Antimicrobial testings, gas chromatoqraphic analysis and olfactory evaluation of an essential oil of hop cones (Humulus lupulus L.) from Bavaria and some of its main compounds

摘要

The essential oil of hop cones (Humulus lupulus L.) was analyzed by GC and GC-MS to assess the composition of volatiles and to evaluate olfactorially the principle aroma compounds. Myrcene (45.3%), α-humulene (31.2%) and β-caryophyllene (9.8%) were found to be the main constituents of this H. lupulus sample. The essential hop oil, the 3 main compounds and three minor concentrated constituents, isobutyl isobutyrate, geraniol and β-pinene, were tested for their antimicrobial activities against some different strains of Gram-positive and Gram-negativebacteria as well as the yeast Candida albicans by using agar diffusion and agar dilution method, respectively. The same was done using the phenolic aroma compound eugenol and the synthetic antibiotics Ciproxin~R, Lidaprim~R and tetracycline hydrochloride as reference-substance. It was found that the essential H. lupulus oil showed antimicrobial activities against the Gram-positive-bacteria Staphylococcus aureus and Enterococcus faecalis, the Gram-negative-bacteria Escherichia coli and Salmonella sp. as well as the yeast Candida albicans. This result was correlated to the antimicrobial testing of the mentioned main and minor constituents of the essential hop oil as well as of the 4 reference-compounds. The obtained data were discussed to get more insight into the influence of pure aroma compounds on the antimicrobial activities of essential oils.