Volatile components and antibacterial effects of pine needle (Pinus densiflora S. and Z.) extracts

The antibacterial effects of the volatile components extracted from Pinus densiflora S. and Z., by simultaneous steam distillation and solvent extraction (SDE), were examined on six foodborne bacteria using Bioscreen C (a computer-controlled shake-incubator-reader). The SDE extracts of P. densiflora obtained after 1.5 or 2.0 h at pH 3.6 exhibited a strong growth inhibitory effect on Escherichia coli O157:H7 and their overall antibacterial activities against the various bacteria tested tended to increase with increased extraction time and with a lower extraction pH. The major volatile components of the SDE extracts obtained at pH 3.6 and 1.5 h, as determined by gas chromatography, were α-ocimene (29.3%), sabinene (10.9%), β-myrcene (9.6%), β-caryophyllene (8.0%), β-cadinene (7.3%), α-terpinolene (4.9%), 2-hexanal (4.5%), and β-pinene (4.3%). The addition of 8% or 10% (v/v) of the SDE extracts to culture broth completely inhibited the growths of Bacillus cereus, Salmonella Typhimurium, and Staphylococcus aureus. The intracellular adenosine triphosphate (ATP) concentration of S. Typhimurium treated with P. densiflora extract reduced to 0.165 μm from 0.595 μm, whereas the ATP concentration in culture supernatants was increased to 0.469 μm form 0.065 μm.