Chemical composition and antimicrobial properties of the essential oil from the leaves of Helichrysum ibityense R.Vig. & Humbert (Asteraceae)

The present work aimed to study the composition and antimicrobial properties of the essential oil of Helichrysum ibityense leaves (HIEO). HIEO was extracted by hydrodistillation from fresh leaves with a yield of 1.9%. It had a relative density of 0.9247 at 20℃, a refractive index of 1.4706, an optical rotation of -0°33, an acid index of 2.10 and an ester index of 54. Gas chromatography analysis/flame ionisation detection of HIEO had identified 17 components, representing more than 99.54% of the overall composition of the HIEO including 1.8-cineole (69.46%) the major component, α-terpinene (4.62%), β-caryophyllene (4.39%), α-pinene (4.13%), β-pinene (2.96%), p-cymene (2.39%) and γ-terpinene (2.16%). The HIEO antimicrobial activity was tested against nine pathogenic bacteria including Staphylococcus aureus, Staphylococcus pneumoniae, Streptococcus pyogenes, Clostridium perfringens, Bacillus cereus, Pseudomonas aeruginosa, Enterobacter cloacae, Enterobacter aerogenes, Yersinia enterocolitica, and Candida albicans using the Disc diffusion and the Microdilution assays. HIEO exhibited broad activity spectrum and high microbial activity with inhibition zones (IZ) ranging from 12 to 35 mm. On Bacillus cereus, the most sensitive bacterium, its Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were 9.37 mg/ml and 13.22 mg/ml respectively. With an MBC/MIC ratio of 1.41, HIEO exerted a bactericidal action on Bacillus cereus. When administered orally to mice at 1000 mg/kg body weight, HIEO caused symptoms of intoxication which disappeared after 24 h. These preliminary results revealed HIEO could be used to treat different infectious diseases if its safety will be confirmed.