Microwave-assisted extraction of raspberry pomace phenolic compounds, and their bioaccessibility and bioactivity

Raspberry pomace (RBP) is rich in phenolic compounds. This study aims to optimize the extraction of phenolics from RBP and assess their bioaccessibility and bioactivity. The extraction process revealed that ethanol 50 % was the most effective solvent. Microwave-assisted hydroethanolic extraction (MAE) significantly outperformed conventional methods, with optimal conditions of 200 °C for 10 min yielding the highest concentrations of total phenolics (68 mg GAE/g RBP) and flavonoids (63 mg RE/g RBP). Eleven phenolic compounds were identified by HPLC-ESI-MS, with gallic acid and protocatechuic acid being the most prevalent. The gastrointestinal digestion revealed that although some phenolics suffered degradation (like ferulic acid and quercetin), phenolics are more bioaccessible and have relevant antioxidant activity. RBP extract exhibited anti-inflammatory activity by downregulating pro-inflammatory IL-1β and upregulating anti-inflammatory IL-10 cytokines in LPS-activated macrophages. These findings underscore the effectiveness of MAE in extracting bioactives from RBP, highlighting its potential in developing functional foods and nutraceuticals.