Herbal Medicine Processing By-Products as Bioactive Resources: In Vivo Evidence for Antioxidant, Anti-Inflammatory, and Immunomodulatory Effects

Processing herbal medicine generates substantial quantities of by-products that are discarded as waste. These residues may retain polysaccharides, flavonoids, saponins, terpenoids, and other constituents with pharmacological relevance. This review discusses the bioactive potential of by-products derived from single traditional Chinese and Korean herbal medicines, with emphasis on antioxidant, anti-inflammatory, and immunomodulatory mechanisms documented in preclinical in vivo studies. Representative in vivo evidence suggests that selected residues, marc fractions, fermentation products, and re-extracted by-products were reported to modulate oxidative stress markers, inflammatory cytokines, immune responses, and tissue-protective pathways across diverse experimental models. Processing method appears to be a key determinant of activity, as fermentation, high-temperature/high-pressure treatment, re-extraction, and targeted purification may enhance or diversify residual bioactivity. Current evidence remains limited by inconsistent chemical characterization, heterogeneous animal models, and incomplete reporting of experimental design. Re-evaluating herbal medicine processing by-products as bioactive resources may support sustainable herbal medicine manufacturing and circular bioeconomy frameworks.