Purification, Characterization, and Anti-Inflammatory Potential of Free and Bound Polyphenols Extracted from Rosa roxburghii Tratt Pomace

Rosa roxburghii Tratt pomace (RRTP), an underutilized byproduct, is rich in polyphenol compounds. This study aimed to further explore the purification, characterization, anti-inflammatory activities, and underlying molecular mechanisms of free polyphenols (RRTP-FP) and bound polyphenols (RRTP-BP) from RRTP. The results indicated that AB-8 macroporous resin emerged as the preferred choice for subsequent separation and purification. The purities of purified RRTP-FP (P-RRTP-FP) and purified RRTP-BP (P-RRTP-BP) increased by 103.34% and 66.01%, respectively. Quantitative analysis identified epigallocatechin, epicatechin, and ellagic acid as the main phenolic compounds in P-RRTP-FP. In P-RRTP-BP, the primary phenolic compounds were ellagic acid, epicatechin, and gallic acid. In vitro antioxidant assays demonstrated the superior DPPH and ABTS radical scavenging activities of P-RRTP-FP and P-RRTP-BP compared to vitamin C. Treatment with P-RRTP-FP and P-RRTP-BP reduced nitric oxide (NO) and reactive oxygen species (ROS) production, mitigated the decline in cellular membrane potential, and significantly downregulated the mRNA expression of pro-inflammatory cytokines and inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Additionally, P-RRTP-FP and P-RRTP-BP inhibited the phosphorylation of pertinent proteins in the nuclear factor kappa-B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. This finding suggests potential utility of RRTP-derived polyphenols as anti-inflammatory agents for managing severe inflammatory conditions.