Correlation Phenolic Concentration to Antioxidant and Antibacterial Activities of Several Ethanolic extracts from Indonesia

Abstract

Increasing concerns on the adverse effect of synthetic antioxidants and the emergence of antibiotic-resistant Staphylococcus aureus have become two essential problems to be addressed. To tackle them, exploration of natural resources to discover novel antioxidants and/or antibacterial agents is urgently required. The aim of this research was to investigate the correlation of phenolic and flavonoid contents of extracts to their antioxidant and antibacterial activities. Green tea, green coffee, cocoa pod husks, bee pollen, and rosella calyces were processed and subjected to 80% ethanol-based maceration procedure to obtain extracts with appropriate condition. Each extract was examined for its phenolic and flavonoid concentrations using the Folin–Ciocalteau method and the aluminum chloride colorimetric assay, respectively. Further analysis on the free-radical scavenging potential and antibacterial/antibiofilm activity against S. aureus were carried out. Samples were found to contain total phenolics (TP) and total flavonoids (TF) at different concentrations. The highest level of TP and TF was identified in green tea extract and corresponded to the lowest IC50 against DPPH and the lowest MIC against S. aureus colonies or to their respective biofilm. In contrast, low amounts of TP and TF were found in cocoa pod husks and bee pollen which were further demonstrated high IC50 and high MIC. Collectively, our results suggested the linear correlation of phenolic- and flavonoid contents to the antioxidant and antibacterial/antibiofilm activities of plant extracts. The higher the phenolics and flavonoids level, the better the antioxidant and antibacterial/antibiofilm activities obtained from the corresponding extracts.