The Aqueous Extract of Ramie Leaves Attenuate OxidativeStress and Inflammation: In Vitro and Cellular Investigations

Oxidative stress and chronic inflammation, driven by reactive oxygen species (ROS) and pro-inflammatory cytokines, contribute significantly to diseases like inflammatory bowel diseases (IBD), yet the therapeutic potential of phenolic compounds-rich agricultural byproducts like ramie leaves (Boehmeria nivea L.) remains underexplored for multi-target antioxidant and anti-inflammatory applications. Using response surface methodology, optimal ultrasonic extraction conditions for ramie leaf aqueous extract (RLAE) were determined as a 1:30 g/mL solid-to-liquid ratio, 43 min, and 50 °C, yielding 2.26 ± 0.16 mg/g total phenolic content. RLAE exhibited strong antioxidant activity with IC50 values of 1.09 ± 0.06 mg/mL (DPPH), 0.60 ± 0.02 mg/mL (ABTS), and 0.93 ± 0.03 mg/mL (O2−), a FRAP equivalent of 11.85 ± 0.47 mmol FeSO4/g, and notable SOD-like activity. In LPS-stimulated IEC-6 cells, RLAE (0.1–0.2 mg/mL) significantly reduced pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and enhanced IL-10 expression, with low cytotoxicity up to 0.4 mg/mL. HPLC identified 21 compounds, including pyrocatechuic acid, rutin, and hyperoside, driving these effects via ROS scavenging and NF-κB modulation. RLAE’s multi-mechanistic antioxidant and anti-inflammatory properties position it as a sustainable candidate for nutraceutical development in gastrointestinal health, warranting further in vivo studies.