1. Abstract: Agave contains phytochemicals that could provide health benefits and have antimicrobial properties. In commercially available agave nectar, these compounds have
the potential to be degraded due to processing. We measured growth rates of several bacterial species treated with agave that had been subject to a spectrum of commercial
processing. All agave treatments had diminished bacterial growth compared to a nutrient broth control. However, none of the agave treatments demonstrated bacterial inhibition
that was different from the sugar control (a treatment containing the same carbohydrate composition as the agave, but with no phytochemicals). These results suggest that the
processing of commercially available agave nectar either degrades phytochemicals OR the phytochemicals are present and have no antimicrobial effects.
Analyzing the Potential Antimicrobial Effects of Phytochemicals in Agave Nectar
Heather Sprengel, Tiffany Dang & Gabriel Colbeck
Intro:
Agave nectar is produced from polysaccharides stored
at the core of the agave plant and processed agave
nectar may retain some of the flavonoids and
polyphenols that confer antimicrobial activity or
nutraceutical properties. Our previous experiments
demonstrated the potential antimicrobial properties
of both the agave plant and agave nectar, although
we were unable to control for the anti-microbial
properties of the sugar content (which can reduce
water availability for bacteria). Here, we sought to
evaluate the antimicrobial properties of commercially
processed agave nectar when compared to a sugar
control.
Methods:
Agave nectar – light, amber, and raw
varieties
Agave control – mixture of composite
sugars of agave nectar
Plate reader and 96 well plates –
tracked the optical density of E. coli, P.
vulgaris, and S. epidermidis in
concentrations of agave nectar of 22 –
40% by volume and nutrient broth over
6 hours to calculate the growth rate.
Growth rate is presented as (change in
optical density)/minute as measured
during the exponential growth phase.
Discussion:
Similar growth rates among different concentrations
of agave nectar, levels of processing and the sugar
control suggest that commercial agave nectar lacks
phytochemicals in a significant quantity (and/or that
the retained phytochemicals do not have
antimicrobial properties). Alternatively, the sugar
concentrations used in these experiments might be
sufficiently high that subtle anti-microbial effects are
overwhelmed. In future experiments, we would like to
use much lower concentrations, using a range from
1% to 22%.
Results:
The growth rates of each of the three
types of bacteria in the agave nectar
solutions demonstrated no significant
difference compared to the different
types of agave nectar or sugar control.
Additionally, the growth rates of the
bacteria in solutions containing agave
nectar or sugar control remained well
below the growth rate of the control
bacteria grown in nutrient broth. This
suggests that concentrations of agave
nectar above 22% by volume show no
increased inhibitory effect and that the
inhibition by agave nectar is due to the
high sugar content.
0
0.00005
0.0001
0.00015
0.0002
22% 24% 26% 28% 30% 32% 34% 36% 38% 40%
GrowthRate
Concentration by Volume
S. epidermidis
Light
Amber
Raw
Sugar Control
Nutrient Broth
0
0.00005
0.0001
0.00015
0.0002
0.00025
0.0003
22% 24% 26% 28% 30% 32% 34% 36% 38% 40%
GrowthRate
Concentration by Volume
P. vulgaris
Light
Amber
Raw
Sugar Control
Nutrient Broth
0
0.0001
0.0002
0.0003
0.0004
0.0005
0.0006
0.0007
22% 24% 26% 28% 30% 32% 34% 36% 38% 40%
GrowthRate
Concentration by Volume
E. coli
Light
Amber
Raw
Sugar Control
Nutrient Broth
Growth Rates Over Concentrations