tailieunhanh - Chemical constituents of the lichen Dermatocarpon luridum and pKa value of isolated mycosporine

Their structures were determined by extensive spectroscopic analyses including UV, IR, ESI-HRMS, 1D, 2D NMR and specific rotation as well as by comparison of the data with those in the literature. The pKa value in an aqueous solution of (1) was determined by UV-VIS spectrophotometry at 298 K. With the low pKa value , only the neutral form of (1) was present and responsible for the UV absorption in water at pH 7. | Vietnam Journal of Chemistry, International Edition, 55(4): 527-531, 2017 DOI: Chemical constituents of the lichen Dermatocarpon luridum and pKa value of isolated mycosporine Nguyen Thi Thu Tram1,2*, Nguyen Trong Tuan3, Chollet-Krugler Marylène2, Ferron Solenn2, Boustie Joël2 1 Department of Chemistry, Faculty of Science, Can Tho University of Medicine and Pharmacy, Vietnam 2 Equipe PNSCM "Produits Naturels, Synthèses et Chimie Médicinale", UMR CNRS 6226, Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes 1, France 3 College of Natural Sciences, Cantho University Received 27 July 2017; Accepted for publication 28 August 2017 Abstract A phytochemical study on the lichen Dermatocarpon luridum led to the isolation of four known compounds, including mycosporine glutaminol (1), 2-amino-3-acetylaminopropionic acid (2), (22E,24R)-ergosta-7,22-diene3 ,5 ,6 -triol (3) and (2S,3S,4R,2’R)-2-(2’-hydroxytetracosanoylamino)octadecan-1,3,4-triol (4). Their structures were determined by extensive spectroscopic analyses including UV, IR, ESI-HRMS, 1D, 2D NMR and specific rotation as well as by comparison of the data with those in the literature. The pKa value in an aqueous solution of (1) was determined by UV-VIS spectrophotometry at 298 K. With the low pKa value , only the neutral form of (1) was present and responsible for the UV absorption in water at pH 7. Keywords. Dermatocarpon, mycosporine, lichen, pKa. 1. INTRODUCTION Lichens are fungal and algal/cyanobacterial symbioses resulting in the production of a large number of unique secondary metabolites [1]. So far, investigation on chemical constituents of Dermatocarpon luridum has not been noticed well. Previous studies revealed that instead of containing common lichen subtances as phenolic compounds, dibenzofuranes, depsides, depsidones, quinones, pulvinic acid derivatives etc., lichen species belonging to genus Dermatocarpon included several sugar alcohols as .