Industrial Mung Bean Shell–Derived Polysaccharides as Potential Dual-Function Cosmetic Actives: Physicochemical and Structural Elucidation, Antioxidant Activity, and Moisturizing Property

Mung bean (Vigna radiata L.) processing generates large quantities of shell byproducts that are typically discarded despite their potential as a renewable source of bioactive polysaccharides. In this study, polysaccharides were extracted from mung bean shells using cellulase-assisted extraction (MbSP-1) and hot-water extraction (MbSP-2), purified by ethanol precipitation, papain deproteinization, dialysis, and freeze-drying, and characterized by total sugar analysis, HPSEC, monosaccharide profiling, NMR, FTIR, XRD, SEM, and TGA. MbSP-1 and MbSP-2 were acidic, uronic-acid-rich polysaccharides with pectin-associated features, differing in molecular weight and neutral sugar composition. Both fractions exhibited concentration-dependent antioxidant activities in DPPH, ABTS, FRAP, hydroxyl, and superoxide assays; at corresponding concentrations, MbSP-1 generally exhibited significantly greater radical-scavenging and/or ferric-reducing capacity than MbSP-2 (p < 0.05, where applicable). HaCaT cell tests revealed that MbSP maintained >80% viability between 0.04 and 0.63 mg/mL, with cytotoxic effects appearing only at higher concentrations, indicating acceptable in vitro cytocompatibility. Moisture absorption and retention measurements under 43% and 81% relative humidity demonstrated that MbSP possesses promising moisturizing-related potential, with MbSP-1 showing moisture absorption and retention behavior comparable to selected conventional polysaccharide humectants under the tested conditions. These hydration behaviors correlate with the high galacturonic and glucuronic acid contents and hydrophilic monosaccharide profiles of MbSP. Overall, mung bean shell polysaccharides show promise as candidates for moisturizing-related cosmeceutical applications, combining antioxidant activity with favorable in vitro cytocompatibility.