Photoremovable protecting groups as controlled-release device for sex pheromone

Photoremovable protecting groups (PRPGs) were demonstrated as a delivery device for controlled release of pheromone under both UV light (≥350 nm) and direct sunlight irradiation. In the present work, ( Z )-11-hexadecen-1-ol (sex pheromone of Chilo infuscatellus Snellen) was chemically caged by four different photoremovable protecting groups (7-hydroxy-4-hydroxymethylcoumarin, 1-pyrenemethanol, 9-anthracenemethanol and 2-(hydroxymethyl)anthraquinone) individually. Photophysical studies showed that the caged pheromone with coumarin, pyrene and anthracene derivatives exhibited strong fluorescence. Controlled release of ( Z )-11-hexadecen-1-ol was achieved by irradiating the caged compounds in aqueous ethanol both under UV and sunlight. Further, to mimic the environmental conditions, controlled release of ( Z )-11-hexadecen-1-ol was also studied in soil medium under direct sunlight. Thermogravimetric analysis showed that caging of ( Z )-11-hexadecen-1-ol by PRPGs significantly reduced its volatility. Bioassay experiments indicated that PRPGs are harmless to soil bacteria ( Azotobacter sp. and Pseudomonas aeruginosa ) and in vitro cytotoxicity studies on eukaryotic L929 cells showed that PRPGs are also non-toxic. Field bioassays were performed using caged pheromone against maize stalk borer ( Chilo partellus ) and the results showed that the caged alcohol is effective in a number of moths catches instead of free alcohol in a blend for a longer period of time. Our studies indicated that use of PRPGs as delivery device for controlled release of pheromone by sunlight holds great interest for field applications.