Scientific Name(s): Bupleurum falcatum L.
Common Name(s): Beichaihu, Bupleuri Radix, Bupleurum root, Chai-hu, Chaihu, Hare's ear root, Radix Bupleuri, Saiko (Japanese), Thorow wax, Thorowax
Bupleurum is a perennial herb that grows mainly in China, but is also cultivated in other areas. The plant grows to approximately 1 m in height and requires abundant sun to flourish. The leaves are long and sickle-shaped with parallel veining. Terminal clusters of small, yellow flowers appear in autumn. The long cone or column-shaped, single or branched root is 10 to 20 cm in length and 0.5 to 1.5 cm in diameter. It is light brown to brown, may be wrinkled, and is easily broken.1, 2, 3 Synonyms include Bupleurum chinense DC. and Bupleurum scorzonerifolium Willd. and the family Umbelliferae.
More than 20 species have been described in the genus Bupleurum, including a toxic species, Bupleurum longiradiatum, found in northeast China, and Bupleurum kaoi, which is indigenous to Taiwan.3, 4 The root of B. chinense DC. is considered to be the genuine Chaihu, but other species have been included in the Pharmacopoeia of the People's Republic of China since 1963, including Bei Chaihu and Nan Chaihu (referring to northern and southern thorowax root). B. falcatum is used in Japan.5 Confusion exists regarding the species called B. scorzonerifolium Willd., which may be the same as B. falcatum L. var scorzonerifolium.3, 6
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. It forms an integral part of many Kampo medicines (the Japanese adaptation of traditional Chinese medicine), including shosaikoto, daisaikoto, saikokeishito, hochuekkito, saibokuto, and saireito.5, 7 One of China's harmony herbs purported to affect organs and energy in the body, bupleurum has been used as a liver tonic, with spleen and stomach toning properties. The plant has also been used to promote perspiration and treat fever, flu, distending pain in the chest, and menstrual disorders.3, 5, 7
Bupleurum contains triterpene saponins or saikosides, also known as saikosaponins. Levels of these saikosaponins vary widely between species (ie, B. falcatum 2% to 8% and B. chinense 1.7%) and between wild and cultivated species. Levels also depend upon growing conditions.5 Root parts of bupleurum have been analyzed, resulting in the discovery of many saikosaponins. Saponins, along with flavonoid compounds and indole alkaloid glucosides, have been found in the aerial parts of some species. Saikogenins A, B, C, and D are also present in the plant. Spinasterol, stigmasterol, and rutin have been found, as well as pectin-like polysaccharides (bupleurans).9 The essential oil contains multiple different chemical compounds; Li05b and long-chain unsaturated fatty acids have been described.10 Chemical constituents have been assayed by high performance liquid chromatography, capillary gas chromatography, and capillary zone electrophoresis.5, 8, 11, 12, 13
Uses and Pharmacology
Animal experiments suggest bupleurum extracts and sapogenin A may possess analgesic effects.3
Oral decoctions of bupleurum, subcutaneous injection of the root extract, and oral saikosaponins have shown antipyretic effects in rats and rabbits.3 Nasal gel and nasal spray made from the essential oil of bupleurum reduced fever in rats and rabbits in a dose-dependent manner.14, 15
Radix Bupleuri reportedly reduces fever in influenza, the common cold, malaria, and pneumonia, with antipyretic effects in the majority of patients.3 However, research reveals no clinical trial data regarding the antipyretic effect of bupleurum.
Bupleurum inactivated enveloped viruses, including measles and herpes, but had no effect on nonenveloped viruses, such as polio.16 Saikosaponins inhibit coxsackie B virus17 and saikosaponin B inhibited the human coronavirus, which is responsible for severe acute respiratory syndrome.18
Saikosaponin A reduced antigen challenge-induced bronchoconstriction in experiments conducted on guinea pigs.19
The saponin fraction of B. kaoi, the acetone extract of the roots of B. scorzonerifolium, a polysaccharide bupleuran from the roots of B. falcatum, a novel lignin (isochaihulactone), and the extract from the root of B. longiradiatum have all been evaluated for antiproliferative and apoptotic effects.20, 21, 22, 24, 25, 26, 27
Limited in vivo animal experiments have been conducted. Studies in mice with lung adenocarcinoma showed a dose-dependent antiproliferative effect on tumor growth for B. scorzonerifolium extracts.20, 26 Extracts from the roots of B. longiradiatum were antiangiogenic in vitro, but they were not effective against lung tumors in mice and were fatally toxic at higher dosages.27
Research reveals no clinical trial data regarding the use of bupleurum in cancer.
The chloroform extract of roots of Bupleurum fruticosum exerted vaso-relaxant effects on rat aorta.28
In animal experiments, the polysaccharide bupleurans and saikosaponins reduced the effect of induced gastric ulcers and increase healing rates and were comparable with sucralfate. Suggested mechanisms of action include the reinforcement of the gastric mucosal barrier and an antisecretory action on acid and pepsin.3, 29, 30, 31 An ethanol extract of the aerial parts of the plant exhibited anti-H. pylori action in vitro.32
Research reveals no clinical trial data regarding the use of bupleurum in gastrointestinal conditions.
Saikosaponins and root and leaf extracts have demonstrated protective effects on acetaminophen and carbon tetrachloride-induced hepatic injury in rats. Most, but not all, experiments have shown positive effects on ALT and AST as well as histological changes, such as cell membrane malfunctions and cell death. The effects are attributed mainly to decreased oxidative stress.3, 33, 34, 35, 36, 37, 38, 39
Research reveals no quality clinical data regarding the use of bupleurum for hepatoprotective effect, and concerns regarding hepatotoxicity of Radix Bupleuri at high dose exist.4 High-quality clinical trials are lacking.
Immune system modulation/inflammation
In vitro studies have shown both up- and down-regulation effects of root extracts, polysaccharide bupleurans, and individual saikosaponins, especially saikosaponin D, on the immune system. Increased antibody response, induction of type 1 interferons, and up-regulation of macrophages have been demonstrated.3, 17, 40, 41, 42, 43 Bidirectional effects on T lymphocytes have also been demonstrated, possibly a dose-dependent effect.3, 40, 41, 44, 45, 46 Anticomplementary effects by polysaccharide extracts of Bupleurum smithii roots47 and inhibition of cyclooxygenase and lipoxygenase by the aerial part of Bupleurum fruitcescens have been demonstrated.48
Rat paw edema experiments have been conducted using crude extracts of B. falcatum, purified saponins 3 and 7, and some saikosaponins A and D. The anti-inflammatory effect was similar to that of prednisolone3 but not of dexamethasone.49 Saikosaponin C prevented nephritis in mice treated with nephrotoxic serum, but it did not prevent the formation or deposition of immune complex, suggesting an upregulation of enzymes or mechanisms that digest and clear the immune complexes.50 A review of the anti-inflammatory mechanisms and studies has been published.4
Research reveals no quality clinical data regarding the use of bupleurum for anti-inflammatory or immunomodulatory effect.4
Dosage of Radix Bupleuri is 3 to 9 g/day3; however, no clinical trials have been performed to validate this range as safe or effective.
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Antiaggregation effects on platelets have been demonstrated in vitro by the lactone bupleurumin extracted from the aerial parts of B. falcatum.51 Therefore, potentiation of thrombolytic and antiaggregating medicines is theoretically possible. Saikosaponins antagonized the stimulatory effects of caffeine and methamphetamine in mice; synergism with CNS depressants is possible.3, 52 Inhibition of cytochrome CYP3A4 by aqueous extracts has been demonstrated.53
Bupleuri Radix forms an integral part of many Kampo medicines (eg, shosaikoto, daisaikoto, saikokeishito, hochuekkito, saibokuto, saireito) for which interactions have been reported. Preparations include combinations of bupleurum with glycyrrhiza, scutellaria root, ginseng, jujube fruit, astragalus root, magnolia bark, alisma rhizome, and rhubarb.7 Assigning causality in reported drug interactions to individual plant components is difficult.
Bupleurum has produced mild lassitude, sedation, and drowsiness in some patients.3 Large doses have been reported to increase flatulence and bowel movements.3 Allergy to injected bupleurum has been reported.52
Bupleuri Radix forms an integral part of many combination preparations for which adverse reactions have been reported. Assigning causality in reported drug interactions to individual plant components is difficult.54 Adult respiratory distress syndrome has been reported, with one case attributed to bupleurum.55
Limited pharmacokinetic information is available in humans. Crude saikosaponins show low-medium toxicity in mice (oral median lethal dose = 4.7 g/kg and intramuscular median lethal dose = 112 mg/kg).40 Methanolic extracts of B. falcatum have not shown mutagenic effects in most modified Ames Salmonella tests; however, one report found enhanced mutagenic activity with a hot-water extract of B. falcatum.3 Concerns regarding hepatotoxicity of saikosaponins and the essential oil of Radix Bupleuri at high dose exist.4
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