Ian A. Southwell

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

Hypericin and pseudohypericin, bioactive constituents in St. Johns 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.

Hypericin content variation in Hypericum perforatum in Australia

Abstract A Soxhlet extraction and subsequent spectrophotometry was used to determine hypericin in different varieties of Hypericum perforatum in Australia. The leaves of the broadleaved varieties contained from 370 to 580 ppm compared with 1040 to 1630 ppm for the narrowleaved varieties. These concentrations correlated well with leaf oil gland counts of 2.2 and 6.2 per mm 2 respectively and support the presence of both varieties in Australia. Within an individual broadleaved specimen, main stem contained 40, side stem 120, bottom leaf 290, top leaf 380, capsules 730 and flowers 2150 ppm. Livestock consuming flowering tops could ingest 3 g (sheep) and 7 g (cattle) of hypericin in a day. Despite varietal differences, the high hypericin concentrations in the flowers of both varieties indicate both must be considered dangerous weeds.

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 cureall 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 lo lea 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 farther 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 lea tree oil may assist the growing industry to produce safer products.

Ontogenetical changes in monoterpenoids of Melaleuca alternifolia leaf

Abstract Individual leaves on Melaleuca alternifolia branches were examined for variation in volatile oil composition. Gas chromatography of solvent extracts revealed flush growth rich in sabinene, trans -sabinene hydrate and cis -sabinene hydrate. Sequential examination of apical to basal single leaf extracts showed a dramatic decrease in thujane precursors and concomitant increase in the concentration of p -menthanes γ-terpinene, terpinen-4-ol and α-terpineol. Steam distillation of flush growth gave an oil rich only in the p -menthanes typical commercial oil of Melaleuca . The significance of these in vivo and in vitro transformations is discussed.

Skin Irritancy of Tea Tree Oil

Abstract The essential oil of Australian tea tree (Melaleuca alternifolia) has been investigated for skin irritancy using an occlusive patch test on 25 human subjects for 21 days. 1,8-Cineole, the constituent reported as being responsible for tea tree oil skin irritancy, was similarly tested. Irritancy was not detected from any of eight preparations containing pure cineole in concentrations of 0.0, 3.8, 8.0, 12.0, 16.0, 19-9, 24.0 and 28.1% in soft white paraffin. Eight tea tree oil preparations containing similar concentrations of cineole did not show skin irritation when tested at 25% in soft white paraffin. However, 3 of 28 panelists were withdrawn from the trial because of a severe allergic (as distinct from irritant) response to tea tree oil. These subjects were then tested with either pure tea tree oil major constituents or crude fractions. One panelist showed a strongly positive reaction to α-terpinene and all three reacted (two strongly) to two sesquiterpenoid fractions. None showed allergic respo...

Monoterpenoid accumulation in 1,8-cineole, terpinolene and terpinen-4-ol chemotypes of Melaleuca alternifolia seedlings.

Individual leaves of the three most common chemotypes of Melaleuca alternifolia were examined both quantitatively and qualitatively for volatile constituents from the emergence of the first true leaves, through to 6-week-old tenth leaf set material. The 1,8-cineole and terpinolene chemotypes were investigated and compared with the recently reported commercial terpinen-4-ol chemotype. The 1,8-cineole chemotype was found to accumulate 1,8-cineole and associated p-menthanes limonene, terpinen-4-ol and alpha-terpineol gradually with increasing leaf set number. As with the terpinen-4-ol variety, higher than expected concentrations of the pinenes and terpinolene were found only in the early leaf sets. The terpinolene variety showed two stages of terpinolene accumulation, the first at leaf sets 2-3 similar to the unexpected biosynthesis of terpinolene in the terpinen-4-ol chemotype and the second at leaf sets 8-9 which is characteristic of the terpinolene variety.

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,13C and1H NMR, GC, and CoGC was (+)-2β-hydroxycineole. Both male and female adults and larvae metabolizedMelaleuca oils in similar ways.

Differentiation between Melaleuca alternifolia and M. Linariifolia by monoterpenoid comparison

Abstract Leaf pairs on Melaleuca linariifolia terpinen-4-ol type branches were examined for variation in volatile oil composition. GC of ethanolic extracts revealed flush growth rich in sabinene, trans and cis-sabinene hydrates. Sequential examination of apical to basal leaf pair extracts showed a dramatic decrease in thujane precursors and concomitant increase in p-menthane end products, γ-terpinene and terpinen-4-ol. Steam distillation of flush growth gave an oil rich only in the p-menthanes typical of commercial oil of Melaleuca, terpinen-4-ol type. When compared with M. alternifolia terpinen-4-ol type, M. linariifolia showed greater concentrations of trans-sabinene hydrate in the extract consistent with formation from geranyl pyrophosphate via (3S)-linalyl pyrophosphate rather than (3R)-linalyl pyrophosphate, the favoured substrate for marjoram. This, coupled with an inverse α-pinene/α-thujene ratio provides a facile chemical way of distinguishing between the two commercially important sources of oil of Melaleuca, terpinen-4-ol type. These interspecific chemical differences are further evidence that the two taxa should maintain individual species status.

Differential metabolism of 1,8-cineole in insects.

In order to compare the metabolism of 1,8-cineole in the pyrgo beetle, Paropsisterna tigrina, three other herbivorous insect species, Faex nigroconspersa, Chrysophtharta bimaculata, and Oxyops vitiosa, were fed 1,8-cineole leaf diets. F. nigroconspersa adults excreted predominantly 9-hydroxy-1,8-cineole (36.2% of the volatile constituents) with some 2α-hydroxy-1,8-cineole (11.4%). In contrast, larvae excreted predominantly 2α-hydroxy-1,8-cineole (27.4%) and smaller proportions of 9-hydroxy-1,8-cineole (5.2%) and 3α-hydroxy-1,8-cineole (4.3%). C. bimaculata adults excreted predominantly 3α-hydroxy-1,8-cineole (16.5%). Oxyops vitiosa adults, on a lower 1,8-cineole diet, excreted predominantly 2α,9-dihydroxy-1,8-cineole (4.2%) and 2α-hydroxy-1,8-cineole (3.5%), with smaller proportions of 3α-hydroxy-1,8-cineole (1.1%) and 9-hydroxy-1,8-cineole (0.5%). This is the first reported occurrence of a dihydroxycineole as an insect metabolite. Gas chromatographic and mass spectral data for hydroxycineoles are recorded and interspecific metabolite variation discussed.

Monoterpenoid accumulation in Melaleuca alternifolia seedlings

Individual leaves of the commercial terpinen-4-ol type of Melaleuca alternifolia were examined both quantitatively and qualitatively for volatile constituents from the emergence of the first true leaves, through to 6-week-old tenth leaf set material. A GC internal standard addition method was used to measure changes in oil composition and the accumulation of volatile constituents expressed on a dry weight, unit leaf area and whole leaf basis. In the early stages of seedling growth, leaves contained higher concentrations of terpinolene, alpha-pinene and beta-pinene and lower concentrations of terpinen-4-ol, sabinene and cis-sabinene hydrate than mature leaf. Concentrations of the former constituents fell and the latter rose by the time leaf set 10 was 6 weeks old. Key constituent, 1,8-cineole remained in similar concentration throughout ontogeny. The variation in concentration of other key constituents during early stages of seedling development suggests that caution is required in extrapolating seedling leaf data to mature tree oil quality.