Chestnut Burs as a Source of Natural Antioxidants

The potential of chestnut bur as a source of natural antioxidants has been studied. Extracts in solvents of varying polarity (acetone, ethanol, methanol and water) were obtained and compared with respect to extraction yield, total phenols content, antioxidant activity, molecular weight distribution and composition. The extraction with water led to the highest extraction yield (21.2%) and extract total phenols content (37.6 g GAE/100g), FRAP antioxidant activity (2120 nmol AAE/mg extract), DPPH and ABTS radical scavenging activity (3.68 and 3.59 mmol TRE/g extract, respectively) together with the lowest EC50 values for the DPPH (0.044 mg/mL) and ABTS (0.337 mg/mL) essays. The extraction yield, the extract total phenols content and the antioxidant activity (FRAP, DPPH and ABTS) decreased when the polarity of the solvent decreased (water > methanol > ethanol > acetone) and the EC50 values increased in the same order. Chestnut bur extracts have been characterized as hydrolysable gallotannins as revealed its MALDI-TOF spectrum showing a major peak series exhibiting a mass increment of 152 Da corresponding to the repeat unit of the galloyl group. In addition to gallic acid esters of glucose, ellagic acid, quercetin, quercetin-3 beta-D-glucoside and vescalagin/castalagin were found in chestnut bur extracts.