Abstract. Eucalyptus magnificata L.A.S.Johnson & K.D.Hill is an endangered species endemic to the New England Tablelands Bioregion of eastern Australia, with taxonomic conflict regarding its recognition. Analyses of morphology, phytochemistry and genomic DNA were used to test species limits of E. magnificata. Morphometric and phytochemical phenetic analyses found distinct differences among E. magnificata, E. baueriana and a putative entity recognised during field collection, i.e. E. sp. Dalveen. Another putative entity, E. sp. Oxley, was morphologically and phytochemically intermediate between E. magnificata and E. conica. Phenetic analysis of single-nucleotide polymorphism (SNP) data supported the results from morphological and phytochemical analyses. The original circumscription of E. magnificata, as distinct from E. baueriana, was strongly corroborated. Eucalyptus magnificata was found to be restricted in distribution to the Macleay Gorges area south-east of Armidale. Multiple lines of evidence provided strong support for the recognition of E. sp. Dalveen as a separately evolving entity at a species level, here described as Eucalyptus dalveenica T.L.Collins, R.L.Andrew & J.J.Bruhl. A full description of the new species, a table distinguishing E. dalveenica from closely related taxa, and an identification key are provided. Distribution, habitat and conservation status are discussed.
Phytochemistry is a source of data for plant systematics. This tool has much more value if herbarium specimens can be used without major damage and if results are comparable with fresh samples. A modified method for the solvent extraction of eucalypt leaf oils for phytochemical analysis and chemotaxonomy studies, including historical herbarium samples by gas chromatography–mass spectrometry (GC-MS), has been statistically assessed using Eucalyptus magnificata L.A.S.Johnson & K.D.Hill leaves. Leaf sample size was reduced by a factor of 250 to minimise damage to herbarium specimens, reduce solvent volume and simplify preparation of solvent extract before analysis. Leaf sampling treatments assessed the effects of the number of leaves and post-harvest air-drying on variation in components in the solvent extract. The results showed no statistically significant effect of leaf mass or the number of leaves used in GC-MS analyses on the precision of the measurements, but a significant difference among treatments for some oil constituents, particularly 1,8-cineole. Most differences in terpenoid concentration were due to variation among plants rather than extraction treatments. Extracts from air-dried herbarium leaves up to 44 years old were directly comparable with those from fresh leaves. Solvent extraction in 2 mL GC-MS vials of ~0.5 cm2 (16 mg) of leaf material, using fragments of fresh or air-dried leaves, drastically reduced sample and solvent volumes and showed that sampling from E. magnificata herbarium specimens for chemotaxonomy and chemotyping is a valid method, enabling broader sampling with much lower costs than for traditional fieldwork collections.
The strongly aromatic Australian desert species Eremophila dalyana is an Aboriginal medicinal plant that continues to be used today in Central Australia in the treatment of respiratory complaints and Sarcoptes scabiei infestation. Using hydrodistillation of aerial parts of the plant, the new natural product myodesert-1ene was isolated in two disjunct populations at up to 98% of the volatiles present in the hydrodistilled oils. Weak antimicrobial activities were observed for whole oils and myodesert-1-ene. Activities in the hydrodistilled oil were attributed to the antimicrobial sesquiterpenes elemol and eudesmol which showed good activity when isolated and were relatively abundant in the chemotype used medicinally. The biogenesis of myodesert-1-ene from iridodial is proposed.
Hydrodistilled essential oils and dichloromethane (DCM) extracted volatiles were taken from cultivated specimens of Prostanthera centralis, endemic to central Australia. All volatiles were chemically characterised by Gas Chromatography-Mass Spectroscopy (GC-MS) with the use of authentic standards, followed by Nuclear Magnetic Resonance (NMR) Spectroscopy. The antimicrobial activity of the essential oils was measured against a range of Gram-negative and Gram-positive bacterial species using a micro-titre plate broth dilution assay. Twenty-two compounds were identified as components of the sweet smelling aromatic essential oil and DCM extracts, both showing a relatively high abundance of prostantherol. The volatiles extracted using DCM, differed only in the relative abundance of the major components and the lack of ledol and squamulosone. This study constitutes the first time ledol and squamulosone have been identified in a Prostanthera species. Antimicrobial assays showed moderate to high inhibitory activity against some Gram-positive bacteria and the yeast Candida albicans. OPEN ACCESSAgriculture 2014, 4 309
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