Generation and reaction of alanyl radicals in open flasks

The generation and Giese-type reaction of alanyl radicals under metal-free reaction conditions is described. The procedure is operationally simple, occurring at ambient temperature in an open reaction vessel, and requiring short reaction times (≤5 min). The reaction occurs without epimerization and provides ready access to non-proteinogenic amino acids and peptides. Importantly, the process is tolerant of light absorbing groups including commonly used fluorescent tags.

Degradation of the Indospicine Toxin from Indigofera spicata by a Mixed Population of Rumen Bacteria

The leguminous plant species, Indigofera linnaei and Indigofera spicata are distributed throughout the rangeland regions of Australia and the compound indospicine (L-2-amino-6-amidinohexanoic acid) found in these palatable forage plants acts as a hepatotoxin and can accumulate in the meat of ruminant livestock and wild camels. In this study, bovine rumen fluid was cultivated in an in vitro fermentation system provided with Indigofera spicata plant material and the ability of the resulting mixed microbial populations to degrade indospicine was determined using UPLC–MS/MS over a 14 day time period. The microbial populations of the fermentation system were determined using 16S rRNA gene amplicon sequencing and showed distinct, time-related changes occurring as the rumen-derived microbes adapted to the fermentation conditions and the nutritional substrates provided by the Indigofera plant material. Within eight days of commencement, indospicine was completely degraded by the microbes cultivated within the fermenter, forming the degradation products 2-aminopimelamic acid and 2-aminopimelic acid within a 24 h time period. The in vitro fermentation approach enabled the development of a specifically adapted, mixed microbial population which has the potential to be used as a rumen drench for reducing the toxic side-effects and toxin accumulation associated with ingestion of Indigofera plant material by grazing ruminant livestock.

Bioaccumulation and Distribution of Indospicine and Its Foregut Metabolites in Camels Fed Indigofera spicata

In vitro experiments have demonstrated that camel foregut-fluid has the capacity to metabolize indospicine, a natural toxin which causes hepatotoxicosis, but such metabolism is in competition with absorption and outflow of indospicine from the different segments of the digestive system. Six young camels were fed Indigofera spicata (337 µg indospicine/kg BW/day) for 32 days, at which time three camels were euthanized. The remaining camels were monitored for a further 100 days after cessation of this indospicine diet. In a retrospective investigation, relative levels of indospicine foregut-metabolism products were examined by UHPLC-MS/MS in plasma, collected during both accumulation and depletion stages of this experiment. The metabolite 2-aminopimelamic acid could be detected at low levels in almost all plasma samples, whereas 2-aminopimelic acid could not be detected. In the euthanized camels, 2-aminopimelamic acid could be found in all tissues except muscle, whereas 2-aminopimelic acid was only found in the kidney, pancreas, and liver tissues. The clearance rate for these metabolites was considerably greater than for indospicine, which was still present in plasma of the remaining camels 100 days after cessation of Indigofera consumption.

Assessing the risk of residues of the toxin indospicine in bovine muscle and liver from north-west Australia

Indospicine is a natural toxin occurring only in Indigofera plant species, including the Australian native species I. linnaei. These perennial legumes are resistant to drought and palatable to grazing livestock including cattle. Indospicine accumulates in the tissues (including muscle) of animals grazing Indigofera and these residues persist for several months after exposure. Dogs are particularly sensitive to indospicine with reports in past decades of hepatotoxicosis and mortalities in dogs after dietary exposure to indospicine-contaminated horse and camel meat. The risk for human consumption is not known, and the current study was undertaken to assess indospicine levels in cattle going to slaughter from divergent regions of Western Australia, and to predict the likelihood of significant residues being present. Muscle and corresponding liver samples from 776 cattle originating from the Kimberley and Pilbara Regions in the tropical north of the state, where I. linnaei is prevalent, and 640 cattle from the South West and South Coast Regions in the temperate south west of the state, where the plant is not known to occur, were collected at abattoirs over four seasons in 2015-2017. Indospicine levels were measured by LC-MS/MS and ranged from below detection to 3.63 mg/kg. No indospicine residues were detected in any of the animals originating from the South West and South Coast Regions. Prevalence of indospicine residues in cattle from the Kimberley Region was as high as 33% in spring and 91% in autumn, with positive animals being present in most consignments and on most properties. The average prevalence of indospicine residues from the Kimberley and Pilbara Regions throughout the survey period was 63%. @Risk best fit probability distributions showed ninety-fifth percentile (P95) indospicine concentrations of 0.54 mg/kg for muscle and 0.77 mg/kg for liver in cattle originating from the Kimberley and Pilbara Regions during the survey period. When considered with average Australian meat consumption data, the estimated consumer exposure from this P95 muscle was 0.32 μg indospicine/kg bw/day, which compared favourably with our calculated provisional tolerable daily intake (PTDI) of 1.3 μg indospicine/kg bw/day. However canine exposure is of potential concern, with active working dog exposure calculated to exceed this PTDI by a factor of 25, based on a P95 indospicine concentration of 0.54 mg/kg in muscle.

Release of Indospicine from Contaminated Camel Meat following Cooking and Simulated Gastrointestinal Digestion: Implications for Human Consumption

Indospicine, a hepatotoxic arginine analog, occurs in leguminous plants of the Indigofera genus and accumulates in the tissues of grazing animals that consume these plants. Furthermore, indospicine has caused toxicity in dogs following consumption of indospicine-contaminated meat; however, the potential impact on human health is unknown. The present study was designed to determine the effect of simulated human gastrointestinal digestion on the release and degradation of indospicine from contaminated camel meat following microwave cooking. Results showed no significant (p > 0.05) indospicine degradation during cooking or in vitro digestion. However, approximately 70% indospicine was released from the meat matrix into the liquid digesta during the gastric phase (in the presence of pepsin) and increased to >90% in the intestinal phase (with pancreatic enzymes). Following human consumption of contaminated meat, this soluble and more bioaccessible fraction of intact indospicine could be readily available for absorption by the small intestine, potentially circulating indospicine throughout the human body to tissues where it could accumulate and cause detrimental toxic effects.

Metal-Involving Synthesis and Reactions of Oximes

This review classifies and summarizes the past 10-15 years of advancements in the field of metal-involving (i.e., metal-mediated and metal-catalyzed) reactions of oximes. These reactions are diverse in nature and have been employed for syntheses of oxime-based metal complexes and cage-compounds, oxime functionalizations, and the preparation of new classes of organic species, in particular, a wide variety of heterocyclic systems spanning small 3-membered ring systems to macroheterocycles. This consideration gives a general outlook of reaction routes, mechanisms, and driving forces and underlines the potential of metal-involving conversions of oxime species for application in various fields of chemistry and draws attention to the emerging putative targets.

Thermo-alkaline Treatment as a Practical Degradation Strategy To Reduce Indospicine Contamination in Camel Meat

Ingestion of indospicine-contaminated camel and horse meat has caused fatal liver injury to dogs in Australia, and it is currently not known if such contaminated meat may pose a human health risk upon dietary exposure. To date, indospicine-related research has tended to focus on analytical aspects, with little information on post-harvest management of indospicine-contaminated meat. In this study, indospicine degradation was investigated in both aqueous solution and also contaminated meat, under a range of conditions. Aqueous solutions of indospicine and indospicine-contaminated camel meat were microwaved (180 °C) or autoclaved (121 °C) with the addition of food-grade additives [0.05% (v/v) acetic acid or 0.05% (w/v) sodium bicarbonate] for 0, 15, 30, and 60 min. An aqueous sodium bicarbonate solution demonstrated the greatest efficacy in degrading indospicine, with complete degradation after 15 min of heating in a microwave or autoclave; concomitant formation of indospicine degradation products, namely, 2-aminopimelamic and 2-aminopimelic acids, was observed. Similar treatment of indospicine-contaminated camel meat with aqueous sodium bicarbonate resulted in 50% degradation after 15 min of heating in an autoclave and 100% degradation after 15 min of heating in a microwave. The results suggest that thermo-alkaline aqueous treatment has potential as a pragmatic post-harvest handling technique in reducing indospicine levels in indospicine-contaminated meat.

Level of natural hepatotoxin (Indospicine) contamination in Australian camel meat

Camel meat production for human consumption and pet food manufacture accounts for a relatively small part of overall red meat production in Australia. Reliable statistical data for the Australian production and consumption of camel meat are not available; however, it is estimated that 300,000 feral camels roam within the desert of central Australia, with an annual usage of more than 3000 camels for human consumption, 2000 for pet food manufacture and a smaller number for live export. Despite a small Australian camel meat production level, the usage of camel meat for pet food has been restricted in recent years due to reports of serious liver disease and death in dogs consuming camel meat. This camel meat was found to contain residues of indospicine, a non-proteinogenic amino acid found in certain Indigofera spp., and associated with mild to severe liver disease in diverse animals after dietary exposure to this hepatotoxin. The extent of indospicine-contaminated Australian camel meat was previously unknown, and this study ascertains the prevalence of such residue in Australian camel meat. In this study, indospicine levels in ex situ (95 samples collected from an abattoir in Queensland) and in situ (197 samples collected from camels after field culling in central Australia) camel meat samples were quantitated using a validated ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The quantitation results showed 46.7% of the in situ- and 20.0% of the ex situ-collected camel meat samples were contaminated by indospicine (more than the limit of detection (LOD) of 0.05 mg kg^-1 fresh weight). The overall indospicine concentration was higher (p < 0.05) in the in situ-collected samples. Indospicine levels detected in the present study are considered to be low; however, a degree of caution must still be exercised, since the tolerable daily intake for indospicine is currently not available for risk estimation.

Seasonal and Species Variation of the Hepatotoxin Indospicine in Australian Indigofera Legumes As Measured by UPLC-MS/MS

Livestock industries have maintained a keen interest in pasture legumes because of the high protein content and nutritive value. Leguminous Indigofera plant species have been considered as having high feeding values to be utilized as pasture, but the occurrence of the toxic constituent indospicine in some species has restricted this utility. Indospicine has caused both primary and secondary hepatotoxicosis and also reproductive losses, but has only previously been determined in a small number of Indigofera species. This paper validates a high-throughput ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to determine the indospicine content of various Indigofera species found in Australian pasture. Twelve species of Indigofera together with Indigastrum parviflorum plants were collected and analyzed. Of the 84 samples analyzed, *I. spicata (the asterisk indicates a naturalized species) contained the highest indospicine level (1003 ± 328 mg/kg DM, n = 4) followed by I. linnaei (755 ± 490 mg/kg DM, n = 51). Indospicine was not detected in 9 of the remaining 11 species and at only low levels (<10 mg/kg DM) in 2 of 8 I. colutea specimens and in 1 of 5 I. linifolia specimens. Indospicine concentrations were below quantitation levels for other Indigofera spp. (I. adesmiifolia, I. georgei, I. hirsuta, I. leucotricha, *I. oblongifolia, I. australis, and I. trita) and Indigastrum parviflorum. One of the more significant findings to emerge from this study is that the indospicine content of I. linnaei is highly variable (from 159 to 2128 mg/kg DM, n = 51) and differs across both regions and seasons. Its first regrowth after spring rain has a higher (p < 0.01) indospicine content than growth following more substantial summer rain. The species collected include the predominant Indigofera in Australia pasture, and of these, only *I. spicata and I. linnaei contain high enough levels of indospicine to pose a potential toxic threat to grazing herbivores.