Pheromone Study on Acarid Mites XI. Function of Mite Body as Geometrical Isomerization and Reduction of Citral (the Alarm Pheromone)

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Abstract
Body-effect of mites on citral composition was determined by incubating a known amount of a substrate (neral or geranial) in hexane at room temperature with the hexane-washed bodies of mites (0.5 g). Half of the substrate (100 ppm, each) was consumed within 30 min and the products of the incubation consisted of 4 compounds: isomerized citral to an equilibrium state [neral (40%) and geranial (60%), total 26-43 ppm] and reduction products (total 27-59 ppm) of citral, which were identified as nerol and geraniol. The isomerization rate was affected by the incubation solvent and was observed in the following order: ether > hexane > benzene > acetone > ethanol. Reduction products were detected in the ether, benzene and hexane incubation. Treatment of washed mites with formalin and trichloroacetic acid retarded the isomerization reaction. Treatment of washed mites with tap water did not affect the isomerization rate, but inhibited the reduction of citral. Both reactions were commonly observed in all species of acarid mites tested [Tyrophagus putrescentiae, Aleurophagus ouatus, Carpoglyphus lactis, Lardoglyphus konoi, Dermatophagoides farinae].