Dietary influences on terpenoids sequestered by the biological control agent Oxyops vitiosa: effect of plant volatiles from different Melaleuca quinquenervia chemotypes and laboratory host species.

The weevil Oxyops vitiosa is an Australian species imported to Florida, USA, for the biological control of the invasive species Melaleuca quinquenervia. The larvae of this species feed on the leaves of their host and produce a shiny orange secretion that covers their integument. Previous results indicated that a major component of this secretion, viridiflorol, is sequestered from the host plant and repels a generalist predator, the red imported fire ant, Solenopsis invicta. When the larvae fed on a different chemotype of M. quinquenervia, which lacked viridiflorol but was rich in a different sesquiterpene, (E)-nerolidol, similar protection occurred. Solvent washes of these larvae indicated that (E)-nerolidol was sequestered from M. quinquenervia leaves and repelled S. invicta workers when applied to dog food baits at physiological concentrations (17.5, 35.0, and 52.5 microg/mg). Additionally, beta-caryophyllene also repelled S. invicta workers when applied to dog food baits at concentrations that approximated those in the O. vitiosa larval secretions (3.5 and 35 microg/mg). When the O. vitiosa larvae were fed leaves from laboratory hosts (nonfield hosts), similar repellent activity was found. This activity was traced to several of the same compounds (e.g., 1,8-cineole, viridiflorol) found to be active in their field host M. quinquenervia. These weevil larvae are opportunistic, sequestering the primary terpenoids in their host leaves that confer antipredator activity.

Antipredator defense of biological control agent Oxyops vitiosa is mediated by plant volatiles sequestered from the host plant Melaleuca quinquenervia.

The weevil Oxyops vitiosa is an Australian species imported to Florida, USA, for the biological control of the invasive weed species Melaleuca quinquenervia. Larvae of this species feed on leaves of their host and produce a shiny orange secretion that covers the integument. When this secretion is applied at physiological concentrations to dog food bait, fire ant consumption and visitation are significantly reduced. Gas chromatographic analysis indicates that the larval secretion qualitatively and quantitatively resembles the terpenoid composition of the host foliage. When the combination of 10 major terpenoids from the O. vitiosa secretion was applied to dog food bait, fire ant consumption and visitation were reduced. When these 10 terpenoids were tested individually, the sesquiterpene viridiflorol was the most active component in decreasing fire ant consumption. Fire ant visitation was initially (15 min after initiation of the study) decreased for dog food bait treated with viridiflorol and the monoterpenes 1,8-cineole and alpha-terpineol. Fire ants continued to avoid the bait treated with viridiflorol at 18 microg/mg dog food for up to 6 hr after the initiation of the experiment. Moreover, ants avoided bait treated with 1.8 microg/mg for up to 3 hr. The concentrations of viridiflorol, 1,8-cineole, and alpha-terpineol in larval washes were about twice that of the host foliage, suggesting that the larvae sequester these plant-derived compounds for defense against generalist predators.

Seasonal variation in hypericin content of Hypericum perforatum L. (St. John's Wort).

Hypericin and pseudohypericin, bioactive constituents in St. John's Wort (Hypericum perforatum), have been determined in the soft tops of the plant that are most likely to be browsed by foraging livestock. In two consecutive seasons, the hypericin/pseudohypericin concentration in a broad leaf biotype varied from a winter minimum of less than 100 ppm to a summer maximum approaching 3000 ppm. In contrast the narrow leaf biotype increased from similar winter values to summer maxima approaching 5000 ppm. The latter biotype was slower in returning to low levels of hypericin/pseudohypericin.

Comparison of oil recovered from tea tree leaf by ethanol extraction and steam distillation.

Two methods for the determination of oil and oil major components from tea tree (Melaleuca alternifolia) leaf are quantitatively compared. A microwave assisted ethanol extraction and a 2-h hydrodistillation technique were used on both dry and fresh leaf from a low and a high oil concentration tree. There was no significant difference between dry and fresh leaf. The distillation technique recovered 88% and 82% of the extractable oil for the low and high concentration material, respectively. For both samples this distilled oil was composed of lower absolute amounts of sesquiterpenoids and marginally lower amounts of monoterpenoids. Extending the distillation to 6 h increased the sesquiterpenoid recovery but this resulted in a reduction in both the absolute and relative amounts of the oxygenated monoterpenoids, terpinen-4-ol and 1,8-cineole.

Tea tree oil allergy: what is the offending agent? Report of three cases of tea tree oil allergy and review of the literature.

Tea tree oil is currently enjoying popularity as a 'cure-all' for a variety of skin conditions, from infections to psoriasis, and many household and personal products containing Melaleuca oil are available. However, despite its chemical complexities and enthusiastic use, there have been only a few reports of allergic reactions to tea tree oil. At the Skin and Cancer Foundation (Sydney, NSW, Australia), three of 28 normal volunteers tested strongly positive to patch testing with tea tree oil. Following further patch testing with tea tree oil constituents, all three patients reacted strongly to two preparations containing sesquiterpenoid fractions of the oil. Because patients often neglect to mention that they have used 'natural' remedies, it is important that physicians are aware of the potential adverse effects of these products. Furthermore, identification of the allergenic ingredients in tea tree oil may assist the growing industry to produce safer products.

Metabolism of 1,8-cineole in tea tree (Melaleuca alternifolia andM. linariifolia) by pyrgo beetle (Paropsisterna tigrina).

The frass of the pyrgo beetle (Paropsisterna tigrina) feeding on commercial plantations of the terpinen-4-ol chemical variety of the Australian tea tree.Melaleuca alternifolia, was found to contain a volatile oil almost identical to the essential oil of the ingested leaf. When beetles were fed leaf containing substantial quantities of 1,8-cineole, the predominant frass metabolite as determined by MS, IR,(13)C and(1)H NMR, GC, and CoGC was (+)-2ß-hydroxycineole. Both male and female adults and larvae metabolizedMelaleuca oils in similar ways.

Presence of long-chain dialkyl ethers in cuticular wax of the Australian chrysomelid beetleMonolepta australis.

Investigation of the lipid extract of the Australian chrysomelid beetle,Monolepta australis, has revealed a novel homologous series of long-chain, unsaturated-saturated dialkyl ethers in the cuticular wax. Gas chromatography-mass spectrometry, proton magnetic resonance, infrared spectroscopy, and chemical degradation have shown that ethers of formula CH3(CH2)9CH=CH(CH2)6O(CH2)12-16CH3 predominate.

Metabolism of alpha- and beta-pinene, p-cymene and 1,8-cineole in the brushtail possum, Trichosurus vulpecula.

1. The nature of the non-conjugated metabolites of the Eucalyptus oil terpenoid components alpha-pinene, beta-pinene, p-cymene and 1,8-cineole in the urine and faeces of the brushtail possum was investigated. 2. alpha-Pinene was metabolized to myrtenic acid and trans-verbenol, beta-pinene to myrtenic acid, p-cymene to p-cresol and cumic acid, and 1,8-cineole to p-cresol, 9-hydroxycineole and cineol-9-oic acid.