(Gram-negative) bacteria. This variation could have
been attributed to differences in the morphological
nature of these microorganisms. Normally, Gramnegative bacteria contain an outer phospholipid membrane with structural lipopolysaccharide parts, thus
making the cell wall impermeable to several antimicrobial agents, whereas Gram-positive bacteria contain an
outer peptidoglycan membrane which is more permeable, and thus more susceptible to many antimicrobial
agents. This is consistent with Hiroshi Nikaido and
Marti Vaara’s (1985) findings on the molecular basis
of bacterial outer membrane permeability and further
explained by Hasara et al. (2019) in their study on
medicinal plants against some human pathogenic bacteria.Also, Chanda and Baravalia, (2010) evaluated the
antioxidant and antimicrobial potentiality of different
medicinal plants against various skin diseases which
are a result of different bacteria and fungi. The results
obtained showed that indeed the antibacterial activities
of C. longa and C. amada were higher on Grampositive bacteria (S. aureus and B. subtilis) compared
to Gram-negative bacteria.
On the control experiment, it was confirmed that
the solvents (water and ethanol) used in extraction process had no any effect on the bacterial activity against
the selected bacterial strains, compared to Ciproflaxin
and Amikacin standard antibiotics which had antimicrobial influence on the tested microorganisms. These
findings were in agreement with previous research
done by Yavuz et al. (2017) where dimethyl sulfoxide
was found to have no antimicrobial effect, compared
with ceftriaxone and gentamicin which affected the
bacterial strains used.
To accurately compare the effectiveness of different
plant extraction methods concerning their respective
inhibition zone diameters obtained from disc diffusion tests, MIC was employed and the values obtained
demonstrated slight variation in antibacterial activity
from all the selected plants. This variation could have
been a result of the different solvents used in the extraction processes, and the chemical and volatile nature of
different plant constituents among other factors. In the
study by Mostafa et al. (2018), who used the disc diffusion method to evaluate the efficiency of the most
effective plant extracts that had shown better antibacterial activity against food poisoning pathogens, the
results also showed variation in MIC values of the
different plant extracts considered. Furthermore, the
present study demonstrated that Galinsoga parviflora
ethanolic extract had activity (MIC) at 30 mg/mL
against the tested bacterial strains whereas aqueous
extracts didn’t have any activity. This negative result
may not necessarily mean that there are no bioactive
constituents or the plant is inactive. The active agents
may have been available in small quantities and thus
unable to show any activity with the extract concentration employed (Chanda & Baravalia 2010). On the
other hand, Racinus communis aqueous extract showed
activity (MIC) at 3 mg/mL against tested bacterial
strains which is the lowest compared to that obtained
with ethanolic extracts, thus demonstrating the highest
bacteriostatic activity. This dispersion could have been
attributed to the presence of various phytochemicals,
like phytate, cyanogenic glycosides, among others,
which are capable of dissolving completely in water
and are slightly or sometimes insoluble in ethanol
(Udochukwu et al. 2015). In addition to that, this result
is in agreement with previous studies (Akanmu et al.
2019; Fg et al. 2016).
6 CONCLUSIONS AND RECOMMENDATIONS
This study has shown that, all the extracts (aqueous and ethanolic) of Datura stramonium, Racinus
communis, and Galinsoga parviflora medicinal plant
leaves demonstrated bacteriostatic activity against the
selected bacterial strains even though aqueous extracts
proved to be better. High susceptibility of the plant
extracts to Gram-positive bacteria was confirmed
and based on the concentration used, their antibacterial activities were significantly lower than those
of ciproflaxin and amikacin standard antibiotics. It
has also proven that Racinus communis leaf extract
was more potent against bacterial strains than other
plants tested. These plants are known to possess various phytochemicals and pharmacological properties
that contribute to their potential activity against different pathogens. This also justifies the persistent use of
these herbs in traditional medicine. Further attention
and research should be on using a mixture of water and
ethanol at varying ratios during the extraction process,
identifying the phytochemical constituents obtained,
and evaluating their antimicrobial properties against
Gram-positive and Gram-negative bacterial strains.
ACKNOWLEDGMENT
My acknowledgment goes to Busitema University in
collaboration with the African Centre of Excellence
II in Phytochemicals, Textile and Renewable Energy
(ACE II PTRE) at Moi University for financial support. On the same note, I am thankful to Dr. Iramoit
Jacob and his team who guided me through several experiments in the Microbiology labs, Busitema
University-Mbale Campus.
REFERENCES
Adlhart, C., Verran, J., Azevedo, N. F., Olmez, H., Minna,
M., & Gouveia, I., …Crijns, F. (2018). Surface Modifications For Antimicrobial Effects in the Healthcare Setting:
A Critical Overview. Journal of Hospital Infection, (1),
1–29. https://doi.org/10.1016/j.jhin.2018.01.018
Ahad, H. A., U, A. B., Nagesh, K., D, S. K., & K, B. M. (2012).
Fabrication of Glimepiride Datura Stramonium Leaves
Mucilage and Polyvinyl Pyrolidone Sustained Release
Matrix tablets: In Vitro Evaluation. Journal of Science
and Technology, 8(I), 63–72.
100
been attributed to differences in the morphological
nature of these microorganisms. Normally, Gramnegative bacteria contain an outer phospholipid membrane with structural lipopolysaccharide parts, thus
making the cell wall impermeable to several antimicrobial agents, whereas Gram-positive bacteria contain an
outer peptidoglycan membrane which is more permeable, and thus more susceptible to many antimicrobial
agents. This is consistent with Hiroshi Nikaido and
Marti Vaara’s (1985) findings on the molecular basis
of bacterial outer membrane permeability and further
explained by Hasara et al. (2019) in their study on
medicinal plants against some human pathogenic bacteria.Also, Chanda and Baravalia, (2010) evaluated the
antioxidant and antimicrobial potentiality of different
medicinal plants against various skin diseases which
are a result of different bacteria and fungi. The results
obtained showed that indeed the antibacterial activities
of C. longa and C. amada were higher on Grampositive bacteria (S. aureus and B. subtilis) compared
to Gram-negative bacteria.
On the control experiment, it was confirmed that
the solvents (water and ethanol) used in extraction process had no any effect on the bacterial activity against
the selected bacterial strains, compared to Ciproflaxin
and Amikacin standard antibiotics which had antimicrobial influence on the tested microorganisms. These
findings were in agreement with previous research
done by Yavuz et al. (2017) where dimethyl sulfoxide
was found to have no antimicrobial effect, compared
with ceftriaxone and gentamicin which affected the
bacterial strains used.
To accurately compare the effectiveness of different
plant extraction methods concerning their respective
inhibition zone diameters obtained from disc diffusion tests, MIC was employed and the values obtained
demonstrated slight variation in antibacterial activity
from all the selected plants. This variation could have
been a result of the different solvents used in the extraction processes, and the chemical and volatile nature of
different plant constituents among other factors. In the
study by Mostafa et al. (2018), who used the disc diffusion method to evaluate the efficiency of the most
effective plant extracts that had shown better antibacterial activity against food poisoning pathogens, the
results also showed variation in MIC values of the
different plant extracts considered. Furthermore, the
present study demonstrated that Galinsoga parviflora
ethanolic extract had activity (MIC) at 30 mg/mL
against the tested bacterial strains whereas aqueous
extracts didn’t have any activity. This negative result
may not necessarily mean that there are no bioactive
constituents or the plant is inactive. The active agents
may have been available in small quantities and thus
unable to show any activity with the extract concentration employed (Chanda & Baravalia 2010). On the
other hand, Racinus communis aqueous extract showed
activity (MIC) at 3 mg/mL against tested bacterial
strains which is the lowest compared to that obtained
with ethanolic extracts, thus demonstrating the highest
bacteriostatic activity. This dispersion could have been
attributed to the presence of various phytochemicals,
like phytate, cyanogenic glycosides, among others,
which are capable of dissolving completely in water
and are slightly or sometimes insoluble in ethanol
(Udochukwu et al. 2015). In addition to that, this result
is in agreement with previous studies (Akanmu et al.
2019; Fg et al. 2016).
6 CONCLUSIONS AND RECOMMENDATIONS
This study has shown that, all the extracts (aqueous and ethanolic) of Datura stramonium, Racinus
communis, and Galinsoga parviflora medicinal plant
leaves demonstrated bacteriostatic activity against the
selected bacterial strains even though aqueous extracts
proved to be better. High susceptibility of the plant
extracts to Gram-positive bacteria was confirmed
and based on the concentration used, their antibacterial activities were significantly lower than those
of ciproflaxin and amikacin standard antibiotics. It
has also proven that Racinus communis leaf extract
was more potent against bacterial strains than other
plants tested. These plants are known to possess various phytochemicals and pharmacological properties
that contribute to their potential activity against different pathogens. This also justifies the persistent use of
these herbs in traditional medicine. Further attention
and research should be on using a mixture of water and
ethanol at varying ratios during the extraction process,
identifying the phytochemical constituents obtained,
and evaluating their antimicrobial properties against
Gram-positive and Gram-negative bacterial strains.
ACKNOWLEDGMENT
My acknowledgment goes to Busitema University in
collaboration with the African Centre of Excellence
II in Phytochemicals, Textile and Renewable Energy
(ACE II PTRE) at Moi University for financial support. On the same note, I am thankful to Dr. Iramoit
Jacob and his team who guided me through several experiments in the Microbiology labs, Busitema
University-Mbale Campus.
REFERENCES
Adlhart, C., Verran, J., Azevedo, N. F., Olmez, H., Minna,
M., & Gouveia, I., …Crijns, F. (2018). Surface Modifications For Antimicrobial Effects in the Healthcare Setting:
A Critical Overview. Journal of Hospital Infection, (1),
1–29. https://doi.org/10.1016/j.jhin.2018.01.018
Ahad, H. A., U, A. B., Nagesh, K., D, S. K., & K, B. M. (2012).
Fabrication of Glimepiride Datura Stramonium Leaves
Mucilage and Polyvinyl Pyrolidone Sustained Release
Matrix tablets: In Vitro Evaluation. Journal of Science
and Technology, 8(I), 63–72.
100