Metabolic profiling of Amaranthus retroflexus L. and detection of cytotoxic constituents associated with livestock toxicity

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    Amaranthus retroflexus is an annual upright plant that grows rapidly and flowers in summer through to early autumn. Native to North America, it has recently established as a noxious weed across southern Australia. Nitrate poisoning is known to occur in livestock after ingestion of Amaranthus, particularly in ruminants through the formation of methaemoglobin resulting in hypoxia (Aslani and Vojdani, 2007). In 2013 and 2014, sheep grazing in pastures containing predominantly A. retroflexus were poisoned following ingestion of the noxious weed (Kessell et al., 2015). Post-mortem examination of the affected animals showed strong evidence of renal failure and dehydration while histological examination of the kidneys revealed acute tubular necrosis distinctly different to symptomology associated with nitrate poisoning. Nutritional analysis of the plant tissues revealed high levels of nitrates in the stem but not leaf and inflorescence tissues. To identify the active constituents in A. retroflexus associated with livestock toxicity, methanolic extracts of leaf, stem, root and floral tissues were prepared from mature plants collected from affected fields for further laboratory analysis. A useful bioassay for assessment of cytotoxicity utilised the murine cell line NIH3T3. Cell cultures were treated with plant extracts at various concentrations for 48 hours and cell viability was assessed. Methanolic extracts were further analysed using UPLC/MS QToF for metabolic profiling. Cytotoxicity was significantly higher in leaf extracts when compared to extracts of other tissue types. Metabolic profiling indicated the predominance of non-protein amino acids, alkaloids and N-containing compounds, particularly in the leaf and stem extracts. Abundance of one principal unidentified constituent was strongly correlated with observed cytotoxicity. Future experimentation is directed towards structural elucidation of this putative causal agent.
    Original languageEnglish
    Publication statusPublished - 2016
    EventRACI Natural Products Chemistry Group Symposium. Annual One-day Symposium: RACI - Science Teaching Facility, University of Wollongong, Wollongong, Australia
    Duration: 30 Sep 201630 Sep 2016


    ConferenceRACI Natural Products Chemistry Group Symposium. Annual One-day Symposium


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