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Inhalte Verbergen
1 Where does monk’s pepper come from and where is it found?
2 Therapeutic use of monk’s pepper
3 Use of monk’s pepper in horses

Herb profile

NameMonk’s pepper / Also known as chastetree, Abraham’s balm, chasteberry or vitex
Latin nameVitex agnus-castus (there are several species of Vitex worldwide, some of which are also known as monk’s pepper, for example Vitex negundo, the leaves of which are mainly used in Indian Ayurvedic medicine)
Traditional usesMonk’s pepper (Vitex agnus castus) was used in ancient times to protect female chastity and as an anti-aphrodisiac for men. The fruits are used in folk medicine for menopausal symptoms, endometriosis and menstrual problems. Leaves are used against fever.
Scientifically proven effect(s)Influences various hormone receptors, has antioxidant, chemoprotective, immunomodulatory, tumoricidal, antimutagenic, antimicrobial, fungicidal, antiepileptic, analgesic, opioid and insect repellent/killing effects. kills insect larvae. More than 60 different substances have now been isolated, including iridoid glycosides, diterpenes, 2% essential oils (bornyl acetate, 1,8-cineole, limonene, a-pinene, ß-pinene) and above all flavonoids (casticin, quercetagetin, isovitexin), which can bind to oestrogen receptors (a- and ß-types), with casticin presumably being the most potent active ingredient. Extracts from the fruits also act as dopamine (D2 receptor) agonists in vitro and in vivo and as prolactin inhibitors. Leaves contain higher levels of essential oils and have an antimicrobial effect.
ContraindicationsDo not use in pregnant mares due to the influence on the oestrogen and progesterone balance, and also not in lactating mares as this influences milk yield.
When is it collected?Fruits are harvested in autumn
Which parts of the plant are usedFruits (leaves)
How is it prepared?The fruits are ground, crushed or used as an alcoholic extract (drops). They can be prepared as a tea or ground / crushed and mixed directly with food (although they taste a little pungent).
TriviaThe botanical name means “chaste tree”, which refers to its traditional use by monks to fulfil their vow of chastity. The name “monk’s pepper” has the same background: the fruits were used to flavour monastic dishes, with the well-known side effect. The Greek goddess Hera (patron goddess of women) is said to have been born under a chaste tree. Sometimes used in ritual practices as a protective plant and to promote inner peace.

Where does monk’s pepper come from and where is it found?

Monk’s pepper originally comes from the Mediterranean region and is now widespread in southern Europe, the Mediterranean and western Asia. Only Vitex agnus castus is found in Europe, although other Vitex species with medicinal properties (e.g. Vitex negundo) can also be found in other countries. Monk’s pepper is a woody, perennial shrub with a height of up to three metres. The violet-blue flowers, which attract many bees and butterflies in July and August, are the plant’s most striking feature. The flower colours can vary depending on the variety. After the flowering period, the usable brown-black fruits are formed. Monk’s pepper can also be grown in our region, but is not hardy. It prefers wind-protected, warm and full-sun locations and should be well protected in winter or kept in winter quarters. The soil should be well-drained and rich in nutrients, which is why the plant favours river valleys.

Therapeutic use of monk’s pepper

Even Hippocrates described monk’s pepper as an important medicinal plant to support difficult births, and both the ancient Egyptians and the ancient world considered it one of the most important plants in medicine at the time due to its many qualities. Its name refers on the one hand to the pepper-shaped form of the fruit and its pungent, pepper-like flavour, and on the other to its use by monks to make it easier for them to observe their celibacy.

In human medicine, extracts from monk’s pepper seeds are mainly used. The recommendation is 30-40mg/day of monk’s pepper extract with 0.6% casticin for the treatment of menstrual irregularities, premenstrual syndrome (PMS), mastalgia (non-specific breast pain) and menopausal symptoms as well as for increasing fertility in women. The flavonoids apigenin, penduletin and vitexin have been shown to be able to activate the ß-oestrogen receptors, while other components also bind to the a-oestrogen receptors. The high affinity to oestrogen receptors explains the strong effect of monk’s pepper extracts on symptoms attributable to a disturbed oestrogen balance, as well as the suppression of the male libido, as the existing oestrogen receptors are also activated in the male organism and thus the effects of the male sex hormones – especially testosterone – are suppressed.

Due to its strong phytoestrogenic effect, monk’s pepper should only be used for appropriate indications and not as a general “hormone phytotherapeutic agent”, as is often suggested, as its active ingredients primarily have a strong effect on the sex hormone balance.

In addition, individual components from monk’s pepper fruits are also being investigated with regard to their therapeutic value in the treatment of various forms of cancer, as an insect repellent or for larvae reduction and as an antimicrobial therapeutic agent. However, a distinction must always be made in such applications between the use of individual active ingredients and the use of whole (ground or crushed) fruits or complete extracts. In contrast to individually isolated active ingredients, the fruits or extracts from the fruits can also have undesirable effects on the oestrogen system in addition to the desired effects, for example against insects. It is therefore generally not advisable to feed monk’s pepper to horses in an attempt to deworm them.

Furthermore, to the oestrogen balance, monk’s pepper also influences the dopamine balance in particular. Dopamine is a neurotransmitter that is active at various points in the central nervous system (CNS). The effect of monk’s pepper (extract) on the dopamine balance has been studied intensively in connection with the hormone prolactin. Chronic stress generally leads to reduced dopamine secretion, which can result in increased prolactin secretion in female mammals. High prolactin levels in turn lead to changes in breast tissue, mastalgia and reduced fertility, among other things.

A panicle of monk's pepper bears brownish red-black spherical fruits.
It is generally not recommended to feed monk’s pepper, for example, in an attempt to deworm the horse. ©AdobeStock/Roswitha

Monk’s pepper (extract) is able to activate the dopamine receptors of the pituitary gland – despite low dopamine concentrations during chronic stress – and the negative effects on fertility and breast tissue are reduced. It is known from these studies that monk’s pepper can act as a dopamine agonist in the area of the pituitary gland. More precisely, it is the terpenes, especially clerodane, rotundifuran and 6ß,7ß-diacetoxy-13-hydroxylabda-8,14-diene, which bind to the dopamine receptors and activate them, but not other receptors, for example for histamine, benzodiazepine or histamine transporters. Studies on isolated pituitary cells have shown that clerodan (or clerodadienol) in particular is able to stimulate the dopamine receptors.

In addition, the body’s own opioid receptor system is closely linked to the hypothalamic-pituitary axis. It has been shown that monk’s pepper extracts are able to activate the m-, k- and d-receptors of the opioid system, which explains the strong analgesic and sedative effect.

Use of monk’s pepper in horses

Monk’s pepper is given to horses with Cushing’s symptoms (also known as PPID) in particular due to its dopaminergic effect. Interestingly, monk’s pepper (extract) is not considered at all as a therapy for Cushing’s disease in humans. The use of monk’s pepper in horses with Cushing’s symptoms is essentially based on a theory about the development of Cushing’s disease. According to current knowledge, the symptoms that we call Cushing’s in horses are associated with changes in the melanotrophic cells in the middle part of the pituitary gland. These melanotrophic cells are not directly involved in the feedback axis (hypothalamus-pituitary-adrenal glands).

Instead, they have dopamine receptors (D2), which are regulated and in particular inhibited by dopaminergic neurones from the hypothalamus. One of the theories for the development of Cushing’s symptoms states that the visible symptoms are due to an age-related degeneration of the dopaminergic hypothalamic neurones. As these dopaminergic neurones are no longer able to regulate the melanotrophic cells of the pituitary gland, they hypertrophy and eventually undergo neoplastic changes, which ultimately leads to the symptoms. Therefore, the idea was derived that Prascend, as a dopamine agonist, should be able to continue to stimulate the dopamine receptors of the melanotrophic cells of the pituitary gland and thus be able to stop hypertrophy and degeneration.

Unfortunately, however, it was realised that it is not that simple after all. Although there are studies that show that the symptoms associated with Cushing’s disease decreased in a significant proportion of test horses after administration of Prascend (a pharmaceutical dopamine agonist derived from ergot alkaloids), there are also a whole series of horses in which the medication does not cause any improvement in symptoms, but instead can cause severe side effects in some cases. So not all horses’ symptoms seem to be associated with a lack of dopamine activation of the melanotrophic cells.

A (manufacturer-independent) study of monk’s pepper also showed that its active ingredients have no statistically significant influence on the symptoms in horses with Cushing’s disease, so it is not necessary to feed it. Monk’s pepper also has no effect on ACTH levels. This suggests that a lack of dopamine in the pituitary gland is not the cause in all horses with Cushing’s symptoms.

Against this background, the common use of monk’s pepper in horses with Cushing’s symptoms is highly questionable. Especially when you consider that monk’s pepper has a strong effect on the oestrogen balance (in mares as well as in stallions and geldings, which also have oestrogen receptors!), administration on suspicion should be viewed more critically. Monk’s pepper has no effect whatsoever on other hormonal disorders, such as thyroid hormones or the insulin-glucagon system.

Only in broodmares with poor fertility can the administration of monk’s pepper be considered, although no systematic studies are available. Pregnant and lactating mares should not be fed it under any circumstances.

Many more herbal advice awaits you HERE!

Sources

  • Fritz, Dr. C., Maleh, S. (2020): Zivilisationskrankheiten des Pferdes – ganzheitliche Behandlung chronischer Krankheiten. Thieme Verlag, Stuttgart. 2.updated edition.
  • Jagel, A. et al. (2023): Vitex agnus-castus – Mönchspfeffer, Kuschlammstrauch (Lamiaceae) – Arzneipflanze des Jahres 2022. Jahrb. Bochumer Bot. Ver. Nr. 14, S. 340-347.
  • Korz, N. und Müller, A-K. (2020): Der Kräuterguide für Pferde.
  • Nagersheth, Dr. med. K. (2018): Vergleich westlicher Pflanzen mit ayurvedischen Pflanzen. zaenmagazin. 10. Jahrgang 4/2018. S. 45-47.
  • Planatura GmbH – Alina: Mönchspfeffer: Pflanzen, Schneiden Wirkung von Vitex agnus-castus. https://www.plantura.garden/kraeuter/moenchspfeffer-pflanzenportrait (zuletzt aufgerufen am 28.02.2024).
  • Sanoanimal (3.2.2021): Wie wirkt Prascend? https://wissen.sanoanimal.de/2021/02/03/wie-wirkt-prascend/ (zuletzt aufgerufen am 28.02.2024).
  • Wittek, C. (2019): Heilpflanzen Hausmittel für Pferde. Franckh-Kosmos Verlags-GmbH Co, Stuttgart.
  • Gill, Balraj Singh, et al. “Vitex negundo and its medicinal value.” Molecular biology reports 45.6 (2018): 2925-2934.
  • Zahid, Hina, Ghazala H. Rizwani, and Sumaira Ishaqe. “Phytopharmacological review on Vitex agnus-castus: a potential medicinal plant.” Chinese Herbal Medicines 8.1 (2016): 24-29.
  • Niroumand, Mina Cheraghi, Fatemeh Heydarpour, and Mohammad Hosein Farzaei. “Pharmacological and therapeutic effects of Vitex agnus-castus L.: A review.” Pharmacognosy Reviews 12.23 (2018).
  • Daniele, Claudia, et al. “Vitex agnus castus: a systematic review of adverse events.” Drug safety 28 (2005): 319-332.
  • Puglia, Lídice Tavares, and Gianluca Tamagno. “Vitex agnus castus effects on hyperprolactinaemia.” Frontiers in Endocrinology 14 (2023): 1269781.
  • Adamov, Grigory Vasilievich, et al. “Vitex agnus-castus: Botanical features and area, chemical composition of fruit, pharmacological properties, and medicinal uses.” Journal of Applied Pharmaceutical Science 12.3 (2022): 034-044.
  • van Die, M. Diana, et al. “Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials.” Planta medica 79.07 (2013): 562-575.
  • Chan, E. W. C., Wong, S. K., Chan, H. T. (2018). Casticin from Vitex species: a short review on its anticancer and anti-inflammatory properties. Journal of integrative medicine, 16(3), 147-152.
  • Kamal, Nurkhalida, et al. “Traditional medicinal uses, phytochemistry, biological properties, and health applications of Vitex sp.” Plants 11.15 (2022): 1944.
  • Meena, Ajay Kumar, et al. “A review of the important chemical constituents and medicinal uses of Vitex genus.” Asian Journal of Traditional Medicines 6.2 (2011): 54-60.
  • Ooi, Soo Liang, et al. “Vitex agnus-castus for the treatment of cyclic mastalgia: A systematic review and meta-analysis.” Journal of Women’s Health 29.2 (2020): 262-278.
  • Verkaik, Saskia, et al. “The treatment of premenstrual syndrome with preparations of Vitex agnus castus: a systematic review and meta-analysis.” American Journal of Obstetrics and Gynecology 217.2 (2017): 150-166.
  • Van Die, Margaret Diana, et al. “Vitex agnus-castus (Chaste-Tree/Berry) in the treatment of menopause-related complaints.” The Journal of Alternative and Complementary Medicine 15.8 (2009): 853-862.
  • Mollazadeh, Sanaz, Mojgan Mirghafourvand, and Nafiseh Ghassab Abdollahi. “The effects of Vitex agnus-castus on menstrual bleeding: A systematic review and meta-analysis.” Journal of Complementary and Integrative Medicine 17.1 (2020): 20180053.
  • Sojka, Janice E., et al. “Domperidone causes an increase in endogenous ACTH concentration in horses with pituitary pars intermedia dysfunction (Equine Cushing’s Disease).” (2006): 320-323.
  • McFarlane, Dianne. “Equine pituitary pars intermedia dysfunction.” Veterinary Clinics: Equine Practice 27.1 (2011): 93-113.
  • Mende, Susan A. “Equine Cushing’s Disease or Equine Pituitary Pars Intermedia Dysfunction (PPID) Keeping up with Evolution.” (2016).
  • Fortin, Jessica S., et al. “Restoring pars intermedia dopamine concentrations and tyrosine hydroxylase expression levels with pergolide: evidence from horses with pituitary pars intermedia dysfunction.” BMC veterinary research 16 (2020): 1-8.
  • Huang, Luoyi, Chiara Palmieri, and François-René Bertin. “Correlation of pituitary histomorphometry with dopamine and dopamine D2 receptor expression in horses with pituitary pars intermedia dysfunction.” Research in Veterinary Science 152 (2022): 427-433.
  • Li, Fang I., et al. “Association between insulin dysregulation and adrenocorticotropic hormone in aged horses and ponies with no clinical signs of pituitary pars intermedia dysfunction.” Equine Veterinary Journal 55.6 (2023): 1003-1011.
  • Beech, Jill, Mark T. Donaldson, and Sue Lindborg. “Comparison of Vitex agnus castus extract and pergolide in treatment of equine Cushing’s syndrome.” AAEP Proceedings. Vol. 48. 2002.
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