Optimizing the extraction of phenolic antioxidants from chestnut shells by subcritical water extraction using response surface methodology

The objective of this study was to evaluate the optimal Subcritical Water Extraction (SWE) conditions of antioxidants and polyphenols from chestnut shells using Response Surface Methodology (RSM). A central composite design (CCD) was conducted to analyse the time (6-30 min) and temperature (51-249 degrees C) effects in antioxidant activity (ABTS, DPPH and FRAP) and Total Phenolic Compounds (TPC). TPC ranged from 315.21 to 496.80 mg gallic acid equivalents (GAE)/g DW; the DPPH from 549.23 to 1125.68 mg Trolox equivalents (TE)/g DW; ABTS varied between 631.16 and 965.45 mg ascorbic acid equivalents (AAE)/g DW and FRAP from 2793.95 to 11393.97 mg ferrous sulphate equivalents (FSE)/g DW. The optimal extraction conditions were 30 min/220 degrees C, revealing excelling scavenging efficiencies against HOCl (IC50 = 0.79 mu g/mL) and O-2(-) (IC50 = 12.92 mu g/mL) without toxicity on intestinal cells (0.1 mu g/mL). The phenolic composition revealed high amounts of pyrogallol and protocatechuic acid. SWE can be a useful extraction technique for the recovery of polyphenolics from chestnut shells.

Automated summary

This study evaluated the optimal Subcritical Water Extraction conditions for antioxidants and polyphenols from chestnut shells using Response Surface Methodology. The results showed that the best extraction conditions were 30 min/220 degrees C, with excellent scavenging efficiencies against various radicals and no toxicity on intestinal cells.