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Antimicrobial Activities of Leaf Extracts of Guava (Psidium guajava L.) on Two Gram-Negative and Gram-Positive Bacteria


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Aim. To determine the antimicrobial potential of guava (Psidium guajava) leaf extracts against two gram-negative bacteria (Escherichia coli and Salmonella enteritidis) and two gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) which are some of foodborne and spoilage bacteria. The guava leaves were extracted in four different solvents of increasing polarities (hexane, methanol, ethanol, and water). The efficacy of these extracts was tested against those bacteria through a well-diffusion method employing 50 μ L leaf-extract solution per well. According to the findings of the antibacterial assay, the methanol and ethanol extracts of the guava leaves showed inhibitory activity against gram-positive bacteria, whereas the gram-negative bacteria were resistant to all the solvent extracts. The methanol extract had an antibacterial activity with mean zones of inhibition of 8.27 and 12.3 mm, and the ethanol extract had a mean zone of inhibition of 6.11 and 11.0 mm against B. cereus and S. aureus, respectively. On the basis of the present finding, guava leaf-extract might be a good candidate in the search for a natural antimicrobial agent. This study provides scientific understanding to further determine the antimicrobial values and investigate other pharmacological properties.
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International Journal of Microbiology
Volume , Article ID , pages.//
Research Article
Antimicrobial Activities of Leaf Extracts of
Guava (Psidium guajava L.) on Two Gram-Negative
and Gram-Positive Bacteria
Bipul Biswas,1Kimberly Rogers,1Fredrick McLaughlin,2
Dwayne Daniels,3and Anand Yadav1
1MS Biotechnology Program, College of Agriculture, Family Sciences and Technology, Fort Valley State University,
Fort Valley, GA 31030, USA
2Department of Biology, Fort Valley State University, Fort Valley, GA 31030, USA
3Department of Chemistry, Fort Valley State University, Fort Valley, GA 31030, USA
Correspondence should be addressed to Bipul Biswas;
Received  July ; Accepted  September 
Copyright ©  Bipul Biswas et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Aim. To determine the antimicrobial potential of guava (Psidium guajava) leaf extracts against two gram-negative bacteria
(Escherichia coli and Salmonella enteritidis) and two gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) which are
some of foodborne and spoilage bacteria. e guava leaves were extracted in four dierent solvents of increasing polarities (hexane,
methanol, ethanol, and water). e ecacy of these extracts was tested against those bacteria through a well-diusion method
employing  𝜇L leaf-extract solution per well. According to the ndings of the antibacterial assay, the methanol and ethanol
extracts of the guava leaves showed inhibitory activity against gram-positive bacteria, whereas the gram-negative bacteria were
resistant to all the solvent extracts. e methanol extract had an antibacterial activity with mean zones of inhibition of . and
. mm, and the ethanol extract had a mean zone of inhibition of . and .mm against B. cereus and S. aureus,respectively.
On the basis of the present nding, guava leaf-extract might be a good candidate in the search for a natural antimicrobial agent.
is study provides scientic understanding to further determine the antimicrobial values and investigate other pharmacological
1. Introduction
Recently there has been a lot of attention focused on pro-
ducing medicines and products that are natural. Several
fruits and fruit extracts, as well as arrowroot tea extract []
and caeine [], have been found to exhibit antimicrobial
activity against E. coli O:H. is suggests that plants
which manifest relatively high levels of antimicrobial action
may be sources of compounds that can be used to inhibit
the growth of foodborne pathogens. Bacterial cells could be
killed by the rupture of cell walls and membranes and by the
irregular disruption of the intracellular matrix when treated
with plant extracts [].
e guava (Psidium guajava)isaphytotherapicplantused
in folk medicine that is believed to have active components
that help to treat and manage various diseases. e many
to manage conditions like malaria, gastroenteritis, vomiting,
diarrhea, dysentery, wounds, ulcers, toothache, coughs, sore
throat, inamed gums, and a number of other conditions
[]. is plant has also been used for the controlling
of life-changing conditions such as diabetes, hypertension,
and obesity [,]. In this study, we aim to evaluate
the total extracts of P. g u a j a v a leaves, growing at Fort
Valley State University, using various aqueous and organic
solvents to establish if it is eective against killing or
inhibiting the growth of foodborne bacterium Staphylo-
coccus aureus, Escherichia coli, Salmonella enteritidis,and
Bacillus cereus which can cause foodborne illness and
International Journal of Microbiology
F : USDA plant database. distribution of guava in USA.
e genus Psidium belongs to the family Myrtaceae,
which is considered to have originated in tropical South
America. Guava crops are grown in tropical and subtropical
areasoftheworldlikeAsia,Egypt,Hawaii,Florida(Figure ),
Palestine, and others. e genus Psidium comprises approx-
imately  species of small trees and shrubs in which only
 species produce edible fruits and the rest are wild with
inferior quality of fruits []. e most commonly cultivated
species of Psidium is P. g u a j a v a L. which is the common
guava. Other species are utilized for regulation of vigor, fruit
quality improvement and resistance to pest and disease [].
Guava fruit today is considered minor in terms of commercial
world trade, but it is widely grown in the tropics, enriching
the world.
e guava tree is an evergreen small tree. e guava
leaves are  to  inches long and  to  inches wide,
aromatic when crushed, and appear dull-green with sti but
coriaceous with pronounced veins []. ere are bioactive
components in the guava leaf that can ght against pathogens,
regulate blood glucose levels, and can even aid in weight loss.
e leaves of guava contain an essential oil rich in cineol,
cellulose, chlorophyll, mineral salts, and a number of other
xed substances [].
e general techniques of medicinal plant extraction
include maceration, infusion, percolation, digestion, decoc-
tion, Soxhlet extraction, aqueous-alcoholic extraction by fer-
mentation, counter-current extraction, microwave-assisted
extraction, ultrasound extraction, supercritical uid extrac-
tion, and phytonic extraction. Maceration extraction is crude
extraction; solvents diuse into solid plant material and
solubilize compounds with similar polarity []. Eect of
plant material depends on its origin, variations in the
extraction technique, the time, temperature of extraction,
solvent concentration and polarity, quantity, and secondary
metabolite composition of an extract []. Variations in
extraction methods are usually found in the length of the
extraction period, the solvent used pH, temperature, particle
size, and the solvent-to-sample ratio [].
Gonc¸alves et al. [] conducted a study where they
screened the antimicrobial eect of essential oils and
methanol, hexane, and ethyl acetate extracts from guava
leaves. e extracts were screened against bacteria strains
isolated from seabob shrimp and laboratory culture strains.
e guava leaves were extracted using a Soxhlet extractor
and solvents in order of polarity and then concentrated in
a rotary evaporator. e essential oil was obtained from
fresh leaves of guava using a Clevenger type doser and the
extraction methodology of Gottlieb and Magalh˜
aes []. e
fresh leaves were submerged in distilled water in a L glass
 h. e water and oil mixture were separated by drying with
anhydrous sodium sulphate and then ltered. e extracts
and the essential oil were evaluated by the disc diusion
method with the three extracts being tested at four concentra-
tions. ey found that the methanol extract showed greatest
bacterial inhibition. No statistically signicant dierences
were observed between the tested extract concentrations
and their eect. e essential oil extract showed inhibitory
activity against S. aureus and Salmonella spp. e researchers
concluded that guava leaf extracts and essential oil are very
active against S. aureus, thus making up important potential
sources of new antimicrobial compounds.
Antibacterial screening has been done selectively by
many researchers in guava essential oil and solvent extract
[,,,]. e mechanism by which they can inhibit
the microorganisms can involve dierent modes of action.
It has been reported that these oils and extracts penetrate
the lipid bilayer of the cell membrane, rendering it more
permeable, leading to the leakage of vital cell contents [,
]. Sanches et al. [] evaluated the antibacterial activities
of guava against gram-positive and gram-negative bacteria
testing ethanol and water extract of P. g u aj a v a leaves, stem,
bark and root, and aqueous extract against Staphylococcus
aureus werefoundtobemoreactivebyusingethanoland
water extract than with just aqueous extract [,]. Sacchetti
et al. [] reported that the oil showed a strong resistance
against Yar r o w ia l i p oly t i ca which is a pathogenic yeast. Vieira
et al. []havealsoreportedtheantibacterialeectofguava
leaves extracts and found that they inhibited the growth of the
S. aureus. Gnan and Demello [] testing guava leaf extract
found good antimicrobial activity against nine dierent
strains of Staphylococcus aureus. e antibacterial activity
of guava leaf extract was tested against acne developing
organisms by Qadan et al. []concludingthattheleaf
extracts may be benecial in treating acne especially when
they are known to have anti-inammatory activities.
Phytochemicals are nonnutritive chemicals produced by
plants for their own protection, but they have been found to
protect humans against diseases through recent research. Sci-
only small fractions have been studied closely and each one
works dierently []. Begum et al. []reportedtheisolation
of two triterpenoids: guavanoic acid and guavacoumaric
acid from the leaves of guava. Four avonoids were isolated
to inhibit the growth of Salmonella enteritidis and Bacillus
cereus. A study was done to evaluate the spasmolytic activity
International Journal of Microbiology
F : (a) Existence of saponin tests; L to R: n-hexane, methanol, ethanol, and distilled water extracts. (b) Existence of phenols and tannins
tests; L to R: n-hexane, methanol, ethanol, and distilled water extracts. (c) Existence of terpenoids tests; L to R: n-hexane, methanol, ethanol,
and distilled water extracts. (d) Existence of avonoids tests; L to R: n-hexane, methanol, ethanol, and distilled water extracts. (e) Existence
of glycosides tests; L to R: n-hexane, methanol, ethanol, and distilled water extracts.
of guava leaf and was found that a compound called “aglycone
quercetin” is responsible for spasmolytic activities, which is
formed when avonoids of guava leaves are hydrolyzed by the
gastrointestinal uids.
2. Materials and Methods
2.1. Preparation of Plant Extract. e leaf samples were
collected from the guava trees growing at the Specialty Plant
House at Fort Valley State University. Random leaf samples
were collected into plastic zip lock bags with appropriate
to the laboratory for extraction.
2.2. Extraction Methods Used on Guava. e leaf samples
were washed in tap water, dried, and placed into a blender
to be grounded into powder. Four solvents were arranged
in increasing polarity; n-hexane (>%), methanol (>%),
ethanol (>.%),andboilingdistilledwaterwereusedfor
the maceration extraction procedure. e leaf powder was
e mixtures were made in sterile  mL Erlenmeyer ask
wrapped in aluminum foil to avoid evaporation and exposure
on a platform shaker at  rpm. Aer  days of soaking in
solvent, the mixtures were transferred to  mL tubes and
C. e supernatant
2.3. Phytochemical Analysis. Chemical tests for the screening
and identication of bioactive chemical constituents in the
guava were carried out with the extracts using the standard
procedure as described []. For each test, mL of each
solvent extract was used for analysis, in exception for the
saponin test in which  mL solvent extract was used.
2.4. Test for Saponins. Extract was placed in a test tube and
shaken vigorously. e formation of stable foam was taken as
an indication for the presence of saponins (Figure (a)).
2.5. Test for Phenols and Tannins. Extract was mixed with
3. A blue-green or black coloration
indicated the presence of phenols and tannins (Figure (b)).
International Journal of Microbiology
2.6. Test for Terpenoids (Salkowski’s Test). Extract was mixed
with  mL of chloroform. en  mL of concentrated sulfuric
acid was added carefully and shaken gently. A reddish brown
coloration of the interphase was formed to show positive
results for the presence of terpenoids (Figure (c)).
2.7. Test for F l a v o n o i ds (Shin o d a Te s t ). Extract was mixed
with magnesium ribbon fragments, and concentrated
hydrochloric acid was added drop wise. Orange, red, pink,
or purple coloration indicates the presence of avonoids
(Figure (d)).
2.8. Test for Glycoside. Extract was mixed with  mL of glacial
acetic acid containing  drops of % FeCl3.emixturewas
poured into another tube containing  mL of concentrated
sulfuric acid. A brown ring at the interphase indicates the
presence of glycosides (Figure (e)).
2.9. Panel of Microorganisms. A board of organisms compris-
ing  Gram-negative bacteria, Escherichia coli (Escherichia
coli B, Living Bacteriophage Host, item no. ) and
Salmonella enteritidis ((Salmonella enteritidis,MicroKwik
Culture, Pathogen, item no. A), and  Gram-positive
bacteria, Staphylococcus aureus (Staphylococcus aureus, coag-
ulase positive), MicroKwik Culture, Pathogen, item no.
A) and Bacillus cereus (Bacillus cereus, Living, item
no. ) was selected to test the guava extracts ability to
inhibit the growth. All strains were purchased from Carolina
Biological Supply Company, (Burlington, NC -,
USA). Prior to sensitivity testing, each of the bacteria strains
were cultured onto nutrient agar plates and incubated for 
to  h at C to obtain colonies. Aer overnight incubation,
colonies were selected with a sterile disposable inoculating
loop and transferred to a glass tube of sterile physiological
turbidity is then compared to that of the . McFarland
standard solution (containing about . ×8CFU/mL).
2.10. Antibacterial Activity. Antimicrobial susceptibility test-
ing was done using the well-diusion method according
to the standard of the National Committee for Clinical
Laboratory Standards []. e plant extracts were tested on
Mueller Hinton II plates to detect the presence of antibacterial
activity. Prior to streaking the plates with bacteria,  mm
diameter wells were punched into the medium using a sterile
borer. All plates were inoculated with the test bacterium
which has been previously adjusted to the . McFarland
standard solution; a sterile cotton swab was dipped into the
suspension, rotated several times, and pressed rmly on the
inside wall of the tube above the uid level removing excess
inoculum. e surface of the agar plate was streaked over
an even distribution of inoculum with a nal swab around
the rim. e plates are allowed  to  min to dry the excess
moisture. Fiy uL aliquots of each test extract was dispensed
into each well aer the inoculation of the plates with bacteria.
apart. e same extract was used on each plate, with a total of
T : Phytochemical constituents of Psidium guajava extracts.
Saponins Terpenoids Flavonoids Glycosides
n-Hexane −− −
Methanol + +++
Ethanol + +++
water ++ + + +
+: presence of constituent (positive); : absence of constituent (negative).
three plates used for each extract for selecting bacterium. For
each bacterial strain, controls were maintained where pure
solvents were used instead of the extract. e plates are sealed
with paralm, labeled, and placed in an incubator set to C.
Aer  hours of incubation, each plate was examined for
inhibition zones. A ruler was used to measure the inhibition
zones in millimeters. Every experiment was carried out in
parallel, and the results represented the average of at least
three independent experiments.
3. Results and Discussions
3.1. Phytochemical Analysis. Tab l e  shows the summarized
phytochemical screening of chemical constituents of guava
extracts under study on qualitative basis. e results revealed
extracts. As the table shows, the methanol and ethanol
extracts indicate the presence of tannins, phenols, avonoids,
terpenoids, and glycosides, but absence of saponins. Distilled
water is the only that showed the presence of all the phyto-
chemicals, whereas solvent n-hexane failed to have any of the
chemical compounds present.
e analysis of the plant extracts revealed the presence
of phytochemicals which are known to exhibit medical and
physiological activities. For example, tannins are polypheno-
lic compounds that bind to proline rich protein that interferes
with protein synthesis [,,] and has shown to have
antibacterial activity [,]. Flavonoids are hydroxylated
polyphenolic compounds known to be produced by plants in
response to microbial infections to which this aspect has been
against an array of microorganisms in vitro []. eir ability
extracellular and soluble proteins and bacterial cell walls
[]. Terpenoids although mainly used for their aromatic
inhibiting bacteria []. Saponins which are glycosides have
organism, S. aureus. erefore, the phytochemical analysis
revealed that the methanol, ethanol, and distilled water
extract have chemical compounds that have been found
to possess antibacterial activities, which could contribute
to the results obtained from antibacterial analysis. Figures
(a) to (e) show the colorimetric results for the solvent
International Journal of Microbiology
T : Antibacterial activity of Psidium guajava leaves of the
screened solvents extracts.
Plant extracts Zone of inhibition(mm)
B. cereus S. aureus E. coli S. entertidis
n-Hexane — —
Ethanol 6.11 ± 0.60 11.0 ± 0.52 ——
Methanol 8.27 ± 0.44 12.3 ± 0.78 ——
Wat e r — —
Inhibition zones are the mean including borer ( mm) diameter ±standard
—: no inhibitory activity.
3.2. Antibacterial Activity. e results of the study indi-
cated that only two of the crude solvent extracts prepared
from the leaves of Psidium guajava, methanol and ethanol,
showed inhibitory activity against bacteria (Table ). Only
Gram-positive bacteria, Bacillus cereus and Staphylococcus
aureus, were susceptible to the two extracts, while neither
 mg/ 𝜇L, the methanol extract had a slightly higher
antibacterial activity with mean zones of inhibition . and
. mm than ethanol extract with mean zone of inhibition
. and . mm against B. cereus and S. aureus,respec-
tively. e resistance of the Gram-negative bacteria could be
attributed to its cell wall structure. Gram-negative bacteria
have an eective permeability barrier, comprised of a thin
lipopolysaccharide exterior membrane, which could restrict
the penetration of the extruding the plant extract. It has
been reported earlier that Gram-negative bacteria are usually
more resistant to the plant-origin antimicrobials and even
show no eect, compared to Gram-positive bacteria [
]. Gram positive bacteria have a mesh-like peptidoglycan
layer which is more accessible to permeation by the extracts
Results found in this study were supported and/or
opposed in the data reported in literature. Nascimento et al.
[] conducted a study which supports the nding of the
present study in which the guava extract was able to have
inhibitory eects against Staphylococcus and Bacillus and no
eect on the Escherichia and Salmonella, whereas Chanda
and Kaneria [] oppose the ndings concerning the Gram-
negative bacteria. Mahfuzul Hoque et al. [] found no
antibacterial activity of ethanolic extracts of guava against E.
coli and S. entertidis; however Vieira et al. [] found guava
sprout extracts were eective against inhibiting E. coli.
Sanches et al. [] found that the aqueous extract of
guava was eective against Staphylococcus and Bacillus.e
methanolic extracts of guava reported by Lin et al. []
showed signicant inhibitory activity against the growth of
isolatesofSalmonella and enteropathogenic E. coli.
4. Conclusions
e present work demonstrates the antimicrobial potential
of Psidium guajava leaves extract by using various solvents.
e results indicate that ethanol and methanol are better than
n-hexane and water for the extraction of the antibacterial
properties of guava. e results also indicate that the plant
extracts have no antibacterial eect on the Gram-negative
bacteria, showing that they do not contain active ingredients
against the organisms. e observed inhibition of Gram-
positive bacteria, Bacillus cereus and Staphylococcus aureus,
suggests that guava possesses compounds containing antibac-
terial properties that can eectively suppress the growth
when extracted using methanol or ethanol as the solvent.
Comparisons with related data from the literature indicate
that according to the dierent methodologies of studies
on antibacterial activity, the most diverse outcomes can be
obtained. is study provides scientic insight to further
determine the antimicrobial principles and investigate other
pharmacological properties of guava. On the basis of the
present nding, P. g u a j a v a leaves possess the capabilities
of being a good candidate in the search for a natural
antimicrobial agent against infections and/or diseases caused
by B. cereus and S. aureus.
is work was apprehended by the nancial support provided
to one of the authors, Kimberly Rogers, (MS student) through
the “Advancing Graduate Education in the STEM Disciplines
for the Underserved African American and Low Income
American Population” grant (FVSU Project no. -
---, Dr. Anand K. Yadav, PD/PI)
funded by the College of Agriculture, Family Sciences and
Technology, Fort Valley State University by the United States
Department of Education.
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... Acacia nilotica water and methanolic extract have also been shown to have antimicrobial properties against some fungus species, gram-negative and gram-positive bacteria (Naqvi et al. 2011). Pharmacological studies on P. guajava have shown anti-cestode (Tangpu and Yadav 2006), anti-bacterial (Biswas et al. 2013), anti-Toxoplasma gondii (Lee et al. 2013), anti-helminthic activity against Haemonchus contortus (Molla andBandyopadhyay 2014), anti-Trypanosoma, anti-Leishmania (de Souza et al. 2017), and anti-malarial activity (Yadav et al. 2020). Based on these results, herein we investigated the possible acaricidal activities of these plants. ...
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Infestation by Sarcoptes scabiei var. cuniculi mite causes scabies in humans and mange in animals. Alternative methods for developing environmentally friendly and effective plant-based acaricides are now a priority. The purpose of this research was the in silico design and in vitro evaluation of the efficacy of ethanol extracts of Acacia nilotica and Psidium guajava plant leaves against S. scabiei. Chem-Draw ultra-software (v. was used to draw 36 distinct compounds from these plants that were employed as ligands in docking tests against S. scabiei Aspartic protease (SsAP). With docking scores of − 6.50993 and − 6.16359, respectively, clionasterol (PubChem CID 457801) and mangiferin (PubChem CID 5281647) from A. nilotica inhibited the targeted protein SsAP, while only beta-sitosterol (PubChem CID 222284) from P. guajava interacted with the SsAP active site with a docking score of − 6.20532. Mortality in contact bioassay at concentrations of 0.25, 0.5, 1.0, and 2.0 g/ml was determined to calculate median lethal time (LT 50) and median lethal concentration (LC 50) values. Acacia nilotica extract had an LC 50 value of 0.218 g/ml compared to P. guajava extract, which had an LC 50 value of 0.829 g/ml at 6 h. These results suggest that A. nilotica extract is more effective in killing mites, and these plants may have novel acaricidal properties against S. scabiei. Further research should focus on A. nilotica as a potential substitute for clinically available acaricides against resistant mites.
... The blend of secondary metabolites from mesquite caused quadratic effects on nutrient digestibility, MP synthesis, molar proportion of propionic acid, and serum glucose and lactate concentrations when the level varied from 3.09 to 3.80 g/day, with an average value of 3.43 ± 0.17 g/day. Secondary compounds are particularly able to inhibit Gram-positive bacteria, affecting them to a greater extent (Benchaar and Greathead, 2011), but without inhibiting Gram-negative bacteria (Biswas et al., 2013), suggesting that Gram-positive bacteria are more susceptible to the antibacterial properties of secondary compounds (Benchaar et al., 2008;García-González et al., 2010;Bodas et al., 2012). ...
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Although chemical additives are able to improve the efficiency of ruminal fermentation, they can leave residues in the meat. However, a blend of secondary metabolites can improve ruminal fermentation without harming the population welfare. Five levels (0.0, 1.5, 3.0, 4.5, and 6.0 g/day) of a blend of secondary metabolites from mesquite extract in sheep feed to promote increases in the nutritional value, ruminal parameters, nitrogen (N) use efficiency, microbial protein (MP) synthesis, and blood metabolites. Ten intact male Santa Inês sheep with average body weight of 55 ± 9.81 kg were used in a 5 × 5 Latin square design, replicated twice. There was a quadratic response of the digestibility of dry matter (DM), organic matter (OM), crude protein (CP), and total digestible nutrients (TDN). Microbial protein concentrations, MP synthesis efficiency, propionic acid levels, and acetic/propionic acid ratio also showed a quadratic response. The blend promoted a quadratic effect on plasma glucose and lactate levels. On the other hand, it decreased the concentrations of ammoniacal nitrogen, plasma urea, and plasma cholesterol. It is recommended to supply a blend of secondary metabolites at 3.43 g/day.
... At similar concentrations (23 mg), the hydrophilic extract did not show any inhibitory activity (Supplementary Fig. S4). Investigations by Biswas et al. previously noted that while some extracts of P. guajava pose modest antimicrobial activities, the aqueous extract was found to have no inhibitory effect on all the tested microbes including S. aureus (Biswas et al., 2013). Our finding are in accord with these previous reports. ...
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There had been some reports demonstrating the green synthesis of silver nanoparticles using guava (Psidium guajava (L.) extract); however, detailed and in-depth interrogation of the vital synthesis parameters for rapid, facile, efficacious synthesis at room temperature, and robust characterization of the as-prepared nanoparticle is currently lacking. This study presents a comprehensive delineation of the sustainable phyto-fabrication of biogenic guava phenolic extract functionalized silver nanoparticles (GVE-SNP) based on guava phenolic extract as the sole reductant/stabilizer, as well as the synthesis optimization, thorough physicochemical characterization and potential biological applications of the as-prepared nanosilver. The results revealed that successful synthesis of GVE-SNP was instantaneous and maximum intensity of the plasmonic peak at 425 nm was achieved in less than 10 min. GVE-SNP was found to present stable, well-dispersed, round, uniform, and crystalline nanoparticles of about 5.88 nm. The FTIR and RAMAN spectra indicated that GVE-SNP surface was properly capped by bioactives from GVE. The nanoparticles displayed potent radical scavenging activity against ABTṠ⁺ and DPPḢ. Also, GVE-SNP exhibited a significant and dose-response inhibitory effect against tyrosinase. Furthermore, the nanoparticles displayed good cytotoxicity against L929 fibroblast and were found to possess strong antimicrobial properties, inhibiting the growth of S. aureus and S. epidermidis.
... The reason why the samples were not effective against E.coli bacteria in this study; It was thought that the chitosan concentration lower than previous studies 85,86 . On the other hand, it has been reported earlier gram-negative bacteria are more resistant to antibacterial polymers and even show no effect, compared to gram-positive bacteria 87,88 . Gram-positive bacteria have a mesh-like peptidoglycan coating that allows polymers to penetrate more easily 89 . ...
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In this study, foaming-agent free novel polyvinyl acetate (PVAc) foams reinforced with bio polymers were manufactured through freeze-drying technique. The physical, morphological and antibacterial properties of foams which were reinforced with different ratio of zinc borate and water-soluble chitosan were investigated according to relevant standards. The PVAc foams showed low densities (0.12 g/cm 3-0.21 g/cm 3) and high porosity rates (87.50%-79.05%). The results showed that although the foams have no antibacterial character against Escherichia Coli, they have antibacterial character against Staphylococcus Aureus bacteria. This study mainly focusses on physical and morphological properties of the foams. However, researchers also performed accelerated weathering tests to determine its usability in different industries. The effects of accelerated weathering on the surface of foams were investigated by measuring surface color. The highest color difference was determined 8.09. This foam can be used as a low-density packaging material and/or medical box with its promising physical and morphological properties with hazardous-chemical free structure.
... Sometimes, these natural medications serve as , Ischnosiphon polyphyllus (arumã), Jatropha gossypiifolia (Pinhão-Roxo or Pião-Roxo) was used to design a protocol in order to regress and cure necrotizing fasciitis. This decoction has shown antibiotic and anti-inflammatory properties with no side effects based on the scientific literature that reports experiments carried out in vitro and/or in vivo with these plants [3][4][5][6][7][8][9][10][11][12][13][14][15]. ...
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Necrotizing fasciitis (flesh-eating disease) is a rare but life-threatening condition. We report one case of severe necrotizing fasciitis affecting the leg at risk of being amputated due to infection, before and after treatment with medicinal plants which have empirical broad-spectrum antibiotic and anti-inflammatory properties. All the medical attempts with conventional antibiotics failed and we had to act rapidly in order to cure the infection and prevent the amputation. These results suggest that certain medicinal plants could represent a treatment option and that further studies are considered.
... Neem contains several active chemical compounds (Mondali et al., 2009;Sudhir et al., 2010), the most commonly active compounds in Neem are azadirachtin, nimbin and nimbidine (Mondali et al., 2009). The result for Guava leaves corroborates with the results of Biswas et al. (2013) who also showed inhibitory activity of ethanolic extract against S. aureus. Many researchers too have reported that the Guava leaf extract had a potent antibacterial activity against various bacteria including S. aureus (Kummee et al., 2015), Streptococcus spp., and E. coli (Gutierrez et al., 2008;Kanbutra et. ...
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The in vitro efficacy of ethanolic and aqueous extract of selected plants namely Neem (Azadirachta indica), Guava (Psidium guajava), Lemongrass (Cymbopogon citratus), Mango (Mangifera indica), Tulsi (Ocimum sanctum) and Seasum (Dalbergia sissoo) leaves was studied against E. coli, Staphylococcus aureus and whole milk culture. The antibiogram revealed that S. aureus isolates were 100% susceptible to ethanolic extracts of only Neem and Guava in addition to standard drug Streptopenicillin followed by Lemongrass that showed 60 % sensitivity. The percent sensitivity of ethanolic extract of these plants against isolates of E. coli was 60, 40, 40, 0, 0 and 0, respectively. In whole milk culture the sensitivity percent was 100% for Neem, Guava, Lemon grass in comparison to 40% for Mango leaves and 0 % each for Tulsi and Seasum leaves. The aqueous extract of Neem, Lemongrass and Mango leaves did not show any activity against the isolates of S. aureus (0% sensitivity). All the leaf extracts were inactive against E. coli (0% sensitivity). The extract of Neem exhibited sensitivity against 40% isolates of whole milk culture
... Before preparing the petri plates, liquid cultures of the microbial strains were prepared by inoculating lactose broth with previously prepared sub cultures and incubating it for 24 hours at 37C to observe the turbidity. [13] The nutrient agar containing petri plates were inoculated with these liquid cultures using spread plating method. ...
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The traditional medical practice is an integral part of the culture and the interpretation of health by indigenous populations in most of the world. Guava (Psidium guajava L.) leaves have traditionally been used to manage several diseases such as rheumatism, diarrhea, diabetes mellitus, and cough. In this present investigation antifungal and antibacterial property of guava leaves were estimated using Bacillus subtilis (Gram positive bacterial strain), Escherichia coli (Gram negative bacterial strain), Saccharomyces cerevisiae (Yeast, fungal strain) and Aspergillus niger (Mould, fungal strain) strains. The growth of gram positive bacteria and fungal strains were inhibited strongly, whereas gram negative bacterial strain displayed less sensitivity against the antimicrobial (antifungal and antibacterial) property of guava leaf extract. Zone inhibition assay also confirmed the result. Phytochemical analysis (qualitative and quantitative) revealed that guava leaf extract was rich in wide range of poly phenols. It was found that guava leaves are rich in phenols, flavonoids and tannins whereas components like alkaloids, flavonoids, saponins and triterpenes are present in comparatively lesser amounts. As polyphenols have strong antimicrobial property, it can be concluded that rich source of phenols, flavonoids and tannins are the probable cause of anti microbial property of guava leaves.
... Guava (Psidium guajava) is a popular fruit in the tropics and subtropics, and belongs to the family Myrtaceae (Naseer et al. 2018).Guava leaf exhibits medicinal, immunomodulatory, antioxidant, and antimicrobial properties (Nwinyi et al. 2008;Metwally et al. 2010;Biswas et al. 2013;Jang et al. 2014;Naseer et al. 2018). Some works have explored the potential of guava leaf as a dietary protein source in broiler chickens (Rahman et al. 2013;Daing et al. 2020). ...
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This study investigated the effects of dietary supplementation of guava leaf (GL), oxytetracycline, and tert�butylhydroxytoluene on growth, immune status, gut microbial population, and meat quality of broiler chickens. A total of 280 Ross 308 one-day-old chicks were randomly allotted to either G-0; basal diet (BD) without additive; G-1; BD + 0.5 g/kg oxytetracycline + 0.15 g/kg tert-butylhydroxytoluene; G-2; BD + 2.5 g/kg GL; or G-3; BD + 5 g/kg GL for six weeks. At 1-21 d, G-1 and G-2 birds had higher (P<0.05) body weight gain (BWG) and feed efficiency compared with G-0 and G-3 birds. At 22-42 d, the supplemented birds consumed more feed than the G-0 birds. At 1-42 d, BWG and feed intake were higher (P<0.05) in the supplemented birds compared with the G-0 birds. Hematological indices were not affected by the diets. GL�supplemented birds had lower (P<0.05) serum and meat cholesterol than the G-0 and G-1 birds. The G-0 birds had higher tumor necrosis factor-α (83.69 pg/mL) and lower interleukin-10 (5.84 pg/mL) than birds fed other diets. The G-3 birds had lower (P<0.05) interleukin-1β and immunoglobulin M than other birds. Dietary supplements lowered (P<0.05) clostridium, coliforms, and salmonella counts in caecum and ileum. GL-supplemented birds had a higher ileal Lactobacillus count than G-0 and G-1 birds. Carbonyl and malondialdehyde contents were lower (P<0.05) in the supplemented meat on day 4 postmortem. Antioxi�dant enzymes and total antioxidant capacity were higher in the G-3 meat compared with other meats. Breast meat quality was not affected by diet. GL could be a potent antioxidant and antimicrobial in broiler diets.
Given the intense interest in the use of herbal extracts to improve fish growth, fish health, and disease resistance in fish in culture systems, in this study, we examined the effects of a blend of Guava, Bitter and Neem leaf extracts (GBNL) (i.e., 1:1:1 for GL, BL, and NL respectively) at different inclusion (i.e. 0 GBNL gkg⁻¹, 1 GBNL gkg⁻¹, 3 GBNL gkg⁻¹, 5 GBNL gkg⁻¹, 7 GBNL gkg⁻¹ and 10 GBNL gkg⁻¹) levels on growth, haematology, immunity, liver toxicity and resistance to bacterial co-infections in Nile tilapia. After 8 weeks of feeding, Nile tilapia fed 3 GBNL gkg⁻¹ diets showed significant effects in improving weight gain compared to those fed the control diet. GBNL fed fish showed improved health of fish by stimulating significant increases in levels of White blood cells, Red blood cells, Hemoglobin, and Hematocrit in relation to those fed the control diet. Also, the applications of deferent GBNL levels in Nile tilapia diets showed the potential to upregulate the expression of the immune-related genes heat shock protein 70, chicken type lysozymes, and Beta-defensin, with significant effects shown in fish fed 5GBNL gkg⁻¹ diets in comparison to the control. The results also indicate that GBNL supplementation can decrease mortalities to co-infection of Streptococcus agalactaie and Aeromonas jandaie in Nile tilapia with the lowest mortalities of 13.65% and relative per cent survival of 82.57 % in fish fed 5GBNL gkg⁻¹. Despite the potential of GBNL applications in Nile tilapia, findings of this study indicate fish fed the different concentrations of GBNL, particularly with 7 GBNL gkg⁻¹ can promote the leaching of the liver enzymes ALT, AST, and ALT into the bloodstream which is suggestive of potential liver damage in Nile tilapia. Histological examinations of a cross-section of the liver tissues of fish fed GBNL showed various injuries including hydropic changes, pyknosis nuclei, erythrocytes congestion and vacuolation with the severest seen in those fed 7 GBNL gkg⁻¹. Taking all of the above into consideration, 5GBNL gkg⁻¹ application could improve the health and disease resistance of Nile tilapia; however, prolong use thus after 8 weeks of administration could be injurious to fish liver health.
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This study reports on the chemical compound composition of 78 species of plants traditionally used as medicines on the North coast of Peru. This first assay serves as a baseline for more in-depth studies on plant compound composition and serves as background to understand and better apply bio-assays results. Resumen Este estudio reporta sobre la composición de compuestos químicos en 78 plantas tradicionalmente usadas como medicina en la región de costa norte de Perú. Este ensayo preliminar sirve como base para estudios mas avanzados sobre composición química de plantas medicinales, y también como fondo para entender y mejorar bio-ensayos. Palabras clave: Análisis fitoquímico, plantas medicinales, norte del Perú.
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North-eastern India has been known for its rich biological diversity. For this study, seven medicinal plants such as Bryophyllum pinnatum, Ipomea aquatica, Oldenlandia corymbosa, Ricinus communis, Terminalia bellerica, Tinospora cordifolia, and Xanthium strumarium, were selected. The aim of the present study was to investigate the presence of phytochemicals and to determine the total phenolic and flavonoid contents of the selected medicinal plants. Soxhlet apparatus was used for the organic solvent extraction. Solvents used were water, methanol, ethanol, and acetone. Total phenolic contents of the aqueous extracts of the plants were determined by the Folin-Ciocalteus reagent method whereas total flavonoid contents of the aqueous extracts were determined by the Aluminium Chloride method. Proteins, carbohydrates, phenols, tannins, flavonoids, saponins, were detected in all of the plants tested. Total phenolic contents obtained were 18.4mg/gm, 18.8mg/gm, 11.6mg/gm, 29.2mg/gm, 29.6mg/gm, 40.8mg/gm, 12.8mg/gm, 71.6mg/gm of the extract and total flavonoid contents obtained were 8.4mg/gm, 37.6mg/gm, 4.4mg/gm, 6mg/gm, 42.8mg/gm, 18mg/gm, 6mg/gm, 28.8mg/gm of the extract for the plants Bryophyllum pinnatum (Leaves), Ipomea aquatica (Leaves), Oldenlandia corymbosa (Whole plant), Ricinus communis (Roots), Terminalia bellerica (Leaves), Tinospora cordifolia (Leaves), Tinospora cordifolia (Stem), and Xanthium strumarium (Leaves) respectively. Our findings provided evidence that crude aqueous and organic solvent extracts of these tested plants contain medicinally important bioactive compounds and it justifies their use in the traditional medicines for the treatment of different diseases.
Medicinal plants have recently received the attention of the pharmaceutical and scientific communities and various publications have documented the therapeutic value of natural compounds in a bid to validate claims of their biological activity. Attention has been drawn to the antimicrobial activity of plants and their metabolites due to the challenge of growing incidences of drug-resistant pathogens. Some plants have shown the ability to overcome resistance in some organisms and this has led to researchers’ investigating their mechanisms of action and isolating active compounds. Particular focus is on establishing the effect of the plant(s) extracts in terms of their microstatic and microcidal action and the spectrum of organisms affected. This has enabled exploitation of plants for the treatment of microbial infections and in the development of new antimicrobial agents. This requires rigorous research and it is therefore imperative to follow standard methods to authenticate claims of antimicrobial action. Results comparability is largely dependent on the techniques employed in the investigations and conclusive results can only be obtained if methods are standardized and universal. This paper reviews the current methods used in the investigations of the efficacy of plants as antimicrobial agents and points out some of the differences in techniques employed by different authors.
Three strains of pathogenic bacteria were treated with condensed tannins (CT) purified from eight different woody plant species to investigate their inhibition effect on the growth of these bacteria in vitro. Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were tested against low (0, 2, 4 and 8 mg CT/ml) and high dose levels (0, 50, and 100 mg CT /ml) of CT extracted from different plant species. When exposed to purified tannin extracts at 4 mg extract/ml dosage, growth inhibition of S. aureus was dose dependent manner and observed in the following order: Shinnery oak > Post oak > Locust > Blackjack oak Skunk bush > Sericea lespedeza > commercial Quebracho Sumac > Plum. The extracts from Shinnery and Post oaks were particularly inhibitory against S. aureus, having growth inhibition zones exceeding 23 mm at 8 mg tannin extract/ml. S. aureus and E. coli exhibited dose dependent and susceptibility (P < 0.01) when exposed to 4 mg/ml of the following tannin monomers which exhibited differential inhibitory activity: catechin > ellagetannin tannic acid epi-catechin gallotannin. In the presence of high dose levels at 0, 50, and 100 mg tannin extract/ml, inhibition zones of growth were varied among plant species. The findings indicated that source and concentration are important factors that influence antimicrobial activity of tannins. Because some of the plant tannin extracts are highly inhibitory to selected pathogens, they may provide alternatives and supplements to conventional antimicrobial feed additives.
The macromolecules of plants are distinguished from all other constituents by their high molecular weight. This may vary from 10000 to over 1000000, whereas in other plant metabolites the molecular weight is rarely above 1000. Chemically, macromolecules consist of long chains of small structural units or ‘building blocks’, linked covalently in a number of different ways. Chemical characterization in the first instance therefore depends on identifying these smaller units. Proteins, for example, are long chains of amino acids (up to twenty different ones) joined together through peptide (—CO—NH—) links. Polysaccharides are similarly derived from the union of simple sugar units, such as glucose, joined through ether (—O—) links. The nucleic acids, by contrast, are more complex and have three types of structural unit: purine and pyrimidine bases, pentose sugars and phosphate groups. The three main classes of macromolecules found in plants are thus proteins, polysaccharides and nucleic acids. However, mixed polymers are also known. such as the glycoproteins, which contain both sugars and amino acids in covalent linkage.
Six new complex tannins, guajavins A (5) and B (1), psidinins A (9), B (11) and C (13), and psiguavin (15), together with a variety of condensed, hydrolyzable and complex tannins, have been isolated from the bark of Psidium guajava L. (Myrtaceae). On the basis of chemical and spectroscopic evidence, the structures of guajavins and psidinins were established to consist of a (+)-gallocatechin unit and a hydrolyzable tannin moiety linked C-glycosidically, while psiguavin was found to be a novel metabolite probably derived from eugenigrandin A (7) through successive oxidation, benzylic acid-type rearrangement, decarboxylation and oxidative coupling of the gallocatechin B-ring and one of the aromatic rings in the hydrolyzable tannin moiety.