Bupleurum falcatum

Bupleurum falcatum: A Comprehensive Reference

1. Identity, Botanical Classification, and Common Forms

Bupleurum falcatum L. is a flowering perennial herb belonging to the family Apiaceae (the carrot or umbelliferous family). It is also known as sickle-leaved hare's ear. Its scientific name is Bupleurum falcatum L., and it carries a range of common names including Beichaihu, Bupleuri Radix, Bupleurum root, Chai-hu, Chaihu, Hare's ear root, Radix Bupleuri, and Saiko (Japanese), as well as Thorow wax or Thorowax.

Bupleurum falcatum is a slender-leaved herb native to East Asia, especially China, Korea, and Japan, and is one of the most revered herbs in Traditional Chinese Medicine (TCM), where it is known as Chai Hu (柴胡). The genus Bupleurum includes approximately 200 species that are widely distributed in the Northern Hemisphere, Eurasia, and North Africa.

There is notable taxonomic complexity surrounding this species. Confusion exists regarding the species B. scorzonerifolium Willd., which may be the same as B. falcatum L. var scorzonerifolium. The two major Chinese commercial medicinal Chaihu species, North Chaihu and South Chaihu, were initially referred to as B. falcatum and B. sachahnense around 1954; their names were later corrected to B. chinense and B. scorzoneraefolium, as they show different morphological features from the European species. Accordingly, Chaihu used in herbal medicine was finally defined as Bupleuri Radix, representing the dried roots of these two species. B. falcatum is the species primarily used in Japan.

Morphologically, B. falcatum subsp. falcatum has distinctly petiolate, elliptical to oblong leaves, while B. falcatum subsp. cernuum has sessile, linear leaves.

Parts Used and Common Preparations

The part used medicinally is the root. Levels of saikosaponins vary widely between species — B. falcatum contains 2% to 8% and B. chinense approximately 1.7% — and between wild and cultivated specimens. Common preparations include:

• Dried root decoction (tea): Traditionally, and in some clinical studies, bupleurum was prepared as a tea in which the root is decocted or cooked for hours before use; some sources note 1–4 grams per cup of water, taken three times daily.
• Capsule/tablet (standardized dry root extract): Generally 500–2,000 mg of bupleurum dry root are taken three times daily in capsules.
• Tincture: A 1:2 tincture at 40% ethanol, at a reported dose of 2–6 mL once daily, has been described in naturopathic practice.
• Combination Kampo formula (Sho-saiko-to / TJ-9): In this standardized Japanese formula, the preparation is typically given in capsules of 1.8–2.5 grams, three times per day.
• Injectable preparation: Injectable bupleurum preparations have been used in Japan; however, adverse effects including renal and liver injury were associated with this route of administration in the 1980s.

2. Traditional and Historical Use

China

B. chinense and B. falcatum roots are listed in the oldest Chinese materia medica documents, the Shennong's Herbal (Shennong Ben Cao Jing). Bupleurum was described therein as having the action of "soothing liver and relieving constraint," useful for improving both frank liver symptoms and emotional instability such as depression, anxiety, and phobia. Bupleurum is a traditional Chinese herb dating back to the first century BC and is one of the most commonly used herbs in traditional Chinese medicine. Bupleuri Radix has a 2000-year history of medicinal use, and its first published use was in the Shennong Ben Cao Jing.

Bupleurum is first mentioned in texts from the 1st century BCE, and has a first recorded medicinal use appearing in the Treatise on Cold Induced Febrile Disease, a Chinese medical text dating to the close of the Eastern Han Dynasty in the 3rd century AD. Xiao Chai Hu Tang is one of the 269 formulas in this text and combines bupleurum with licorice, ginger, ginseng, Chinese skullcap, and peony root; it is also known as the Japanese Kampo medicine Sho-Saiko-To.

Bupleurum has been used in Traditional Chinese Medicine for thousands of years to help relieve numerous conditions — most particularly, infections with fever, liver problems, indigestion, hemorrhoids, and uterine prolapse. Many species of genus Bupleurum L. have been pharmaceutically used mainly in Asia and Europe for thousands of years, with their roots being the most popular ingredients in Chinese materia medica prescriptions for the treatment of inflammatory diseases and autoimmune diseases.

In TCM practice, B. falcatum has been used for over 2,000 years in Chinese medicine, where it is a key ingredient in many classical formulas aimed at balancing the internal organs and treating alternating chills and fevers — a hallmark of shao yang disorders. The formula Xiao Chai Hu Tang (Minor Bupleurum Decoction), developed in the Han Dynasty, remains one of the most prescribed herbal combinations in East Asia for sub-acute infections, stress-related disorders, and liver stagnation.

Japan (Kampo Medicine)

Bupleurum forms an integral part of many Kampo medicines (the Japanese adaptation of traditional Chinese medicine), including shosaikoto, daisaikoto, saikokeishito, hochuekkito, saibokuto, and saireito. In Japanese Kampo medicine, bupleurum is foundational, appearing in formulas like Shosaiko-to, which is used for liver inflammation, immune disorders, and emotional dysregulation. Sho-saiko-to is a Japanese Kampo or traditional herbal medicine formula based on the traditional Chinese formula xiao-chai-hu-tang, also called in English the "minor bupleurum formula." Bupleurum makes up 16% of the formula for sho-saiko-to.

Korea

The medicinal plant Bupleurum falcatum is a popular herbal medicine used throughout East Asia, including Korea. Traditionally, its dried roots (known as "Shiho" in Korean) have been widely used for treating the common cold, fever, hepatitis, inflammation, and also the symptoms of menopausal syndrome, such as hot flashes and depressive mood change.

Other Traditional Uses

Other traditional uses not supported by human scientific studies include the treatment of deafness, dizziness, diabetes, wounds, and vomiting. Bupleurum is also used in folk medicine as an anti-inflammatory and pain remedy.

3. Key Constituents and Active Compounds

A wide range of chemical constituents has been isolated and identified from species of Bupleurum L., including saikosaponins, polysaccharides, volatile oils, flavonoids, polyacetylenes, lignins, and coumarins, most of which possess a variety of biological activities, especially hepatoprotective effect, antitumor activity, immunoregulation, and febrifuge efficacy.

Triterpenoid Saponins (Saikosaponins)

The pharmacologically significant chemical constituents of B. falcatum have been well documented, particularly its triterpenoid saponins, such as saikosaponins A, C, and D, which represent the major bioactive compounds. Saikosaponins are one of the major active components of radix bupleurum and a triterpenoid saponin group extracted only from Bupleurum plants; they can be further categorized as saikosaponin A, B1, B2, B3, B4, C, D, E, F, G, H, and I.

Saikosaponin a (SSa) and Saikosaponin d (SSd) are the major active components of triterpene saponins in Bupleurum falcatum. Saikosaponin D (SSD), a triterpenoid saponin extracted from Bupleurum, exhibits extensive pharmacological properties, including anti-inflammatory, antioxidant, anti-apoptotic, anti-fibrotic, and anti-cancer effects. Saikogenins A, B, C, and D — the aglycone metabolites — are also present in the plant.

Polysaccharides (Bupleurans)

Rare monosaccharides such as ribitol, xylose, and arabinose, and pectic polysaccharides such as bupleuran 2IIb and bupleuran 2IIc, have been isolated from B. falcatum and many other species; these compounds exert anti-ulcer, anti-inflammatory, anti-infective, and immunomodulatory effects in autoimmune diseases. Pectic polysaccharides bupleuran 2IIb and 2IIc, which possess anticomplementary activity, Fc receptor up-regulating activity on macrophages, and antiulcer activity, were isolated from the important Sino-Japanese medicinal herb the roots of Bupleurum falcatum.

Phytosterols and Lignans

The phytosterol composition of B. falcatum was identified to include β-sitosterol, stigmasterol, Δ7-stigmastenol, Δ22-stigmastenol, and α-spinasterol. Spinasterol, stigmasterol, and rutin have also been found, as well as pectin-like polysaccharides (bupleurans). Lignans are the second most common class of secondary metabolite within this genus, with almost 50 isolated compounds.

Coumarins

Complex pyranocoumarin derivatives, such as anomalin and praeruptorin A, have been isolated from B. falcatum roots.

Polyacetylenes and Volatile Oil

About 25 bioactive polyacetylenes (polyines) have been reported from seven different species of Bupleurum. Previous work on structurally related falcarinol-type polyacetylenes in other Apiaceae species suggests possible anti-inflammatory and anticancer potential. The essential oil contains various chemical compounds including long-chain unsaturated fatty acids.

Other Constituents

Free organic and fatty acids — including pinellic acid, angelic acid, petroselic acid, and lignoceric acid — have also been identified in many species of the genus. Chemical analyses have identified benzoic and cinnamic acid derivatives and flavonoid glycosides alongside saikosaponins in B. falcatum extracts.

4. Established Mechanisms of Action

Anti-inflammatory Mechanisms

Saikosaponins A, C, and D have been shown to exhibit potent anti-inflammatory, hepatoprotective, antitumor, and immunomodulatory effects. Saikosaponin A (SSa) exerts anti-inflammatory activity by inhibiting the expression of pro-inflammatory cytokines and regulating inflammation-associated signaling pathways, such as the MAPK pathway and the nuclear factor-κB (NF-κB) pathway. Because SSD increased I-κBα activity in the liver and decreased liver TNF-α, IL-6, and NF-κBp65 expression, it may have hepatoprotective and anti-inflammatory actions that reduce CCl4-induced hepatic fibrosis in experimental models.

Hepatoprotective Mechanisms

SSD downregulates NF-κB and STAT3-mediated inflammatory pathways to protect against acetaminophen (APAP)-induced hepatotoxicity in animal models. Saikosaponin a and Saikosaponin d have a common steroid-like structure and are reported to have steroid-related pharmacological activities, including analgesic, anti-inflammatory, immunomodulatory, antiviral, and hepatoprotective activities. Studies have demonstrated that SSa and SSd can protect the liver from injury in rat models induced by CCl4 and dimethylnitrosamine.

Immunomodulatory Mechanisms

In in vitro studies, root extracts, polysaccharide bupleurans, and individual saikosaponins (especially saikosaponin D) have demonstrated effects on the immune system including upregulation and downregulation. Increased antibody response, induction of type 1 interferons, and upregulation of macrophages have been demonstrated. Bidirectional effects on T lymphocytes have also been demonstrated, possibly in a dose-dependent manner. Polysaccharides (bupleurans) have been shown to upregulate macrophage activity, stimulate the secretion of IL-6, and partially contribute towards the enhancement of IgM secretion.

HPA Axis Modulation

Saiko agents stimulate corticotropin-releasing factor (CRF) release from the hypothalamus, adrenocorticotropin (ACTH) secretion, and proopiomelanocortin gene expression in the anterior pituitary. Both saikosaponin a and saikosaponin d affect hypothalamic CRF gene expression in experimental models. Saikosaponins also enhance the activity of corticosterone by inducing liver enzymes involved in the activation of corticosterone and by stimulating adrenocortical function, with effects leading to an overall anti-inflammatory action.

Antiviral Mechanisms

The active components of B. falcatum — including SSA and SSD — are reported to impart immunomodulatory, anti-inflammatory, antibacterial, antiviral, and anticancer effects. Saikosaponin c (SSc), a compound purified from Radix Bupleuri, has been identified as exhibiting anti-HBV replication activity in cell-based studies.

Anti-fibrotic Mechanisms

Experimental results in hepatic stellate cells indicate that SSa and SSd suppress proliferation, wound healing activity, and cell migration in a time- and dose-dependent manner, and significantly induce apoptosis. Additionally, SSa and SSd decreased the expressions of extracellular matrix-related proteins.

Anticancer Mechanisms (Preclinical)

The anti-tumorigenic effects of SSD act through the intermediary p-STAT3/C/EBPβ signaling pathway to suppress cyclooxygenase (COX)-2 in human hepatocellular carcinoma cell lines. Using a rat model of DEN-induced hepatocellular carcinoma (HCC), SSD inhibited C/EBPβ and COX-2 to prevent the development of hepatocarcinogenesis.

Antioxidant Mechanisms

Saikosaponins interact with key proteins including CASP3, VEGFA, and STAT3 among the core targets of antioxidant action; VEGFA expression affects cell proliferation, cell cycle progression, and reactive oxygen species (ROS) content, and alters the levels of antioxidant enzymes and inflammatory factors.

5. Scientific Evidence by Area of Use

5.1 Liver Disease (Hepatitis, Cirrhosis, Hepatocellular Carcinoma)

This is the area with the most accumulated clinical data, though primarily for the multi-herb formula Sho-saiko-to (which contains B. falcatum as a key constituent) rather than for the herb in isolation. Although bupleurum is used in traditional Chinese medicine to treat liver diseases, human data for the isolated herb are lacking.

Clinical evidence for Sho-saiko-to / Xiao Chai Hu Tang: Human trials — only one of which was double-blind — have shown that the bupleurum-containing formula Sho-saiko-to may help reduce symptoms and blood liver enzyme levels in children and adults with chronic active viral hepatitis. Most of these studies were in people with hepatitis B infection, though one preliminary human trial has also shown a benefit in people with hepatitis C. In a prospective randomized clinical trial, Oka et al. (1995) showed that Xiao Chai Hu Tang (XCHT) prevented the development of HCC in patients with cirrhosis.

In laboratory and animal studies, Sho-saiko-to appears to prevent liver injury, reduce inflammation, and stimulate or enhance immune functioning. However, only a few clinical trials have been conducted in humans. These studies suggest it may be helpful for some types of patients with hepatitis, but studies to confirm this are needed.

A meta-analysis determined that the efficacy of Sho-saiko-to for chronic hepatitis B is unclear, with small trials of low methodological quality.

Clinical trial registration: Sho-saiko-to, an herbal medicine used for many years in Asia to treat liver disease, was studied in a phase II trial to evaluate whether it may improve liver swelling and injury caused by chronic hepatitis C. This study was a single-arm, single-center trial of Sho-saiko-to in patients with chronic active hepatitis C who could not tolerate or had contraindications to interferon therapy; patients received 52 weeks of therapy and outcome was assessed by comparing pre- and posttreatment liver biopsies.

Preclinical hepatoprotective evidence: Saikosaponin A (SSa), a compound found in Radix Bupleuri, has shown promising hepatoprotective, anti-inflammatory, and antioxidant properties in preclinical research. In animal models, Sho-saiko-to inhibited hepatic necroinflammation and fibrosis, prevented liver injury, and promoted liver regeneration.

Evidence strength: Weak-to-moderate for the combination formula Sho-saiko-to, based on small human trials, predominantly for hepatitis B; largely preclinical for the isolated herb or its constituents. High-quality RCT evidence is lacking.

5.2 Inflammation and Immune Modulation

Laboratory studies show that components of bupleurum interfere with the processes that cause inflammation. Preclinical studies suggest that bupleurum has antiviral, hepatoprotective, anti-inflammatory, immune-modulating, antiproliferative, and chemopreventive properties. However, to treat infections, bupleurum may have antibacterial and antiviral activity, but human studies are lacking.

Evidence strength: Preclinical (in vitro and animal data) only; no confirmed human clinical trials specifically evaluating bupleurum's anti-inflammatory or immune-modulating activity as the sole intervention.

5.3 Antipyretic (Fever-Reducing) Effects

Although bupleurum is used in traditional Chinese medicine to reduce fever, there are no clinical data to back this claim. In an in vivo study, B. falcatum was reported to have potent hypothermic and antipyretic effects.

Evidence strength: Traditional use and animal-model evidence only; no human clinical trial data.

5.4 Depression, Anxiety, and Neuropsychiatric Effects

B. falcatum is used as one of the major ingredients to treat psychosomatic disorders in Oriental traditional medicine, and some researchers have reported that decoctions including B. falcatum as a major ingredient ameliorated the chronic stress-induced depressive state.

Animal and mechanistic evidence: Saikosaponin A, a triterpene saponin extracted from Bupleurum, has anti-inflammatory and antioxidant effects; in a perimenopausal depression model of female rats induced by chronic unpredictable mild stress, saikosaponin A improved the behavioral performance of these rats and reduced CRH mRNA, CRH protein, and serum CORT levels. Administration of SSA over four weeks resulted in the reversal of corticosterone elevation in conditions of chronic unpredictable mild stress, and analysis of CRH mRNA and protein levels in the hypothalamus demonstrated increased CRH expression in the stress group and a decrease in the SSA group.

In a clinical trial, a decoction including B. falcatum as a major ingredient showed overall efficacy for relieving both the vasomotor and psychological symptoms of postmenopausal women with climacteric symptoms. This is one of the very few clinical data points suggesting psychological benefit, though the trial involved a multi-herb decoction and not the isolated herb.

Evidence strength: Primarily animal/in vitro; very limited and confounded clinical data from multi-herb formulations. No confirmed human RCT data for bupleurum as a single agent for depression or anxiety.

5.5 Bone Health (Anti-osteoclastogenic Effects)

A preclinical study investigated B. falcatum extract specifically in the context of bone loss. The medicinal plant Bupleurum falcatum is a popular herbal medicine used throughout East Asia, and its dried roots have been traditionally used for treating symptoms of menopausal syndrome, including hot flashes and depressive mood changes. Several in vitro, in vivo, and clinical studies have demonstrated that crude extracts or active components such as saikosaponins have potential anti-inflammatory, antipyretic, hepatoprotective, neuroprotective, and immunomodulatory effects, and in a clinical trial, a decoction including B. falcatum as a major ingredient showed overall efficacy for relieving vasomotor and psychological symptoms of postmenopausal women with climacteric symptoms.

Evidence strength: Preclinical only for bone-specific endpoints; the referenced clinical data relate to a combined herbal formula for climacteric symptoms.

5.6 Gastric Ulcer and Gastrointestinal Effects

The polysaccharide fraction of B. falcatum possesses potent antiulcer activity against HCl/ethanol-induced lesions in mice. The roots of Bupleurum falcatum have been used in Chinese and Japanese herbal medicines for the treatment of chronic hepatitis, inflammatory diseases, and ulcers of the digestive organs; pharmacologically active polysaccharides bupleuran 2IIb and 2IIc with anticomplementary, macrophage Fc-receptor up-regulating, and antiulcer activities were isolated from hot-water extracts of the roots.

Evidence strength: Preclinical (animal and in vitro) only; no human clinical trial data specifically for gastrointestinal applications.

5.7 Antiviral Activity

Bupleurum may have antiviral activity, but clinical trials for antiviral applications, such as the common cold, have not been conducted. In preclinical research, saikosaponin c (SSc), purified from Radix Bupleuri, was identified as exhibiting anti-HBV replication activity in cell-based studies. Additionally, extracts of B. falcatum showed strong antimicrobial activity against Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MIC as low as 0.5 mg/mL) in in vitro testing.

Evidence strength: In vitro and animal data only; no human antiviral clinical trials for isolated bupleurum.

5.8 Anticancer Activity

Test tube studies have found that saikosaponins can inhibit growth of liver cancer cells. Research explored the mechanism of action of SSD as an anti-cancer agent for liver cancer in two human hepatocellular carcinoma cell lines, demonstrating that the anti-tumorigenic effects of SSD act through the p-STAT3/C/EBPβ signaling pathway to suppress cyclooxygenase (COX)-2; SSD effectively inhibited cell proliferation in a dose-dependent manner. Experiments have also suggested that bupleurum might exert some influence over multidrug resistance in drug-resistant cells.

Evidence strength: Preclinical (in vitro and animal) only for anticancer effects of isolated constituents; the clinical data referenced pertain to combined formulas (Sho-saiko-to) for prevention of HCC in cirrhotic patients, not isolated bupleurum as a cancer treatment.

6. Body Systems and Health Areas Associated with Bupleurum falcatum

• Hepatic / Hepatobiliary system: B. falcatum has been used in Chinese medicine for over 2,000 years as a "liver tonic" and is commonly prescribed by both Chinese and Japanese traditional medicine practitioners for inflammatory and infectious diseases.
• Immune system: Immunoregulatory activity has been documented in multiple constituents; the species may serve as a potential immunomodulator.
• Neuroendocrine / HPA axis: Effects on corticosterone and CRH pathways suggest interactions with the hypothalamic-pituitary-adrenal axis, as supported by the studies on saikosaponin A described above.
• Musculoskeletal / Bone: Preclinical evidence points toward anti-osteoclastogenic activity and potential benefit in estrogen-deficiency-related bone loss.
• Gastrointestinal system: Polysaccharides from B. falcatum exert anti-ulcer effects documented in experimental models.
• Respiratory system (adverse effects context): Relevant principally for safety purposes — see Section 8.
• Neuropsychiatric system: Preclinical and limited clinical multi-herb data suggest possible relevance to depression, anxiety, and psychosomatic disorders.

7. Dosage Forms and Doses Reported in Studies

The following dosage information is drawn directly from sources; no independent dosing recommendations are implied.

• Generally 500–2,000 mg bupleurum dry root are taken three times daily in capsules; traditionally and in some clinical studies, bupleurum was prepared as a tea with the root decocted or cooked for hours before use.
• Some sources note 1–4 grams per cup of water, three times daily, as a decoction.
• A tincture (1:2, 40% ethanol) at 2–6 mL per day has been described in naturopathic monographs.
• Sho-saiko-to formula is typically given in capsules of 1.8–2.5 grams, three times per day; the amount given to children is proportionally reduced based on individual weight and height.
• In the Xiao Chai Hu Tang formula recorded in classical texts, the Bupleurum falcatum (chai hu) component is listed at 12 grams for a two-day supply, within a total seven-herb decoction.
• In an experimental animal study on saikosaponin D hepatoprotection, SSD was administered at 2 mg/kg twice daily for five days.
• Clinical trial data are lacking to support specific dosing recommendations for bupleurum as a sole agent for any indication.

8. Safety Considerations and Drug Interactions

General Tolerability

When taken by mouth, bupleurum is possibly safe; it has been used as part of the Japanese herbal formula Sho-saiko-to for up to 5 years and is usually well tolerated. Side effects may include nausea. It can be sedating in some individuals and may cause stomach upset.

Hepatotoxicity Risk

Despite its hepatoprotective effects, bupleurum can also exert hepatotoxic effects at a very high dose and duration, and even induce fatal hepatotoxicity at doses from 50 to 125 g/kg in 1–2 weeks in rats. The toxic effects included fatty degeneration at moderate doses, progressing to necrotic lesions at the highest dosages. Alcohol extractions of bupleurum have shown greater hepatotoxicity than water extracts. Possible liver injury in humans has been reported from B. chinense, with anecdotal reports of inducing fibrosis, even though research has shown the plant to prevent liver fibrosis. An increased risk of liver injury in hepatitis B patients has been observed in those using Chinese herbal products containing more than 19 g of bupleurum.

Pulmonary Toxicity (Interstitial Pneumonitis)

Eighty or more cases of drug-induced pneumonitis (inflammation of the lungs) have been associated with the use of Sho-saiko-to alone or in combination with interferon. Since 1994, therapy with interferon has been contraindicated in combination with Sho-saiko-to; in 1996, the Japanese Ministry of Health issued an official warning of interstitial pneumonia as a side effect.

A proposed mechanism was investigated in a PubMed-indexed study: Sho-saiko-to alone may not injure lung tissue, but it increases the effect of interferon; when stimulated by some antigen, Sho-saiko-to may overstimulate the neutrophils. Although Sho-saiko-to alone did not change lung myeloperoxidase content in experimental models, myeloperoxidase in the lung was significantly increased by interferon administration, and this increase was further enhanced by pretreatment with Sho-saiko-to.

Because its use is associated with interstitial pneumonitis, liver injuries, and hepatitis, Sho-saiko-to should only be used under the supervision of a qualified practitioner. Concurrent use of interferon or low platelet counts may increase this risk. Patients should be carefully monitored, and the product discontinued immediately if fever, cough, dyspnea, abnormal pulmonary sounds (fine crackle), or X-ray abnormalities are observed.

Contraindications

Sho-saiko-to is reportedly contraindicated in patients taking interferons, patients with liver cirrhosis or hepatoma, and patients with chronic hepatitis and a platelet count of 100 × 10⁹/L. Bupleurum is not recommended in pregnant or breastfeeding women due to a lack of available scientific evidence.

Drug Interactions

Concurrent use of interferon may increase the risk of interstitial pneumonitis. Preclinical studies show that Sho-saiko-to upregulates CYP2B, CYP3A1, and CYP4A1 expression, and can interact with drugs metabolized by CYP2C9. Patients taking drugs metabolized by CYP450 enzymes should be aware that preclinical studies show Sho-saiko-to can affect the blood concentrations of these drugs; one study in healthy humans also suggests it may interact with some drugs, though clinical relevance has yet to be fully determined.

Theoretical interactions with NSAIDs, antibiotics, and immunosuppressants have also been described based on the herb's pharmacological profile.

Renal Adverse Events

There were reports of renal and liver injury associated with the use of an injectable bupleurum preparation in Japan in the 1980s that combined the herb with interferon and other compounds. The adverse effects were proposed to be the result of hypersensitivity reactions and included cases of hypokalemia and renal failure associated with intravenous preparations.

Saikosaponin-Specific Toxicity

Despite the therapeutic potential of saikosaponin D, it has poor bioavailability, stability, and solubility, which limits its clinical application. Potential toxicities have been discovered in some constituents, and it has been considered urgent to establish comprehensive quality evaluation systems to ensure the safety and efficacy of bupleurum herbs.

9. Summary of Evidence Landscape

Bupleurum has traditionally been used for various purposes, including analgesic, antipyretic, immunomodulatory, anti-inflammatory, and hepatoprotective effects; however, clinical trial data are lacking to recommend use for any indication. The most robustly studied applications are in the context of multi-herb Kampo and TCM formulas — particularly Sho-saiko-to — where preliminary human data exist for hepatitis B and HCC prevention in cirrhotic patients, but these studies are of limited methodological quality and involve a complex mixture of herbs, making attribution to B. falcatum alone difficult. Current research interest is focused on the bioactivity of the isolated triterpene saponins acting as immunomodulatory, anti-inflammatory, and antiviral agents, as well as on the observed anti-ulcer activity of the polysaccharides; it has been established that bupleurum contains multiple bioactive components, such as saponins, flavonoids, and polysaccharides, which often exert synergistic pharmacological effects. The bulk of mechanistic evidence remains in the preclinical domain — animal studies and cell-based assays — and translation to confirmed human benefit across most claimed therapeutic areas has not yet been achieved.

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