Molecular Markers for Pyrethrin Autoxidation in Stored Pyrethrum Crop: Analysis and Structure Determination

Area of Science:

• Agricultural Science
• Organic Chemistry
• Insecticide Development

Background:

• Pyrethrum, derived from Tanacetum cinerariifolium, is a natural insecticide.
• Six pyrethrin esters confer its insecticidal properties.
• Oxidative degradation of pyrethrins is a significant cause of product loss during manufacture.

Purpose of the Study:

• To investigate the autoxidation chemistry of individual pyrethrin esters.
• To understand the degradation pathways of pyrethrins during storage and processing.
• To identify specific oxidation products and their formation mechanisms.

Main Methods:

• Isolation and purification of the six major pyrethrin esters.
• Controlled autoxidation experiments under laboratory conditions.
• Chromatographic analysis (e.g., HPLC) to separate and quantify oxidation products.
• Characterization of isolated oxidation products using spectroscopic methods.

Main Results:

• Pyrethrins I and II, the primary active components, exhibit higher susceptibility to autoxidation compared to jasmolins and cinerins.
• Observed autoxidation patterns in isolated esters correlate with degradation products found in stored T. cinerariifolium extracts.
• Two specific pyrethrin II autoxidation products were identified and confirmed in crop extracts stored for 12 weeks without antioxidants.

Conclusions:

• Autoxidation is a key degradation pathway for pyrethrin esters, particularly pyrethrins I and II.
• The findings confirm that pyrethrin degradation occurs during the storage of T. cinerariifolium crops.
• Understanding these autoxidation mechanisms is crucial for improving pyrethrum manufacturing and storage stability.