the quality of an extract mostly for the case of plants.
These include the part of the plant used, the extraction
solvent, and the extraction procedure, among others
(Prashant Tiwari et al. 2011).
2.5 Maceration process
This technique has been developed mainly to be
applied in the extraction of dyes from medicinal plants.
Its operation covers the soaking of grounded plant
materials in a solvent (i.e., ethanol, water, methanol,
etc.) which is left to stand for a period of time considering temperature and agitation as key parameters in
the process. Then the extract is filtered and evaporated
in the rotavapour to obtain a dry mass of the extract
(Colvin 2018). The most important role of using this
extraction procedure for crude drugs is to obtain the
therapeutically desirable portion and eliminate the
inert material by treatment with a selective solvent
commonly known as the Menstruum. The maceration
method is wellknown as a traditional and conventional extraction process thus being easy and more
convenient as compared to other methods (Colvin
2018).
2.6 Infusion, percolation, and decoction processes
The same principles are followed as for the case of
maceration though with slight modifications. Infusion
involves macerating the solids for a short time with
cold or boiling water (Prashant Tiwari et al. 2011). In
percolation the dried powdered samples are usually
packed in the percolator, boiling water is added and
they are macerated for 2 hours. Thereafter, the process continues at a moderate rate (e.g. 6 drops/min)
until the extraction is complete before evaporation to
get a concentrated extract. Decoction is only suitable
for extracting heat-stable compounds from hard plants
materials (e.g. roots and barks) and usually results in
more oil-soluble compounds compared to maceration
and infusion (Nn 2015a).
2.7 Antimicrobial efficacy and Minimum Inhibition
Concentration (MIC) of medicinal plant
extracts
Plants and their products have been in use in folk
medicine for a long time and are linked with traditional
medicine (Ajayi & Ojelere 2014). Since then, different
plant species have been reported to have phytochemical and pharmacological properties with antimicrobial
activities against a number of different microorganisms (Alapati 2015; Gaire & Subedi 2013; McArthur,
Tuckfield & Baker-Austin 2012; Sayyed & Shah 2014;
Zameer &Yaqoob 2017). Considering the thousands of
different herbal plant species in existence worldwide,
studies done by Das, Tiwari & Shrivastava (2010)
clearly show that a small portion of them have been
assessed for both phytochemicals and pharmacological properties and yet there is still a very big portion
of plants not investigated yet, hence there is an urgent
need for efficient, simpler, and cost-effective methods to evaluate the efficacy of herbal plant extracts as
well as their MICs. Sakha, Hora, Shrestha, Acharya,
and Dhakal (2019) evaluated the antimicrobial activity
of ethanolic extract from medicinal plant parts (like
seeds, buds, and leaves) against various pathogenic
bacteria using disc diffusion method. Then MICs of
the extracts were investigated using micro broth dilution. The results exhibited good antimicrobial activity against bacterial strains though the extracts from
leaves of different plants showed better inhibition as
compared to extracts from other plant parts (seeds and
bud). The MICs were found to be 12.5–25 mg/mL.
Similarly, Batra (2012) used the agar well-diffusion
method and serial dilution technique (96-well microliter plates) to evaluate the antimicrobial activity and
MIC, respectively, of different solvent extracts from
Melia azedarach l plant. The results clearly showed
that all the solvents used resulted in extracts having significant activity against the bacterial strains,
although ethanolic extracts demonstrated a better inhibition zone compared to others (methanol, ethanol,
petroleum ether, and water). For the case of MIC,
petroleum ether and aqueous extracts demonstrated
the lowest activity against the bacterial strains compared to the rest. There are other recent innovative
techniques which are used to evaluate the antimicrobial efficacy of different plant extracts and their
MIC as discussed by different researchers (Balouiri,
Sadiki, & Ibnsouda 2016; Elisha, Botha, Mcgaw, &
Eloff 2017; Eloff 2019; Ohikhena, Wintola &Afolayan
2017; Zeeshan A. Khan 2019). These techniques are
not commonly used since they require specified equipment and more assessment to achieve reproducible
and standardised results. Also, it was noted that these
techniques can be influenced by many factors like
inoculum size, selection of positive controls among
others.
3 MATERIALS AND METHODS
3.1 Collection of medicinal plant leaves
On the basis of their traditional uses, phytochemicals and pharmacological properties reported in the
literature, fresh and mature Datura stramonium (DS),
Ricinus communis (RC), and Galinsonga parviflora
(GP) plant leaves were considered for this study. They
were collected from the wild in Biharwe, Mbarara District, Uganda, washed thoroughly, and allowed to dry
under the shed.
3.2 Source of microorganisms
Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) bacterial strains
were obtained from Microbiology lab, Busitema University, Mbale campus, Uganda. They were recovered
from the storage media following the manufacturer’s
96
These include the part of the plant used, the extraction
solvent, and the extraction procedure, among others
(Prashant Tiwari et al. 2011).
2.5 Maceration process
This technique has been developed mainly to be
applied in the extraction of dyes from medicinal plants.
Its operation covers the soaking of grounded plant
materials in a solvent (i.e., ethanol, water, methanol,
etc.) which is left to stand for a period of time considering temperature and agitation as key parameters in
the process. Then the extract is filtered and evaporated
in the rotavapour to obtain a dry mass of the extract
(Colvin 2018). The most important role of using this
extraction procedure for crude drugs is to obtain the
therapeutically desirable portion and eliminate the
inert material by treatment with a selective solvent
commonly known as the Menstruum. The maceration
method is wellknown as a traditional and conventional extraction process thus being easy and more
convenient as compared to other methods (Colvin
2018).
2.6 Infusion, percolation, and decoction processes
The same principles are followed as for the case of
maceration though with slight modifications. Infusion
involves macerating the solids for a short time with
cold or boiling water (Prashant Tiwari et al. 2011). In
percolation the dried powdered samples are usually
packed in the percolator, boiling water is added and
they are macerated for 2 hours. Thereafter, the process continues at a moderate rate (e.g. 6 drops/min)
until the extraction is complete before evaporation to
get a concentrated extract. Decoction is only suitable
for extracting heat-stable compounds from hard plants
materials (e.g. roots and barks) and usually results in
more oil-soluble compounds compared to maceration
and infusion (Nn 2015a).
2.7 Antimicrobial efficacy and Minimum Inhibition
Concentration (MIC) of medicinal plant
extracts
Plants and their products have been in use in folk
medicine for a long time and are linked with traditional
medicine (Ajayi & Ojelere 2014). Since then, different
plant species have been reported to have phytochemical and pharmacological properties with antimicrobial
activities against a number of different microorganisms (Alapati 2015; Gaire & Subedi 2013; McArthur,
Tuckfield & Baker-Austin 2012; Sayyed & Shah 2014;
Zameer &Yaqoob 2017). Considering the thousands of
different herbal plant species in existence worldwide,
studies done by Das, Tiwari & Shrivastava (2010)
clearly show that a small portion of them have been
assessed for both phytochemicals and pharmacological properties and yet there is still a very big portion
of plants not investigated yet, hence there is an urgent
need for efficient, simpler, and cost-effective methods to evaluate the efficacy of herbal plant extracts as
well as their MICs. Sakha, Hora, Shrestha, Acharya,
and Dhakal (2019) evaluated the antimicrobial activity
of ethanolic extract from medicinal plant parts (like
seeds, buds, and leaves) against various pathogenic
bacteria using disc diffusion method. Then MICs of
the extracts were investigated using micro broth dilution. The results exhibited good antimicrobial activity against bacterial strains though the extracts from
leaves of different plants showed better inhibition as
compared to extracts from other plant parts (seeds and
bud). The MICs were found to be 12.5–25 mg/mL.
Similarly, Batra (2012) used the agar well-diffusion
method and serial dilution technique (96-well microliter plates) to evaluate the antimicrobial activity and
MIC, respectively, of different solvent extracts from
Melia azedarach l plant. The results clearly showed
that all the solvents used resulted in extracts having significant activity against the bacterial strains,
although ethanolic extracts demonstrated a better inhibition zone compared to others (methanol, ethanol,
petroleum ether, and water). For the case of MIC,
petroleum ether and aqueous extracts demonstrated
the lowest activity against the bacterial strains compared to the rest. There are other recent innovative
techniques which are used to evaluate the antimicrobial efficacy of different plant extracts and their
MIC as discussed by different researchers (Balouiri,
Sadiki, & Ibnsouda 2016; Elisha, Botha, Mcgaw, &
Eloff 2017; Eloff 2019; Ohikhena, Wintola &Afolayan
2017; Zeeshan A. Khan 2019). These techniques are
not commonly used since they require specified equipment and more assessment to achieve reproducible
and standardised results. Also, it was noted that these
techniques can be influenced by many factors like
inoculum size, selection of positive controls among
others.
3 MATERIALS AND METHODS
3.1 Collection of medicinal plant leaves
On the basis of their traditional uses, phytochemicals and pharmacological properties reported in the
literature, fresh and mature Datura stramonium (DS),
Ricinus communis (RC), and Galinsonga parviflora
(GP) plant leaves were considered for this study. They
were collected from the wild in Biharwe, Mbarara District, Uganda, washed thoroughly, and allowed to dry
under the shed.
3.2 Source of microorganisms
Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) bacterial strains
were obtained from Microbiology lab, Busitema University, Mbale campus, Uganda. They were recovered
from the storage media following the manufacturer’s
96