Quantification of the neurotoxins Annonaceous acetogenins in the edible fruits of several Annona species using 1H NMR

Case-control studies evidenced the association of sporadic Parkinsonism – dementia complexes with the consumption of Annonaceae fruits in several tropical areas. The mitochondrial complex I inhibitors Annonaceous acetogenins, a homogenous class of aliphatic polyketides, proved neurotoxic in several models and are proposed as candidate toxins. These compounds were evidenced in various food products as complex mixtures of closely related analogues [1, 2]. We developed a simple and reliable qNMR method for the direct quantification of total acetogenins in fruit pulps extracts [3 – 5]. Optimization of conditions and analytical validation were performed using isolated acetogenins (annonacin and squamocin) and crude extracts, towards direct routine analysis in CDCl₃ containing dimethyl fumarate as an internal standard, at 300 MHz. Limits of detection (LOD) and of quantification (LOQ) were 0.5 and 2.5 mM respectively for annonacin. This method was applied to Annona fruits harvested in New Caledonia, Indian Ocean and Western Africa, providing new insight on dietary exposure to these compounds. Inter-species and batch to batch variations were evidenced, with various samples of Annona glabra (with a content Annonaceous acetogenins content <LOD or <LOQ), A. muricata (<LOD to 2.7 mmol/kg fresh pulp), A. reticulata (<LOD or <LOQ) and A. squamosa (<LOD to 20µmol/kg fresh pulp).

Keywords: Annona, annonaceous acetogenins, neurotoxins, qNMR.

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