Abstract
Abstract
Background
Plants are rich and valuable sources of phytochemical constituents that can contribute to a variety of biological activities. The research in discovering novel antimicrobial compounds from plants has been of increased interest due to the global rise of antibiotic resistance. The present study aims to evaluate the in vitro antibacterial, antibiotic synergistic potential and the chemical profile of plant extracts associated with
Cleistanthus bracteosus
Jabl
.
found in Malaysian rainforests for the first time.
Methods
The antibacterial activity and synergistic antibacterial activity of chloroform, methanol and
n
-hexane crude extracts of
C. bracteosus
were determined against bacterial pathogens of
Escherichia coli
,
Bacillus subtilis
,
Staphylococcus aureus, B
.
cereus
,
Pseudomonas aeruginosa
,
Salmonella typhi
and
Acinetobacter baumannii
. The chloroform extracts were subjected to fractionation, chemical profiling, and field emission scanning electron microscopic (FE-SEM) analysis.
Results
The chloroform stem extract exhibited the highest antibacterial activity which indicated a mean inhibition zone diameter (IZD) of 10 ± 0.26 mm against the Gram-positive bacterium
B
. cereus. The best synergistic activity was shown for chloroform wood extract when combined with ampicillin against
A. baumannii,
with a growth inhibitory index (GIIs) of 1.33. Potassium clavulanate actively synergised with chloroform stem extract against
E. coli
ATCC 10536 (IZD = 27 ± 0.56 mm) and chloroform bark extract against
S. typhi
(IZD = 28 ± 0.54 mm).
C. bracteosus
extracts showed the presence of secondary metabolites like flavonoids, phenols, tannins, alkaloids, coumarins, saponins and traces of terpenoids, with chloroform extracts of bark, stem and wood consisting of 20 bioactive phytochemical compounds according to gas chromatography–mass spectrometry analysis (GC–MS). Further analysis with high-performance liquid chromatography (HPLC) implied the presence of digoxigenin and lauric acid. The FE-SEM observations further elucidated the effects of
C. bracteosus
chloroform extracts on the morphology of susceptible organisms.
Conclusion
The findings of this investigation justify that chloroform extracts of
C. bracteosus
can function as a novel antibacterial agent with synergistic potential.