UPLC–QTOF–MS and NMR analyses of graviola (Annona muricata) leaves

Abstract

Graviola leaves (Annona muricata L., Annonaceae) are used by some people to try to treat or evencure cancer, even though over-consumption of the fruit, which contains the neurotoxins annonacinand squamocin has caused an atypical form of Parkinson’s disease. In previous analyses, the fruits wereextracted with methanol under ambient conditions before analyses. In the present study, UPLC–QTOF–MSand NMR were used to analyze freeze-dried graviola leaves that were extracted using dry methanol andethanol at 100◦C and 10 MPa (100 atm) pressure in a sealed container. Methanol solubilized 33% of themetabolites in the lyophilized leaves. Ethanol solubilized 41% of metabolites in the lyophilized leaves. Theconcentrations of total phenolic compounds were 100.3 ± 2.8 and 93.2 ± 2.0 mg gallic acid equivalents perg of sample, for the methanolic and ethanolic extracts, respectively. Moreover, the toxicophore (unsat-urated γ-lactone) that is present in neurotoxic acetogenins was found in the lipophilic portion of thisextract. The concentrations of the neurotoxins annonacin and squamocin were found by UPLC–QTOF–MSto be 305.6 ± 28.3 and 17.4 ± 0.89 μg/g-dw, respectively, in the dried leaves. Pressurized methanol solubi-lized more annonacin and squamocin than ethanol. On the other hand, a hot, aqueous infusion solubilizedonly 0.213% of the annonacin and too little of the squamocin to be detected. So, graviola leaves containsignificant amounts of the neurotoxins annonacin and squamocin, as well as some potentially healthyphenolic compounds. Finally, the potential neurotoxicity of whole leaves in dietary supplements couldbe much higher than that of a tea (hot aqueous infusion) that is made from them.