Garcinia mangostana L. fruits and derived food supplements: Identification and quantitative determination of bioactive xanthones by NMR analysis

Mangosteen (Garcinia mangostana L.), known as "the queen of fruits", is one of the most praised tropical fruit due to its delicious taste. In the last years, the use of mangosteen in functional products has been increasing, mainly in food beverages and nutraceutical formulations due to its biological activities related to the content of xanthones. The quantitative Nuclear Magnetic Resonance (qNMR) analysis, a rapid and accurate method used for simultaneous quantification of plant metabolites, was here employed to determine the amount of bioactive xanthones in the extracts of G. mangostana arils and shells obtained by using solvent of increasing polarity along with ''eco-friendly'' solvents like ethanol and ethanol-water. Furthermore, the content of xanthones was compared with that occurring in four selected commercial food supplements, among which tablets and capsules, and two fruit juices, based on mangosteen. Quantitative results highlighted a significant variability: the extracts of the shells displayed a higher amount of bioactive xanthones than those of the arils, in particular, of gamma-mangostin and alpha-mangostin, while beta-mangostin, demethylcalabaxanthone, mangostanin, 8-deoxygartanin occurred in higher amounts in arils. A certain variability in the amount of biologically active xanthones (i.e. alpha-mangostin and gamma-mangostin) could be observed in commercial food supplements.