Chemical Composition and Determination of the Antibacterial Activity of Essential Oils in Liquid and Vapor Phases Extracted from Two Different Southeast Asian Herbs—Houttuynia cordata (Saururaceae) and Persicaria odorata (Polygonaceae)

Essential oils obtained via the hydrodistillation of two Asian herbs (Houttuynia cordata and Persicaria odorata) were analyzed by gas chromatography coupled to mass spectrometry (GC–MS) and gas chromatography with flame ionization detector (GC–FID). Additionally, both the liquid and vapor phase of essential oil were tested on antimicrobial activity using the broth microdilution volatilization method. Antimicrobial activity was tested on Gram-negative and Gram-positive bacteria—Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Streptococcus pyogenes, Klebsiella pneumoniae, Seratia marcescense and Bacillus subtilis. Hydrodistillation produced a yield of 0.34% (Houttuynia cordata) and 0.40% (Persicaria odorata). 41 compounds were identified in both essential oils. Essential oils contained monoterpenes and their oxidized forms, sesquiterpenes and their oxidized forms, oxidized diterpenes, derivates of phenylpropene and other groups, such as, for example, aldehydes, alcohols or fatty acids. Both essential oils were antimicrobial active in both vapor and liquid phases at least in case of one bacterium. They expressed various antimicrobial activity in the range of 128–1024 μg∙mL(−1), 512–1024 μg∙mL(−1) in broth and 1024 μg∙mL(−1), 512–1024 μg∙mL(−1) in agar, respectively. Research showed new interesting information about P. odorata and H. cordata essential oils and demonstrated that both essential oils could be possibly used in the field of natural medicine or natural food preservation.