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By: Bethany Vogeney and Pahua Cha
Mentor: Rachel McKenna
Abstract
Plants are growing all around us. Their chemical
compounds serve many functions, including
medicinal ones. For our experiment, 13 plant
samples were collected from our “backyard” and
were tested using bioassays to determine whether
they had antibacterial and antifungal properties.
Because more and more bacteria are beginning to
build resistance against the tools we have at hand,
it is important to keep searching for new medicinal
options to fight microorganisms.
Microorganisms We Tested On
- To test for antibacterial properties we used
two organisms: E. Coli which is gram
negative and Pediococcus pentosaceus
which is gram positive. These represent the
two main types of bacteria. The main
difference is the structure of the cell wall.
- To test antifungal potential of plants, yeast
was used.
Plant Name
Japanese Pieris Flowers
Japanese Pieris Berries
Cedar
3-point leave
English Ivy
Rose
Garlic
Cloves
5 star yellow flower
Rusty leaves
St. John's Wort
Green leaves
Lichen
Solvent
E. Coli
Pediococcus
pentosaceus
Yeast
Ethanol
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Hexane
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Ethanol
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Hexane
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Ethanol
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Hexane
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Hexane
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Hexane
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Ethanol
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Hexane
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Ethanol
Hexane
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Ethanol
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Hexane
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Ethanol
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Hexane
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Ethanol
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Hexane
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The Bioassays
Bioassays are a method of testing a substance
using living organisms. We conducted three types of
bioassays to test for antibacterial (gram positive and
gram negative), and antifungal properties. The
microorganisms were cultured and put into a nutrient
agar plate to grow. We loaded our compounds onto the
plate, using the hexane and ethanol solutions. If the
samples have any antimicrobial properties, there will be
a clear zone around the sample in which the
microorganism could not grow.
Bioassays
Making the plates:
After the extraction of the two solutions, Petri dishes had to be prepared with
a special media to promote the growth of the test subjects.
To make the nutrient agar:
1) Dissolve the nutrient media and
agar in water.
2) Sterilize by autoclaving
3) Inoculate sterile media with
microorganism
4) Pour media into Petri dishes to
make bioassay plates.
-Use one plate for hexane
extracts and one plate for the
ethanol extracts. Pour the media
and let it harden.
Test the samples:
1)After media has hardened, bore wells
in media and fill each with the
sample.
2)Put each plate into the incubator
overnight.
3)In the morning, measure the size of
each zone around the samples. (A
zone is a clear circle around a sample
with no bacterial growth.)
Plant Samples
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Japanese Pieris
flowers
Japanese Pieris
berries
Cedar
English Ivy
Rose
Garlic
Cloves
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Five star yellow
flower
Green leaves
Rusty leaves
St. Johns Wort
Lichen
Three point leaves
Extraction Procedure
1)
2)
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4)
Collect plant
samples
Cut or crush
plant samples
Pour samples into
70% ethanol and
homogenize
Filter mixtures
and add hexane
to the filtered
ethanol
5)Mix gently and let the
layers formulate and
settle
6) Pipette the hexane
layer and store
separately do the same
w/ the ethanol
7)The samples will be
tested for antimicrobial
compounds
Plant Extraction Abstract
To determine whether antimicrobial substances exist within a
plant, it’s chemical compounds first must be extracted.
Proteins, sugars, and lipids are the main molecular
components in plants. These components may contain useful
substances but stay undetected until they’re extracted and
experimented on.
Ethanol and Hexane are the solvents we used to extract the
active compounds. The ethanol and hexane separate the
proteins and sugars from the lipids. Ethanol is polar and
attracts the polar sugars and protein, and hexane is non-polar
and attracts the non-polar lipids. The two repel, separating the
non-polar and polar matter. This makes it easier to determine
which component of the plant effects certain organisms.
Conclusion
For centuries plants have provided us with
the tools to fight off diseases. Many of
these plants could easily be those found in
our own backyard. Four out of thirteen or
31% of the plant samples tested positive for
antibacterial or antifungal compounds.
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Antibacterial (gram+): Sugar, proteins and
lipids of St. John’s wort and lichen
Antibacterial (gram -) Sugars and proteins of
clove and garlic
Antifungal: Sugars and proteins of garlic