Hou Po
StarMagnolia officinalis Rehd. et Wils.
Traditionally used for
- Cough & breathing
- Digestion
- Sleep
Cautions & contraindications
- Pregnancy
- Young children
- Heart conditions
☯ TCM Properties
Dries Dampness and Transforms Phlegm; Descends Qi and Relieves Distension; Moves Qi and Resolves Stagnation; Calms Wheezing
Traditional Chinese Uses
Hou Po (magnolia bark) is a warm, bitter-pungent herb that moves Qi, dries Dampness, and descends rebellious Qi in the Stomach and Lung. It is a primary herb for abdominal fullness, distension, and obstruction from Qi stagnation and Dampness in the middle burner. Its descending action also calms Lung Qi to relieve cough and wheezing with chest fullness. Because it moves and dries, it must be used cautiously in Yin deficiency and is contraindicated in pregnancy without careful formulation.
Western Herbalism Properties
Pharmacological Effects
- Anti-emetic: Methanol extract of M. obovata bark (1 g/kg oral) was anti-emetic in frogs with copper sulphate-induced emesis; magnolol and honokiol were active at 20 mg/kg.
- Muscle relaxation: Magnolol (100 mg/kg i.p., mice) gave strong central muscle relaxation for 2 h; higher doses of magnolol/honokiol abolished righting reflex; magnolol inhibited chicken extensor reflex (antagonized by strychnine); both inhibited K+ and Ca++ contraction of rat aorta.
- Antiulcerative: Magnolol inhibited Shay pylorus-ligation and water-immersion stress ulcers, histamine-induced duodenal spasm, and stimulated gastric acid secretion in anesthetized rats.
- Central inhibitory: Ether extract (i.p., mice) reduced spontaneous activity, antagonized methamphetamine/apomorphine excitation, produced slow-wave EEG and raised brain serotonin; magnolol and honokiol were the depressant principles.
- Antimicrobial: Decoction active in vitro against S. aureus, Streptococcus hemolyticus, B. diphtheriae, B. subtilis, B. dysenteriae and skin fungi; prolonged survival of anthrax-infected guinea pigs; magnolol and honokiol bactericidal to Streptococcus mutans at 6.3 µg/ml, stronger than berberine.
- Antiplatelet: Magnolol and honokiol inhibited collagen-induced rabbit platelet aggregation with IC50 1.9 x 10^-6 M, about three times more potent than aspirin.
Source: Zhu YP. Chinese Materia Medica: Chemistry, Pharmacology and Applications. Harwood Academic, 1998, p. 304.
Used In Formulas (83)
Relationships
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Botanical Description
Magnolia officinalis is a deciduous tree in the Magnoliaceae, endemic to mountainous regions of central and southern China, where it grows in mixed broadleaved forests between 300 and 1,500 m elevation. Mature specimens reach 15-25 m tall with a straight trunk, ascending branches and a broad, rounded crown. The bark is smooth and pale grey on young trees, becoming thicker, fissured and brownish with age, and is strongly aromatic when cut. The large, alternate leaves are obovate to elliptic, 20-45 cm long, leathery, dark green above and pale glaucous beneath, often clustered toward the branch tips. In early summer the tree bears solitary, fragrant, cup-shaped flowers 10-15 cm across, with 9-12 fleshy, creamy-white tepals. The aggregate fruit is a long, cylindrical, cone-like structure of follicles that split to release scarlet, fleshy-coated seeds. Cultivated trees are typically harvested for medicinal bark after 15-20 years.
Active Constituents
Magnolol
Biphenolic neolignanConcentration: Principal neolignan of the stem and root bark; the Chinese Pharmacopoeia requires magnolol plus honokiol to total not less than 2.0% of the dried bark
Positively modulates synaptic and extrasynaptic GABA-A receptors, which underlies the anxiolytic and sleep-promoting activity attributed to the bark, and is anti-inflammatory, antimicrobial and antispasmodic in preclinical models.
This drug is the bark. The flower bud of the same species is a separate item of materia medica, Hou Po Hua, whose magnolol and honokiol content is roughly an order of magnitude lower; evidence generated on bark extracts should not be read across to it.
Honokiol
Biphenolic neolignanConcentration: Second major neolignan, assayed jointly with magnolol to the 2.0% Pharmacopoeia minimum
An isomer of magnolol that also potentiates GABA-A receptor currents and shows anti-inflammatory, neuroprotective and antitumour activity in preclinical work; it is the more studied of the pair for anticancer and neuroprotective endpoints.
beta-Eudesmol
Sesquiterpene alcoholConcentration: Major component of the bark essential oil, which itself is a minor fraction of the drug
A volatile sesquiterpene contributing to the aromatic, qi-moving character of the bark; reported to affect gastrointestinal motility and neuromuscular transmission in preclinical models.
Magnocurarine
Quaternary benzylisoquinoline alkaloidConcentration: Trace alkaloid of the bark; substantially higher in some other Magnolia and Manglietia species used as substitutes
Structurally related to tubocurarine and carries the same curare-like neuromuscular blocking liability, which is the basis of regulatory caution about magnolia bark in infants and small children.
Levels in authentic Magnolia officinalis bark are low, and the concern is greatest where a related species with higher magnocurarine content has been supplied in its place.
Magnoflorine
Aporphine alkaloidConcentration: Minor alkaloid of the bark
One of several minor isoquinoline-type alkaloids identified in the bark by HPLC-ESI-MSn alongside magnocurarine and tembetarine; not a target of Pharmacopoeia assay and not a principal contributor to the drug's recognised actions.
⚠ Drug Interactions
Benzodiazepines, Z-drugs, alcohol and other CNS depressants
Magnolol and honokiol are positive modulators at synaptic and extrasynaptic GABA-A receptors, the same target class as benzodiazepines and Z-drugs, so co-administration is expected to be additive. Human data are limited to small trials of proprietary bark extracts on stress and sleep endpoints, so the size of the effect at decoction doses is not quantified.
Clinical note: Warn patients taking hypnotics or sedating antihistamines about additive drowsiness, and about driving. The interaction is pharmacodynamic and dose-related; it is not a reason to withhold the herb but is a reason to start low.
QT-prolonging drugs
Both magnolol and honokiol block the hERG potassium channel in vitro, and their blockade is additive when the two are present together, as they always are in the bark. This is patch-clamp evidence in a heterologous expression system, not a clinical arrhythmia signal, and no case reports of torsades attributable to Hou Po are on record.
Clinical note: Take the concern seriously in patients already on QT-prolonging medication such as sotalol, amiodarone, methadone or macrolides, or with known long QT, hypokalaemia or hypomagnesaemia. For everyone else the in vitro finding does not warrant avoiding a standard course.
CYP1A2 and CYP2C substrates
Honokiol and magnolol modulate rat hepatic CYP1A and CYP2C activity and change the pharmacokinetics of phenacetin and diclofenac in vivo, with the two neolignans acting differently from each other. The work is in rats; human interaction studies have not been done.
Clinical note: Watch for altered effect of theophylline, clozapine, warfarin, phenytoin and NSAIDs when a bark extract is used at concentrated doses over weeks. Species extrapolation is imperfect here, so monitoring the drug rather than avoiding the herb is the proportionate response.
Non-depolarising neuromuscular blocking agents
The bark contains magnocurarine, a quaternary benzylisoquinoline alkaloid structurally analogous to tubocurarine, and Health Canada has warned that magnolia bark contains tubocurarine-related substances capable of causing respiratory paralysis in animals. No human interaction with anaesthetic neuromuscular blockers has been reported, and magnocurarine content in authentic Magnolia officinalis bark is low.
Clinical note: Include Hou Po in the herbal history taken before general anaesthesia and stop it in the standard pre-operative window. The regulatory caution about infants and small children is the more practically relevant point for routine dispensing.
Hou Po Hua (Flos Magnoliae Officinalis, the flower bud of the same species)
Hou Po Hua is the dried flower bud of Magnolia officinalis and is a separate Pharmacopoeia drug with its own assay and a far lower magnolol and honokiol content than the bark, on the order of a tenth. Because the pinyin names differ by only one syllable and both derive from the same species, the two are occasionally conflated in supply and in reference databases.
Substituting the flower bud for the bark is not toxic, but it under-delivers the constituents the bark's evidence rests on, and the flower is traditionally regarded as a gentler drug for qi stagnation rather than an equivalent of the bark.
Clinical note: Confirm that a supplier's Hou Po is Cortex Magnoliae Officinalis and not Flos Magnoliae Officinalis, and do not read bark studies onto flower-bud products.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 3–10 g | Daily | — | — | 中国药典 2020 【用法与用量】3~10g。 【性味与归经】苦、辛，温。归脾、胃、肺、大肠经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Transforms phlegm and descends counterflow while moving qi and dispersing constraint, dissolving the phlegm-qi knot in the throat.
Plum-pit qi: sensation of something stuck in the throat that cannot be swallowed or coughed up.
Core pair of a classical formula — Ban Xia Hou Po Tang, Jin Gui Yao Lue (Zhang Zhongjing)
Dries dampness and moves qi together, relieving the fullness and distention of dampness encumbering the spleen and stomach.
Epigastric and abdominal distention, no appetite, thick greasy tongue coating.
Core pair of a classical formula — Ping Wei San, Taiping Huimin Hejiju Fang
Clears heat and dries dampness while moving qi, resolving damp-heat obstructing the middle burner.
Damp-heat sudden turmoil disorder with vomiting and diarrhea.
Core pair of a classical formula — Lian Po Yin, Huo Luan Lun (Wang Shixiong)
Releasing summer-cold from the exterior combines with transforming dampness and moving qi internally, addressing summertime cold invasion with dampness.
Summer: chills and fever without sweating plus abdominal fullness, nausea or diarrhea.
Core pair of a classical formula — Xiang Ru San, Tai Ping Hui Min He Ji Ju Fang
Descend lung qi and transform phlegm to calm wheezing.
Wheezing in an exterior pattern or chronic wheezing with phlegm. Xing Ren is mildly toxic in overdose.
Core pair of a classical formula — Gui Zhi Jia Hou Po Xing Zi Tang, Shang Han Lun (Zhang Zhongjing)
Move qi and break up stagnation in the stomach and intestines, relieving distention, fullness and constipation.
Abdominal fullness and pain with constipation from qi stagnation.
Core pair of a classical formula — Hou Po San Wu Tang, Jin Gui Yao Lue (Zhang Zhongjing)
Descends lung qi and transforms phlegm while moving qi and calming wheezing, addressing excess above with phlegm-qi counterflow.
Core pair of a classical formula — Su Zi Jiang Qi Tang, Tai Ping Hui Min He Ji Ju Fang
Evidence Tier
Moderate evidence · 5 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
2
2 verified · 0 unverified
Other clinical trial
0
Observational / case report
0
In vitro / animal
3
1 verified · 2 unverified
Show 3 studies
- hERG channel blockade and additive interactions of magnolol and honokiol from Magnolia species
- Modulation of Rat Hepatic CYP1A and 2C Activity by Honokiol and Magnolol: Differential Effects on Phenacetin and Diclofenac Pharmacokinetics In Vivo
- Studies on the Alkaloids of the Bark of Magnolia officinalis: Isolation and On-line Analysis by HPLC-ESI-MSn
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Effects of Ban-Xia-Hou-Pu-Tang and Western medicine on patients with globus sensation: A randomized controlled trial
Randomized controlled trial comparing Ban-Xia-Hou-Pu-Tang against Western medical management in patients with globus sensation, the classical plum-pit qi presentation for which this formula is the standard prescription.
Hou Po is one of five ingredients in the formula, so the trial supports the traditional indication but does not isolate the bark's contribution.
Effect of a proprietary Magnolia and Phellodendron extract on stress levels in healthy women: a pilot, double-blind, placebo-controlled clinical trial
Pilot double-blind placebo-controlled trial of a proprietary Magnolia officinalis bark and Phellodendron amurense extract in premenopausal women reporting stress-related eating, showing improvement in transient anxiety measures over six weeks.
Small, pilot-scale, industry-linked, and testing a two-herb combination product rather than Hou Po alone; it is among the very few human trials of a magnolia bark extract and should be weighted accordingly.
hERG channel blockade and additive interactions of magnolol and honokiol from Magnolia species
Patch-clamp study finding that magnolol and honokiol each block the hERG potassium channel and that their effects are additive when combined, which matters because the bark always delivers both together.
In vitro only; it establishes a cardiac liability signal for the isolated neolignans rather than a clinical arrhythmia risk for the crude drug.
Modulation of Rat Hepatic CYP1A and 2C Activity by Honokiol and Magnolol: Differential Effects on Phenacetin and Diclofenac Pharmacokinetics In Vivo
In rats, honokiol and magnolol altered hepatic CYP1A and CYP2C activity and changed the pharmacokinetics of the probe substrates phenacetin and diclofenac, with the two neolignans producing different effects.
This is the principal experimental basis for the CYP-mediated interaction caution; it has not been reproduced in humans.
Studies on the Alkaloids of the Bark of Magnolia officinalis: Isolation and On-line Analysis by HPLC-ESI-MSn
Analytical characterisation of the alkaloid fraction of Magnolia officinalis bark, identifying magnocurarine, magnoflorine, tembetarine and related isoquinoline alkaloids by HPLC-ESI-MSn.
Documents that the curare-like alkaloid is genuinely present in the bark, alongside the much better known neolignans.
⚠ Safety & Contraindications
- Pregnancy
- Young children
- Heart conditions
Contraindications
Its use is cautious in patients with qi deficiency and fluid consumption or pregnant women.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 131–133.
Historical Texts
Shen Nong Ben Cao Jing
Han dynasty, compiled c. 200 BCE to 200 CEShang Han Lun (Treatise on Cold Damage), Zhang Zhongjing
Eastern Han dynasty, c. 200 to 210 CEJin Gui Yao Lue (Essential Prescriptions of the Golden Cabinet), Zhang Zhongjing
Eastern Han dynasty, c. 220 CEMing Yi Bie Lu (Miscellaneous Records of Famous Physicians)
Attributed to Tao Hongjing, c. 500 CEBen Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1578, printed 1596References
- Poivre M, Duez P. Biological activity and toxicity of the Chinese herb Magnolia officinalis Rehder & E. Wilson (Houpo) and its constituents . Journal of Zhejiang University-SCIENCE B (2017) [DOI]
- Sarrica A, Kirika N, Romeo M, Salmona M, Diomede L. Safety and Toxicology of Magnolol and Honokiol . Planta Medica (2018) [DOI]
- Luo H, Wu H, Yu X, Zhang X, Lu Y, Fan J, Tang L, Wang Z. A review of the phytochemistry and pharmacological activities of Magnoliae officinalis cortex . Journal of Ethnopharmacology (2019) [DOI]
- Yuan Y, Zhou X, Wang Y, Wang Y, Teng X, Wang S. Cardiovascular Modulating Effects of Magnolol and Honokiol, Two Polyphenolic Compounds from Traditional Chinese Medicine-Magnolia Officinalis . Current Drug Targets (2020) [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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