Baical Skullcap

The root of Scutellaria baicalensis (known as Baical skullcap or Huangqin) is an important plant medicine in China, Russia, Mongolia, Korea and Japan.  It is a prominent constituent of many Traditional Chinese Medicine formulations, including those used for allergic diseases, respiratory tract infections, pneumonia, colitis, hepatitis, dementia, Parkinson’s disease and cancer ⁽¹⁾.

Scutellaria baicalensis is botanically related to Scutellaria lateriflora (commonly known as Skullcap or American Skullcap). This skullcap species is better known in western herbal medicine, particularly for its anxiolytic and sedative properties⁽²⁾. 

Over 50 compounds have been isolated and identified from Baical skullcap, including flavonoids, terpenoids, volatile oils and polysaccharides. Most research implicates various flavonoids including baicalein (5,6,7-trihydroxyflavone) and its metabolite baicalin and wogonin, as being key active phytochemicals⁽³⁾. 

Neurological effects

Neuroprotective effects have been reported for Baical skullcap as well as baicalin, baicalein and wogonin in a range of animal models and in vitro systems^(4-6). These include protection against damage to dopamine neurons in the striatum, hippocampus and substantia nigra, suggesting a potential role in Parkinson’s disease^{(7, 8)}. Alleviation of both abnormal motor behavioural and depression-like behavior in rodent models of Parkinson’s disease, has also been reported for baicalein^{(9, 10)}.

Mitigation of brain injury in the acute stage of ischaemic stroke, and a lessening of subsequent motor dysfunction and cognitive impairment, has been reported following Baical skullcap administration in several rodent studies ^{(5, 11-14)}. Improved cognition in aged rats, vascular dementia and in animal models of Alzheimer’s disease, are other reported outcomes following administration of concentrated flavonoid extracts made from this plant ^{(15, 16)}. These include those also extracted from its stem and leaf, as per my herbblurb article posted in April, on additional uses for the aerial parts of Baical skullcap⁽¹⁷⁾. Antioxidant, anti-inflammatory, mitochondrial protective and gut microbiome modulatory effects, seem to be contributory to these various neuroprotective actions^{(5, 13, 18-20)}. 

These are impressive findings. The potential applications of Baical skullcap as part of the clinical management of ischaemic stroke in humans, a leading cause of mortality and disability, are of great interest, and clinical studies are warranted.

Effects in anxiety and depression

Anxiolytic effects have been shown in animal studies for Baical skullcap and some of its flavonoid constituents^(21-23). Baicalein, baicalin and wogonin are positive modulators of the benzodiazepine binding site of GABA_A receptors, the same sites of action of benzodiazepine drugs such as diazepam, a possible mechanism of action in anxiety disorders^{(21, 24-26)}. Unfortunately however, human studies involving its use as a single herb rather than as part of a formulation, are lacking.

Behavioural studies have also revealed a potential for Baical skullcap to alleviate prenatal stress-induced anxiety and depression-like behaviours in the offspring of mice. Mechanisms of action were related at least partially through protecting placental barrier function, reversing an overactive hypothalamic-pituitary-adrenal (HPA) axis, and reducing neurodevelopmental dysfunction⁽²⁷⁾.

I recently presented on antidepressant herbs apart from St Johns Wort, to a practitioner audience, something I’ve done several times in the past, and which I regard as a very important subject⁽²⁸⁾. Depression is a very common human illness, and as in many countries, antidepressant prescribing rates in Aotearoa New Zealand have been increasing in recent decades.  Given that as with individual drug treatments, only 60-65% of patients respond to the well researched St John’s Wort, there exists a need to research and increase our knowledge on additional herbal interventions that may be helpful as part of the management of mood disorders.  

Baical skullcap is also an ingredient in many traditional Chinese medicine formulae used to treat a range of nervous system conditions, including depression⁽²⁹⁾.  It is also sometimes combined with another widely used Chinese medicinal plant, Bupleurum (Bupleurum chinense) in these formulations⁽³⁰⁾. Favourable effects have also been shown for its root and flavonoids in animal models of depression⁽¹⁹⁾, although this in itself doesn’t necessarily indicate antidepressant properties in humans.

While much less researched than its Asian cousin, Scutellaria lateriflora has also been reported to have a mood enhancing effect after two weeks treatment, in a British crossover study involving 43 healthy participants⁽³¹⁾.

Recent clinical trial

A six week placebo-controlled clinical trial involving 180 participants with mild to moderate depression who took Baical skullcap with or without saffron, recently took place in Belgium⁽³²⁾.

This trial selected participants aged between 18 and 75 presenting with a depressive episode according to the DSM-5 definition, experiencing mild to moderate depressive symptoms using the Beck Depression Inventory, and having had a depressive episode within the last two years. Those with other mental health conditions or those taking any psychotropic treatment, were excluded.

Four treatment arms were used. The first group (n=42) took an extract of Baical skullcap alone, the second (n=43) a Saffron extract alone, the third (n=48) a combination of these two phytomedicines, and the fourth (n=47) a placebo capsule daily, for 42 days. The Saffron used was standardised for its content of crocins and safranal, and the Baical skullcap was standardised for baicalin.

Participants were assessed prior to commencing treatment, then after three and six weeks of treatment, and at two weeks following the end of treatment. Primary outcomes were the standardized depression scale measured using the Beck Depression Inventory and Hamilton Depression score. Subjects also completed other questionnaires assessing positive and negative affects, anxiety levels, quality of life, and wellbeing levels.

Improvements occured in both mood and sleep in all four groups, particularly between the 21 day and 42 day treatment period. While differences between groups in terms of the depression measurements weren’t statistically significant, anxiety levels were decreased with all three treatment but not the placebo group. Scores for Emotional Assessment, a self-rated scale describing feelings and emotions, were also improved but maintained at 56 days only for the Baical skullcap and combined Baical skullcap and Saffron treated groups. Minimal adverse effects were reported across all treatment groups. 

While this study failed to reveal evidence of an antidepressant effect for Baical skullcap, Saffron also failed to achieve this to statistical significance, despite several trials having reported such effects for it already ⁽³³⁾. Methodological issues such as low participant numbers and/or the dosages used being too low, may have been contributory. The study did however, produce data suggesting an anti anxiety or anxiolytic effect, and overall improvement in self rated feelings and emotions. Given the link  between chronic and poorly controlled anxiety and a predisposition to depression, further studies with larger numbers and using different dosages are recommended.

This is one of the first well designed clinical trials published in an English language journal implicating an anxiolytic and possible antidepressant effect for Baical skullcap.

References:

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