Magnolia

The drug is houpo, the dried bark of Magnolia officinalis, decocted ^{18Reference 18Luo et al. · 2019ReviewA review of the phytochemistry and pharmacological activities of Magnoliae officinalis cortex — reviewView study →}. It is classified as bitter, acrid and warm, and enters the Spleen, Stomach, Lung and Large Intestine channels ^{25Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}.

Its main action is to move stagnant qi in the middle of the body, dry damp and transform phlegm, and send rebellious qi downward ^{25Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}.

On the digestive side it treats abdominal distension, vomiting, diarrhoea, food stagnation and constipation ^{18,25Reference 18Luo et al. · 2019ReviewA review of the phytochemistry and pharmacological activities of Magnoliae officinalis cortex — reviewView study →Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}. On the respiratory side it treats phlegm, fluid retention and cough with wheezing ^{18,25Reference 18Luo et al. · 2019ReviewA review of the phytochemistry and pharmacological activities of Magnoliae officinalis cortex — reviewView study →Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}.

Magnolia bark and ginger are a traditional pair in Chinese prescriptions for mental disorders ^{8Reference 8Yi et al. · 2009AnimalAntidepressant-like synergism of extracts from magnolia bark and ginger rhizome alone and in combination in mice — animal modelView study →}.

It is used with caution in qi deficiency ^{25Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}. It is also traditionally avoided in depleted, dry (yin-deficient) states and in convalescence.

Three placebo-controlled trials have tested Relora, a standardised blend of Magnolia officinalis and Phellodendron amurense bark extracts.

In 56 moderately stressed adults (35 men and 21 women), 500 mg a day for 4 weeks lowered salivary cortisol exposure by 18% compared with placebo. Tension, depression, anger, fatigue and confusion scores were also lower, and vigour higher. The blend was standardised to at least 1.5% honokiol and 0.1% berberine ^{2Reference 2Talbott et al. · 2013RCTEffect of Magnolia officinalis and Phellodendron amurense (Relora) on cortisol and psychological mood state in moderately stressed subjects — randomised placebo-controlled trialView study →}.

In overweight premenopausal women who eat more under stress, 250 mg three times a day for 6 weeks reduced state (passing) anxiety compared with placebo, but not trait (long-standing) anxiety or depression. Salivary cortisol, sleep quality and sleep latency did not change significantly. The intent-to-treat group was 40 women, of whom 26 completed the study, with no significant adverse events ^{3Reference 3Kalman et al. · 2008RCTEffect of a proprietary Magnolia and Phellodendron extract on stress levels in healthy women — randomised placebo-controlled trialView study →}.

In a similar group of women, the same dose for 6 weeks prevented weight gain: the placebo group gained an average 1.5 kg and the treatment group none. Evening cortisol tended to be lower in the treatment group ^{4Reference 4Garrison et al. · 2006RCTEffect of a proprietary Magnolia and Phellodendron extract on weight management — pilot randomised placebo-controlled clinical trialView study →}.

Magnolol and honokiol potentiate GABA-A receptor currents ^{1Reference 1Sarrica et al. · 2018ReviewSafety and toxicology of magnolol and honokiol — reviewView study →}.

Gap: no RCT of magnolia bark alone; the cortisol and anxiety effects are shown only for a combination product in small cohorts.

In mouse macrophage cells stimulated with fimbriae from the gum bacterium Porphyromonas gingivalis, magnolol and honokiol suppressed COX-2 expression and blocked NF-κB activation at non-toxic concentrations ^{9Reference 9Murakami et al. · 2012In vitroComparative inhibitory effects of magnolol, honokiol, eugenol and bis-eugenol on cyclooxygenase-2 expression and nuclear factor-kappa B activation in RAW264.7 macrophage-like cells — in vitroView study →}.

Reviews describe NF-κB inhibition, lower pro-inflammatory cytokines and COX-2, and radical scavenging across the bark’s pharmacology ^{17,20Reference 17Niu et al. · 2021ReviewThe rich pharmacological activities of Magnolia officinalis and secondary effects based on significant intestinal contributions — reviewView study →Reference 20Rauf et al. · 2021ReviewHonokiol: a review of its pharmacological potential and therapeutic insights — reviewView study →}.

All of this is cell-based or animal work; there is no human anti-inflammatory trial of the herb or its constituents.

Magnolia bark extract, magnolol and honokiol had minimum inhibitory concentrations of 8–31 µg/mL against Porphyromonas gingivalis, Fusobacterium nucleatum and Streptococcus mutans, bacteria involved in bad breath and tooth decay. Mints with 0.2% extract killed more than 99.9% of these bacteria within five minutes ^{10Reference 10Greenberg et al. · 2007Clinical trialCompressed mints and chewing gum containing magnolia bark extract are effective against bacteria responsible for oral malodor — in vitro and human studyView study →}.

In nine healthy volunteers, the mints cut total salivary bacteria by 61.6% at 30 minutes, against 3.6% for a flavourless mint ^{10Reference 10Greenberg et al. · 2007Clinical trialCompressed mints and chewing gum containing magnolia bark extract are effective against bacteria responsible for oral malodor — in vitro and human studyView study →}.

Reviews also list antibacterial and antifungal activity for honokiol ^{20Reference 20Rauf et al. · 2021ReviewHonokiol: a review of its pharmacological potential and therapeutic insights — reviewView study →}.

Gap: the evidence is for oral bacteria in mints and gum; none supports systemic antimicrobial use.

In mice, honokiol at 10–20 mg/kg, given by injection, shortened the time to fall into non-REM sleep and increased non-REM sleep. It activated sleep-promoting neurons in the ventrolateral preoptic area. The benzodiazepine-site antagonist flumazenil abolished the effect ^{6Reference 6Qu et al. · 2012AnimalHonokiol promotes non-rapid eye movement sleep via the benzodiazepine site of the GABA-A receptor in mice — animal modelView study →}.

Honokiol did not change REM sleep or EEG power ^{6Reference 6Qu et al. · 2012AnimalHonokiol promotes non-rapid eye movement sleep via the benzodiazepine site of the GABA-A receptor in mice — animal modelView study →}.

In a 24-week randomised trial in 89 menopausal women, a daily tablet containing magnolia bark extract (60 mg), soy isoflavones, lactobacilli, magnesium, calcium and vitamin D reduced insomnia, anxiety and low mood compared with calcium and vitamin D alone. The design cannot separate magnolia’s contribution from the other ingredients ^{5Reference 5Mucci et al. · 2006RCTSoy isoflavones, lactobacilli, Magnolia bark extract, vitamin D3 and calcium — controlled clinical study in menopause (randomised controlled trial)View study →}.

Gap: the mechanism is shown in animals given injected honokiol, and the only human sleep data come from a multi-ingredient product.

The phenolic groups of magnolol and honokiol scavenge free radicals directly; in one assay honokiol was the stronger of the two ^{9Reference 9Murakami et al. · 2012In vitroComparative inhibitory effects of magnolol, honokiol, eugenol and bis-eugenol on cyclooxygenase-2 expression and nuclear factor-kappa B activation in RAW264.7 macrophage-like cells — in vitroView study →}. Reviews cite reduced lipid peroxidation and stronger antioxidant defences across the bark’s pharmacology ^{17,21Reference 17Niu et al. · 2021ReviewThe rich pharmacological activities of Magnolia officinalis and secondary effects based on significant intestinal contributions — reviewView study →Reference 21Lin et al. · 2021ReviewPharmacology, toxicity, bioavailability, and formulation of magnolol: an update — reviewView study →}.

No human antioxidant or oxidative-stress study exists for the herb.

In isolated intestine, magnolol and honokiol relaxed smooth muscle by reducing calcium entry into the cells. They inhibited both TRPV4 and TRPC4 channels, and the TRPC4 effect was the main one ^{11Reference 11Niu et al. · 2022In vitroMagnolol and honokiol target TRPC4 to regulate extracellular calcium influx and relax intestinal smooth muscle — in vitro / ex vivoView study →}.

In a rat model of diarrhoea-predominant irritable bowel syndrome, magnolol, honokiol and obovatol improved gut motility, gut-barrier function and inflammatory markers. The study used network pharmacology and machine learning to choose its targets, and tested the compounds in rats ^{12Reference 12Wang et al. · 2026AnimalDeciphering the multi-target mechanism of Magnolia officinalis in irritable bowel syndrome with diarrhea — network pharmacology, machine learning and in vivo (rat) validationView study →}.

Gap: there is an ex vivo mechanism and one rat study, and no controlled human trial in functional gut disorders.

Systematic reviews of animal and cell work report that honokiol, magnolol, 4-O-methylhonokiol and obovatol improved learning and memory in Alzheimer’s models. They inhibited amyloid-β formation and aggregation, neuroinflammation and acetylcholinesterase, and reduced oxidative stress, acting through NF-κB, ERK, AMPK/mTOR/ULK1 and cAMP/PKA/CREB pathways ^{13,22Reference 13Li et al. · 2024Systematic reviewNeolignans in Magnolia officinalis as natural anti-Alzheimer’s disease agents — systematic reviewView study →Reference 22Zhu et al. · 2022Systematic reviewNeuroprotective potency of neolignans in Magnolia officinalis cortex against brain disorders — systematic reviewView study →}.

Both compounds are reported to cross the blood-brain barrier. A 2023 review concluded that their clinical potential remains untapped ^{14Reference 14Dai et al. · 2023ReviewThe neuropharmacological effects of magnolol and honokiol — review of signal pathways and molecular mechanismsView study →}.

Every study is in vitro or in animals, with no human neuroprotection or dementia trial.

A honokiol and magnolol mixture given by mouth reduced immobility in the mouse forced-swim and tail-suspension tests and reversed anhedonia in rats under chronic mild stress. At 20 and 40 mg/kg it restored serotonin levels in several brain regions and normalised raised corticosterone ^{7Reference 7Xu et al. · 2008AnimalAntidepressant-like effects of the mixture of honokiol and magnolol from the barks of Magnolia officinalis in stressed rodents — animal modelView study →}.

A follow-up in mice found that the honokiol and magnolol mixture combined with ginger essential oil worked better than either alone, and that the magnolia fraction was the main active component ^{8Reference 8Yi et al. · 2009AnimalAntidepressant-like synergism of extracts from magnolia bark and ginger rhizome alone and in combination in mice — animal modelView study →}.

There is no human antidepressant trial; the evidence is from rodent models.

Mechanistic reviews describe honokiol and magnolol inducing cancer-cell death, suppressing proliferation and inhibiting metastasis across many cancer cell types, with little toxicity to normal cells ^{15Reference 15Mottaghi et al. · 2022ReviewNatural lignans honokiol and magnolol as potential anticarcinogenic and anticancer agents — comprehensive mechanistic reviewView study →}.

A registered trial of honokiol in early-stage resectable non-small-cell lung cancer is recruiting, and no results are available.

Gap: there is extensive cell and animal work and one recruiting trial, and no human efficacy data.

A review of magnolol in type 2 diabetes collects preclinical data on blood sugar, lipid metabolism and oxidative stress, and describes it as a possible support to standard treatment ^{16Reference 16Szałabska-Rąpała et al. · 2021ReviewEffectiveness of magnolol, a lignan from magnolia bark, in diabetes, its complications and comorbidities — reviewView study →}.

There are no human trials and no defined dose for a metabolic use.

Toxicology. Concentrated magnolia bark extract showed no mutagenic or genotoxic potential in laboratory and animal tests. A subchronic study following OECD guidelines found no adverse effect at more than 240 mg/kg a day, and several food safety authorities have judged magnolol and honokiol safe ^{1Reference 1Sarrica et al. · 2018ReviewSafety and toxicology of magnolol and honokiol — reviewView study →}.

Human use. Trials using concentrated extract for up to a year reported no adverse effects ^{1Reference 1Sarrica et al. · 2018ReviewSafety and toxicology of magnolol and honokiol — reviewView study →}. The Relora trials at 500–750 mg a day for 4–6 weeks reported no significant adverse events ^{2,3,4Reference 2Talbott et al. · 2013RCTEffect of Magnolia officinalis and Phellodendron amurense (Relora) on cortisol and psychological mood state in moderately stressed subjects — randomised placebo-controlled trialView study →Reference 3Kalman et al. · 2008RCTEffect of a proprietary Magnolia and Phellodendron extract on stress levels in healthy women — randomised placebo-controlled trialView study →Reference 4Garrison et al. · 2006RCTEffect of a proprietary Magnolia and Phellodendron extract on weight management — pilot randomised placebo-controlled clinical trialView study →}.

Sedatives. Honokiol promotes sleep through the benzodiazepine site of the GABA-A receptor ^{6Reference 6Qu et al. · 2012AnimalHonokiol promotes non-rapid eye movement sleep via the benzodiazepine site of the GABA-A receptor in mice — animal modelView study →}, so the effect may add to benzodiazepines, alcohol, sleeping pills and other sedatives.

Drug interactions. Magnolol and honokiol are cleared by glucuronidation, and an interaction with drugs or other herbs cannot be excluded ^{1Reference 1Sarrica et al. · 2018ReviewSafety and toxicology of magnolol and honokiol — reviewView study →}. No clinical interaction study has been done.

Blood-thinning drugs. Honokiol has antithrombotic activity ^{20Reference 20Rauf et al. · 2021ReviewHonokiol: a review of its pharmacological potential and therapeutic insights — reviewView study →}, and Chinese materia medica sources advise care alongside anticoagulant and antiplatelet drugs ^{25Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}.

Magnocurarine. The bark contains magnocurarine ^{19Reference 19Yan et al. · 2013In vitroStudies on the alkaloids of the bark of Magnolia officinalis: isolation and on-line analysis by HPLC-ESI-MSⁿ — in vitroView study →}, an alkaloid with curare-like activity. Long-term or high-dose use is best supervised by a practitioner.

Traditional cautions. Chinese medicine uses the bark with caution in qi deficiency ^{25Reference 25PennerPenner, J. (n.d.). Hou Po — 厚朴 — Cortex Magnoliae Officinalis — properties, channels, actions, dosage and cautions — materia medica reference. American Dragon. https://www.americandragon.com/Individualherbsupdate/HouPo.htmlView study →}, and avoids it in depleted, dry (yin-deficient) states and in convalescence.