Phytochemical investigation of Tephromela atra: NMR studies of collatolic acid derivatives |
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| Institution: | 1. Institut de Chimie de Rennes, EA 4090 “Substances Lichéniques et Photoprotection”, Université de Rennes 1, Faculté de Pharmacie, 2 Avenue du Professeur Léon Bernard, 35043 Rennes Cedex, France;2. Centre Régional de Mesures Physiques de l’Ouest, Université de Rennes 1, Bâtiment 11A, Campus de Beaulieu, 35042 Rennes Cedex, France |
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| Abstract: | Six known compounds, atranorin (1) and its derivatives methyl β-orcinol carboxylate (2) and methyl haematommate (3), the depsidones α-alectoronic acid (4) and α-collatolic acid (5), with its hydrolysis derivative β-collatolic acid (6), and a new compound, deoxycollatolic acid (7) have been isolated from the lichen Tephromela atra (Huds.) Hafellner (syn. Lecanora atra). The characterization of the new compound 7 was carried out by extensive NMR studies using COSY, HMQC, HMBC in addition to other spectroscopic methods. 1H NMR spectra recorded at low temperature showed β-collatolic acid (6) was corresponding to an equilibrium of conformers.Compounds 5 and 6 showed a better superoxide anion scavenging activity (IC50 = 463 and 122 μM, respectively) than quercetin (IC50 = 754 μM). |
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