Antibacterial activity and bioactive compounds of 50% hydroethanolic extract of Alpinia zerumbet (Pers.) B.L. Burtt & R.M. Sm.

Objective: To evaluate antibacterial activity and the bioactive compounds of 50% hydroethanolic extract of Alpinia zerumbet (A. zerumbet) rhizomes. Methods: Eight reference microbial strains including two Gram-positive bacteria [Staphylococcus aureus (ATCC 29213) and Enterococcus faecalis (ATCC 29212)] and six Gram-negative bacteria [Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATTC 700603), Proteus mirabilis (DMST 8212), Salmonella enterica subsp. enterica serovar Vellore. (ATCC 15611), Shigella flexneri (ATCC 12022) and Pseudomonas aeruginosa (ATCC 27853)], were used to test antimicrobial susceptibility by the broth microdilution method. Bioactive compounds were analyzed by using HPLC. Results: The minimum inhibitory concentration values of A. zerumbet extract were 8 mg/mL for Staphylococcus aureus, Escherichia coli and Shigella flexneri and 16 mg/mL for Enterococcus faecalis and the other four Gram-negative bacilli. HPLC chromatograms revealed that the A. zerumbet extract contained hydroxybenzoic acids, hydroxycinnamic acids and flavonoids. Conclusions: The constituents of A. zerumbet rhizomes could be a potential source of antibacterial compounds, warranting further study of A. zerumbet extract.