1Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 29 | Number 03 | Article 349996
Capacidad Antioxidante e Inhibitoria del Extracto Etanólico de la Hoja de Tomate contra Streptococcus mutans, Porphyromonas gingivalis y Candida albicans
JOURNAL VITAE
School of Pharmaceutical and
Food Sciences
ISSN 0121-4004 | ISSNe 2145-2660
University of Antioquia
Medellin, Colombia
Filliations
1 Master Student in Dental Sciences,
Faculty of Dentistry, CES University,
Medellín, Colombia.
2 Adjunct Professor, Faculty of Sciences
and Biotechnology, CES University,
Medellín, Colombia.
3 Assistant Professor, Faculty of
Dentistry, CES University, Medellín,
Colombia.
4 Director, Pharmaceutical Chemistry
Program, Faculty of Sciences and
Biotechnology, CES University,
Medellín, Colombia.
5 Associate Professor, Faculty of
Dentistry, CES University, Medellín,
Colombia.
*Corresponding
Jairo Robledo-Sierra
jrobledo@ces.edu.co
Received: 15 Jun 2022
Accepted: 10 October 2022
Published: 12 October 2022
Antioxidant and Inhibitory Capacity of
Tomato Leaf Ethanolic Extract against
Streptococcus mutans, Porphyromonas
gingivalis, and Candida albicans
Capacidad Antioxidante e Inhibitoria del Extracto Etanólico
de la Hoja de Tomate contra Streptococcus mutans,
Porphyromonas gingivalis y Candida albicans
Yeiner Mendoza1 , Mónica Arias-Londoño2 , Juliana Sánchez-
Garzón3 , Diego Fernando Rojas-Vahos4 , Jairo Robledo-Sierra5,*
ABSTRACT
Background: Tomato is a source of bioactive compounds, antimicrobials, and antioxidants.
Tomato leaf preparations have been empirically used for anti-inflammatory, analgesic,
antibiotic, and antiseptic purposes. However, research on the potential activity of tomato leaf
extracts against oral microorganisms and in managing oropharyngeal infections is scarce.
Objective: To investigate tomato leaf ethanolic extract’s antioxidant and growth inhibitory
capacity against common oral pathogenic microorganisms, namely, Streptococcus mutans,
Porphyromonas gingivalis, and Candida albicans. Methods: Ethanolic extracts were made from
‘Chonto’ tomato (Lycopersicon esculentum) leaves. The antimicrobial activity was measured
with the microdilution technique using vancomycin and fluconazole as positive controls. The
antioxidant capacity was measured with the ORAC assay using Trolox as a positive control.
Results: We found a high percentage of growth inhibition (≥100%) against S. mutans and P.
gingivalis at a concentration of 500 mg/L. However, the extract was ineffective in inhibiting
the growth of C. albicans. Finally, we observed that the extract exerted a high antioxidant
capacity (126%) compared to the positive control. Conclusions: This study provides new insights
into the potential antimicrobial effect of tomato leaf extracts on common oral pathogenic
bacteria, which may ultimately result in the development of new herbal products that might
help prevent and treat oral infections, such as dental caries and periodontal disease. Our
findings also support previous studies on the high antioxidant capacity of tomato leaf extracts.
Keywords: Antioxidant capacity; Candida albicans; Ethanolic extract; Lycopersicon
esculentum; Porphyromonas gingivalis; Streptococcus mutans; Tomato
ORIGINAL RESEARCH
Published 12 October 2022
Doi: https://doi.org/10.17533/udea.vitae.v29n3a349996
2Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 29 | Number 03 | Article 349996Yeiner Mendoza, Mónica Arias-Londoño, Juliana Sánchez-Garzón, Diego Fernando Rojas-Vahos, Jairo Robledo-Sierra
INTRODUCTION
Tomato (Lycopersicon esculentum) is a plant of the
Solanaceae family native to the low Andes. The
plants can be propagated by seed or clonally by tip
or shoot cuttings, have a high yield of fruit, and have
a reasonable biomass and protein content (1). Early
observational studies linked tomato consumption
to reduced prostate cancer risk, which prompted
people to use this fruit to prevent this and other
conditions such as colorectal and stomach cancer,
diabetes, and osteoarthritis. However, although
tomatoes as a non-starchy vegetable may decrease
the overall risk of cancer and all-cause mortality
(2), there is no solid scientific evidence to support
these uses to date. In contrast, tomato products
potentially have beneficial effects in preventing and
treating cardiovascular diseases, mainly due to their
high content of potent antioxidants, such as vitamin
A, carotenoids, vitamin E, and phenolic compounds
(2-4). A recent systematic review and meta-analysis
concluded that standardized tomato extract
significantly decreases systolic blood pressure
compared to placebo in healthy and hypertensive
patients (5). Additional studies suggest that in food
and therapeutic doses, tomatoes effectively prevent
preeclampsia and hyperlipidemia in pregnancy and
reduce platelet aggregation (6, 7).
The global rise of antibiotic resistance has also
increased the research interest in the antimicrobial
potential of natural products in recent years,
including tomatoes. Several studies testing various
extracts from different parts of the tomato plant have
identified antimicrobial properties against bacteria
–particularly Gram-positive– (4, 8-10), fungi (11), and
protozoan parasites (11). Some Latin American rural
populations have used tomato leaf preparations
for anti-inflammatory, analgesic, antibiotic, and
antiseptic purposes (12). In Colombia, for example,
tomato leaves as an antiseptic for external use are
an accepted medicinal herb (13), and mouthwashes
based on tomato leaf extracts are commercially
available. However, research on the potential activity
of tomato leaf extracts against oral microorganisms
and in managing oropharyngeal infections is scarce.
Streptococcus mutans and Porphyromonas gingivalis
are the primary agents in the pathogenesis and
progression of dental caries and periodontal disease,
respectively. It is estimated that oral diseases affect
nearly 3.5 billion people worldwide, with caries of
permanent teeth and periodontal disease being
the most common conditions. Globally, around
2 billion people suffer from caries of permanent
teeth, and 520 million children suffer from caries
of primary teeth (14). Severe periodontal diseases
affect approximately 14% of the adult population,
representing more than one billion cases worldwide
(14). These oral diseases are largely preventable
through lifestyle modification, such as promoting
a well-balanced diet low in free sugars and high
in fruit and vegetables, improving oral hygiene,
and stopping the use of all forms of tobacco. Also,
fluoride exposure can substantially reduce the risk
of dental caries. Unfortunately, however, in most
low- and middle-income countries, the prevalence
of these conditions continues to increase (15). This
public health problem, together with the rapid
emergence of antibiotic-resistant bacteria, makes
RESUMEN
Antecedentes: El tomate es una fuente de compuestos bioactivos, antimicrobianos y antioxidantes. Las hojas de tomate se han
utilizado empíricamente con fines antiinflamatorios, analgésicos, antibióticos y antisépticos. Sin embargo, los estudios sobre la
actividad de los extractos de hojas de tomate contra los microorganismos orales y en el manejo de las infecciones orofaríngeas
son escasos. Objetivo: Investigar la capacidad antioxidante del extracto etanólico de la hoja de tomate y su actividad inhibitoria
de crecimiento contra microorganismos patógenos orales comunes, a saber, Streptococcus mutans, Porphyromonas gingivalis y
Candida albicans. Métodos: Se realizaron extractos etanólicos a partir de hojas de tomate ‘Chonto’ (Lycopersicon esculentum). La
actividad antimicrobiana se midió con la técnica de microdilución utilizando vancomicina y fluconazol como controles positivos.
La capacidad antioxidante se midió con el ensayo ORAC utilizando Trolox como control positivo. Resultados: Encontramos
un alto porcentaje de inhibición del crecimiento (≥100%) contra a S. mutans y P. gingivalis a una concentración de 500 mg/L.
Sin embargo, el extracto fue ineficaz en la inhibición el crecimiento de C. albicans. Finalmente, observamos que el extracto
tuvo una alta capacidad antioxidante (126%) en comparación con el control positivo. Conclusiones: Este estudio proporciona
nuevos conocimientos sobre el posible efecto antimicrobiano de los extractos de hojas de tomate en bacterias patógenas
orales comunes, lo cual puede resultar en el desarrollo de nuevos productos naturales que podrían ayudar a prevenir y tratar
infecciones orales, como la caries dental y la enfermedad periodontal. Nuestros hallazgos también respaldan los estudios
previos sobre la alta capacidad antioxidante de los extractos de hojas de tomate.
Palabras Clave: Candida albicans; Capacidad antioxidante; Extracto etanólico; Lycopersicon esculentum; Porphyromonas
gingivalis; Streptococcus mutans; Tomate
3Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 29 | Number 03 | Article 349996
Capacidad Antioxidante e Inhibitoria del Extracto Etanólico de la Hoja de Tomate contra Streptococcus mutans, Porphyromonas gingivalis y Candida albicans
it imperative to search for inexpensive natural
products that might aid in controlling common oral
infections.
Therefore, this study aimed to investigate tomato
leaf ethanolic extract’s antioxidant and growth
inhibitory capacity against common oral pathogenic
microorganisms, namely, S. mutans, P. gingivalis,
and Candida albicans.
MATERIALS AND METHODS
Sampling procedure
Leaf samples of ‘Chonto’ tomato (L. esculentum)
were collected in a commercial crop in Rionegro,
Antioquia, Colombia. The crop had approximately
4,000 plants, was protected with mesh netting,
maintained between 18–24°C, and supplied using
an irrigation system. Non-chemical methods were
used to control pests and diseases.
The foliar tissue was collected in the morning, using
gloves, when the flowers began to open and were
stored and transported to the CECIF (Center for
Pharmaceutical Science and Research, Sabaneta,
Antioquia, Colombia) laboratory for further analysis
in airtight plastic bags. There, primary asepsis
of the leaves was performed with 0.3% sodium
hypochlorite to eliminate traces of contaminating
substances from their surface. Finally, the physically
damaged leaves were discarded.
Preparation of ethanolic extract
The selected and disinfected leaves were dried in
a convection oven for 24 h at 45°C and pulverized
using a mortar and pestle. Twenty grams of the
pulverized material were mixed with 500 mL of
absolute ethanol. Then, without artificial light, a
mechanical disruption was performed with Ultra-
Turrax ® (T 25 digital, IKA, Staufen, Germany) (five
1-min cycles at 12,000 rpm with 1-min rest between
cycles). The resulting mixture was stored for two
weeks in an amber bottle in the dark at room
temperature with periodic manual agitation.
Later, the mixture was filtered through a 0.42 μm filter
paper to remove particulate matter. An evaporation
process was then carried out at 98 mbar, 40°C, and
110 rpm for three h, using a rotary evaporator (Büchi
Heating Bath B-490, Buchi Rotavapor R-205).
The extract was transferred to a previously weighed,
partially aerated amber glass container with a pipette
and stored in the extraction cabinet for two weeks
to guarantee complete ethanol evaporation. Finally,
4.27 grams of a viscous, lumpy consistency and dark
green color ethanolic extract were obtained. The
extract was kept in a closed bottle in the dark at
room temperature for later use.
Microorganisms and culture conditions
Bacterial strains S. mutans ATCC ® 25175™ and
P. gingivalis ATCC® 33277™, and fungal strain C.
albicans ATCC® 10231™ were purchased from MDM
Científica (Medellín, Antioquia, Colombia).
In a vertical laminar flow cabinet (BIOBASE Meihua
Trading Co, model BBS-DDC, Shandong, China),
three tubes were served with 10 mL Brain Heart
Infusion (BHI) agar (for S. mutans and P. gingivalis)
and Yeast Malt (YM) broth (for C. albicans). The
tubes were incubated with constant shaking at 150
rpm and 37°C for 24 h. At the end of the incubation,
aliquots were taken in sterile 1.5 mL tubes to which
15% glycerol was added, and they were stored at
-80°C for later use. Finally, the cultures of S. mutans
and C. albicans were maintained in Tryptic soy
agar and YM broth at 37°C in aerobic conditions.
In contrast, the P. gingivalis culture was maintained
in anaerobiosis at 37°C in blood agar. This process
and the antimicrobial and antioxidant evaluations
were conducted at the Biology Laboratory of CES
University.
Antimicrobial assays
We followed the standards on antimicrobial
susceptibility testing of bacteria (16) with some
modifications. First, the inoculum of each bacterium
was prepared by making a direct suspension in
the Mueller-Hinton broth of a colony isolated from
one of the agar cultures. Next, suspensions were
incubated for 24 h at 37°C and 150 rpm, and their
absorbance at 600 nm was adjusted to 0.08. Finally,
the inoculum was diluted in the plate until it reached
an absorbance of 0.04 (10).
The antimicrobial activity reading was performed
after 24 h of incubation using a spectrofluorometer
(Cytation 5, BioTek, Santa Clara, CA, USA) consisting
of a 96 -well ELISA-type plate reader and a
monochromator. The microplates containing the
cultures exposed to the tomato extract were placed
in the plate reader, and the absorbance at 600 nm
was registered.
We followed the standards on antifungal susceptibility
testing of yeasts (17) with some modifications. First,
the inoculum was prepared by making a suspension
4Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 29 | Number 03 | Article 349996Yeiner Mendoza, Mónica Arias-Londoño, Juliana Sánchez-Garzón, Diego Fernando Rojas-Vahos, Jairo Robledo-Sierra
in YM broth from one of the tubes stored at -80°C
and incubated for 24 h, shaking at 150 rpm and 37°C.
Then, the suspension was adjusted to an absorbance
of 0.1 at 450 nm. Finally, the inoculum was diluted
in the plate until it had an absorbance of 0.05 (10).
The antifungal and antimicrobial activity was
determined by obtaining the percentage of growth
inhibition for each concentration of the extract,
using the following equation:
Percentage inhibition =(Control absorbance – Extract absorbance) x 100
Control absorbance
The antif ungal f luconazole (MK ® 20 0 mg,
Tecnoquímicas, Medellín, Colombia) was used as a
positive control against C. albicans, according to the
Performance Standards for Antifungal Susceptibility
Testing of Yeasts (Clinical & Laboratory Standard
Institute). Conversely, the antibiotic vancomycin
(Vanbiotic ® 500 mg, Vitalis, Bogotá, Colombia)
was used as a positive control for S. mutans and P.
gingivalis (18).
Fluconazole and vancomycin were diluted in
dimethyl sulfoxide (DMSO), while the extract was
diluted in absolute ethanol. The concentrations
used to evaluate the antifungal activity (fluconazole
and tomato leaf extract) were 5, 10, 20, 40, 60,
80, 100, and 120 mg/L. On the other hand, the
concentrations used to evaluate the antimicrobial
activity (vancomycin and tomato leaf extract) were
0.1, 0.25, 0.5, 10, 20, 250, 500, and 1000 mg/L. We
evaluated lower, intermediate, and higher values
compared to the Clinical and Laboratory Standards
Institute (CLSI) guidelines range.
To qualitatively evaluate the growth inhibitory
capacity of the extract on S. mutans and P. gingivalis,
20 μL samples of 10, 20, 50, 500, and 1000 ppm
were poured in Muller-Hinton agar. Vancomycin
(800 ppm) and DMSO were used as controls, and
the Petri dishes were incubated for 48 h at 37 °C.
Antioxidant assay
The oxygen radical absorbance capacity (ORAC)
assay was utilized to measure the antioxidant
capacity of the tomato leaf ethanolic extract using
96-well flat-bottom black microplates. We used
2,2’-azobis(2-amidinopropane) dihydrochloride
(AAPH) as an oxidant, Trolox® as a control antioxidant,
and fluorescein (FL) as a fluorescent indicator. The
protection grade was quantified with a fluorometer
(Cytation 5, BioTek). The dissolutions were prepared
the same day of the assay and kept in the dark.
Twenty-five μL of the antioxidant solution (Trolox®
or tomato leaf ethanolic extract) was added to each
microwell. First, to determine the natural oxidation
of FL, 25μL of buffer solution was added. Then, 150
μL of the solution, 40 nM, was added in FL. The
solution was agitated and incubated at 37ºC for 10
min. Next, 25μL of the solution, 700 mM, was added
in AAPH, and the fluorescence reading of the well
was registered for 34 min, at 2-min intervals. The
fluorescence was measured with 495 nm excitation
and 520 nm emission. The microplate was protected
from direct exposure to light and the time of adding
the oxidant (AAPH).
Statistical analysis
We obtained the dose-response plot s and
determined inhibitory concentrations and IC50
doses using nonlinear regression. In addition,
normality was verified with the Shapiro-Wilk test,
the mean difference was analyzed with the Kruskal-
Wallis test, and the origin of the differences between
concentrations and samples was analyzed with
Tukey’s multiple comparisons test. A P-value <0.05
was considered significantly different at a 95%
confidence level. We used the statistical software
GraphPad Prism (San Diego, CA, USA), version
9. Each extract concentration had five biological
replicates and three repetitions.
Ethical considerations
This in vitro study was approved by the Ethics
Committee of CES University (Act 15, 2019).
RESULTS
Growth inhibitory activity on S. mutans
We observed inhibition halos in the tomato leaf
extracts, whose area increased according to the
concentration. However, vancomycin had the most
prominent inhibition halo. As for DMSO, an inhibition
halo was observed, but its area was notably smaller
than the extracts.
Moreover, the percentage of inhibition was
90% using an extract concentration of 20 mg/L.
However, no significant increase was observed
when using extract concentrations of 20–500 mg/L,
after which a percentage of inhibition of 100% was
reached. At lower concentrations (10, 0.5, 0.25,
and 0.1 mg/L), no percentage of inhibition was
observed (Figure 1).
5Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 29 | Number 03 | Article 349996
Capacidad Antioxidante e Inhibitoria del Extracto Etanólico de la Hoja de Tomate contra Streptococcus mutans, Porphyromonas gingivalis y Candida albicans
Figure 1. Percentage of growth inhibition of S. mutans under
different concentrations of tomato leaf ethanolic extract over time.
Growth inhibitory activity on P. gingivalis
Here, we also observed inhibition halos in the
tomato leaf extracts; however, the halos did not
increase according to changes in concentration.
Vancomycin also had the most significant inhibition
halo, and the DMSO halo was imperceptible.
In contrast to S. mutans, we obser ved high
percentages of inhibition (94%) from a lower
concentration (10 mg/L). No significant increase was
seen at higher concentrations (500 and 1000 mg/L).
The highest percentages of inhibition (>100%) were
obtained at a concentration over 500 mg/L. At
lower concentrations (0.5, 0.25, and 0.1 mg/L), no
percentage of inhibition was observed (Figure 2).
Figure 2. Percentage of growth inhibition of P. gingivalis under
different concentrations of tomato leaf ethanolic extract over time.
Growth inhibitory activity on C. albicans
The YM broth pre-inocula obtained an optical
density of 0.596 at 450 nm after 24 h at 150 rpm and
26°C. Notably, the highest percentage of inhibition
on C. albicans was 37% for the extract and 83%
for fluconazole (Figure 3). The EC50 values of the
evaluated compounds are described in Table 1.
Figure 3. Percentage of growth inhibition of C. albicans under
different concentrations
Table 1. EC 50 values. Tomato leaves extract vs commercial antibiotic and antifungal
S. mutans P. gingivalis C. albicans
Tomato extract Vancomycin Tomato extract Vancomycin Tomato extract Fluconazole
EC50
(mg/L) 4.23± 1.4 11.1± 0.18 18.20± 1.4 3.86± 0.8 202± 24 10.44± 1.8
Antioxidant capacity
The tomato leaf ethanolic extract obtained an
antioxidant capacity of 126%. As is shown in Figure
4, the FL indicator preserves its absorbance over
time, indicating that the extract protects the FL
from oxidation for 30 min, compared to 5 min, after
which FL oxidates in the absence of an antioxidant.
6Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 29 | Number 03 | Article 349996Yeiner Mendoza, Mónica Arias-Londoño, Juliana Sánchez-Garzón, Diego Fernando Rojas-Vahos, Jairo Robledo-Sierra
DISCUSSION
To our knowledge, this is the first study to investigate
the antimicrobial potential of tomato leaf extracts
against P. gingivalis and S. mutans. We found a high
percentage of growth inhibition (≥100%) against
these bacteria at a concentration of 500 mg/L. Only
one study, conducted in Nigeria, has previously
evaluated the antimicrobial effect of tomatoes against
S. mutans (19). The authors reported that aqueous and
methanolic extracts had no inhibitory effect on this
microorganism at various concentrations (12.5, 25, 50,
and 100 mg/mL). However, the extracts were made
from the fruit, which could explain the divergence
from our findings (11). Another study analyzing the
antimicrobial capacity of leaves, stems, roots, and
whole-plant extracts of two tomato varieties, i.e.,
Pitenza and Floradade, found a significant activity
against Staphylococcus aureus, Escherichia coli,
Salmonella typhimurium, and Listeria ivanovii.
Interestingly, the leaf extracts showed the highest
antimicrobial activity in both varieties, followed by
the stem and whole-plant extracts (4). Similarly, a
recent study found that leaf extracts exhibited the
highest growth inhibition against Bacillus cereus and
Salmonella enterica, as well as Trichomonas vaginalis,
compared to stem, peel, and fruit extracts (11). Finally,
based on the existing reports, it is evident that Gram-
positive bacteria (e.g., S. aureus) are more sensitive
to tomato extracts than Gram-negative bacteria (10,
20, 21), which is in line with our results. It has been
hypothesized that the lipopolysaccharides content
in the external cell membrane of Gram-negative
bacteria could provide higher resistance to the
antimicrobial compounds of the tomato plant (10, 21).
In this study, we also investigated the antifungal
activity of tomato leaf extract against C. albicans –an
opportunistic pathogenic yeast that causes oral and
vaginal candidiasis– and found that it was ineffective
in inhibiting its growth. However, the strain used in
our study likely presented with resistance genes, as
the percentage of inhibition was 37% for the extract
and only 83% for fluconazole. The few studies that
have been published on the antifungal activity of
tomato extracts show conflicting results. Tomato
leaves, stems, and green tomato fruit inhibited the
growth of C. albicans to a significant extent (63–74%)
relative to the positive control octyl gallate (11).
Furthermore, another study showed that tomato
seed extracts displayed antifungal properties,
although they seemed solvent-dependent and
less effective than against Gram-positive bacteria
(21). Of note, all the five different extracts tested
(i.e., chloroform, methanol, ethyl acetate, hexane,
and sulfuric acid) were active against C. albicans,
except for the ethyl acetate extract. Other studies
have found no growth-inhibiting activity of tomato
fruit aqueous and methanolic extracts against C.
albicans (19, 22). Hence, the contrasting results might
be attributed to the solvents used in the extraction
protocols, as it has been shown that the solubility of
antimicrobial and antioxidant compounds in tomato
extracts largely depends on the solvent polarity (23).
In general, organic extracts yield a more potent
antimicrobial activity due to the presence of non-
polar residues in the solvent compared to aqueous
extracts, which tend to have lower bactericidal and
bacteriostatic properties (19, 24).
Figure 4. Antioxidant capacity of the tomato leaf extract using the ORAC assay.
7Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 29 | Number 03 | Article 349996
Capacidad Antioxidante e Inhibitoria del Extracto Etanólico de la Hoja de Tomate contra Streptococcus mutans, Porphyromonas gingivalis y Candida albicans
Finally, we observed that the tomato leaf extract
exerted high antioxidant activity compared to
the positive control (Trolox ® ), which is in line
with previous results (4, 10, 20). The primary
antioxidants that have been identified in tomato
fruit, leaf, and waste (peel and seed) extracts include
phenolic compounds, flavonoids, carotenoids
(e.g., β-carotene, α-carotene, β-cryptoxanthin,
lycopene, and lutein), and chlorophyll (4, 10, 20,
25). For instance, Silva-Beltrán et al. measured the
antioxidant capacity of stem, root, leaf, and whole-
plant extracts of two tomato varieties using the
ORAC assay. The leaf extracts exhibited the highest
antioxidant activity in both varieties, which correlates
with the high content of phenolic compounds
(especially gallic acid, chlorogenic acid, and rutin),
flavonoids, and chlorophyll in the leaves compared
to other parts of the plant (4). However, the total
antioxidant activity of an extract results from the
interaction between several constituents, which may
include synergistic or additive effects (26).
Identifying and quantifying bioactive compounds
of tomato leaf extracts were beyond the scope
of this study, which might be considered a
limitation. However, antimicrobial and antioxidant
metabolites in different parts of the tomato plant
have been widely investigated. As the results of
potent antioxidants, some studies have shown
that the leaves are the primary source of bioactive
compounds with antimicrobial properties, such
as glycoalkaloids (i.e., tomatine and tomatidine),
phenolic compounds, terpenoids, and flavonoids
(4, 11, 27). The primary antimicrobial action of some
of these compounds, such as phenols, flavonoids,
and terpenoids, is conferred by the presence of
hydroxyl groups, which destroy the cell membrane
of bac teria, causing the leakage of cellular
components. Moreover, these hydroxyl groups can
act in the active site of enzymes and damage the
metabolic processes of microorganisms (28). The
free hydroxyl groups in phenolic compounds and
flavonoids also act as antioxidants, as they inhibit
the generation of reactive oxygen species and
scavenge free radicals, thereby reducing the redox
potential of the growth medium (29).
CONCLUSIONS
This study provides new insights into the potential
antimicrobial effect of tomato leaf extracts on
common oral pathogenic bacteria, which may
ultimately result in the development of new herbal
products that might help prevent and treat oral
infections, such as dental caries and periodontal
disease. Our findings also support previous studies
on the high antioxidant capacity of tomato leaf
extracts.
CONFLICTS OF INTEREST
The authors declare no financial disclosure or
conflicts of interest.
ACKNOWLEDGEMENTS
This study was financed by CES Universit y
(INV.022019.013) and supported by the Center for
Pharmaceutical Science and Research (CECIF).
AUTHOR CONTRIBUTION
YM participated in the conception of the study,
collected the samples, conducted the laboratory
analyses, and contributed to the manuscript
preparation. MA-L par ticipated in the study
design, super vised the laborator y analyses,
performed the statistical analysis, and contributed
to the manuscript preparation. JS-G and DFR-V
participated in the conception and design of the
study, and critically revised the manuscript. JR-S
contributed to the study’s conception, design, and
supervision, and participated in the manuscript
preparation. All authors have read and approved
the final manuscript.
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