Bai Jie Zi
StarSinapis alba L.
☯ TCM Properties
Warms the Lungs and Transforms Phlegm-Fluids; Moves Qi and Dissipates Nodules; Unblocks the Channels and Alleviates Pain; Drains Water and Expels Phlegm-Fluids; Reduces swelling and disperses clumps
Traditional Chinese Uses
Bai Jie Zi (white mustard seed) is a warm, pungent herb that warms the Lung, transforms cold Phlegm, and promotes the movement of Qi in the channels. It is used for cold-type coughs and wheezing with white, clear, abundant phlegm, as well as for Phlegm obstructing the channels and sinew — causing joint pain, numbness, and cold abscesses deep in the tissue. Applied externally as a poultice, it warms and draws circulation to an area for musculoskeletal pain and deep cold-type swellings.
Western Herbalism Properties
Traditional Uses
The Cherokee employed Sinapis alba as a stimulant and tonic. The Hoh and Quileute used it as a pulmonary aid for respiratory complaints (mapped to expectorant) and as a kidney aid (mapped to diuretic). Several other tribes recorded analogous drug-class uses for respiratory and general toning purposes.
Botanical Description
Sinapis alba L. (Brassicaceae), white mustard, is an annual herb 30-80 cm tall with bristly stems, pinnately lobed lyrate leaves, and racemes of bright yellow four-petaled flowers. Bristly elongate siliques contain 4-6 pale yellow to tan globose seeds 2-2.5 mm in diameter. The seeds, known as Bai Jie Zi in Chinese medicine, are harvested when pods turn brown, threshed, and dried. In TCM, Bai Jie Zi is acrid in flavor and warm in nature, entering the Lung channel; it warms the Lungs, expels cold phlegm, frees the channels, and disperses nodules. The species is cultivated worldwide as a condiment, oilseed, and forage crop.
Active Constituents
Sinalbin
Glucosinolate (thioglucoside)Concentration: ~2-4% of seed; dominant glucosinolate of S. alba
Sinalbin is the principal glucosinolate of white mustard seed. On grinding of moist seed it is hydrolysed by endogenous myrosinase to 4-hydroxybenzyl (p-hydroxybenzyl) isothiocyanate, the pungent, warming, locally irritant and expectorant principle that underlies the herb's phlegm-transforming and channel-unblocking actions.
4-Hydroxybenzyl isothiocyanate
Isothiocyanate (hydrolysis product)Concentration: Generated on hydrolysis of sinalbin
The active hydrolysis product responsible for mustard's counter-irritant, rubefacient and antimicrobial effects. It stimulates local circulation and mucosal secretion (aiding expectoration) and shows broad-spectrum antibacterial and antifungal activity, but is unstable and can blister skin on prolonged topical contact.
Myrosinase (thioglucosidase)
Enzyme (beta-thioglucosidase)Concentration: Present in intact seed
The endogenous enzyme that cleaves sinalbin to release the active isothiocyanate when seeds are crushed with water. Heat and prolonged decoction inactivate it, which is why the herb is often crushed and added late, or used topically.
Sinapine
Alkaloid (choline ester of sinapic acid)Concentration: ~1-2.5% of seed
Sinapine is the major alkaloidal constituent, an ester of choline and sinapic acid. It contributes antioxidant activity and mild cholinergic properties, and is a marker compound used in quality control of Sinapis Semen.
Sinapic acid
Hydroxycinnamic (phenolic) acidConcentration: Minor free phenolic
A phenolic acid with documented antioxidant and anti-inflammatory activity, present free and as the acyl portion of sinapine.
Fixed (fatty) oil
Triglycerides / fatty acids (erucic, oleic, linoleic)Concentration: ~25-37% of seed
White mustard seed contains a substantial fixed oil rich in erucic, oleic and linoleic acids. It is the demulcent, lubricating fraction of the crushed seed but high erucic-acid content is a reason to avoid large or prolonged internal doses.
Flavonoids and mucilage
Flavonoid glycosides / polysaccharideConcentration: Minor
Seed-coat mucilage and flavonoid glycosides contribute soothing and antioxidant properties and influence the texture of mustard pastes used for topical acupoint application.
⚠ Drug Interactions
Levothyroxine / thyroid medication
Glucosinolates and their thiocyanate/isothiocyanate breakdown products are goitrogenic in animal models, potentially interfering with iodine uptake and thyroid hormone synthesis. In theory this could oppose thyroid-hormone therapy or aggravate hypothyroidism, though culinary and standard medicinal doses are unlikely to be clinically significant.
Clinical note: Patients with hypothyroidism or on levothyroxine should avoid large or prolonged intake; monitor thyroid function if used chronically.
Topical irritants / transdermal medications (co-applied)
The isothiocyanate liberated from crushed seed is a strong rubefacient and vesicant. Co-application with other counter-irritants, keratolytics or occlusive transdermal patches over the same site can potentiate blistering, chemical burn and enhanced systemic absorption of co-applied drugs.
Clinical note: Limit topical (acupoint/plaster) application time, avoid broken skin, and do not layer over transdermal drug patches; discontinue at first sign of excessive burning.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 6-15g | Daily | — | — | — |
Preparation Methods
Decoction (crushed, added late)
Parts: Ripe seed
Typical dose 3-9 g. Seeds are lightly crushed and, because prolonged boiling destroys myrosinase and the volatile isothiocyanate, are usually added toward the end of decoction. Used to warm the Lung, transform cold phlegm and relieve cough and chest fullness.
Dry stir-frying (chao Bai Jie Zi)
Parts: Ripe seed
Gentle stir-frying moderates the seed's harsh, dispersing nature and reduces gastric irritation, making it more suitable for internal use in weaker patients while retaining phlegm-moving action.
Topical paste / acupoint plaster (San Fu Tie)
Parts: Ripe seed (powdered)
Powdered seed is mixed with fresh ginger juice or water (often with Xi Xin, Yan Hu Suo and Gan Sui) into a paste applied to back Shu points during the hottest summer days to treat cold-type asthma and chronic cough. Application is kept short (typically 1-4 hours in adults, less in children) to avoid blistering.
Clinical Studies
A Systematic and Narrative Review of Acupuncture Point Application Therapies in the Treatment of Allergic Rhinitis and Asthma during Dog Days
Review of acupoint (San Fu Tie) application therapies, in which white mustard seed (Bai Jie Zi) is the core paste ingredient, for allergic rhinitis and asthma. The pooled clinical literature suggests symptom improvement with the summer 'winter-disease-treated-in-summer' protocol, while noting methodological limitations and the need for higher-quality trials.
Historical Texts
Ming Yi Bie Lu (Miscellaneous Records of Famous Physicians)
Attributed to Tao Hongjing, c. 500 CEBen Cao Gang Mu (Compendium of Materia Medica)
Li Shizhen, 1578 (Ming dynasty)Zhang Shi Yi Tong (Zhang's Comprehensive Medicine)
Zhang Lu, 1695 (Qing dynasty)References
- Yang L, Yin P, Fan H, et al.. Sinapis Semen: A review on phytochemistry, pharmacology, toxicity, analytical methods and pharmacokinetics . Frontiers in Pharmacology (2023) [DOI]
- Boscaro V, Boffa L, Binello A, et al.. Antiproliferative, Proapoptotic, Antioxidant and Antimicrobial Effects of Sinapis nigra L. and Sinapis alba L. Extracts . Molecules (2018) [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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