Rapid Absorption of Dietary 1,8-Cineole Results in Critical Blood Concentration of Cineole and Immediate Cessation of Eating in the Common Brushtail Possum (Trichosurus vulpecula)
- 176 Downloads
The blood concentration of 1,8-cineole and its metabolites was measured in six male brushtail possums while they voluntarily fed on diets laced with varying concentrations of cineole for 3 d. On the third day, blood samples were collected during and after each bout of feeding for 3 hr. Blood cineole was measured by using headspace solid-phase microextraction (SPME), while cineole metabolites were measured by liquid–liquid extraction followed by gas chromatography-mass spectroscopy. Feeding patterns were measured by continual recording of residual food weight and time. Cineole absorption was rapid, resulting in a peak blood concentration at the end of each feeding bout. The blood concentration of cineole did not exceed a critical value (51.8 ± 14.1 μmol/l) regardless of the concentration in the diet. Food and, therefore, cineole intake was regulated. The amount of food ingested in the first feeding bout decreased from 236 ± 52 g on the control diet to 36 ± 20 g on the 4% cineole diet. The amount of cineole ingested in the first bout (1.18 ± 1.10 g) was the same regardless of the dietary concentration and was controlled by the size of the meal. Total food eaten during the 7-hr feeding session decreased by 64% from 368 ± 94 g (control diet) to 131 ± 52 g (4% diet). Total cineole intake increased from 2.47 ± 0.60 g (1% diet) to 5.05 ± 2.41 g (4% diet). Cineole metabolites accumulated throughout the sampling period and were generally still rising at the end of blood sampling period. Blood levels of metabolites were at least 10-fold higher than cineole levels. The immediate control of feeding seems to be regulated by blood levels of cineole, whereas metabolites are likely to be more important in regulating the chronic ingestion of cineole.
Key WordsAbsorption antifeedant blood concentrations Brushtail possum 1,8-cineole cineole metabolites plant secondary metabolites terpenes
This research was supported by a grant from the Australian Research Council. The authors thank the staff at the Central Animal House, University of Tasmania for care and assistance with possum husbandry; particularly Barbara Arnst for preparing diet and care in the maintenance of vascular access ports. We are grateful for the surgical expertise and enthusiasm of Dr Eileen Wronski and Dr Rupert Woods, who were responsible for the implantation of vascular access ports. We also acknowledge and thank Dr Noel Davies for GC-MS expertise, and Dr Omar Hassan who wrote the Qbasic program.
- Barnes, W. 1996Eucalyptus oil poisoning in childrenAust. J. Emerg. Care31520Google Scholar
- Cork, S. J. 1984Utilization of Eucalyptus foliage by arboreal marsupialsProc. Nutr. Soc. Aust.988Google Scholar
- Guglielmo, C. G., Karasov, W. H., Jakubas, W. J. 1996Nutritional costs of a plant secondary metabolite explain selective foraging by ruffed grouseEcology7711031115Google Scholar
- Lawler, I. R., Stapley, J., Foley, W. J., Eschler, B. M. 1999Ecological example of conditioned flavor aversion in plant–herbivore interactions: effect of terpenes of Eucalyptus leaves on feeding by common ringtail and brushtail possumsJ. Chem. Ecol.25401415Google Scholar
- Mangione, A. M., Dearing, M. D., Karasov, W. H. 2000Interpopulation differences in tolerance to creosote bush resin in desert woodrats (Neotoma lepida)Ecology8120672076Google Scholar
- Marsh, K. J., Foley, W. J., Cowling, A., Wallis, I. R. 2003Differential susceptibility to Eucalyptus secondary compounds explains feeding by the common ringtail (Pseudocheirus peregrinus) and common brushtail possum (Thichosurus vulpecula)J. Comp. Physiol., B Biochem. Syst. Environ. Physiol.1736978Google Scholar
- Palo, R. T., Robbins, C. 1991Plant Defenses Against Mammalian HerbivoryCRC PressBoca Raton, FLGoogle Scholar
- Raven, P. P., Evert, R. F., Eichhorn, S. E. 1986Biology of PlantsWorth PublishersNew YorkGoogle Scholar
- Southwell, I. A. 1973Variation in the leaf oil of Eucalyptus punctata Phytochemistry1213411343Google Scholar
- Whitman, B. W., Ghazizadeh, H. 1993Eucalyptus oil: therapeutic and toxic aspects of pharmacology in humans and animalsJ. Paediatr. Child Health29368371Google Scholar