Saddleback Journal of Biology - Saddleback College

Spring 2010 Biology 3B Paper
The Effect of Essential Oil of Oregano (Origanum vulgare) on the In Vitro Growth of the
Bacteria Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus
Eric T. Rueda
Department of Biological Sciences
Saddleback College
Mission Viejo, CA 92692
Oregano oil (Origanum vulgare) is a very potent source of the antimicrobial substance
Carvacrol. Three bacteria, Escherichia coli, Salmonella typhimurium, and Staphylococcus
aureus, were exposed to this natural active chemical to see the effect Carvacrol has on their
growth. They were incubated at 37.0°C and data was collected by measuring the total area
of inhibition and subtracting the area of the chad paper disk. The average area of
inhibition was calculated, and although previous experiments exhibited inhibition to be
great at the small dose of 0.625 mg/mL, the results showed that the oil used only mildly
affected the growth of all three bacterial cultures.
Introduction
The immune system is a complex defense
system constantly fighting off infection and assisting
the body as it strives to achieve homeostasis. These
functions will continue regardless of the macroscopic
environment that we consciously expose ourselves to.
The body thrives under control of the brain and its
collective use of complex systems, such as the
nervous, lymphatic, and digestive systems. Electrical
and chemical messages relay from exterior or interior
stimuli and the body will react accordingly.
In the case of an unwanted microbe or
bacterium within our body, the immune system
works to destroy this parasite by surface markers,
cytokines, phagocytosis, or antibodies (Campbell et
al., 2008). Multiple cells and tissues are affected by
these changes. When the body encounters a never
before seen foreign substance, it will develop a
memory of the most efficient way to destroy it. This
system of retaining information about a certain
substance and how to manage it is called acquired
immunity. We do an excellent job micromanaging a
broad spectrum of infection, however, when a
pathogen reproduces too rapidly within our body or it
is extremely unfamiliar, we may be working to catch
up to it to destroy it. If this is the case, then one may
seek medical attention.
Medical practice has developed and grown
exponentially over an incredible amount of time.
Dating back to before 1400 B.C. (McCall et al.,
2003), society made use of simple, yet misunderstood
blood letting techniques to remove excess bile. In
modern medicine, when an infection occurs,
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Saddleback Journal of Biology
Spring 2010
prescription antibiotics are administered to the patient
in the hope that they will eliminate the parasite.
Prescription medication is used regularly and has
become a multibillion dollar industry (Wechsler,
2010). Through private investors and government
funding, this field targets FDA approval of
microbiological based medicines. Scientists draw
inspiration from nature to fuel cognition and fabricate
new medications and medical techniques. Over time,
plants and fungi have developed adaptations to
survive extreme environments and to keep them free
of certain microbes.
In particular, the oregano plant (Origanum
vulgare) (Morris 2005) makes use of two phenol
compounds: Carvacrol (C 10 H 14 O) and Thymol
(C 10 H 14 O) (Preuss et al. 2005). The main body
constructed in a benzene ring with different
appendage hydroxyl groups. Carvacrol, specifically,
has been shown through many in vitro experiments to
be a strong antibacterial compound (Nutraceuticals,
2001; Preuss et al., 2005; Ott et al., 2008; Sarac et
al., 2008; Erickson, 2009; Wong et al., 2008;
Patrone, 2010). Carvacrol has repeatedly displayed
antimicrobial activity against related bacteria found
in animals and plants, such as strains of Aspergillus,
Streptococcus, Bacillus, and Candida. These
concentrations are as low as 0.625 mg/mL (Can
Baser, 2008). Carvacrol inhibits bacteria by creating
an ionic imbalance on the cell membrane by allowing
K + ions to leak from the cell resulting in unstable
cytoplasmic pH levels and osmotic pressure. This
membrane now leaks ATP due to the breakdown of
the cellular membrane leaving the cell unable to
function. Carvacrol will also inhibit ATPase, the
enzymatic active-transport pump located on the
cellular membrane which functions to regulate proton