Chestnut bur extracts as antioxidants: optimization of the extraction stage

Abstract

In this work the exploitation and subsequent valorization of chestnut bur, a forest waste product from chestnut processing in the food industry, is proposed. The experimental design and response surface methodology were applied to optimize the extraction of chestnut bur polyphenols with aqueous methanol. An incomplete factorial design 33 was applied to study the influence of temperature (25-50-75°C), time (30-75-120 min) and methanol concentration (50-70-90% by weight) on extraction yield, extract total phenols content (using the Folin- Ciocalteu method), FRAP antioxidant activity, DPPH and ABTS radical scavenging activity. Temperatures in the range 60-75°C, an extraction time of 75 min and MeOH concentrations in the range 50-60% led not only to extracts with high antioxidant activity (30.89-36.32 g GAE/100 g extract for the total phenol content, 2220-2292 nmol AAE/mg extract for FRAP antioxidant activity; 3.22- 3.40 mmol TRE/g extract for the DPPH assay and 3.26-3.45 mmol TRE/g extract for the ABTS assay), but also to high extraction yields (15.06-19.30%). Chestnut bur extracts were analysed by RP-HPLC-ESI-TOF, which revealed the presence of gallic acid esters of glucose, ellagic acid and small proportions of quercetin and quercetin-3β-D-glucoside. © 2010 WIT Press.