COMPARISON AMONG EXTRACTION TECHNIQUES FOR ANTIOXIDANTS PRODUCTION FROM AGRONOMIC RESIDUES.

Different extraction methods were tested in order to recover phenolic molecules from chestnut shells, a solid waste originating from the industrial chestnut peeling process. Boiling water, ultrasounds at 40°C, and autoclave treatments were chosen, and the most effective technique was evaluated through the determination of the highest phenolic and ortho-diphenolic content in the resulting extracts. The best method was proved to be the extraction by autoclave for 60 min. This procedure gave 0.836 mg GAE/mL extract (±0.018) and 0.297 mg CAE/mL extract (±0.003) for total phenols and ortho-diphenols, respectively. Measurement of the Radical Scavenging Activity by 2,2-diphenyl-1- picrylhydrazyl (DPPH?) assay showed that the extracts exhibited an antioxidant power higher than ascorbic acid, used as reference compound. Analysis by High Performance Liquid Chromatography revealed that gallic acid was the main simple phenol detected in the extract independently from the extraction method used. Its amount varied from 159.66±0.31 to 284.14±0.72 microg/mL extract.