Volatile constituents from the leaves of Polygonum cuspidatum S. et Z. and their anti-bacterial activities

Volatile substances extracted from leaves of Polygonum cuspidatum S. et Z. by simultaneous steam distillation and solvent extraction (SDE) were investigated in terms of their inhibitory activities against six foodborne micro-organisms using Bioscreen C. The SDE extracts from P. cuspidatum S. et Z. obtained after 1.5 or 2.0 h at pH 4.5 exhibited strong growth inhibition upon the six micro-organisms tested; their volatile contents were 5.74 and 8.89 μl/100 g, respectively. Anti-bacterial activities against the bacterial strains examined increased upon reducing SDE pH from 6.5 to 3.5 and by increasing the extraction time from 0.5 to 2.0 h. The major volatile components of the SDE extracts obtained after 1.5 h at pH 4.5 were 2-hexenal (73.36%), 3-hexen-1-ol (6.97%), n-hexanal (2.81%), 1-penten-3-ol (2.55%), 2-penten-1-ol (2.21%), and ethyl vinyl ketone (1.13%) by Gas chromatography. The addition of 10% (v/v) of the SDE extracts to broth completely inhibited the growth of Bacillus cereus and of Vibrio parahaemolyticus for 72 h.