Strong antioxidant phenolics from Acacia nilotica: Profiling by ESI-MS and qualitative-quantitative determination by LC-ESI-MS

Acacia nilotica (L.) Del. syn is a species rich in polyphenolic constituents, in which catechins are hypothesized to possess antioxidant properties and to play a role in the anti-inflammatory activity of several plants. Due to the complexity of catechin derivatives, the investigation of this class of natural compounds has been limited by difficulties in their separation. In this paper, rationalization of the phenolics occurring in the 80% EtOH extract of Acacia nilotica pods, on the basis of ESI-MS and ESI-MS/MS profiles, has been proposed. Additionally, an LC-ESI-MS qualitative study has been performed by using a C18 polar endcapped stationary phase. The fragmentation pattern obtained evidenced the presence in A. nilotica pods of galloylated catechin- and gallocatechin derivatives along with galloylated glucose derivatives. The structures were confirmed by NMR, after isolation of the pure compounds. In addition, the radical scavenging activities of extracts and pure compounds were investigated, by using the TEAC assay. Furthermore quantitative analyses were performed by LC-ESI-MS/MS, confirming the interest of this species as a rich source of very strong antioxidant principles.