Isolation of antioxidant phenolics from Schinopsis brasiliensis based on a preliminary LC-MS profiling

The phenolic content of the ethanol extract of the stem bark of the Brazilian plant Schinopsis brasiliensis Engl. (Anacardiaceae) has been evaluated together with the antioxidant activity. The good antioxidant activity exhibited in the Trolox Equivalent Antioxidant Capacity (TEAC) assay (TEAC value = 3.04 mg/mL) encouraged us to investigate its constituents. An analytical approach based on LC-ESIMSⁿ was applied to rapidly obtain a metabolite profile of the ethanol extract of the stem bark of S. brasiliensis. Sixteen phenolic compounds, among which five galloyl derivatives, never reported before, have been isolated and their structures have been unambiguously elucidated by extensive spectroscopic methods, including 1D (¹H, ¹³C, TOCSY) and 2D (DQF-COSY, HMBC, and HSQC) NMR experiments. Moreover, the antioxidant activity of all the isolated compounds was evaluated, along with the cytotoxicity against the cancer cell lines A549 (human alveolar basal carcinoma) and Hela (human epitheloid cervix carcinoma). The previously undescribed compounds exhibited a high free-radical-scavenging activity, in the range of 1.10-1.86 mM. None of the tested compounds, in a range of concentrations between 12.5 and 100 μM, caused a significant reduction of the cell number.