Aguoru CU et al. / Journal of Science / Vol 5 / Issue 9 / 2015 / 729-733.
e ISSN 2277 - 3290
Print ISSN 2277 - 3282
Journal of Science
Botany
www.journalofscience.net
EVALUATION OF THE PHYTOCHEMICAL AND ANTIMICROBIAL
ACTIVITIES OF SELECTED MEDICINAL PLANTS (PSIDIUM
GUAJAVA, CARICA PAPAYA AND CYMBOPOGON CITRATUS) IN
BENUE STATE, NIGERIA
C.U. Aguoru, N. Inda and J.O. Olasan
Department of Biological Sciences, Botany Unit, University of Agriculture, Makurdi. Nigeria.
ABSTRACT
This study aimed at evaluating the phytochemical and antimicrobial activities of three selected medicinal plants in
Benue State, Nigeria. The bioactive components in the leaves of guava (Psidium Guajava), Pawpaw (Carica Papaya) and
Lemon grass (Cymbopogon citratus) were extracted using organic solvent (methanol) and tested against Staphylococcus
aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pyogenase, Salmonella typhi, Shigella flexneri. The
methanolic extracts of the three plants inhibited the growth of tested microbes at different MICs and MCBs. P. guajava
methanolic extract was the most effective of the three extracts which demonstrated the highest activities against all the gram
positive and negative bacteria followed by C. papaya and Cymbopogon citratus. Hence, this suggests the medicinal uses of
the plants against pneumonia, wound infections, typhoid fever, gastro intestinal infections, urethritis and shigellosis, all of
which are caused by the microbes investigated in this study.
Keywords: Psidium guajava; Carica papaya; Cymbopogon citratus; Extract; Antimicrobial activities.
INTRODUCTION
Plants and their organs house many active
ingredients which are precursors in drug synthesis
Therefore, medicinal plants are important in
pharmacological research and drug development [1].
Various authors have worked on phytochemical screening
using guava, pawpaw and other plants. For instance, [2]
selected six Nigerian plants based on ehnobotanical
reports of their antifungi and anti-bacterial actions and
subjected them to phytochemical and antimicrobial
screening.The results revealed the presence of alkaloids,
saponins and combined anthraquinones which justify their
antimicrobial activities. Similarly, [3] worked on
antioxidant and antimicrobial properties of five medicinal
Libyan plants extract to evaluate their biological
activities. Their crude extract showed pontential
proportional to their concentration. The aqueous extract
displayed weak antimicrobial activity whereas,
methanolic extracts where profoundly effective against
both G+ve and G-ve bacteria. Additionally, [4] evaluated
antibacterial activities of some Nigerian Medicinal plants
against some resistant bacterial pathogens using agar well
diffusion method.Results of this study revealed that all the
leaf extracts had antibacterial activity against the test
organisms at various concentrations. Again, [5] examined
antimicrobial and antioxidant activities of some Nigerian
medicinal plants. In view of the above, the present study
is aimed at evaluating the bioactive ingredients and
antibacterial activities of selected Nigerian plants, which
are commonly used in treating many known ailments and
diseases in a traditional way.
The selected plants are Lemon grass
(Cymbopogon Citratus), Guava (Psidium guajava) and
Pawpaw (Carica papaya). The importance of this study
cannot be overemphasized owing to the rising level of
resistance of pathogenic microorganisms to available
conventional drugs.
Corresponding Author:- C.U. Aguoru Email:- [email protected]
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Aguoru CU et al. / Journal of Science / Vol 5 / Issue 9 / 2015 / 729-733.
RESULTS AND DISCUSSION
The phytochemical profile of methanol extracts
of the three plants is presented in table 1. This work
presents the antimicrobial activity of each extract on the
test organisms. MIC is defined as the lowest
concerntration of an antimicrobial agent that inhibited the
visible growth of a microorganism after overnight
incubation [7]. The least concentration where no bacteria
growth is recorded is the MBC.
In Psidium guajava leaf extract, low MIC was
observed in S. flexneri, E. coli and S. typhi (12.5mg each)
at 100mg of MBC. However, S. aureus and P. aeruginosa
developed resistance to the plant extract (table 2, figure
1). Low MIC of 12. 5mg was recorded against S.
pyogenase, E. coli and S.typhi using Carica papaya (leaf)
(table 3, figure 2) but it was ineffective against P.
aeruginosa. However, the fruit and seed of this plant were
highly effective against S. aureus, S. flexneri and S. typhi
at low MIC value but high MBC (table 4, figure 3).
Psidium guajava stem was found to inhibit S.aureus and
E.coli at low MIC and MBC values (25mg and 100mg
respectively) (table 5, figure 4). Cymbopogon citratus was
also highly effective against S.aureus, S. pyogenase and
E.coli and S.typhi (table 6, figure 5).
P. guajava revealed the presence of saponnins,
tannins, reducing sugar, flavonoids and other bioactive
component. All these active ingredients have been widely
reported to have antimicrobial effect (Grover and Bala,
1993). Some are stringent in nature used for treating
gastro intestinal disorders such as diarrhea and dysentery
caused by bacteria [9, 10, 11, and 12]. Among the grampositive and gram-negative bacteria tested using C.
papaya, the gram-negative bacteria were more susceptible
to the extracts. Most of the various concentration of the
water extract of the plant had no significant effect on the
microbes except at 200mg where slight antimicrobial
activity was observed. In addition to the observed active
ingredients, [13] detected isoflavones in isoflavones and it
was believed to be of huge therapeutic benefit. [14]
reported that unripe pawpaw had very potent
antimicrobial effects; henece it is used in treating many
known intestinal ailments of bacterial origin. [15]
similarly reported that the plant has anti-inflamatory
activities by inhibiting bacteria causing the condition.
For lemon grass (C. citratus) phytochemical
analysis showed that the plant possessed the
phytoconstitients of steroids and flavonoid which have
been reported to have anti microbial tendencies [16]. C.
citratus is reported to possess remarkable anti-influenza
activity and also have inhibitory action on
hepatocarcinogenesis [17]. Apart from its antimicrobial
activity, lemon grass has been found to have
hypoglycemic and hypolipidemic effect [18]. The
presence of these phytoconstituents may be responsible
for the antibacterial activity of the plant [19].
In situations where low MIC and MBC values
were recorded, it is an indication of the potency of that
particular plant against the microbe(s) tested. The three
plants
investigated
have
demonstration
strong
antimicrobial activities against both gram-positive and
gram-negative bacteria which are associated with
different types of diseases such as: pneumonia, wound
infections, typhoid fever and urinary tract infection
though under specific MIC’s and MBC’s. [20]. It is also
an indication that the plants are potential sources for
production of drugs with broad spectrum activity that can
be used for the treatment of gastro intestinal disorders,
urethritis, shigellosis, and typhoid fever.
Table 1. Phytochemical profile of methanol extracts
Phytoconstituents
(Psidium guajava)
Saponins
+
Tannins
+
Reducing sugar
+
Carica. papaya
-
MATERIALS AND METHODS
Test organisms (isolates) consisting of
Staphylococcus aureus, Streptococcous pyogenase,
Escheriehia coli, Pseudomonas aeruginosa, Salmonella
typhi and Shigella flexneri isolates were collected from
the General Hospital, North Bank, Makurdi, Bacteria
isolates were purely sub cultured in the Advanced
Biology Laborory of the University of Agriculture,
Makurdi, Nigeria. Fresh leaves of P.guajava, C.papaya
and C.citratus were collected from three villages in Agatu
Local Government Area of Benue State. The plant
materials were extracted using methanolic solvent
following standard protocol [1]. The freshly prepared
extracts of the three plants were subjected to
phytochemical screening for different bioactive principles
using standard qualitative methods as described by [6].
The MIC (minimum inhibitory concentration)
was evaluated on plant extracts that showed anti-bacterial
activity in the agar medium. This was performed at five
concerntration of each extract (100,50,25,12.5and
6.25mg/ml) employing doubling dilutions of plant
extracts in malt extract broth up to the fifth dilution. The
method of [7] and [8] were employed. The minimum
bacteriacidal concerntration (MBC) of the plant extracts
on the laboratory bacterial isolates was carried out..The
MBCs were determined by first, selecting tubes that
showed no growth during MIC determination; a loopful
from each tube was sub-cultured onto extract free agar
plates, incubated for further 24 hours at 37 0C.The least
concentration which recorded no growth was noted as the
MBC.
(Cymbopogon citratus)
-
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Aguoru CU et al. / Journal of Science / Vol 5 / Issue 9 / 2015 / 729-733.
Phlobatonnins
Anthraquinone
Steroids
Flavonoids
Glycocides
Alkaloids
+
+
-
+
+
-
+
+
-
Table 2. Antimicrobial activity of the methanolic extract of guava leaf (Psidium guajava)
Organisms
Extract effect
MIC
S. aureus
R
S. pyogenase
+
25mg
S. flexneri
+
12.5mg
E. coli
+
12.5mg
P. aeruginosa
R
S. typhi
+
12.5mg
Key:
+ = susceptible; R = Resistance
MBC
100mg
100mg
100mg
100mg
Table 3. Antimicrobial activity of methanolic extract of Carica Papaya (leaf)
Organisms
Extract effect
MIC
S. aureus
+
100mg
S. pyogenase
+
12.5mg
S. flexneri
+
25mg
E. coli
+
12.5mg
P. aeruginose
R
S.typhi
+
25mg
Key:
+ = susceptible; R = Resistance
MBC
200mg
100mg
100mg
200mg
200mg
Table 4. Antimicrobial activity of methanolic extract of Carica papaya (fruit and seed)
Organisms
Extract effect
MIC
S. aureus
+
12.5mg
S. pyogenase
+
25mg
S. flexneri
+
12.5mg
E. coli
+
25mg
P. aeruginosa
R
S. typhi
+
12.5mg
Key:
+ = susceptible; R = Resistance
MBC
100mg
200mg
200mg
200mg
100mg
Table 5. Antimicrobial activity of methanolic extract of guava (stem back)
Organisms
Extract effects
MIC
S. aureus
+
25mg
S. pyogenase
+
100mg
S.flexneri
+
100mg
E.coli
+
25mg
P. aeruginosa
R
S. typhi
+
100mg
Key:
R = Resistance; + = susceptible
MBC
100mg
200mg
200mg
100mg
-
Table 6. Antimicrobial activity of methanolic extract of lemon grass (Cymbopogon citratus)
Organisms
Extract effects
MIC
S. aureus
+
12.5mg
S. pyogenase
+
12.5mg
S. flexneri
+
12.5mg
E. coli
+
12.5mg
P. aeruginosa
R
S. typhi
+
12.5mg
Key:
R = Resistance; + = susceptible
MBC
50mg
100mg
200mg
100mg
100mg
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Aguoru CU et al. / Journal of Science / Vol 5 / Issue 9 / 2015 / 729-733.
Figure 1. Antimicrobial activity of methanolic extract of
Psidium guajava on susceptible organisms
Figure 2. Antimicrobial activity of methanolic extract of
Carica papaya leaf on susceptible organisms
Figure 3. Antimicrobial activity of methanolic extract of
Carica papaya fruit and seed on susceptible organisms
Figure 4. Antimicrobial activity of methanolic extract of
Psidium guajava fruit stem bark on susceptible
organisms
Figure 5. Antimicrobial activity of methanolic extract of Cymbopogon citratus on susceptible organisms
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