To investigate the antimicrobial effects of extracted polyphenols from green tea (Camellia sinensis) and banana (Musa sp.) leaves

In recent years, there is an emergence of antibiotic-resistant bacterial strains due to the indiscriminate use of antibiotics, commonly prescribed to treat infectious diseases. The increasing occurrence of antibiotic resistance has undoubtedly made bacterial infections a greater health risk and threat than before. In this project, the use of natural polyphenolic compounds, extracted from green tea (Camellia sinensis) and banana (Musa sp.) leaves, as a novel antimicrobial chemotherapeutic agent was investigated. This study examined their bactericidal effects on Escherichia coli and Micrococcus luteus, and also evaluated the potential synergistic ability of these polyphenol-rich extracts when used alongside the beta-lactam antibiotic ampicillin. For the same dry mass of plant material used (3g), the prepared green tea extract had a higher total polyphenol concentration than that of banana leaves extract (495.1mg/L as compared to 221.6mg/L respectively). Subsequently, bacterial broth of 10⁵ colony forming units/ml was mixed with varying concentrations of the different test compounds before plating 10µl of the mixture and quantifying the compounds’ bactericidal effect by doing a viable count after overnight incubation. The green tea extract showed the greatest bactericidal effect on E. coli and M. luteus as compared to the banana leaves extract and ampicillin. Against E. coli, this difference was confirmed to be significant (p<0.05) using one-way ANOVA and Tukey’s post-hoc analysis. Furthermore, by applying ampicillin in close association with polyphenol-rich extracts of green tea or banana leaves, there was an enhanced bactericidal effect on the tested bacterial strains. This interaction was categorized as synergistic by the fractional bactericidal concentration index calculated (≤0.5). Ultimately, the plant polyphenols studied in this research could provide a potential adjuvant to currently-produced antibiotics and help to reduce antibiotic application concentrations; as well as prolong the effective lifespan of antibiotics through its synergistic action.