Volatile Constituents from the Leaves of Callicarpa japonica Thunb. and Their Antibacterial Activities

Volatile substances of Callicarpa japonica Thunb. were examined for their antibacterial activities against six foodborne microorganisms using the optical densitometer Bioscreen C. Extracts of C. japonica were obtained by simultaneous steam distillation and solvent extraction (SDE), and those extracted for 1.5 and 2.0 h at pH 6.0 strongly inhibited the growth of Bacillus cereus and Salmonella typhimurium; the content of the volatile substances of leaves at these pH levels were 543.1 and 706.7 mg/kg, respectively. All foodborne microorganisms tested were strongly inhibited by the addition of >8% (v/v) of the SDE extracts to broth medium. The major volatile components of the SDE extracts obtained at 1.5 h and pH 6.0 were γ-caryophyllene, 1-octen-3-ol, 2-hexenal, germacrene B, and aromadendrene II, with corresponding peak areas of 44.14, 15.6, 9.86, 5.24, and 4.01%, respectively, and major antibacterial components were 1-octen-3-ol and 2-hexenal. Among the 32 materials identified as volatile flavor components, 2-hexenal, 2,4-hexadienal, 1-octen-3-ol, 2,4-heptadienal, and epiglobulol strongly inhibited microorganism growth. In particular, 2-hexenal (107.52 mg/L) and 1-octen-3-ol (678.64 mg/L) inhibited the growth of most microorganisms tested by >90%. Keywords: Callicarpa japonica; volatile substances; SDE; antibacterial activity; foodborne microorganisms