Evaluation of Bioactive Compounds and Antimicrobial Potency of
Persea americana leaf extracts against specific Bacteria
OGUNLADE, AYODELE OLUWAYEMISI
Department of Food Technology
The Federal Polytechnic, Ado Ekiti
P.M.B 5351, Ekiti state
NIGERIA
Abstract: - Medicinal plants has gained a lot of interest in search of plants with a strong antimicrobial compounds
that has the ability to cure diseases caused by specific organisms. This is due to the resistance of these organisms
to some antibiotics of importance thereby rendering the drugs ineffective against diseases. The aim and objective
of this research is therefore to evaluate the antimicrobial potency and bioactive compounds of Persea americana
leaf extract against specific bacteria that had previously been identified in the laboratory. Different solvents were
used such as ethanol and sterile distilled water to extract the bioactive compounds of the plants and it showed a
high level of potency against the isolates. The concentrations of the extracts used for the determination of zones
of inhibition were 250µg/ml, 125µg/ml and 62.5µg/ml. The largest zone of inhibition was recorded against
Salmonella typhi (14.00mm) while Escherichia coli had the lowest zone of inhibition (8.00mm) for plants extract
using ethanol. Salmonella typhi had the largest zone of inhibition (16.00mm) while Escherichia coli had the
lowest zone of inhibition (6.0 mm) when the plant was extracted using sterile distilled water. Phytochemical
analysis of the extract revealed that both ethanolic and aqueous extract are rich in saponins, tannins, flavonoids,
alkaloids and steroids. Conclusively, P. americana can be utilized as an effective antibiotic substitute for the
treatment of infections caused by Salmonella typhi and Escherichia coli. This is as a result of its demonstrated
antibacterial activity.
Key-Words: - Antimicrobial, Phytochemical, Avocado, Clinical isolates, Medicinal, infections
Received: November 25, 2023. Revised: April 17, 2024. Accepted: June 12, 2024. Published: July 19, 2024.
1 Introduction
Most of the potential for using higher plants to make
novel drugs remains untapped. For most of the world,
plants are the only source of medications because
most people in developing nations get their primary
medical care from medicinal plants. (Adegoke and
Adebayo, 2009). The worldwide pursuit of strong
antimicrobial compounds to fight resistant
microorganisms that have been making many
traditional medications ineffective in treating
infections has led to a growing interest in medicinal
plants. The most unusual source of pharmaceuticals
is plants. (Latha et al., 2006). The use of medicinal
plants as an alternative to conventional antibiotics for
the treatment, management, and prevention of
infectious diseases is becoming more and more
popular throughout the world. (Akpomie et al.,
2021). Furthermore, because natural extracts with
pharmacological action have few side effects and
therapeutic promise for treating a variety of
disorders, their use has gained a lot of attention
(Akwam et al., 2022).
Avocado peas come in 150 kinds, one of which being
Persea americana (Lauraceae) (Pacific Health,
2005). The tree is commonly planted in tropical and
subtropical countries; it may reach a height of around
80 feet and has leathery, evergreen leaves. Unisexual
blossoms are uncommon. In ethnomedicine, Persea
americana seeds are used for a variety of purposes,
such as treating intestinal parasites, diarrhea,
dysentery, toothaches, and skin conditions (Pamplora
and Roger, 1999). It has been reported that P.
americana leaves contain analgesic and anti-
inflammatory properties. (Adeyemi et al., 2002).
Traditional methods of treating illnesses involved the
use of plant concoctions, either in single form or in
mixes, prior to scientists making progress in their
study into medications that heal human infections.
The main benefit is that plants are still the most
affordable and efficient alternative source of
medication. Many millennia have passed since the
first recorded uses of medicinal plants to treat
ailments. It is an ancient form of art. (Latha et al.,
2006). According to Bibitha et al., (2011) due to the
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pharmacological qualities, natural plants are
frequently used locally in Asia, Latin America, and
Africa as basic health remedies. Herbs were first used
in the manufacturing of pharmaceuticals and the
pharmacological treatment of illnesses (Taylor et al.,
2011). Many plants are eaten without fully
understanding their precise chemical makeup or
health benefits, despite the fact that their use has been
passed down through multiple ancestral generations
who most likely learned from experience how helpful
particular plant food ingredients are (Coe, 2005).
Additionally, avocado leaves (Persea americana
Mill.) have long been utilized as an antihypertensive
(Dwi, 2023). It is therefore very important to
investigate the phytochemical constituents and
antimicrobial effect of avocado leaf against clinical
isolates.
2 Materials and Methods
2.1 Collection of sample and preparation
Persea americana fresh leaves were collected from
the Federal Polytechnic Ado Metropolis in Ekiti
State. The leaves were harvested from the trees
weighing a total of 50g. It was thereafter washed with
sterile distilled water and air dried until the leaves
becomes brittle. The dry leaves were ground into
powder with the use of a mill. It was stored in a
transparent air-tight container, labeled and preserved
at room temperature.
2.2 Isolates
The following bacteria served as test organisms
during the course of this work: Escherichia coli and
Salmonella typhi. The isolates were obtained from
the Federal Medical Centre Laboratory Ido, Ekiti-
State, Nigeria.
2.3 Phytochemical screening of Avocado leaf
extract
A preliminary phytochemical analysis was
performed to identify the bioactive components
found in the leaf extract (Trease, 1989).
2.4 Preparation of Plant extract
After carefully weighing two grams (2g) of extract
into a 250 mL conical flask, 50 mL of distilled water
was added. It was combined, sealed with a rubber
band, and heated to 370C degrees Celsius for two
hours before being taken out to cool. Whattman filter
paper No. 1 was used to filter the content, and the
filtrate was saved for analysis.
2.5 Media preparation
Nutrient agar was prepared in a conical flask, 2.8 g of
agar powder were suspended in 100 ml of distilled
water, shaken rapidly to dissolve, autoclaved for 15
minutes at 121°C, cooled to 47°C, and then
transferred into sterile petri dishes.The medium was
then allowed to solidify (Cheesbrough, 2003).
In order to prepare MacConkey agar, a conical flask
was filled with 4.8 g of agar powder and 100 ml of
sterile distilled water. The flask was shaken and
corked, then let to soak for around 10 minutes. It was
autoclaved for fifteen minutes at 121°C. The media
was cooled to 470C and poured into sterile plates
(Cheesbrough, 2003).
2.6 Antimicrobial Analysis
The Potency of the extracts were determined using
agar well diffusion method. Sterile cork borer was
used to create six wells on the media used. Following
that, 100 µl of the plant extracts at a concentration of
1 mg/ml were added to wells and given five minutes
to diffuse. As a control, 1 mg/ml of tetracycline was
utilized. The petri dishes were incubated for 24hours
at 37°C (Igbinosa et al., 2009). Zones of inhibition
were measured and recorded. The mean ± standard
deviation represents the experiment's results, which
were conducted in triplicate.
3 Results and Discussion
The phytochemical screening results of Persea
americana leaf are displayed in Table 1, wherein the
presence of tannins, saponins, flavonoids, alkaloids,
terpenoids, anthraquinines, glycosides, and cardiac
glycosides was found. The plant's antibacterial effect
may be attributed to these physiologically active
phytochemicals. These secondary metabolites have
different ways by which they carry out their
antibacterial actions. According to Shimada (2006),
tannins have the ability to form permanent
compounds with proline-rich proteins, which
prevents cells from synthesizing new proteins.
(Parekh and Chanda, 2007). Herbs has been used in
the treatment of Intestinal disorders such as diarrhea
and dysentery and tannins is the main components.
Alkaloid is another secondary metabolite in the leave
extract P. americana which contain analgesic effects
(Sutradhar, 2007) and have been clinically explored.
Alkaloids are well known for their antibacterial
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Volume 3, 2024
properties, which are particularly effective against
gram-negative bacteria. (Cushnie et al., 2014).
Flavonoids and saponins are other secondary
metabolites which are majorly present in P.
americana whose antimicrobial activities have been
well documented (Hodek et al., 2002).
All of the extracts showed a considerable inhibition
against the test microorganisms, as shown in Tables
2 and 3. The highest zone of inhibition was seen in
ethanolic extract. 250µg/ml, 125µg/ml and
62.5µg/ml concentration variations were used. The
highest zone of inhibition was observed on S. typhi
(16.00mm) at 125 µg/ml and the lowest was seen
against E coli (6.00mm) at 62.5 µg/ml when the plant
was extracted using ethanol. However, when the
plants were extracted using sterile distilled water
(aqueous), S. typhi had the largest zone of inhibition
(14.00mm) at 250 µg/ml while E coli was inhibited
at 8.00mm at 125 µg/ml. The bioactive compounds
determined were alkaloids, flavonoids, and phenols
which can enhance the health of the consumers
(Ogunlade et al, 2019).
Table 1. Bioactive compound of aqueous extract
and ethanolic extract of Avocado leaf
Phytochemicals
Aqueous
extract
Ethanolic
extract
Saponins
++
+
Tanins
+
+
Flavoniods
++
+
Alkaloids
+++
++
Steroids
++
+
Terpenoids
++
+
Anthraquinone
+
.
Glycosides
++
+
Cardiac glycosides
+
.
Key: +++ means highly present, ++ means
moderately present, + means Present, - means absent
Table 2. Antimicrobial potency of extracts from
Persea americana leaves at varying concentrations
(Ethanolic extract)
Zone of inhibition (mm)
250
(µg/ml)
125
(µg/ml)
62.5
(µg/ml)
14
16
9
10
12
6
Table 3. Antimicrobial potency of Persea
americana leaves extracts at different
concentrations (Aqueous extract)
Zone of inhibition (mm)
250
(µg/ml)
125
(µg/ml)
62.5
(µg/ml)
14
11
11
10
8
10
4 Conclusion
Conclusively, Diseases caused by Escherichia coli
and Salmonella typhi can be treated with the extracts
from Avocado leafs based on findings from this
study. This is due to the potency of the Antimicrobial
agents it possesses.
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International Journal of Applied Sciences & Development
DOI: 10.37394/232029.2024.3.11
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E-ISSN: 2945-0454
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