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Editor’s note: While conducting
research on skullcap, ABC’s Chief Science Officer Stefan Gafner, PhD, located a
doctoral dissertation from the United Kingdom that was completed in 2012. Although
it has been more than a year since this was published, and it is not available
on some of the usual medical databases, ABC believed that some ABC members will
find it relevant and of interest.
In 2012, the University of
Westminster in London published the 257-page doctoral dissertation of medical
herbalist Christine Brock, PhD, titled “American Skullcap (Scutellaria lateriflora L): A Study of
its Effects on Mood in Healthy Volunteers.”1 This text represents
one of the most detailed works published to date about all aspects of skullcap (also
spelled scullcap) as a medicinal agent.
The general aims of the research, on which Dr. Brock based her dissertation,
were to authenticate a whole skullcap extract and to conduct a randomized,
controlled clinical study to evaluate its effectiveness in reducing mood
disturbances and related conditions, with a particular focus on anxiety and
stress. The introductory work contains a short section on the problems and
frequency of anxiety in the United Kingdom, which includes factors that lead to
anxiety, current therapeutic solutions, and the neurological systems involved
in the development of anxiety. 
The second chapter provides a detailed literature review on the history of skullcap
use. It describes preparations and dosages, the safety profile, side effects,
contraindications, as well as interactions. The author concludes that the use
of skullcap is considered relatively safe based on the absence of adverse events
at normal therapeutic dosages and that there are no known contraindications or
interactions with conventional pharmaceutical drugs. Chapter 2 also discusses
current knowledge of skullcap chemistry and contains an up-to-date status on
research (in vitro, in vivo, and clinical studies) on this often-neglected
medicinal plant.
Next, there is a chapter on the current use of skullcap, its perceived effectiveness, and its safety as
observed by practitioners of herbal medicine in the British Isles. The data was
compiled from an email survey conducted among practitioners in the United Kingdom
and Ireland. Results of the survey suggest that S. lateriflora is highly
regarded as an effective intervention for reducing anxiety and stress and is
commonly prescribed for these conditions and related diseases. However, a word
of caution has to be added as the response ratio to the survey was low, which
makes it difficult to evaluate the significance of these findings. Details of
this survey were published in the Journal of Herbal Medicine in
2012.2
Chapters
4 and 5 summarize issues surrounding the quality control of S. lateriflora herb. The fourth chapter contains
details on the microscopic and macroscopic features of skullcap and some of its
documented adulterants, including Canada germander (Teucrium canadense, Lamiaceae) and Wall germander (T. chamaedrys).* Chapter 5 presents the high-performance
liquid chromatography (HPLC) methodology used by Dr. Brock to authenticate the
powdered herb based on chemical profiling, and there is an extensive section on
the history of adulteration of this plant, which, unfortunately, is ongoing. In
this regard, the importance of proper authentication of botanical materials
cannot be overstated and even peer-reviewed studies have to be viewed with a
critical eye. As an example, Dr. Brock reports on a study on essential oil
contents, which — according to Yaghmai (1988)3 — were obtained from S.
lateriflora growing on riverbanks and marshes in northern Iran. However,
the species known to grow in this region is actually S. pinnatifida.4
Details on the authentication were published in the Journal of Herbal Medicine in 2013.5
Chapters 6, 7, and 8 contain the materials and methods, results, and
discussion sections of a small, randomized, double-blind, placebo-controlled,
crossover study in 43 human subjects. However, only 31 completed the study;
reasons for dropout included non-adherence to the protocol (n=2), start of
conventional anti-depressant therapy (n=2), illness (n=2), scheduling conflicts
(n=2), or personal circumstances (n=2). Two subjects abandoned the trial
without offering any reason.
The subjects received either freeze-dried S. lateriflora (350 mg) or nettle
(Urtica dioica, Urticaceae) leaves
as a placebo (300 mg) three times daily for 14 days. Nettle was
chosen as the placebo due to its similar appearance to the skullcap capsules,
established safety record, and absence of any effects on mood. There was a seven-day
washout period prior to crossover. The author evaluated the effects using the
Beck Anxiety Inventory (BAI) and the Profile of Mood States (POMS) questionnaires.
Liver function (serum alanine aminotransferase levels), blood pressure, and
pulse were assessed at the same time.
Most of the results of the subjective measures showed no difference between S. lateriflora treatment and placebo.
However, the author found an enhanced effect of S. lateriflora compared
to placebo in those who took the placebo first (n=15) and an enhanced effect of
placebo compared to S. lateriflora for those who took S. lateriflora first
(n=16), from inspection of both BAI and the POMS factors. The enhanced effect
of placebo may be due to an insufficient washout in subjects who started with
the skullcap treatment and, in this case, would indicate a mild anxiolytic
effect of the skullcap treatment in some of the subjects. No significant
differences were found in liver enzyme levels, blood pressure, or pulse
indicating the absence of acute toxicity. No participants experienced any
serious adverse reactions during the study. Minor adverse events in the S. lateriflora treatment group included
vivid dreams (n=1), feeling “spaced out” (n=1), mild digestive disturbances
(n=4), and a constant taste of salt in the mouth (n=1). Results of the clinical
study were published in Phytotherapy
Research in 2013.6
Dr. Brock’s dissertation is accessible through the WestminsterResearch online digital archive at the University
of Westminster, here: http://westminsterresearch.wmin.ac.uk/12194/1/Christine_BROCK.pdf. Copyright and Moral Rights remain
with the authors and/or copyright owners. Users
are permitted to download and/or print one copy for non-commercial private
study or research. * Adulteration of skullcap herb has been well
documented by Steven Foster in his 2012 article, “The
Adulteration of Skullcap (Scutellaria
lateriflora) with American Germander (Teucrium
canadense),” in HerbalGram
issue 93.
—Stefan Gafner, PhD
References
1. Brock CA. American
skullcap (Scutellaria lateriflora
L.): a study on its effects in healthy volunteers. PhD thesis. London, United
Kingdom: University of Westminster; 2012. Available here.
2. Brock
C, Whitehouse J, Tewfik I, Towell T. The use of Scutellaria
lateriflora: a pilot survey amongst herbal medicine practitioners. J Herbal Med. 2012;2(2):34-41. Abstract available here.
3. Yaghmai MS. Volatile constituents of Scutellaria lateriflora. Flavour
Fragr J. 1988;3(1):27-31. Abstract available here.
4. Barceloux DG. Medical Toxicology of Natural Substances: Foods, fungi,
medicinal herbs, plants, and venomous animals. Hoboken, NJ: John Wiley
& Sons Inc.; 2008.
5. Brock
C, Whitehouse J, Tewfik I, Towell T. Identity issues surrounding American
skullcap (Scutellaria lateriflora) and an optimised high performance
liquid chromatography method to authenticate commercially available products. J Herbal Med. 2013;3(2):57-64. Abstract
available here.
6. Brock
C, Whitehouse J, Tewfik I, Towell T. American skullcap (Scutellaria
lateriflora): a randomised, double-blind placebo-controlled crossover study
of its effects on mood in healthy volunteers.
Phytotherapy Res. 2013;DOI: 10.1002/ptr.5044. Abstract available here. |