LC/ESI-MS/MS characterisation of procyanidins and propelargonidins responsible for the strong antioxidant activity of the edible halophyte Mesembryanthemum edule L.

Mesembryanthemum edule is used as a food ingredient and in traditional medicine. In this study, we investigated antioxidant activities of several extracts (methanol/acidified water, v/v: 20/80; 40/60 and 60/40) obtained from M. edule leaf, stem and root. Then, individual phenolics were characterised by reverse-phase HPLC coupled to electrospray ionisation mass spectrometry and multi-stage MS fragment analysis. Results showed that 40% methanol leaf extract, 40% methanol root extract and 20% methanol stem extract displayed the highest scavenging activity against DPPH and ABTS radicals. Regarding LC/ESI-MS/MS identification of active phenols, there were significant differences among the fractions of interest. In fact, 40% leaf extract mainly contained procyanidins, whereas propelargonidins were the major phenolics in 20% methanol stem extract, while, in 40% root extract, the active compounds remained unidentified. These results indicate that edible M. edule can be used as a nutraceutical in the pharmaceutical industry.