2001 Volume 10 Issue 1 Pages 19-25
The alarm pheromone activity was detected in the hexane rinse of Schwiebea elongata, the pool mite strain. The GC profile of the large scale extraction of mites revealed four components, and their chemical structures were identified by comparing their GC/MS spectra and GC retention times with those of authentic compounds, as follows; neral {3,7-dimethyl-(Z)-2,6-octadienal}, geranial {3,7dimethyl-(E)-2,6-octadienal}, neryl formate {3,7-dimethyl-(Z)-2,6-octadienal formate}, and n-tridecane. The alarm pheromone activity was only detected in fractions of 5% and 10% ether in hexane eluates from an SiO2 column, and these fractions consisted only of a set of peaks, neral and geranial. Neral was the major component along with tridecane, and its percentage in citral (a mixture of neral and geranial) was differed among samples analyzed such as 94% in the small scale extraction, 90% in large scale extraction, and 79% in the active SiO2 column eluate. The synthetic neral (purity 91% and yield 83%) was active at 10-100 ng-dose, while geranial (purity 98% and yield 32%) was hundred times less active than neral (active at ng-dose ppm), therefore neral was identified as the alarm pheromone.
