Oxeye bean
StarMucuna urens
Synonyms: Clitoria zoophthalmum, Canavalia altissima, Phaseolus pruriens, Dolichos urens, Hornera altissima, Negretia sericea, Hornera urens, Mucuna umbellata, Stizolobium altissimum, Mucuna altissima var. pilosula, Labradia urens, Cacuvallum altissimus, Stizolobium urens
Western Herbalism Properties
Traditional Uses
In Neotropical folk medicine the seed of Mucuna urens is used medicinally: a tincture of the powdered bean macerated in alcohol is used as a soothing, astringent remedy for haemorrhoids, especially those prone to bleeding, and the irritant pod hairs have been taken internally as a vermifuge against intestinal worms (Duke, 2008; Useful Tropical Plants). The astringent action on the haemorrhoidal use is the documented species-specific medicinal property.
Gallery
Botanical Description
Mucuna urens (horse-eye bean, ox-eye bean) is a large, vigorous woody climbing legume of the Fabaceae, native to tropical Central and South America. It produces long, twining stems and large trifoliate leaves. The pendulous racemes bear dark, dull-purplish to greenish pea flowers, followed by thick, leathery, often S-shaped pods densely clothed in irritant orange-brown stinging hairs. Each pod contains a few large, hard, glossy, disc-shaped seeds that are dark brown to black with a conspicuous black encircling hilum (the "eye"), giving the plant its common names; the buoyant seeds are dispersed by water and are sometimes found as sea-beans. It grows in lowland rainforest and along watercourses.
Active Constituents
L-DOPA (levodopa, L-3,4-dihydroxyphenylalanine)
Non-protein aromatic amino acid / catecholamine precursorConcentration: Seed; the hallmark constituent of Mucuna seeds (roughly 3-7% in the genus). Exact content in M. urens is less thoroughly quantified than in M. pruriens
L-DOPA is the direct metabolic precursor of dopamine and crosses the blood-brain barrier, which is the pharmacological basis for the anti-parkinsonian reputation of Mucuna seeds. Its documented, high presence in the genus means M. urens seed should be treated as a dopaminergically active material even though most quantitative work has been done on M. pruriens.
Seed storage protein
Protein / essential amino acidsConcentration: Seed cotyledon; ~20% crude protein across three Nigerian morphotypes (Ezeagu et al., 2005)
The seed is a protein-rich pulse (about 20 g per 100 g), which underlies its use as a minor famine and soup-thickener food after adequate soaking, boiling and dehulling to lower antinutrients.
Tannins and total phenolics
Polyphenols (condensed tannins)Concentration: Seed testa and cotyledon; antinutritional levels reduced by soaking/boiling
Tannins and other phenolics contribute antioxidant capacity but also astringency and reduced protein/mineral bioavailability, which is why traditional processing (soaking, boiling, roasting) is applied before the bean is eaten.
Alkaloids
Indole / guanidine-type alkaloidsConcentration: Seed; not fully characterised for M. urens
Seed alkaloids were proposed as the agents responsible for the antifertility effect of M. urens crude seed extract on male guinea-pig gonads. The alkaloid profile of this species is only partly defined, so identities beyond the catecholamine amino acid L-DOPA remain uncertain.
Mucunain (trichome proteolytic enzyme)
Serine/cysteine proteinase (in urticating pod hairs)Concentration: Pod surface hairs (spicules)
The stiff hairs coating the pods of horse-eye bean carry a proteolytic, histamine-releasing principle (mucunain, together with mechanical spicules) that causes intense itching and dermatitis on contact. This is a well-known hazard of handling the raw pods and is reflected in the plant's old name "cow-itch".
Fixed (fatty) oil
Triacylglycerol seed oilConcentration: Seed; ~2-5% fat (Ezeagu et al., 2005)
The seed yields a small quantity of vegetable oil; in parts of Nigeria the bean is used both as a soup thickener and as a minor source of cooking oil.
⚠ Drug Interactions
Levodopa / carbidopa (anti-Parkinson therapy)
Because Mucuna seed is naturally rich in L-DOPA, ingesting the seed together with prescription levodopa adds an uncontrolled dose of the same active compound, which can potentiate both benefit and dopaminergic side effects.
Clinical note: Patients on levodopa should not add Mucuna seed preparations without neurologist supervision and dose adjustment.
Monoamine oxidase inhibitors (MAOIs)
MAO inhibition prevents breakdown of the dopamine formed from seed L-DOPA, allowing catecholamines to accumulate and potentially precipitating a hypertensive reaction.
Clinical note: Avoid combining L-DOPA-bearing Mucuna seed with non-selective MAOIs.
Dopamine antagonists (antipsychotics, metoclopramide)
Seed-derived dopamine and dopamine-receptor-blocking drugs oppose one another, so each can blunt the intended action of the other.
Clinical note: Relevant for patients taking antipsychotics or anti-emetic dopamine blockers.
Preparation Methods
Boiled / processed seed (food)
Parts: seed, cotyledon
Traditionally the mature beans are shelled, soaked and thoroughly boiled (sometimes roasted) to reduce tannins, L-DOPA and other antinutrients before being used as a soup thickener or protein food, chiefly in West Africa. Because the seed carries meaningful L-DOPA, it should not be treated as an inert pulse; adequate cooking and moderation are important.
Tincture of powdered bean
Parts: seed
A tincture of the powdered bean macerated in alcohol is a traditional (and homeopathic) remedy applied for bleeding haemorrhoids. This is a folk/historical use only; the seed's dopaminergic and antifertility activity means internal use should be regarded as pharmacologically active and approached with caution.
Handling caution (not a remedy)
Parts: pod, trichomes
The pods are covered in urticating hairs that cause severe itching and dermatitis; gloves and eye protection should be worn when collecting or de-hairing pods, and the loose spicules kept away from skin, eyes and airways.
Clinical Studies
Studies on seed characteristics and chemical composition of three morphotypes of Mucuna urens (L.) Medikus – Fabaceae
Three big-grained Nigerian morphotypes of Mucuna urens were analysed for seed morphology and proximate composition, showing the bean to be a good source of crude protein (~20 g/100 g) and carbohydrate (~72-75 g/100 g) with low fat, supporting its role as an underutilised food legume.
Effect of Mucuna urens (horse eye bean) on the gonads of male guinea-pigs
Crude seed extract of M. urens given to male guinea-pigs for eight weeks caused dose-dependent degeneration of testicular tubules and arrest of spermatogenesis, with no pregnancies on mating, indicating a reversible male antifertility potential attributed to seed alkaloids.
Historical Texts
J.H. Clarke, A Dictionary of Practical Materia Medica (entry "Mucuna urens")
Late 19th / early 20th century (homeopathic materia medica)West African (Igbo/Efik/Ibibio/Yoruba) ethnobotany
Traditional, documented in 20th-21st century ethnobotanical surveysReferences
- Ezeagu IE, Maziya-Dixon B, Tarawali G. Studies on seed characteristics and chemical composition of three morphotypes of Mucuna urens (L.) Medikus – Fabaceae . Food Chemistry, 95(4):658-663 (2005) [DOI]
- Udoh P, Ekpenyong J. Effect of Mucuna urens (horse eye bean) on the gonads of male guinea-pigs . Phytotherapy Research, 15(2):99-102 (2001) [DOI]
- Lampariello LR, Cortelazzo A, Guerranti R, et al.. The Magic Velvet Bean of Mucuna pruriens (genus-level context for L-DOPA chemistry) . Journal of Traditional and Complementary Medicine, 2(4):331-339 (2012) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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