Magnolia bark acts like antidepressant



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January 8, 2008  
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CM NEWS – The two active ingredients of the bark of magnolias that have generated research interests to their anti-tumour and anti-inflammatory activities also exhibits antidepressant-like effects, a new study says.

Honokiol (???) and magnolol (????) are the main constituents simultaneously identified in the barks of Magnolia officinalis, which have been used in traditional Chinese medicine to treat a variety of respiratory and intestinal disorders.

What are the traditional applications of magnolia in TCM? Magnolias are a source of Chinese herbal materials that are widely used internationally. There are two basic materials of frequent application: the bark of magnolia, called houpu (??), and the flower bud of a another magnolia, called xinyi (???) or xinyihua (???).

The flower bud is used almost exclusively for treatment of sinus congestion and sinus headaches, and is taken orally or applied topically (for example, by inhaling the essential oils or placing some of the herb powder or extract in the nose).

Magnolia bark, on the other hand, has a very wide range of applications. Many of the formulations with magnolia bark are aimed at treatment of lung disorders (including cough and asthma) or intestinal disorders (infections and spasms); magnolia bark is also a common ingredient in the treatment of abdominal swelling of various causes and edema.

magnolia.gifMore recently, magnolol and honokiol have generated much scientific interests as their potential in treating a number of cancers (see later part of this article). Magnolol and honokiol have also long been used in treating neurosis, anxiety, stroke, fever and headache.

In the present study, a team of researchers at the Nanjing University, China looked at the antidepressant-like effects of oral administration of the mixture of honokiol and magnolol in rats with laboratory-induced depression.

The stress models used in the study greatly reduced the rats’ serotonin levels and platelet levels of adenylyl cyclase. Adenylyl cyclase is an enzyme whose activities have been shown to be lower among depressed patients.

What is serotonin? Serotonin, or 5-hydroxytryptamine, is a hormone found in the brain, platelets, digestive tract, and pineal gland. It acts both as a neurotransmitter (a substance that nerves use to send messages to one another) and a vasoconstrictor (a substance that causes blood vessels to narrow). A lack of serotonin in the brain is thought to be a cause of depression.

Serotonin is also believed to play an important role in the regulation of anger, aggression, body temperature, mood, sleep, vomiting, sexuality, and appetite.

If neurons of the brainstem that make serotonin – serotonergic neurons – are abnormal in infants, there is a risk of sudden infant death syndrome (SIDS). Low levels of serotonin may also be associated with intense religious experiences.

The researchers then fed the rats wtih a mixture of honokiol and magnolol. The main results of the study found that the mixture at 20 and 40 mg/kg significantly attenuated lab-induced decreases of serotonin levels in frontal cortex, hippocampus, striatum, hypothalamus and nucleus accumbens.

Also, the mixture markedly increased the levels of 5-HIAA, a breakdown product of serotonin, in frontal cortex, striatum and nucleus accumbens at 40 mg/kg and in frontal cortex at 20 mg/kg in these rats with lab-induced depression.

Furthermore, the mixture of honokiol and magnolol reduced elevated corticosterone concentrations in serum to normalize the hypothalamic-pituitary-adrenal (HPA) hyperactivity in these rats. It also reversed the lab-induced reduction in platelet AC activity.

These results suggested that the mixture of honokiol and magnolol possessed potent antidepressant-like properties in behaviours involved in normalization of biochemical abnormalities in brain serotonin, serum corticosterone levels and platelet AC activity in rats with lab-induced depression.

“Our findings could provide a basis for examining directly the interaction of the serotonergic system, the HPA axis and AC-cAMP pathway underlying the link between depression and treatment with the mixture of honokiol and magnolol,” the researchers conclude.

[Prog Neuropsychopharmacol Biol Psychiatry. 2007 Nov 28]


BACKGROUNDER – examples of other functions of magnolia in recent scientific research

Anti-fungal, anti-inflammatory:Magnolol displays an array of activities including antifungal, antibacterial, and antioxidant effects. Magnolol has also been shown act as a natural inhibitor to acyl-CoA: cholesterol acyltransferase (ACAT).Magnolol has been shown to demonstrate anti-inflammatory activity by interfering with NF-kB signaling. It also appears to have anti-inflammatory properties related to vascular disorders such as atherosclerosis due to its ability to inhibit IL-6-induced STAT3 activation. (source)

On the gastric system:

The inhibitory effect of magnolol and honokiol on contractility of the smooth muscles of isolated gastric fundus strips of rats and isolated ileum of guinea pigs is associated with a calcium-antagonistic effect. Magnolol and honokiol can improve the gastric emptying of a semi-solid meal and intestinal propulsive activity in mice. (source)

On colorectal cancer:

With its few toxicity to normal cells and potent anticancer activity in vitro and in vivo, honokiol might be a potential chemotherapy candidate in treating human colorectal carcinoma. (source)

On B-cell chronic lymphocytic leukemia:

B-cell chronic lymphocytic leukemia (B-CLL) remains an incurable disease that requires innovative new approaches to improve therapeutic outcome. Honokiol is a natural product known to possess potent antineoplastic and antiangiogenic properties. We examined whether honokiol can overcome apoptotic resistance in primary tumor cells derived from B-CLL patients. Honokiol induced caspase-dependent cell death in all of the B-CLL cells examined and was more toxic toward B-CLL cells than to normal mononuclear cells, suggesting greater susceptibility of the malignant cells. (source)

Honokiol can induce a cell death distinct from apoptosis in HL60, MCF-7, and HEK293 cell lines. The death was characterized by a rapid loss of integrity of plasma membrane without externalization of phosphatidyl serine. (source)

On prostate cancer:

Honokiol causes G0-G1 phase cell cycle arrest in human prostate cancer cells in association with suppression of retinoblastoma protein level/phosphorylation and inhibition of E2F1 transcriptional activity. (source)

On cardiovascular conditions:

Honokiol can protect brain against ischaemic reperfusion injury and preserve mitochondrial function from oxidative stress. Administration of honokiol resulted in significant reductions in brain infarct volume and in synaptosomal production of reactive oxygen species. The decreases in synaptosomal mitochondrial membrane potential, synaptosomal mitochondrial metabolic function and tissue Na+, K+-ATPase activities observed in the ischaemic brains were also attenuated by honokiol treatments. (source)

More info on depression here.