Submitted to: Bioorganic and Medicinal Chemistry Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 1995
Publication Date: N/A
Interpretive Summary: Sap beetles (family Nitidulidae) of the genus, Carpophilus, are serious pests of ripening stone fruits (especially apricots, nectarines, and peaches) in southern Australia. The Australian stone fruit industry is attempting to switch away from insecticides to alternative, environmentally safer means of pest management, such as the use of pheromones. (Pheromones are natural chemicals that insects emit to attract others of their own species). Pheromones are now known and have been synthesized for the three most important sap beetle species in Australian stone fruits, and research is being initiated to learn whether it is possible to control these pests by mass trapping using pheromones. One important issue is trap design; traps must be as efficient as possible for the mass trapping approach to succeed. The present study compared a variety of commercial and experimental traps and identified several commercial traps that had optimal performance.
Technical Abstract: Biosynthesis of pheromones from Carpophilus davidsoni and C. mutilatus was investigated by feeding the beetles diets containing isotopically substituted (13C and deuterium) fatty acids and then analyzing the resulting labeled pheromone components. (2E,4E,6E,8E)-7-ethyl-3,5-dimethyl-2,4,6,8- undecatetraene, (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8- undecatetraene, and (2E,4E,6E)-5-ethyl-3-methyl-2,4,6-nonatriene from C. davidsoni and (3E,5E,7E)-5-ethyl-7-methyl-3,5,7- undecatriene from C. mutilatus were analyzed by both nuclear magnetic resonance spectroscopy and mass spectrometry (MS). Eleven additional minor analogs were analyzed only by MS. Each hydrocarbon can be assembled from just three different acyl units: The initial unit can be acetate, propionate, or butyrate. Propionate is the second unit in all of the analogs encountered so far, extending the chain by two carbons and producing a methyl branch. Subsequent chain-extending units can be either propionate or butyrate, leading to additional methyl or ethyl branches, respectively. The final acyl unit is either propionate or butyrate, and it loses its carboxyl carbon during hydrocarbon biosynthesis. A hydrocarbon with four total units is a triene, and one with five is a tetraene. Assembly is proposed to be as in usual fatty acid anabolism except that other precursor units are used in addition to acetate and that the double-bond reduction step of each chain-elongation cycle does not occur, leaving the conjugated, unsaturated system.