RP-HPLC-ESI-QTOF/MS2 based strategy for the comprehensive metabolite profiling of Sclerocarya birrea (marula) bark

In this research, a non-selective extraction procedure followed by a RP-HPLC-ESI-QTOF/MS2 method was applied to evaluate the metabolic profile of these extracts, allowing the identification of a total of 95 compounds belonging to the chemical classes of organic acids, polyphenols, fatty acid derivatives, and others, most of these being identified for the first time in these extracts. These proved far richer in polyphenols, and more specifically in proanthocyanidins. This methodology successfully detected from monomers up to dimers of (epi)catechin, (epi)gallocatechin, and (epi)afzelechin units with one or two galloyl residues. A very high degree of galloylation was found, which may serve in the bioactivity attributed to these extracts. The chromatographic method had sufficient resolving power to separate up to six isomeric forms of several compounds, and the structure of some of these isomeric compounds has been elucidated. Therefore, the methodology applied proved useful for the metabolite profiling of Sclerocarya birrea stem-bark extracts, providing essential information that could be used to explain the plethora of ethnotherapeutic properties and pharmacological actions that have been attributed to this African tree. (C) 2015 Elsevier B.V. All rights reserved.