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Antibacterial Activity Of The Spice Elettaria cardamomum
Shervin Afghani and Imad Mugatash
Biology Department, Skyline College, San Bruno CA
Abstract
Methods
Results
Discussion & Conclusion
Elettaria cardamomum, green cardamom, has been long used in south Asia
both for medical purposes and as a seasoning. This plant is used in
traditional botanic medicine to treat infectious disease such as pulmonary
tuberculosis and lung congestion. Additionally, green cardamom is used for
its important positive effects on the gastric system, blood pressure, and “gut
modulatory”. The high rate of natural selection for mutations and genome
rearrangement in bacteria resulting in antibiotic resistance, has forced a
search for new antibiotics. Thus, after years of extensive research on soil
microorganisms able to produce antibiotics, we need to look for new sources
of antibiotics such as plants. Our hypothesis is that E. cardamomum can
inhibit bacterial growth. We prepared aqueous, methanolic, ethanolic, and
acetone extracts of E. cardamomum seeds and seed shells. The extracts were
filtered, dried, and reconstituted to 833 mg/mL in their respective solvent.
Each extract was tested against Escherichia coli (gram-negative),
Staphylococcus aureus (gram-positive), Bacillus subtilis (gram-positive),
Streptococcus mutans (gram-positive) and Pseudomonas aeruginosa (gramnegative) bacteria. The well diffusion assay method was used to test for
antimicrobial activity. After incubation at 35°C for 48-72 hours, the 100%
methanolic extracts and the 70% ethanolic and acetone extracts inhibited the
growth of all five bacteria and inhibition of S. aureus, E.coli, B. subtilis,
S.mutans bacteria with 100 % methanolic and 70% ethanolic and acetone
extracts was observed. The acetone, methanol, and ethanol extracts killed all
five bacteria with a MBC of 833mg/ml and inhibited their growth with an
MIC of 417 mg/mL. These results are comparable to reported results for
other spices and suggest that green cardamom could be useful as an
antibacterial for food preservation.
1. Dried Elettaria cardamomum seeds were purchased in bulk from Abu
Kameel store. The manufacturer was M.R. Corp. and they were grown in
Bangladesh.
2. 10 g dried E, cardamomum seeds, was finely ground in an electric mixer
and soaked for 48-72 hr in 13 mL of seven different solvents: water, 100%
methanol, 100% ethanol, acetone, 70% methanol, 70% ethanol, and 70%
acetone for 48 to 72 hr.
3. The mixtures were filtered through Whatman No.1 paper. The supernatant
was diluted to final concentrations of 1667 and 833 mg/mL.
4. 20 µL of each extract and its respective solvent was tested in the well
diffusion assay against the following gram-negative bacteria: Escherichia
coli and Pseudomonas aeruginosa; and against the gram-positive bacteria:
Staphylococcus aureus, Bacillus subtilis, Streptococcus mutans.
5. The minimum inhibitory concentration (MIC) and minimum bacterial
concentration MBC of extract was determined by preparing serial
dilutions of the cardamom extract reconstituted with their respective
solvents in nutrient broth and inoculating each with 100 µL of E. coli, S.
aureus, B. subtilis, Str. mutans, and P. aeruginosa.
• The alcoholic and acetone extracts were most effective against grampositive bacteria. The increasing effectiveness in polar solvents suggests a
non-water soluble protein or lipid (Figure 2).
•
Antibiotics are valuable drugs; however, their overuse has created
worldwide antimicrobial resistance. Therefore, new antibiotics are vital.
•
Green cardamom has antimicrobial compounds that inhibit the growth of
medically important microorganisms.
•
The use of E. cardamomum as a medicine and flavoring in food and
drinks for centuries has shown the seeds lack of toxicity for humans.
Thus, E. cardamomum can be a potential source for new antibiotics that
are effective against a broad collection of bacteria.
•
Further investigation will consist of isolation of the active compound(s),
studying the antimicrobial activity of more concentrated extracts, and
testing against other microorganism.
Hypothesis
Green cardamom has medical uses in folk medicine. It is expected that the
green cardamom will inhibit growth of bacteria tested in this experiment.
• The methanolic extracts were most effective against S. aureus (Figure 3).
• The extracts were 50% less effective against gram-negative bacteria. The
aqueous extract was only effective against Pseudomonas, suggesting there
is a different, water-soluble anti-pseudomonas compounds (Figure 4).
• The minimal inhibitory concentration and the minimal bacterial
concentration of the both alcoholic and acetones extracts against all five
test bacteria was 417 mg/mL and 833 mg/mL respectively.
Controls
All aqueous extracts
70% Acetone
Literature Cited
100% Acetone
70% EtOH
Figure 1. Elettaria
cardamomum, green
cardamom, is in the
Zingiberaceae and is
native to Western
Ghats, India (8). The
seeds are harvested and
dried for use in food as
a spice, in drinks as
flavoring, and in
medicine (4, 7).
100% EtOH
70% MeOH
100% MeOH
0
5
10
15
20
25
Zone of inhibition, mm
S. aureus
B. subtilis
Str. mutans
Figure 2. Inhibition of gram-positive bacteria by 0.36 g/mL extracts in the
well diffusion assay.
Background
•
•
•
New antibiotics are needed. There has been a rise in antibiotic resistance
over the past decades because of the misuse of antibiotics. One case is the
emergence of antibiotic-resistant Staphylococcus aureus (5, 6).
Ancient medicine involved the use of many plants to treat diseases and
infections (2). Cinnamon is an effective antimicrobic against grampositive and gram-negative bacteria (1). Garlic is another effective
antimicrobial that inhibits 16 mycobacteria (3). These observations led us
to question whether other commonly used spices, such as green
cardamom, have antimicrobial activity.
• Elettaria cardamomum, green cardamom (Figure 1), is widely used in
Asia to treat gum and tooth infections, tuberculosis, and digestive
disorders (4, 7). However, its value has not been tested scientifically.
•
Controls
The availability of antibiotics is crucial. Antibiotics are molecules that are
produced by other bacteria, fungi, plants, and other organisms that kill the
infectious bacteria.
All aqueous extracts
Figure 3. Well
diffusion assay
showing inhibition of
S. aureus by extracts
in 100% methanol.
The control well
contains 100%
methanol.
70% Acetone
100% Acetone
70% EtOH
100% EtOH
70% MeOH
100% MeOH
Acknowledgements
0
5
10
15
20
25
Zone of inhibition, mm
E. coli
The purpose of our work is to evaluate whether E. cardamomum has
antibacterial activity.
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P. aeruginosa
Figure 4. Inhibition of gram-negative bacteria by 0.77 g/mL extracts in the
well diffusion assay.
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Genuine appreciation and particular thanks to Dr. Christine Case for her
helpful guidance throughout this project. Also a special thanks to the Skyline
College Biology Department, Patricia Carter and Ruth Arce for providing
laboratory equipments, as well as wise guidance, to conduct this research.
And finally a thank you to MESA directors Stephen Fredricks and Tiffany
Reardon.