Abstract:
Medicinal plants have been traditionally used for the treatment of infectious diseases
worldwide for a long period. Vernonia amygdalina and Croton macrostachyus are important
medicinal plants used in the treatment of various ailments such as diarrhea, malaria, wound
infections, and gastrointestinal complications. Even though, antibiotics reduced the rate of
mortality caused by infectious diseases its effectiveness is reduced due to the emergence of
antibiotic-resistant bacteria. Now a day, the emergence of antibiotic-resistant bacteria is a
major threat to public health. Therefore, developing new antimicrobial compounds should be
the main goal of pharmaceutical companies and any researcher working in this area. Thus, the
aim of this study was to investigate the antibacterial effect of C.macrostachyus and
V.amygdalina leave extracts, and their synergistic use against selected pathogenic bacteria
namely E.coli(ATCC35218), S.aureus(ATCC25923), and P.aeruginosa(ATCC27823) and
clinical isolates of each bacteria. The ethanol, methanol, and chloroform extracts of
C.macrostachyus and V.amygdalina were evaluated alone and in combination against the test
bacteria using the agar well diffusion method. The broth dilution method was used to determine
the minimum inhibitory concentration and the minimum bactericidal concentration.
Gentamicin and ciprofloxacin were used as a positive control, while dimethylsulphoxide was
used as a negative control. The phytochemical presence was identified using standard
phytochemical screening methods. The ethanol and methanol extracts exhibited
significantly(p<0.05) highest growth inhibitory activity as compared to chloroform extract
against most test bacteria. The ethanol extract of C.macrostachyus and V.amygdalina had the
highest zone of inhibition(24.33±1.15-25.66±2.08 mm) against P.aeruginosa clinical isolate,
with MIC and MBC of 3.12mg/ml and 6.25 mg/ml, respectively. The diameter of the zone of
inhibition (13.33±3.05 mm-25.67±1.52mm) of synergistic was higher than the separate use of
these plants. The ethanolic and methanolic extract showed a higher zone of inhibition than
gentamicin. The phytochemical screening revealed the presence of tannin, alkaloid, terpenoid,
and others in the crude leave extracts of these plants. Therefore, this study supports the use of
these medicinal plants in combination for the treatment of bacterial infections in society.
Keywords: Antibacterial activities, Croton macrostachyus, MBC, MIC, Synergistic
