Recovery of phenolic compounds from agro-industrial by-products: Evaluating antiradical activities and immunomodulatory properties

Grape pomace (GP), spent coffee grounds (SCG), tomato pomace (TP) and red corn cobs (RCC) were collected and polyphenols were extracted by optimizing ethanol solvent extractions. Subsequently, extracted phenolic acids, flavonoids and anthocyanins were completely characterized by HPLC, HPLC-DAD and LC-ES-MS. Antiradical activity (DPPH) and anti-inflammatory assays (IL-8 cytokine gene expression in the Caco-2 cell line) were then investigated. Results indicated a total polyphenol content for the by-products in the range: 4.64 ± 0.31–22.77 ± 0.65 mg gallic acid equivalent g−1 dry weight, and an antiradical activity in the range: 21.47 ± 0.09–89.76 ± 0.24 μM Trolox equivalent g−1 dry weight. The best anti-inflammatory performances were reported for SCG and GP and they were due to the high flavonoid contents, playing phenolic compounds a minor role. Taking into consideration the results above reported and the information related to the by-products studied, i.e. geographical provenience, daily availability and biomass potential preservation, the agro-industrial wastes were ranked for their suitability to be potentially upgraded to industrial level in the following order: spent coffee grounds ≫ grape pomace > red corn cobs ≫ tomato pomace.