Essential Oils in the Treatment of Intestinal Dysbiosis: A Preliminary ...

Alternative Medicine Review Volume 14, Number 4 2009
Essential Oils in the Treatment
of Intestinal Dysbiosis: A
Preliminary in vitro Study
Jason A. Hawrelak, PhD, BNat(Hons); Trudi Cattley, BSci;
Stephen R Myers, PhD, BMed, ND
Abstract
INTRODUCTION: Dysbiosis is associated with a number of
gastrointestinal and systemic disorders. There is a need for
selectively acting antimicrobial agents capable of inhibiting
the growth of potentially pathogenic microorganisms, or those
found lo be out of balance, while not negatively impacting the
bulk gastrointestinal tract microflora. OBJECTIVE; The purpose
of this in vitro study is to examine the potential of a selection
of essential oils as agents to treat dysbiosis. MATERIALS AND
METHODS: Eight essential oils were examined using the agar
dilution method, including Carum cam, Citrus aurantium var.
amara, Foeniculum vulgäre dulce, Illicium verum, Lavandula
angustifotia, Mentha arvensis, Menffta x piperita, and
Trachyspermum copticum. Doubling dilutions of the essential
oils were tested against 12 species of intestinal bacteria, which
represent the major genera found in the human gastrointestinal
tract (GIT). RESULTS: Carum carvi, Lavandula angustifolia,
Trachyspermum copticum, and Dims aurantium var. amara
essential oils displayed the greatest degree of selectivity,
inhibiting the growth of potential pathogens at concentrations
that had no effect on the beneficial bacteria examined.
CONCLUSION:The most promising essential oilsforthe treatment
of intestinal dysbiosis are Carum carvi, Lavandula angustifolia.
Trachyspermum copiicum. and Citrus aurantium var. amara. The
herbs from which these oils are derived have long been used
in the treatment of gastrointestinal symptoms and the in vitro
results of this study suggest that their ingestion will have little
detrimental impact on beneficial members of the GIT microflora.
More research is needed, however, to investigate tolerability and
safety concerns, and verify the selective action of these agents,
(^/tern Med Rev 2009:14(4):380-384)
Introduction
Intestinal dysbiosis has been defined as qualitative
and quantitative changes in the gastrointestinal
flora, their metabolic activities, and/or their local di.stribution
that produces harmful efîects on the host.'
Dysbiosis has been associated with a number of conditions,
including atopic eczema,^' rheumatoid arthritis,**
inflammatory bowel disease,^'' and irritable bowel syndrome
(IBS)/"
Evidence suggests a possible etiological role
for dysbiosis in IBS, including epidemiological studies
that have found a significantly increased risk of IBS following
antibiotic use'" and bacterial gastroenteritis.""
Other evidence comes from colonie fermentation studies,
which have found patients with IBS produce significantly
greater amounts of colonie hydrogen than
healthy controls'' and have altered fecal short-chain
fatty acid profiles.'^
Jason A Hawrelak, PhD(SCU), BNat(Hons) - School of Health & Human
Sciences. Southern Cross University; Goulds Naturopathica
Correspondence address: 73 Liverpool St, Hobart TAS Australia 7000
Email: drjahl3@yahoo.com
Trudi Cattley. BSci - Australian Centre for Complementary Medicine Education
and Research, a joint venture of the University of Queensland and Southern
Cross University
Stephen R Myers, PhD(UON), BMed. ND - School of Health & Human Sciences,
Southern Cross Univereity: NatMed-Research
Page 380

Alternative Medicine Review Volume 14, Number 4 2009
Tliete is also direct evidence that the gastrointestinal
tract (GIT) microflora of IBS patients differs from
that of healthy individuals. An older study found IBS patients
have significantly fewer coliform bacteria, lactobacilii,
and bifidobacteria than controls.'' These findings are
supported by more recent smdies that found lower fecal
concentrations of bifidobacteria in IBS patients, as well as
lower levels of lactobacilli in diarrhea-predominant IBS
patients/
Whether this dysbiosis plays a role in the symptomatology
of IBS has not been conclusively proven.
However, the efficacy of probiotic agents in treating this
condition"'''^ in combination with evidence outlined
above suggests a possible etiological role.
Thus, there is a need for selectively acting antimicrobial
agents capable of inhibiting the growth of potentially
pathogenic microorganisms, or those found to
be out of balance, while not negatively impacting the bulk
GIT microflora. In addition, since such agents may be
prescribed concurrent with probiotics, it is beneficial that
the antimicrobial agent not interfere with the growth of
the supplemented probiotic organisms (e.g., lactobacilli
and bifidobacteria).
Objective
The objective of this study is to examine the potential
of a selection of essential oils as agents to treat
intestinal dysbiosis. The essential oils investigated were
chosen from carminative herbs traditionally used in the
treatment of gastrointestinal disorders, including Carum
carvi (caraway). Citrus aurayitium var. amara (bitter orange),
Foeniculum vulgäre dulec (sweet fennel), Illicium
verum (star anise), Lavandula augustifolia (lavender),
Mentha arvensis (Japanese peppermint), Mentha xpiperita
(peppermint), and Trachyspermum copticum (ajowan).
Materials and Methods
Essential Oils
Pure essential oils were purchased from two
sources: New Directions (Sydney, NSW, Australia) and
Sydney Essential Oil Company (Sydney, NSW, Australia).
Tlie essential oils purchased from New Directions included
Carum carvi, Foeniculum vulgäre dulce, JlHcium verum,
Mentha x piperita, and Trachyspermum copticum. Mentha
arvensis, Lavandula angustijoUa, and Citrus aurantium var.
amara were sourced from Sydney Essential Oil Company.
Organisms and Growth Conditions
Microorganisms were obtained from the Australian
Collection of Microorganisms, University of
Queensland, with the exception of Bißdohacterntm hißdum
and Bißdobacterium lotigum, which were obtained
from the CSIRO Starter Culture Collection. Organisms
were as follows: Bacteroides jragilis ACM 4768,
Candida aWicans ACM 4574, Clostridium Mfficile ACM
5047, Clostridium perfringcns ACM 5116, Enterococcus
faecalis ACM 4769, Escherichia coii ACM 1083, Eubacterium
limosum ACM 383, Lactobacillus acidophilus
ACM 547, Lactobacillus plautarum ACM 96, Bißdobacterium
bißdum CSCC 1903, Bißäobacterium longum
CSCC 5188, and Peptostreptococcus anaerolmts ACM
5059. These organisms represent the major genera ot
microorganisms found in the human GIT.^"
Organisms were maintained on Reinforced
Clostridial Agar (Oxoid), Wilkens-Chalgren Anaerobe
Agar (Oxoid), Mueller Hinton Agar (Oxoid), or De-
Man Rugosa Sharpe Agar (Oxoid). Inoculum was prepared
by suspending colonies from 24-72 hour cultures
in sterile saline. Using a CrystalSpec Nephelometer'"
(Becton Dickinson & Company, Maryland, USA) suspensions
were standardized to a 0.5 McFarland standard,
giving ~10" colony forming units (CFU) per mL
for the bacteria and 10' CFU per mL for Candida albicans.
Aerobic bacteria were diluted 1:10 in saline prior
to inoculation.
Minimum Inhibitory Concentration
(MIC) Determination
MICs were determined by agar dilun'on using
Mueller Hinton Agar for anaerobic organisms,
Wilkens-Chalgren Anaerobe Agar for all anaerobes
except the two Lactobacillus species, which were grown
on DeMan Rogosa Sharpe Agar. A series of twofold
dilutions of each essential oil (from 2.0-0.004 percent
volume per volume [v/v]) was prepared and placed
in sterile Petri dishes. Each dilution was placed into
three Petri dishes and one ot three agars was added to
each plate and mixed thoroughly. Tween-20 (Sigma)
was incorporated into the agar at a concentration of
0.5 percent (v/v) to enhance solubility. Clindamycin,
neomycin, ampicillin, and ketoconazole (in doubling
dilutions from 64 to 0.05 fig/mL) were used as positive
controls, while dimethylsulfoxide (DMSO), Tween-20,
Page 381

Alternative Medicine Review Volume 14, Number 4 2009
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Alternative Medicine Review Voiume 14, Number4 2009
Discussion
Tlie antimicrobial properties of eight essential
oils were evaluated against common members ofthe human
gastrointestinal tract microflora. Tlie essential oils
were chosen based on the traditional uses of the herbs
from which the essential oils are derived. For example,
Mentha x piperita,^ Carum carvip Foeniculum vulgäre
dulce/'' Mentha arvensis,"'' Illicium veruin,^'' and Lavandula
angustijolia~ have long been utilised as carminatives
in Western herbal medicine. Citrus aurantium var.
amara has a long history of use in traditional Chinese
medicine for gastrointestinal antispasmodic and carminative
activities,'" and I'rachyspcrmum copticum has
been used in Ayutvedic medicine to relieve colic, flatulence,
diarrhea, and dyspepsia.'"^
Tlie most selectively acting oils were Carum
carvi, Lavandula angustijolia, and Trachyspermum copticum,
which at one concentration inhibited the growth
of a number of potentially pathogenic microorganisms
{Candida alhicans, Clostridium spp., Bactcroides fragiUs),
while having no impact on the tour species of beneficial
microbes examined. Citrus aurantium var. amara essential
oil was also selective in its activity. At concentrations
that inhibited the growth o(Bacteroidcsjragilis and Clostridium
perfringens, no other species of bacteria or fungi
was affected. Hence, these oils appear to have the most
potential in the treatment of dysbiosis, where their use
could help balance the GIT microflora.
IBS patients have been found to have lower
fecal counts of lactobacilii, bifidobacteria, and coliform
bacteria/'^ The results of this study suggest that Carum
carvi, Lavandula angustijolia, Trachyspermum copticum,
and Citrus aurantium var. amara essential oils could be
used in the treatment of IBS without negative ramifications
on already disordered GIT microflora.
Other extracts were equally effective in killing
both beneficial and potentially pathogenic members ot
the GIT flora, including Mentha x piperita, Focnicidum
vulgäre dulce, Mentha arvensis, and ¡llicium verum essential
oils. Foeniculum vulgäre dulce and Illicium verum essential
oils were, however, less active toward lactobacilii
than bifidobacteria or the potentially pathogenic organisms.
Nonetheless, in concentrations that inhibited
the growth ot potentially pathogenic microbes, some
beneficial bacteria were also inhibited.
Of these agents, only Mentha x piperita is commonly
prescribed, due to its demonstrated efficacy in
IBS.^"'" The study results suggest that the ingestion
of M. X piperita essential oil may inhibit the growth oí
some common members ofthe GIT microflora. Until
more research is conducted ascertaining the in vivo effects
of M. X piperita essential oil on GIT microflora,
it is prudent to prescribe a probiotic agent (containing
both bifidobacteria and lactobacilii) concurrently witli
M. X piperita essential oil.
Generalisation of these results to in vivo situations
is limited, however, by the nature of the study
design. It is unknown what impact the processes of
digestion and absorption will have on an essential oil's
antimicrobial activity. Thus, the results of this in vitro
experiment need to be interpreted cautiously and seen
as solely preliminary. In vivo studies are needed to verify
the selectivity of action displayed by these essential oils,
as well as to address tolerability and safety concerns.
Future in vitro studies should take into account
other common members of the GIT flora, such as Ruminococcus
spp.. Streptococcus spp., Peptococcus spp.,
Actinomyces spp., and Fusobacterium spp.,"" as well as
gas-producing microbes like methanogens and sulfatereducing
bacteria.^^ The effects of carminatives on these
latter two groups of bacteria would be particularly interesting.
However, the results would still be preliminary
and would not provide definitive evidence ot in
vivo effectiveness. Definitive answers await randomized,
double-blind, placebo-controlled human trials utilizing
the "gold standard of niicrofiora assessment techniques
- 16S ribosomal RNA sequencing - to accurately delineate
changes in the GIT microfiora after ingestion of
these essential oils.''
Conclusion
The most promising essential oils for the treatment
of intestinal dysbiosis appear to be Carum carvi,
Lavatidula angustijolia, Trachyspermum copticum, and
Citrus aurantium var. amara. The herbs from which these
oils are derived have long been used in the treatment
of gastrointestinal symptoms and these in vitro results
suggest that their ingestion will have little detrimental
impact on beneficial GIT microflora. More research is
needed to investigate tolerability, safety concerns, and
verification of selectivity.
Page 383

Alternative Medicine Review Volume 14, Number 4 2009
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