Not for use in pregnancy except under the supervision of a qualified healthcare practitioner (Bensky et al. 2004; Chen and Chen 2004).
Magnolia bark contains trace amounts of the alkaloids magnocurarine and tubocurarine (Huang 1993). Tubocurarine has also been isolated from curare, the arrow poison used by indigenous hunters of South America that can produce death by asphyxiation when administered intravenously (Blubaugh and Linegar 1948). Intravenous use of magnolia bark is noted as exhibiting some curare-like effects, though the herb is considered generally safe for oral use (Bensky and Gamble 1993), and curare itself has long been recognized as innocuous when taken orally (Blubaugh and Linegar 1948).
Although compounds from magnolia bark have demonstrated anticoagulant activity in vitro (Teng et al. 1988), animal studies indicated no effects of magnolia bark extract on coagulation (Liu et al. 2007).
Reference texts on traditional Chinese medicine indicate that magnolia bark and root bark should be used with caution in pregnancy (Bensky et al. 2004; Chen and Chen 2004). Based on this information, use during pregnancy is not recommended except under the supervision of a qualified healthcare practitioner.
No information on the safety of magnolia bark or root bark in lactation was identified. While this review did not identify any concerns for use while nursing, safety has not been conclusively established.
An increase in anxiolytic activity was observed in mice administered 0.2 mg/kg of the compound honokiol with diazepam as compared to diazepam alone (Maruyama and Kuribara 2000).
No relevant human pharmacological studies were identified.
No effects on coagulation were observed in rats fed diets containing up to 480 mg/kg of magnolia bark extract daily for 21 days or up to 240 mg/kg for 90 days (Liu et al. 2007).
No estrogenic activity of an ethanol extract of magnolia bark was observed in a yeast assay system with human estrogen receptors (Shin et al. 2001).
The compounds magnolol and honokiol inhibited aggregation and ATP release of rabbit platelet-rich plasma induced by collagen and arachidonic acid without affecting that induced by ADP, platelet-activating factor (PAF), or thrombin. Aggregation of washed platelets was more markedly inhibited than that of platelet-rich plasma, while the aggregation of whole blood was least affected by both inhibitors (Teng et al. 1988).
Reference texts on traditional Chinese medicine indicate that magnolia bark and root bark should be used with caution in pregnancy (Bensky et al. 2004; Chen and Chen 2004).
No information on the safety of magnolia bark and root bark in lactation was identified. While this review did not identify any concerns for use while nursing, safety has not been conclusively established.
The LD50 values of a magnolia bark decoction are 6.12 g/kg after intraperitoneal administration in mice, 4.25 g/kg after intravenous administration in cats, and could not be determined at doses up to 60 g/kg after oral administration in mice (Chen and Chen 2004).
In rats fed diets containing 0, 60, 120, 240, or 480 mg/kg of magnolia bark extract daily for 21 days, no treatment-related effects in clinical observations, macroscopic or microscopic findings, or hematology, clinical chemistry, urinalysis, or organ weight measurements were observed, and there were no deaths or significant differences in body weight and weight gain (Liu et al. 2007).
In rats fed diets containing 0, 60, 120, or 240 mg/kg of magnolia bark extract daily for 90 days, no mortality, ophthalmic abnormalities, or treatment-related changes in clinical observations, hematology, coagulation, organ weight measurements, or macroscopic or microscopic evaluations were found (Liu et al. 2007).
In a bacterial reverse mutation assay and an in vivo micronucleus test, no genotoxic activity of magnolia bark extract was observed (Li et al. 2007).
No genotoxic activity of magnolia bark extract was observed in chromosomal aberration assays with Chinese hamster ovary cells and Chinese hamster lung tissue (Zhang et al. 2008).
Bensky, D., and A. Gample. 1993. Chinese herbal medicine: Materia medica. 2nd ed. Seattle: Eastland Press.
Bensky, D., S. Clavey, and E. Stöger. 2004. Chinese herbal medicine: Materia medica. 3rd ed. Seattle: Eastland Press.
Blubaugh, L.V., and C.R. Linegar. 1948. Curare and modern medicine. Econ. Bot. 2(1):73-82.
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Liu, Z., X. Zhang, W. Cui, et al. 2007. Evaluation of short-term and subchronic toxicity of magnolia bark extract in rats. Reg. Toxicol. Pharmacol. 49(3):160-171.
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Shin, T.Y., D.K. Kim, B.S. Chae, and E.J. Lee. 2001. Antiallergic action of Magnolia officinalis on immediate hypersensitivity reaction. Arch. Pharmacol. Res. 24(3):249-255.
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Zhang, B., T. Maniatis, Y. Song, et al. 2008. Evaluation of magnolia bark extract in chromosomal aberration assays. Mutat. Res. 654(2):133-137.