Literature Review


Natural plants have oils that are known to act as natural
antibiotics, but what the scientific and medical world don’t know is how
effective these essential oils are when compared to the commonly prescribed
pharmaceutical antibiotics. The
elements in essential oils come from distilling or extracting various parts of
plants, including the flowers, leaves, bark, roots, resin and peels. Essential
oil benefits come from their antioxidant, antimicrobial and anti-inflammatory
properties.  These therapeutic oils are
rapidly growing in usage because they act as natural medicine with minimal side
effects. Essential oils are generally applied
to your skin in the desired areas or areas of discomfort.

This type of medicine gets absorbed into your body in some
profound ways. The skin is relatively permeable to fat soluble substances and
relatively impermeable to water soluble substances (Miller, 2015). Essential
oil molecules are so miniscule that when applied directly onto the skin they can
pass through the strateum corneum (the outer layer of the epidermis) (Miller,
2015). From here the oil molecules passes through dermis (thick layer of living
tissue below the epidermis containing blood capillaries, nerve endings, sweat
glands, hair follicles, and other structures), into the capillaries and into
the bloodstream (Miller, 2015).  Absorption of essential oils also happens
through the hair follicles and sweat ducts.  There are many factors that affect absorption
of an essential oil molecule; both rate of circulation and the temperature of
the skin affect absorption rate; higher rate of circulation and warmer temperature
of the skin increase blood flow to the surface, therefore increasing the skin’s
ability to absorb the oil (Miller, 2015). Circulation and warmth can be increased
by massage of the skin.  The larger the
area of skin that is covered equates to more essential oils that will be
absorbed. The permeability of the skin is also a factor; thinner skin e.g.:
skin behind the ears and the inside of the wrists are very permeable (Miller,
2015). The palms of the hands and feet, armpits and scalp will more readily
absorb oil molecules than the arms, legs, belly, back etc. (Miller, 2015). Oils
are also easily absorbed through cuts, scrapes and abrasions, burns, eczema etc.
(Miller, 2015). Clean skin pores that are free of dirt have high rates of
absorption (Miller, 2015). The other factor to consider when applying essential
oils to the skin is the viscosity of the carrier oil in which the oil
is diluted (Miller, 2015). Sweet almond and grapeseed oil are less viscous and
will penetrate the skin more easily than thicker olive or avocado oils.

Another way for essential oils to enter the body is through inhalation,
the molecules rise to the top of the nose and meet the olfactory mucous
membrane. The olfactory membrane has thousands of receptors that identify the
smell and thus, the sensory stimulation is sent through the olfactory bulb,
which acts as an amplifier, through the olfactory nerve into the limbic system
of the brain (Miller, 2015).  The limbic system
of the brain deals with emotional and psychological responses. The limbic
system is prompted by nerve impulses. The scent is compared to a known scent,
compared and labeled, thus we can have memories associated with the specific scents
and react emotionally and physically through our autonomic nervous system, the
part of the nervous system that controls bodily functions not consciously
directed, such as breathing, the heartbeat, and digestive processes (Miller,
2015). These stimulated responses are determined by the specific qualities of
the essential oil being used and can range from relaxing to stimulating the brain
and body. The nerve impulse in the limbic system leads to other areas of the
brain that are responsible for secreting hormones and regulating body functions
(Miller, 2015).

One of the essential oils we are going be testing is lemongrass (Cymbopogon citratus). Lemongrass essential oil is used to relieve muscle pain,
externally to kill bacteria, ward off insects, and reduce body aches, and
internally to help your digestive system (Prabuseenivasan, Jayakumar, &
Ignacimuthu, 2006).  Lemongrass is a herb
that belongs to the grass family of Poaceae. Lemongrass
oil has a light and fresh lemony smell with earthy undertones; it is
stimulating, relaxing, soothing, and balancing system (Prabuseenivasan,
Jayakumar, & Ignacimuthu, 2006). The compounds that make up
lemongrass essential oil are known to have anti-fungal,
insecticidal, antiseptic, and anti-inflammatory properties.  Lemongrass oil has shown to prevent the growth/reproduction
of some bacteria and yeast (Smith-Palmer, Stewart, & Fyfe, 1998).  It contains substances that are used to
alleviate muscle pain, reduce fever, and to stimulate uterus and menstrual

Another oil we will be testing is that of the plant (Eucalyptus globulus). The health benefits
of eucalyptus oil are well-known and wide-ranging, and its properties
include being an anti-inflammatory, antispasmodic, decongestant, deodorant,
antiseptic, antibacterial, stimulating, and other medicinal qualities.
Eucalyptus essential oil is colorless and has a distinctive taste and
odor. Eucalyptus essential oil has antiseptic qualities because
of its germicidal quality. Upon exposure to air, ozone is formed which is a
well-researched antiseptic. Eucalyptus essential oil is effective for treating
several respiratory problems including cold,
cough, running nose, sore throat, asthma, nasal congestion, bronchitis,
and sinusitis. Eucalyptus oil is antibacterial, antifungal, antimicrobial,
antiviral, anti-inflammatory and decongestant in nature, which makes it a good
ingredient in many medicines that treat respiratory problems. One very
important reason that many people use eucalyptus oil is that it creates a
cooling and refreshing effect. Normally, people suffering from certain
conditions and disorders are slightly sluggish. Eucalyptus oil, a
stimulant, removes exhaustion.

essential oil gives a cooling sensation and has a calming effect on the body,
which can relieve sore muscles when used topically on areas of discomfort
(Prabuseenivasan, Jayakumar, & Ignacimuthu, 2006). It also has
antimicrobial properties, so it can help freshen bad breath and soothe digestive
issues. Peppermint is a hybrid species of spearmint (Mentha spicate) and water mint (Mentha
aquatica). The essential oils of peppermint are gathered
by steam distillation of the fresh aerial parts of the flowering plant. The most
active ingredients include menthol (35–45%) and menthone (10–30%). Clinically
speaking, peppermint oil is recommended for its anti-nausea benefits and
soothing effects on the gastric lining and colon because of its ability to
reduce muscle spasms (Prabuseenivasan, Jayakumar, & Ignacimuthu, 2006).

antibiotics have been known to cause long-term medical problems, such as: liver
problems, indigestion, significant decrease in beneficial bacteria, “good
bacteria”, upset/sensitive stomach, and, most importantly, eventual antibiotic
resistance.  The usage of large numbers
of antibiotics over the past three decades, in the community and hospitals, has
fueled this crisis of antibiotic resistance in harmful bacteria (Neu,
1992).  Bacteria have become resistant to
antimicrobial agents as a result of chromosomal changes or the exchange of
genetic material via plasmids and transposons (Neu, 1992).  This
antibiotic resistance by harmful bacteria has led to deadlier bacterial
infections varying from the common flu to pneumonia.  The most widely cited case of antibiotic
resistance is tuberculosis – a bacterial infection of the lungs (Noble,
n.d.).  This infection of the lungs is
caused by bacteria, Mycobacterium
tuberculosis, that was once highly responsive to antibiotic treatment, but
that is not the case anymore (Noble, n.d.).   The antimicrobial activity of plant oils and
extracts has been recognized for many years. However, few investigations have
compared large numbers of oils and extracts using methods that are directly
Based on the benefits and lack of side effects of essential oils, the
purpose of the experiment is to determine if treatment by an essential oil, or
combination/blend of essential oils, is more effective in inhibiting the
growth/reproduction K12 E. coli, than commonly used pharmaceutical antibiotics.
In the experiment, the mode of action is to inoculate
the bacteria in petri dishes, containing nutrient agar, then placing a pieces
of filter paper, that have been soaked in the solution of the desired IV, the
essential oil or combination/blend of essential oils.  After time increments, increasing in 30
minutes, from placement of filter papers, containing the variations of
essential oils, up to 5 hours the DV, zone of inhibition, of the experiment
will be measured.  Once again, the DV,
zone of inhibition, will be measured at 48 hours to observe the long term
affect of essential oils on inhibiting the growth/reproduction of K12 E.
coli.  Zone inhibition will be measured
by using a ruler to measure the diameter around each of the filter paper
circles, containing the essential oils; a larger zone of inhibition directly
correlates to the ability of an essential oil or blend of essential oils to
inhibit the growth/reproduction of K12 E. coli. 
The zones of inhibition created by the filter paper circles containing
essential oils will be compared to the zone of inhibition created by the filter
paper circles containing the constant, a solution containing Neosporin (1g:
20mL), a topical antibiotic.  The anticipated
result is that the combination/blend of lemongrass (Cymbopogon citratus) and white thyme (Thymus serpyllum) essential oils will be the most effective
treatment in inhibiting the growth of K12 E. coli (Escherichia coli). 

important characteristic of essential oils and their components is their
hydrophobicity, which enable them to partition the lipids of the bacterial cell
membrane and mitochondria, disturbing the cell structures and rendering them
more permeable (Prabuseenivasan, Jayakumar, & Ignacimuthu, 2006).  Extensive leakage from bacterial cells or the
exit of critical molecules and ions will lead to death (Prabuseenivasan,
Jayakumar, & Ignacimuthu, 2006). 
This leads the claim that the combination of lemongrass and white thyme
is predicted to be the strongest because both lemongrass and white thyme oils
are highly antiseptic, highly antioxidant, highly hydrophobic, and lemongrass
essential oils significantly reduce colony and spore development of pathogens
(Tzortzakis & Economakis, 2007). 

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