97 research outputs found
The chemistry of Pseudocyphellaria impressa S. Lat. in New Zealand
As part of a detailed study of the nomenclature and taxonomy of the New Zealand
species of Pseudocyphellaria it has been noted that the chemistry of the P. impressa
(Hook & Taylor) Vainio aggregate, that is species with a markedly faveolate (honeycomb-
like) upper surface and a green algal phycobiont, is particularly complex.
The 45 lichen substances detected fall into four distinct groupings, here designated
as 'Codings'. The aim of this contribution is to investigate suitable methods for
revealing this chemical assemblage by t.l.c. and, as far as is currently possible, to
identify the range of substances. No conscious attempt is made to assign the four
chemical Codings to particular taxa or species groupings; the taxonomy of the
group will be discussed elsewhere. The four Codings proved to be remarkably
uniform and constant considering the range and number of substances involved;
such variation that occurred was only in the presence and concentration of accessory
substances.
Although this work only concerns New Zealand material, similar patterns occur
in related taxa of the group present in southern South America, south-east Australia
and Tasmania
Structure determination of new algal toxins using NMR methods
Shellfish are considered a delicacy by many consumers. In NZ, as in many overseas countries, there is a now thrivÂŹing shellfish industry servicing both domestic and inter-national markets. Periodically shellfish accumulate harmÂŹful levels of a variety of algal toxins, including domoic acid, yessotoxins, pectenotoxins and brevetoxins. When this occurs, regulatory authorities may impose harvesting closures which have a consequential economic impact on both farmers and staff employed to harvest and market shellfish products
Further nomenclature and chemical notes on Pseudocyphellaria in New Zealand
Nomenclatural notes on the following taxa are provided: Pseudocyphellaria billardierii, P. carpoloma, P. faveolata, P. rufovirescens and P. subvariabilis. Detailed chemical profiles are given for all described species of Pseudocyphellaria in New Zealand. Pseudocyphellaria ardesiaca, P. degelii, P. durietzii, P. fimbriata, P. fimbriatoides, P. gretae, P. knightii, P. maculata and P. sericeofulva spp. nov. are described for the first time
Six-coordinate organotin(IV) complexes formed using the Kläui ligands; [CpCo{P(ORâ˛)2O}3]SnR3 â nCln
The complexes [CpCo{P(ORâ˛)2O}3]SnR3 â nCln [RⲠ= Me, Et; R = Ph, Me] are readily prepared from the corresponding organotin chloride and the sodium salt of the Kläui ligands. The X-ray crystal structures of the full series are reported for R = Ph, n = 0-3, and these show that they are all six-coordinate, including the Ph3Sn derivative which is the first example of a SnC3O3 coordination sphere. 1H, 13C, 31P and 119Sn NMR spectra are reported, and interpreted in terms of significant second-order effects and fluxional processes
Sorption of sulfamethoxazole, sulfachloropyridazine and sulfamethazine onto six New Zealand dairy farm soils
We have investigated the sorption potential of three sulfonamides (SAs) in six New Zealand dairy farming soils using a modified batch equilibrium method employing 0.005 M CaClâ as background solution. Both liquid and solid phases were extracted to analyse for the antibiotic concentrations in order to avoid underestimation that may arise a result of photolysis or biotic degradation. The experimental data were later used to construct Freundlich isotherms to determine the effective distribution coefficients. Low log Koc value for all SAs suggests considerable leaching potential for SAs under conditions that are conducive for leaching. The sorption affinity for all soils followed the trend SCP>SMZ>SMO
Synthesis, characterisation and biological activity of gold(III) catecholate and related complexes
The reactions of the cyclometallated gold(III) complexes [LAuClâ] [L=2-(dimethylaminomethyl)phenyl, 2-benzylpyridyl or 2-anilinopyridyl] with catechol, tetrachlorocatechol, or the cyclic Îą,β-diketone SCH(CO2Et)C(O)C(O)CH(CO2Et) give stable complexes containing five-membered Au-O-C-C-O rings. These represent the first examples of well-characterised gold(III) catecholate complexes. Similarly, reactions with 2-acetamidophenol [HOCâHâNHC(O)CHâ] give complexes with the related Au---N---C---C---O ring. The complexes were characterised by NMR spectroscopy, electrospray ionisation mass spectrometry, elemental microanalysis, and in the case of the complex [(2-benzylpyridyl)Au{OCâHâNC(O)CHâ}] by an X-ray crystal structure determination. Several complexes show high activity towards P388 murine leukemia cells
Novel six-coordinate Aryl- and Alkyltin complexes
Organo-tin compounds have wide applications as pesticides and as intermediates for organic synthesis.š They are invariably Sn(IV) derivatives and are generally four-coordinate.² The mixed organo/chioro compounds of the type RnSnCI4-n do however have the ability to expand their coordination numbers to five or six. This depends critically on the substituents - with four organic groups, RâSn, there is no tendency at all to coordinate extra ligands, while at the other extreme SnClâ readily forms six-coordinate [SnC1âLâ] complexes since the electronegative halo groups increase the Lewis acidity of the tin centre
Developing site-specific guidelines for orchard soils based on bioaccessibility â Can it be done?
Horticultural land within the periurban fringe of NZ towns and cities increasingly is being developed for residential subdivision. Recent surveys have shown that concentrations of As, Cd, Cu, Pb, and ΣDDT (sum of DDT and its degradation products DDE and DDD) in such soils can exceed criteria protective of human health.š Soil ingestion is a key exposure pathway for non-volatile contaminants in soil. Currently in NZ, site-specific risk assessments and the derivation of soil guidelines protective of human health assume that all of the contaminant present in the soil is available for uptake and absorption by the human gastrointestinal tract. This assumption can overestimate health risks and has implications for the remediation of contaminated sites.² In comparison, the bioavailability of contaminants is considered when estimating exposure via dermal absorption and by ingestion of home-grown produce.³ Dermal absorption factors and plant uptake factors are included in the calculations for estimating exposures via these routes
Analysis of the flavonoid component of bioactive New Zealand mÄnuka (Leptospermum scoparium) honey and the isolation, characterisation and synthesis of an unusual pyrrole
The flavonoid components of New Zealand mÄnuka (Leptospermum scoparium) honey have been quantified in a series of 31 honeys of varying non-peroxide antibacterial activity to clarify discrepancies between previous studies reported in the literature. Total flavonoid content was 1.16 mg/100 g honey. The principal flavonoids present were pinobanksin, pinocembrin, luteolin and chrysin and together these represented 61% of the total flavonoid content. 1, 2-formyl-5-(2-methoxyphenyl)-pyrrole, which was weakly correlated with the non-peroxide antibacterial activity, was isolated from the flavonoid fraction and separately synthesised. 1 did not display inhibitory activity against Staphylococcus aureus in vitro and thus the origin of the correlation, which is still unknown, is not a direct contribution
Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid
The reactions of cis-[PtClâLâ] [L = PPhâ, PMeâPh or Lâ = PhâP(CHâ)âPPhâ (dppe)] with endo-8-camphanylphosphonic acid (CamPOâHâ) and AgâO in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(OâPCam)Lâ]. The X-ray crystal structure of [Pt(OâPCam)(PPhâ)â]â˘âCHClâ shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPhâ ligands. This allows the OâPâCHâ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPhâ and dppe derivatives, which contain inequivalent phosphine ligands in their ³šP NMR spectra. These findings are backed up by theoretical calculations on the PPhâ and PPhMeâ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPhâ and PPhMeâ complexes. The X-ray crystal structure of CamPOâHâ is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups
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