Natural deep eutectic solvent-based ultrasound-assisted extraction of phenolics from sunflower seed shells: effects of roasting and bioaccessibility assessment

Abstract Sunflower seed shells, commonly discarded as waste, represent a valuable yet underutilised source of phenolic compounds. This study aimed to recover phenolic compounds from both unroasted and roasted sunflower seed shells using ultrasound-assisted extraction (UAE) in combination with 12 different natural deep eutectic solvents (NADES) and to assess the bioaccessibility of the resulting green extracts. UPLC–ESI–MS/MS analysis identified chlorogenic acid as the predominant phenolic compound in the extracts. Among the tested solvents, glucose:lactic acid (1:5) yielded the highest levels of bioaccessible chlorogenic acid in both unroasted and roasted samples. Most NADES formulations resulted in higher levels of bioaccessible phenolics compared to the ethanolic extract. However, roasting significantly reduced the bioaccessibility of total phenolics, antioxidant capacity, and chlorogenic acid in the majority of the extracts. Overall, the findings demonstrate the effectiveness of combining NADES with UAE to enhance the extraction and bioaccessibility of phenolic compounds from sunflower seed shells.