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

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.