Transformation of phytochemicals and functional properties in Eleutherococcus senticosus leaves during solid-state fermentation with Rhizopus oligosporus

Eleutherococcus senticosus ( E. senticosus ) leaves were subjected to solid-state fermentation with Rhizopus oligosporus KCCM11948P for 120 h to evaluate changes in phytochemicals and functional properties. Fermentation increased water-swelling, water-holding, cholesterol-binding, and oil absorption capacities. Chlorogenic acid decreased by 33.7%, whereas caffeic acid increased by 33.5% after 72 h of fermentation. L-carnitine was first detected at 72 h and reached 15.67 ± 0.50 mg/kg DM after 120 h, while β-sitosterol increased by 105.2%. Total phenolic and flavonoid contents increased by 38.6% and 20.8%, respectively. Antioxidant activities measured by the FRAP, ABTS, and ORAC assays increased throughout fermentation, and nitric oxide (NO)-inhibitory activity in RAW264.7 macrophages was enhanced by 83.0% compared with non-fermented leaves. These results demonstrate that solid-state fermentation with R. oligosporus improves the phytochemical composition and functional properties of E. senticosus leaves, supporting their potential use as functional ingredients.