfaden Phytotherapie, pg. 93
Van Wyk: Handbuch der Arzneipflanzen, pg. 145
Kommentar zum Europäischen Arzneibuch (Bitter fennel, no. 0824; Bitter fennel oil, no. 1826; Bitter fennel herb oil, no. 2380)

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