Chemical Composition, Antioxidant, and Antibacterial Activities of Essential Oils from Etlingera brevilabrum Valeton

Essential oils from fresh parts of Etlingera brevilabrum Valeton (Zingiberaceae) including rhizome, stolon, stem, and leaves were hydrodistilled, and studied for their chemical composition, antioxidant, and antibacterial activity. Characterization by GC-FID and GC-MS showed monoterpene hydrocarbons dominated the oils of the leaves and stems (57.3 and 73.4%) with oxygenated monoterpenes were dominant in the stolon and rhizomes (40.4 and 53.6%). The major compounds of the rhizome oil were perilla aldehyde (19.6%) and bornyl acetate (17.6%); the stolon oil, beta-pinene (30.6%) and p-cymen-7-ol (25.0%); the stem oil, delta-3-carene (43.2%) and alpha-thujene (17.7%); and the leaf oil, alpha-thujene (38.1%) and p-cymen-7-ol (8.0%). The rhizome oil showed the highest antioxidant effects with IC50 = 1236.54+/-12.83 mu g/mL in the DPPH radical scavenging activity, 22.76% inhibition in the beta-carotene bleaching test at 1000 mu g/mL, and IC50 = 878+/-16.54 mu g/mL in the ferrous ion chelating ability. Antibacterial activity demonstrated by disc diffusion assay showed that the rhizome, stem and leaf oils inhibited Staphylococcus aureus and MRSA but not Bacillus subtilis and Bacillus thuringiensis. For Gram negative bacteria, the rhizome oil prevented the growth of Proteus mirabilis; the stem oil inhibited Escherichia coli and Proteus vulgaris; and the leaf oil was active against E. coli, P. vulgaris, and P. mirabilis.