Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3B Paper
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The Comparison of Strawberry Extract on the growth of Different Gram-negative Bacteria.
Mohammad Dadkhah, Amin Najmabadi
Department of Biological Science
Saddleback College
Mission Viejo, California
Strawberry is a rich source of bioactive compounds, such as phenolics and organic acids,
which have antimicrobial activities against human pathogens. Their antimicrobial activity has
gained importance as phenolic berry extracts inhibit the growth of selected Gram-negative
intestinal bacteria. Two types of Gram-negative bacteria were chosen for this experiment.
Escherichia coli is a common type of Gram-negative bacteria that can infect various food, such
as beef and vegetables. Salmonella typhimurium is a gram negative bacterium that causes
systemic infections and typhoid fever in humans. The aim of the present study is to determine
the effects of strawberry extract on selected pathogenic bacteria such as E. coli and
Salmonella typhimurium to identify antibacterial activity. One control group for E. coli and
one for Salmonella typhimurium and an experimental group for each bacterium. 10ml of each
bacteria were obtained from the colonies grown and were placed on to the Petri dishes by a
0.25 lawn spread. Salmonella with DI water 0.30mm 0.13mm. E.coli with Strawberry had a
zone of inhibition of 14.65mm 0.39mm and with DI water 0.25mm 0.11mm. We suggest
that there is no significant difference when comparing Salmonella Strawberry with
Salmonella DI water but there is a significant difference when comparing E.coli Strawberry
with E.coli DI water. There is also a significant difference when comparing Salmonell
strawberry with E.coli Strawberry.
Introduction
Flavonoids are common substances in the
daily diet. These polyphenolic compounds are widely
found in various types of edible plants, especially in
vegetables, fruits, tea and wine. Over 4000 different
favonoids have been described and they are
categorized into several subgroups (Puupponen-Pimia
et al. 2004). Flavanones are typically present in citrus
fruit, and favanols in green tea. Berries, which are
traditionally a part of the Finnish diet, are an excellent
source of favonols while the predominating group of
favonoids, especially in red berries, is anthocyanins
(Puupponen-Pimia et al. 2004). Strawberry is a rich
source of bioactive compounds, such as phenolics and
organic acids, which have antimicrobial activities
against human pathogens.
Berry phenolics possess many interesting biological
activities. Their antimicrobial activity has gained
importance as phenolic berry extracts inhibit the
growth of selected Gram-negative intestinal bacteria.
Strawberries contain ellagitannins or Ellagic acid and
citric acid. Strawberry ellagitannins slow the growth
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Saddleback Journal of Biology
Spring 2010