Abstract:
Piper betle L., commonly chewed as betel quid (paan), has been extensively acclaimed in a panoply of countries
for both its nutritive and medicinal values. The present study was geared towards investigating the antibacterial
activities of P. betle extracts and its antibiotic modulating activity. A decoction of P. betle (AQE) leaves as used traditionally,
as well as ethanolic (EE), ethylacetate (EAE), acetone (ACE), and dichloromethane (DCME) extracts
were evaluated using the broth microdilution assay against six bacterial ATCC strains. The minimum inhibitory
concentration (MIC), bacteriostatic and bacteriocidal activities of the extracts were evaluated. Additionally, the
ability of the extracts to modulate conventional antibiotics (synergistic, additive, indifference, antagonistic)
was assessed using a modified Checkerboard method and the fractional inhibitory concentration index (ƩFIC)
was calculated. The phytochemical profile of each extract was determined and the Pearson’s correlation coefficient
was used to establish any association between the MIC, ƩFIC, and phytochemical content. All the five extracts
inhibited at least one of the six bacterial strains tested with EAE and ACE exhibiting the most potent
antibacterial activity. The lowest MIC (0.2500 μg/μl) recorded was against Staphylococcus aureus. Piper betle has
been further shown to exhibit only bacteriostatic effect. Results from the Checkerboard indicated additive
and synergistic effects of P. betle extracts especially in the 50% EAE-50% antibiotic and 50% ACE-50% antibiotic
combinations. The greatest synergy was observed against Pseudomonas aeruginosa (ƩFIC 0.09) in the 70%
ACE-30% Chloramphenicol combination. Synergy was also observed against S. aureus, Propionibacterium acnes,
Staphylococcus epidermidis, and Streptococcus pyogenes. Phytochemical screening revealed that ACE and EAE contain
the highest amount of phenols while DCME contains the highest amount of flavonoids. Statistical analysis
showed that lower MICs occurred with increasing phenol content (R=−0.392, p ≤ 0.05) and increasing flavonoid
content (R=−0.551, p ≤ 0.01). However, no correlation was established between ƩFIC and phytochemical
content which could indicate a different mechanism of action employed by the combinations. Data amassed
have provided insight into the antibacterial activity, antibiotic modulating activity, and the phytochemical profile
of P. betle.
