3-Oxygenated α-ionone derivatives as potent male attractants for the solanaceous fruit fly, Bactrocera latifrons (Diptera: Tephritidae), and sequestered metabolites in the rectal gland

Abstract

A series of 3-oxygenated derivatives of α-ionone and α-ionol have been characterized as highly specific male lures for the solanaceous fruit fly Bactrocera latifrons (Hendel). In order to optimize the activity, we tested several analogous compounds derived from the three known attractants, 3-oxo-α-ionone, 3-oxo-α-ionol, and 3-hydroxy-α-ionone. 3-Oxo-7,8-dihydro-α-ionone and 3-oxo-7,8-dihydro-α-ionol were found to be potent attractants as well as feeding stimulants for the males in an indoor bioassay. While trans-3-hydroxy-α-ionone showed moderate attractant and feeding stimulant activity, the corresponding cis-isomer was weakly active, indicating the importance of the stereochemistry at the C-3 position. Synthetic trans-3-acetoxy-α-ionone exhibited lower activity than the corresponding 3-hydroxy derivative. B. latifrons males fed actively on 3-oxo-7,8-dihydro-α-ionone, transformed it to 3-oxo-7,8-dihydro-α-ionol, and sequestered this compound in a substantial quantity in the rectal glands. Males that fed on 3-oxo-7,8-dihydro-α-ionol incorporated the compound mostly unchanged in the rectal gland. In both cases, the rectal content was approximately 1 μg/gland at 6 h post-feeding on the chemicals, respectively. Selective accumulation of these 3-oxygenated α-ionone/α-ionol analogs suggests their possible role as a male sex pheromone.