Kristy M. Richards

Determination of Neurotoxic Acetogenins in Pawpaw (Asimina triloba) Fruit by LC-HRMS

The concentrations of the neurotoxins, annonacin and squamocin, were determined in a lyophilized sample of the fruit pulp of the North American pawpaw (Asimina triloba) by LC coupled to high resolution mass spectrometry or LC-HRMS. The sample was extracted using dry methanol at 100 °C and 10 MPa pressure in a sealed container. The extraction of annonacin and squamocin was optimal at 100 °C with 7.72 and 0.162 mg/g, respectively, being found. Also, several isomers of annonacin and squamocin were separated and detected but not quantified.

Neurotoxicity of Dietary Supplements from Annonaceae Species

Dietary supplements containing plant materials of Annonaceae species (Annona muricata L., A. squamosa L., A. mucosa JACQ., A. squamosa × cherimola Mabb.) were extracted by hot, pressurized ethyl acetate and analyzed for their effect in vitro on Lund human mesencephalic neurons. Cell viability was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and cell death was determined by lactate dehydrogenase levels. Three supplements strongly decreased the cell viability at extract concentrations of 1 µg/mL, of which 1 decreased cell viability at 0.1 µg/µL. Also, strong neuronal toxicities of these supplements were found. Cell death was observed at concentrations of 10 µg/mL. The degree of toxicity was comparable to the ones found in Annonaceous fruit extracts. Two fruit pulps of Annonaceae (A. muricata and A. squamosa) showed a reduction in cell viability at lower concentrations. The fruit pulp extract of A. muricata revealed the strongest neurotoxic effect, with 67% cell death at a concentration of 1 µg/mL. A high reduction in cell viability coupled with pronounced cell death was found at 0.1 µg/mL for an Annonaceous seed extract. These results demonstrate that the intake of dietary supplements containing plant material from Annonaceae may be hazardous to health in terms of neurotoxicity.

Bioactive Annonaceous Acetogenins

Abstract Annonaceous acetogenins (ACGs) make up a large and homogeneous class of natural polyketides, with over 400 representatives. They have pesticidal, antiinfective, and cytotoxic properties. Interestingly, they display activity in multidrug resistant cancer cells and show antitumor potential in several tumor-grafted mouse models. ACGs are strong inhibitors of mitochondrial NADH-ubiquinone oxidoreductase (complex I) and may affect alternative targets, with possible covalent interaction. Their ability to inhibit matrix metalloproteinase and modulate histone H3 phosphorylation, to bind calcium or to target mitochondria was shown, among other issues. However, ACGs are suspected of being environmental neurotoxins, responsible for “Guadeloupean parkinsonism” in the French West Indies and for sporadic atypical parkinsonism/dementia in several tropical communities. ACGs induce tau pathology in cultured neurons, and annonacin, a prototypical ACG, proves to be neurotoxic in several animal models. ACGs were identified in edible fruits such as soursop ( Annona muricata L.) and paw paw ( Asimina triloba Dunnal). Leaves, bark, and twigs of both species are sold over the Internet as cures for cancer, with undefined risk/benefit ratio. A method based on MALDI-TOF-MS was used for the analysis of ACGs and annonacin content in plant material and dietary supplements.