Chalcone dimers from Astronium graveolens (Anacardiaceae) and their biological activities

Abstract

This work describes the chemical composition of the stems of Astronium graveolens Jacq. (Anacardiaceae). The CH2Cl2 and EtOAc soluble fractions of this extract were subjected to chromatographic procedures that allowed obtaining the unreported dimers (7"R*, 8"S*) 2′, 4,4′, 5-tetrahydroxychalcone-(2 → 7", 8 → 8")-2′", 4", 4′"- trihydroxy-7", 8’’-dihydrochalcone and (7 S*,8 R*,7"S*,8"S*)-2′,4,4′,5,7-pentahydroxy-7,8-dihydrochalcone-(2→7",8→8")-2′",4",4’’’-7 ", 8 "- dihydrochalcone, the previously isolated chalcone dimer named matosine (7 S*,8 S*,7'' S*,8"R*)-2′,4,4′, 5,7-pentahydroxy-7,8-dihydrochalcone-(2→7", 8→8")-2′", 4", 4′"-trihydroxy-7", 8"- dihydrochalcone). Besides these specific chalcone dimers, sitosterol, sitosterol-3-O-β-D-glucoside, methyl gallate, gallic acid, and quercitrin were also isolated. These compounds were identified by mono and bidimensional NMR data analysis and HRMS. Methanolysis of triacylglycerides yielded a mixture of fatty acid methyl esters, which were identified by GC-MS. The profile indicated this fraction is composed of saturated (54.13 %) and unsaturated (46.21 %) fatty acids, and palmitic acid and oleic acid are the major components. The brine shrimp test of the extract showed that the soluble fraction CH2Cl2 of the stems exhibited high toxicity; meanwhile, the EtOAc soluble fraction presented moderate toxicity. The Elmann test indicated that the EtOAc was considered an expressive AChE inhibitor, and the chalcone dimers 1, 2, and 3 present excellent anticholinesterase activities inhibiting 83.88 %, 70.72 %, and 62.60 % AChE at concentrations of 500 µM, respectively.