Phellodendron

Other Names

Amur cork treeAmur corktreeBarkhat AmurskiyChinese cork treeChinese corktreeChuan Huang BaiCork treeCortex PhellodendriGuan Huang BaiHakubokuHuang BaiHuáng bǎiHuang BòHuang BoHwangbyeokKihadaObakuPhellodendri amurensis cortexPhellodendri chinense cortexPhellodendri CortexPhellodendron amurensePhellodendron amurense var. wilsoniiPhellodendron chinensePhellodendron chinense var. glabriusculumPhellodendron insularePhellodendron japonicumPhellodendron lavalleeiPhellodendron mollePhellodendron nikkomontanumPhellodendron piriformePhellodendron sachalinensePhellodendron sachalinense f. longipesPhellodendron sachalinense var. suberosumSakhalin cork treeSakhalin corktreeShikerebe-niSikerpeZanthoxylum kibadaБархат амурскийキハダ关黄柏川黄柏檗木黃柏黃檗黄柏黄柏 (Obaku)黄檗黄肌황벽

Synopsis

Phellodendron (Phellodendron amurense / Phellodendron chinense): A Comprehensive Reference

1. Identity: Botanical Classification, Common Names, and Natural Source

Phellodendron is a genus of deciduous and dioecious trees in the family Rutaceae and is native to east and northeast Asia. This genus includes two species, P. amurense and P. chinense, and represents relics from the Tertiary period ancient tropical flora, often described as a living fossil within the botanical realm.

According to the scientific database of China Plant Species and the Chinese Pharmacopoeia (2015 edition), Phellodendri Cortex (PC) has two main species: Phellodendron amurense Rupr. (PAR), known in Chinese as "Guan Huang bai," and Phellodendron chinense Schneid. (PCS), known as "Chuan Huang bai." The crude drugs are called Phellodendri amurensis cortex (PAC) and Phellodendri chinense cortex (PCC), respectively, and the medicinal part of the plant is the dried trunk bark.

PAR and PCS are naturally grown in the Northeast and Southwest parts of China, respectively. According to the latest information from the "information system of Chinese rare and endangered plants," PAR is categorized as one of the second-degree endangered plants. PAR and PCS could be interchangeably used in clinical application because both species contain similar chemical constituents.

Phellodendri Cortex has comprehensive therapeutic effects which include anti-inflammatory, antimicrobial, anticancer, hypotensive, antiarrhythmic, antioxidant, and antipyretic agents.

The plant is known by a variety of common names and synonyms. These include Amur Cork Bark, Amur Cork Tree, Amur Corktree, Corktree, Cortex Phellodendri, Huang Bai, Huang Bo, Phellodendri Cortex, and Phellodendron amurense. A critical nomenclatural note: care must be taken not to confuse phellodendron with the houseplant called philodendron; the names are similar but the plants are entirely unrelated.

Common Preparations and Forms

The bark is stripped from the tree from March to June, dried in sunlight, sliced, and used unprepared or stir-baked with salt water. In traditional remedies, Phellodendron bark was often decocted into teas or tinctures, applied topically, or used as an ingredient in healing poultices. In modern supplement contexts, the bark extract is available in standardized capsules and tablets. Commercial standardized extracts may be formulated as a 20:1 extract from the stem bark, standardized to a defined berberine content (for example, 440 mg of a 20:1 extract yielding 200 mg berberine per tablet).

A variety of methods of water and ethanol extraction may have differing activities, and some pharmacological activities of the bark can be standardized by analyzing the level of berberine using thin-layer chromatography, HPLC, potentiometry, or acidic potassium permanganate chemiluminescence.

There are quantitative differences between the two species of Cortex Phellodendri (P. amurense and P. chinense), and it has been suggested they should be used as separate resources. An analysis of 31 commercial samples found that the total level of five alkaloids in samples of P. wilsonii and P. amurense var. sachalinense was 4.1% (mostly berberine), while the level in P. amurense and P. chinense was 1.5%.

2. Traditional and Historical Use

Traditional Chinese Medicine (TCM)

The bark of the Phellodendron tree is an important herbal medicine in China. The earliest known writings about this preparation are found in the Shennong Ben Cao Jing. In TCM, the bark is categorized as bitter and cold, affecting the kidney, urinary bladder and large intestine meridians.

The earliest description of Paozhi processing of Phellodendron can be traced back to 200 BC, and classic methods, including burning, stewing and soaking with wine and vinegar, were recorded in the Wu-Shi-Er-Bing-Fang. In the Ming Dynasty (1368–1644 AD), the processing methods flourished and became more refined and creative as a variety of additional excipients were introduced in herbal medicine processing.

The Chinese name "Huang Bai" reflects this botanical reality: "Huang" means yellow in Chinese, and the name is derived from the bright yellow color of the plant's inner bark. In ancient times, a yellow dye made from the inner bark was also used to color official and religious documents, distinguishing them from other documents.

In TCM, Phellodendron amurense is described as bitter and cold, entering the kidney and bladder meridians, and possessing the effects of heat-clearing and damp-drying, purging fire, and detoxifying. It was used to treat diarrhea under humid heat, jaundice and reddish urine, leukorrhea, pruritus vulvae, heat gonorrhea, beriberi, hectic fever, consumptive fever, night sweating, spermatorrhea, toxic swelling of sores and ulcers, and eczema.

In TCM, Phellodendron amurense is considered one of the top 50 herbs used for healing, and is especially noted for its ability to clear heat and toxins from the body, including eliminating damp-heat from the bladder and kidneys.

Ancient practitioners prescribed Phellodendron bark to address a variety of ailments, most notably as a remedy for urinary tract infections, diarrhea, and arthritis. Its cooling and drying nature made it especially effective for conditions characterized by "damp-heat," such as eczema, jaundice, and some gynecological issues.

Classical Formula Use

Phellodendron is a key component of the classic TCM formula "San Miao Wan" (Three Marvels Pill), where it is combined with Atractylodes and Achyranthes to relieve pain and swelling in the joints. Additionally, it frequently works alongside Coptis root (Huang Lian) and Gardenia fruit (Zhi Zi) to enhance detoxification and support liver health.

For fever with night sweats and seminal emission due to Yin Deficiency, Phellodendron is used with Rhizoma Anemarrhenae (Zhi Mu), Radix Rehmanniae (Sheng Di Huang), and Carapax et Plastrum Testudinis (Gui Ban) in "Rehmmania Bolus of Six Herbs Plus Anemarrhena and Phellodendron" (Zhi Bai Di Huang Wan).

In TCM clinical practice, Phellodendron bark is considered most appropriate for treating inflammation in the lower parts of the body and for heat caused by deficiency. For menopause, a deficiency condition, it can be used to control hot flashes. In the lower parts of the body it is used to control thick yellow vaginal discharges, hemorrhoids, foul-smelling diarrhea and dysentery, and is also used to treat dampness and heat in the legs, such as red, swollen and painful knees, legs or feet.

Other Cultural and Regional Traditions

Koreans have used the plant to break fever. In China the plant was considered, like ginseng, a panacea used to treat, among other things, diabetes, tuberculosis, dysentery, pneumonia, and meningitis.

As an isoquinoline alkaloid isolated from traditional Chinese medicinal herbs including Coptis chinensis and Phellodendron amurense, berberine is renowned for its heat-clearing, damp-drying, and detoxifying properties, and has been employed in Chinese medical practice for thousands of years in the treatment of various inflammatory diseases.

3. Key Constituents and Active Compounds

Alkaloids

The major chemical constituents of the bark are the isoquinoline alkaloids palmatine, jatrorrhizine, and phellodendorine, with berberine found within the leaves. Nexrutine®, a registered proprietary extract of the bark, is reported to contain the alkaloids berberine, palmatine, and phellodendrine.

The bioactive compounds, including berberine and palmatine, exhibit anti-inflammatory, antioxidant, and bone-protective properties, contributing to their potential therapeutic benefits in promoting bone health and preventing bone loss.

While benzylisoquinoline forms the structural backbone of berberine and many other natural alkaloids, protoberberines are characterized by a tetracyclic ring system with a nitrogen atom sitting on the bridge connecting two sets of bicyclic rings. Berberine is a quaternary ammonium salt from the protoberberines group, and is likely the most widely distributed alkaloid among plant alkaloids.

Flavonoids and Other Compounds

Compounds in the leaves (quercetin, quercetin-3-O-beta-D-glucoside, quercetin-3-O-beta-D-galactoside and kaempferol-3-O-beta-D-glucoside) demonstrated significant free radical scavenging activity comparable to vitamin E. The fruit oil also contains a variety of biologically active substances, including flavonoids (diosmin), alkaloids (berberine, jatrorrhizine, palmatine), saponins, and coumarins.

Berberine Biosynthesis in P. amurense

Analysis of the near telomere-to-telomere genome of P. amurense has identified the CNMT gene family (PaCNMT), which may contribute to berberine biosynthesis. The PaCNMT family underwent a gene loss event within the Rutaceae lineage, followed by functional re-emergence in the P. amurense lineage through LTR-mediated gene expansion, which is thought to have shaped the metabolic pathway in this species.

4. Mechanisms of Action

Most documented mechanisms of action for Phellodendron are attributable to its dominant constituent, berberine. Multiple pathways have been identified at the cellular and molecular level, though much of this work is preclinical.

AMPK Activation and Metabolic Effects

Berberine is known as an AMP-activated protein kinase (AMPK) activator. Its insulin-independent hypoglycemic effect is related to inhibition of mitochondrial function, stimulation of glycolysis, and activation of the AMPK pathway. Additionally, berberine may also act as an α-glucosidase inhibitor.

Berberine activates AMP-activated protein kinase (AMPK), a major regulator of metabolic pathways, and inhibits mammalian target of rapamycin (mTOR), a downstream target of AMPK. The antidiabetic activity of berberine has been attributed to its pleiotropic mechanisms involving activation of AMPK, inhibition of mitogen-activated protein kinases (MAPK), inhibition of PI3K/Akt signaling pathway, inhibition of aldose reductase, inhibition of inflammation, inhibition of oxidative stress and modulation of lipid metabolism.

Anti-Inflammatory Pathways: NF-κB Inhibition

Berberine, a bioactive alkaloid isolated from several herbal substances including Phellodendron, possesses multiple pharmacological effects, including anti-inflammatory, antimicrobial, antidiabetic, anticancer, and antioxidant activities. Studies have demonstrated the anti-inflammatory potential of berberine via the NF-κB pathway in activated monocytes, whose interplay is key in the pathophysiology of atherosclerotic development in blood vessel walls, suggesting potential for treating various chronic inflammatory disorders.

Prostate Cancer Cell Mechanisms

In cell line research, Nexrutine (the proprietary Phellodendron extract) inhibits tumor cell proliferation through apoptosis induction and inhibition of cell survival signaling. Nexrutine inhibits prostate cancer cell proliferation through modulation of Akt and cAMP-responsive element binding protein (CREB)-mediated signaling pathways.

Antimicrobial Mechanisms

Studies have shown that berberine has demonstrated exceptional antimicrobial efficacy in the treatment of intestinal infections, conjunctivitis, and suppurative otitis media. The tree has both antibiotic and antimicrobial properties due to the alkaloids contained within the plant material.

5. Scientific Evidence by Area of Use

5.1 Stress, Anxiety, and Cortisol Modulation

The most frequently cited human clinical evidence for Phellodendron specifically involves its use as part of a proprietary combination product, Relora®, which blends Phellodendron amurense bark extract with Magnolia officinalis bark extract.

Relora® is a proprietary blend of a patented extract of the bark of Magnolia officinalis and an extract of the bark of Phellodendron amurense (US Patent Nos. 6,582,735 and 6,814,987). The product is standardized to "not less than 1.5% honokiol and 0.1% berberine."

A key randomized, double-blind, placebo-controlled human study assessed this combination in stressed subjects. Salivary cortisol exposure and psychological mood state were assessed in 56 subjects (35 men and 21 women) screened for moderate stress and supplemented with the standardized/patented Magnolia/Phellodendron combination (Relora®) or placebo for 4 weeks. After 4 weeks of supplementation, salivary cortisol exposure was significantly (p<0.05) lower (−18%) in the Relora group compared to placebo.

A second pilot clinical trial examined the combination in healthy women. This randomized, parallel, placebo-controlled clinical study was conducted with healthy, overweight (BMI 25 to 34.9), premenopausal female adults between the ages of 20 and 50 years, who typically eat more in response to stressful situations and scored above the national mean for women on self-reporting anxiety. The intervention was Relora (250 mg capsules) or identical placebo 3 times daily for 6 weeks, measuring anxiety via the Spielberger STATE-TRAIT questionnaires, salivary amylase and cortisol levels, and Likert Scales/Visual Analog Scores for sleep quality.

Human studies have demonstrated positive changes in DHEA (dehydroepiandrosterone) and cortisol levels, less weight gain (compared to controls), and reductions in perceived stress and transitory feelings of anxiousness in subjects taking Relora (500 mg to 750 mg for four to six weeks).

Berberine, the constituent of the Phellodendron extract, has also demonstrated a significant anxiolytic effect in rodent stress studies, including the elevated plus maze test and the forced swim test. The combination of magnolia plus phellodendron appears to be more effective in controlling stress/anxiety compared to either herb used separately, based on available studies.

Evidence strength: Preliminary. Human trials used a combination product (Relora®), not Phellodendron alone, so effects attributable specifically to Phellodendron cannot be isolated. Studies are small, short-term, and some rely on sponsor-funded unpublished data.

5.2 Osteoarthritis, Joint Health, and Inflammation

A key pilot clinical trial investigated the combination of Phellodendron amurense bark extract with Citrus sinensis (orange) peel extract, formulated as NP 06-1. An 8-week placebo-controlled, randomized, double-blind study was conducted with four groups comparing the effects of NP 06-1 to placebo on overweight and normal weight subjects diagnosed with primary osteoarthritis of the knee. NP 06-1 (a combination of Phellodendron amurense bark and Citrus sinensis peel) or matching placebo were given in a dose of two capsules (370 mg each) twice daily. The outcome measures were the Lequesne Algofunctional Index (LAI) for joint pain and movement as well as biomarkers of inflammation (C-reactive protein [CRP] and erythrocyte sedimentation rate [ESR]).

In this pilot study, NP 06-1 had beneficial effects on symptoms of osteoarthritis of the knee as measured using LAI scores and had anti-inflammatory effects as measured using CRP. Administration of NP 06-1 was also associated with weight loss, which may have been a contributing factor to the other benefits. Eighty (80) subjects were enrolled and 45 subjects completed the study, and no serious adverse events were reported.

In a related trial using the same formulation: NP 06-1 had a beneficial effect on cardiovascular risk factors, namely lipid levels, blood pressure and fasting glucose levels, and its administration was also associated with weight loss in osteoarthritis patients.

Phellodendron species, traditionally used in Chinese medicine for centuries, hold promise as a potential treatment for osteoporosis and osteoarthritis due to their bioactive compounds. The bioactive compounds, including berberine and palmatine, exhibit anti-inflammatory, antioxidant, and bone-protective properties. However, challenges such as the need for standardized preparation and dosing, limited clinical studies, and potential interactions with other medications hinder their clinical use.

Evidence strength: Preliminary. Both studies used a combination product rather than Phellodendron alone, preventing isolation of specific effects. Both were pilot studies with high dropout rates and were industry-funded.

5.3 Prostate Cancer (Preclinical and Early Clinical)

A proprietary extract of P. amurense bark called Nexrutine® has been the subject of a preclinical and one early human clinical tolerance study focused on prostate cancer.

Previous studies showed that Nexrutine (bark extract from Phellodendron amurense) prevents prostate tumor development when given prior to the development of high-grade prostatic intraepithelial neoplasia in the transgenic adenocarcinoma of mouse prostate (TRAMP) model. In a follow-up study, Nexrutine was administered to 28-week-old TRAMP mice to investigate the effect on the progression of established tumors. Efficacy was determined by histopathological evaluation of the prostate, and the data indicated that Nexrutine inhibited progression of prostate tumors correlated with tissue levels of transcription factors nuclear factor kappa B, cyclic-AMP response element-binding protein and phosphorylated CREB.

In the TRAMP mouse model, eight-week-old mice were fed a pelleted diet containing 300 and 600 mg/kg Nexrutine for 20 weeks, and efficacy was evaluated by magnetic resonance imaging and histologic analysis. Nexrutine significantly suppressed palpable tumors and progression of cancer in the TRAMP model, and expression of total and phosphorylated Akt, CREB, and cyclin D1 was significantly reduced in prostate tissue from the Nexrutine intervention group compared with tumors from control animals.

In the only published human clinical study on this extract in prostate cancer patients: Phellodendron amurense bark extract (Nexrutine®) had shown a favorable effect on prostate cancer in vivo and in vitro, prompting an evaluation of its tolerance in patients undergoing surgery or radiation for prostate cancer. Patients received Nexrutine® orally (500 mg three times daily) either 1 to 2 months preoperatively or 1 to 2 months prior to and with radiation therapy. In total, 21 patients (9 surgery and 12 radiation) underwent treatment.

Evidence strength: Very preliminary for human use. Anti-tumor data derives primarily from cell lines and a mouse transgenic model. The single human study evaluated tolerance only, not efficacy, and enrolled only 21 patients. No efficacy conclusions can be drawn from available human data.

5.4 Glycemic Control and Metabolic Health

While there is a substantial body of clinical evidence for berberine itself in glycemic control, studies specifically isolating Phellodendron extract are limited. The glycaemic evidence base is predominantly from berberine used as an isolated compound, not from whole Phellodendron preparations.

The hypoglycemic effect of berberine was first reported in 1988 when berberine was prescribed to treat diarrhea in diabetic patients. Since then, berberine has been used as an anti-diabetic agent in folk medicine in China. In newly-diagnosed type 2 diabetic patients, berberine is able to lower blood insulin levels via enhancing insulin sensitivity.

The antimicrobial activity of berberine is well-established in the treatment of infection caused by bacteria, viruses, fungi, protozoans, and helminths. In China, berberine is an over-the-counter drug for the treatment of bacterial diarrhea.

The cardiovascular and metabolic benefits observed in the NP 06-1 osteoarthritis trial also suggested metabolic activity: NP06-1 was a proprietary blend of Phellodendron amurense tree bark and Citrus sinensis peel standardized to berberine and polymethoxylated flavones (PMFs), respectively, formulated with the goal of combining beneficial effects, with indications in the literature that this combination might reduce inflammation and have beneficial effects on lipid levels.

Evidence strength: The glycemic evidence base is strong for isolated berberine, but Phellodendron whole extract has not been separately evaluated in well-powered human trials for diabetes or dyslipidemia. Extrapolation from berberine studies to Phellodendron preparations requires caution.

5.5 Skin Health and Topical Use

Quercetin and related flavonoids in the leaves of P. amurense demonstrated significant free radical scavenging activity comparable to vitamin E. The plant has both antibiotic and antimicrobial properties due to the alkaloids contained within the plant material, providing a mechanistic rationale for topical applications in inflammatory skin conditions.

When applied to the skin, Phellodendron is considered possibly safe when used short-term.

Evidence strength: Mechanistic rationale exists, but rigorous human clinical trials evaluating topical Phellodendron preparations for specific dermatological conditions are lacking in the available peer-reviewed literature.

6. Body Systems and Health Areas Associated with Phellodendron

Genitourinary system: Historically prescribed for urinary tract infections. Phellodendron amurense is able to inhibit prostatic contractility, suggesting that it may be useful in the treatment of urological disorders caused by prostatic urethral obstruction such as benign prostatic hyperplasia (BPH).
Musculoskeletal system: Phellodendron species hold promise as a potential treatment for osteoporosis and osteoarthritis due to their bioactive compounds, including berberine and palmatine, which exhibit anti-inflammatory, antioxidant, and bone-protective properties.
Endocrine and metabolic system: In conjunction with Magnolia (Magnolia officinalis), Phellodendron can regulate adrenal stress hormones such as dehydroepiandrosterone and cortisol, which can be imbalanced in the diabetic state and in metabolic syndrome.
Gastrointestinal system: In traditional Chinese medicine, P. amurense is used to treat abdominal pain, diarrhea, and gastroenteritis.
Hepatic system: The berberine in Phellodendron might lower blood sugar and cholesterol levels, as well as protect the liver.
Oncology (preclinical): Nexrutine (bark extract from Phellodendron amurense) may have potential to prevent prostate tumor development.
Neuroendocrine/stress response: Phellodendron amurense bark extract, as part of the Relora® formula, has a history of traditional use in treating stress and occasional feelings of anxiousness, and in modern times is used to support relaxation and reduce the perception of stress and stress-related eating.

7. Dosage Forms and Reported Dosages

The following dosages are derived from specific sources; they are not recommendations and represent ranges as reported in traditional or clinical contexts only.

Traditional / TCM Dosing

A traditional dosage for oral use is 3–10 g, decocted in water, or used in bolus and powder form, with an appropriate quantity for external use. Other reported starting dosages include dried powder at 3 to 10 grams per day, or a 4:1 dried decoction at 1 to 3 grams per day.

Clinical Study Dosages

In the Relora® cortisol/stress trial, subjects ingested 500 mg/day at breakfast (250 mg) and dinner (250 mg) in white opaque capsules.
In the women's stress/anxiety pilot trial, the intervention was Relora (250 mg capsules) or identical placebo 3 times daily (750 mg/day total) for 6 weeks.
In the osteoarthritis/cardiovascular pilot study, NP 06-1 (a combination of Phellodendron amurense bark and Citrus sinensis peel) or matching placebo was given in a dose of two capsules (370 mg each) twice daily for 8 weeks.
In the human prostate cancer tolerance trial, patients received Nexrutine® orally at 500 mg three times daily either 1 to 2 months preoperatively or prior to and with radiation therapy.
In a pharmacokinetic study assessing CYP inhibition, 300 mg berberine was administered three times daily (900 mg/day) for 2 weeks before assessment of liver enzyme activities.

8. Safety Considerations and Drug Interactions

Overall Safety Profile

When taken by mouth, Phellodendron is possibly safe when used in combination with other ingredients, short-term. There is not enough reliable information to know if Phellodendron is safe or what the side effects might be when used as a single ingredient.

In published studies, Phellodendron extract has been used for the treatment of osteoarthritis and stress with some modest benefit, and across these published studies, the compound appeared to be well tolerated.

Pregnancy and Breastfeeding

It is considered unsafe to use phellodendron during pregnancy, as it contains berberine, which can cross the placenta and might harm the fetus. It is also considered unsafe during breastfeeding, as berberine can be transferred to the infant through breast milk and can cause brain damage in newborns, especially in premature newborns with jaundice.

Berberine may inhibit biliary conjugation in the fetus or newborn and thus lead to hyperbilirubinaemia. Phellodendron should not be prescribed after the first trimester of pregnancy, in newborns, or during the first month of breastfeeding.

The French Agency for Food, Environmental and Occupational Health & Safety (ANSES) discouraged the use of berberine supplements in pregnant or breastfeeding women, diabetics, and individuals with hepatic or cardiac disorders, and warned against any concomitant drug treatment due to potential interactions. These recommendations were extended to children and adolescents.

Regulatory note: French authorities indicated that isoquinoline alkaloids (berberine and palmatine) are substances to be monitored in Phellodendron amurense, and that labels must include a warning advising pregnant women not to use them.

Long-Term Use

Long-term use should be avoided due to alkaloid content. Long-term use may damage the yin and fluids according to TCM pharmacological principles.

CYP Enzyme Inhibition and Drug Interactions

Because berberine is the primary active constituent responsible for known interactions, the pharmacokinetic drug interaction profile of Phellodendron is effectively that of berberine. Berberine can interact with many medicines because it affects liver enzymes (CYP2D6, CYP3A4, and CYP2C9) and drug transporters that help clear drugs from the body. By slowing these pathways, berberine may raise the blood levels of certain drugs and increase side-effect risks.

Berberine is a CYP3A4 inhibitor and a P-glycoprotein transporter substrate, and interaction studies have shown that co-administration with cyclosporine markedly elevates the blood concentration of cyclosporine. The increase in cyclosporine bioavailability may be partly due to decreased metabolism because of CYP3A4 inhibition and partly due to increased uptake from the gut due to competition for the P-glycoprotein transporter.

In a two-phase randomized-crossover clinical study in healthy male subjects: after 2 weeks of berberine administration (300 mg three times daily), midazolam, omeprazole, dextromethorphan, losartan, and caffeine were used to evaluate enzyme activities of CYP3A4, 2C19, 2D6, 2C9, and CYP1A2, respectively.

Possible interaction concerns include diabetes medicines, blood pressure and heart medicines, cholesterol-lowering medicines, blood thinners such as warfarin, medicines that cause drowsiness, and cyclosporine and other drugs with a narrow safety margin.

Specific Interaction Categories

Antidiabetic agents: When berberine is taken alongside prescribed diabetes medications, the combined glucose-lowering effect could be excessive and unpredictable. The combination with metformin may increase the risk of gastrointestinal side effects—particularly diarrhea, nausea, and abdominal discomfort.
Immunosuppressants: In renal-transplant recipients, berberine was reported to markedly elevate the blood concentration of cyclosporine A, a drug metabolized by CYP3A4.
Statins: Statins relying heavily on CYP3A4 can see increased blood levels when berberine inhibits that enzyme, potentially resulting in more muscle symptoms and, rarely, serious muscle injury.
Antihypertensives: Berberine may enhance the blood pressure-lowering effects of antihypertensives such as ACE inhibitors, calcium channel blockers, and beta-blockers, potentially causing hypotension.

Pediatric Use

Phellodendron is considered unsafe in newborn infants. It can cause brain damage, especially in premature infants with jaundice.

9. Limitations of the Current Evidence Base

Several structural limitations apply across the body of human clinical evidence for Phellodendron:

The majority of clinical trials have tested Phellodendron as part of proprietary combination products (Relora®, NP 06-1, Nexrutine®) rather than Phellodendron bark extract alone, making it impossible to attribute observed effects specifically to Phellodendron.
Challenges include the need for standardized preparation and dosing, limited clinical studies, and potential interactions with other medications that hinder their clinical use.
Most mechanistic evidence for anti-tumor and metabolic effects derives from cell lines and animal models; direct extrapolation to human clinical outcomes is not justified without further evidence.
People use phellodendron for acne, diabetes, obesity, osteoarthritis, stress, and many other conditions, but there is no good scientific evidence to support these uses as of the currently available literature.
Despite substantial progress in understanding berberine's pharmacodynamics, its precise mechanisms of action remain incompletely elucidated and warrant further systematic investigation.

References

Health Conditions

Health conditions that Phellodendron may help support.

HPA Axis SupportScientific
Phellodendron amurense bark is the second component of the Relora® formula for HPA axis and cortisol support. Its berberine content and other alkaloids contribute to cortisol metabolism modulation and stress response regulation. Clinical evidence comes primarily from the Relora® combination RCTs showing significant cortisol reduction in moderately stressed adults.

Body Systems

Body systems that Phellodendron may help support.

No body systems available.