Purification, identification, concentration and bioactivity of (Z)-7-dodecen-1-yl acetate: sex pheromone of the female Asian elephant, Elephas maximus

Abstract

In their natural ecosystems, adult male and female Asian elephants, Elephas maximus, live separately. For several weeks prior to ovulation, female elephants release a substance in their urine which elicits a high frequency of non-habituating chemosensory responses, especially flehmen responses, from male elephants. These responses occur prior to, and are an integral part of, mating. Using bioassay-guided fractionation, quantitatively dependent on these chemosensory responses, a specific sex pheromone was isolated and purified by an alternating series of organic and/or aqueous extractions, column chromatography, gas chromatography and high-performance liquid chromatography. Using primarily 1H-proton nuclear magnetic resonance (NMR) spectrometry and gas chromatography-mass spectrometry (GC-MS) of the urine-derived pheromone and its dimethyl disulfide derivative, we determined the structure of the active compound to be (Z)-7-dodecen-1-yl acetate (Z7-12:Ac). Concentrations of Z7-12:Ac in the female urine increased from non-detectable during the luteal phase to 0.48 microgram/ml (0.002 mM) early in the follicular phase and to 33.0 micrograms/ml (0.146 mM) just prior to ovulation. Bioassays with commercially available authentic synthetic Z7-12:Ac, using 10 Asian male elephants at several locations in the US, demonstrated quantitatively elevated chemosensory responses that were robust during successive tests, and several mating-associated behaviors. Bioassays with Z7-12:Ac with adult male elephants dwelling in more natural social situations in forest camps in Myanmar revealed some differing contextual pre-mating behavioral components. The remarkable convergent evolution of this compound suggests that compounds identified in mammalian exudates that are also present in pheromone blends of insects should be re-evaluated as potential mammalian chemosignals.