Apple Pomace Polyphenols Extracted by Deep Eutectic Solvent Ameliorate Lipopolysaccharide-Induced Inflammation in RAW264.7 Murine Macrophages and Human Monocyte-Derived Macrophages

Apple pomace, the waste product of the apple processing industry, is a significant global waste-management problem and an underutilized source of bioactive molecules, including polyphenols. To help reduce the amount of apple waste sent to landfill, efficient and ecologically sustainable methods to extract bioactive compounds are needed to facilitate the development of value-added products. To this end, we prepared apple pomace extracts with an environmentally friendly deep eutectic solvent (DES) and a commonly used organic solvent. The composition and bioactivity of both extracts are compared. HPLC-DAD MS/MS analysis revealed similar profiles and content of polyphenols in both extracts. Moreover, the extracts have comparable chemical and cellular antioxidant activity. In murine and human models of LPS-induced inflammation, both extracts exhibited potent anti-inflammatory activity as measured by the suppression of pro-inflammatory cytokine gene expression. Mechanistically, the anti-inflammatory effects of the extracts were mediated, at least in part, by inhibiting the pro-inflammatory master transcription factor NF-κB and by inhibiting the rate-liming enzyme of prostaglandin biosynthesis, COX-2. Our findings underscore the value of apple pomace as a rich source of bioactive compounds and the utility of DES extraction. Further refinement and upscale of the DES extraction method could facilitate product development in the food and health industries.