Bioactive coumarins and HPLC-PDA-ESI-ToF-MS metabolic profiling of edible queule fruits (Gomortega keule), an endangered endemic Chilean species

The endemic Chilean tree Gomortega keule (Molina) Baillon (Gomortegaceae) was highly appreciated for its edible fruits. Due to substitution of the native forest by tree monocultures, this species in now endangered. Antioxidant assay-guided fractionation of the methanolic extract led to the isolation of eight antioxidant compounds, including rare highly oxygenated coumarins, besides the more common antioxidant compounds chlorogenic acid (compound 6) and rutin (compound 16). The isolation of the compounds was achieved by preparative reverse phase HPLC and the structural elucidation was performed using H-1 and C-13 NMR techniques. A metabolomic fingerprint was generated and 32 compounds were detected and analyzed on the basis of HPLC-PDA and HR-ESI-ToF-MS. The total phenolic and flavonoid contents of the fruits were determined by spectroscopic means. The content of the major compounds chlorogenic acid (6) and dimethylfraxetin (22) was 51.80 +/- 1.49 mg/100 g dry weight and 9.57 +/- 0.11 mg/100 g dry weight, respectively, while compounds 6 and 16 showed the highest antioxidant capacity (42.37 +/- 3.72 mu g/ml and 23.91 +/- 1.50 mu g/ml in the DPPH scavenging assay, respectively). This is the first report of antioxidant capacity and polyphenolic content of the edible queule fruits. (C) 2013 Elsevier Ltd. All rights reserved.