Antioxidant, Anti-α-Glucosidase, Antityrosinase, and Anti-Inflammatory Activities of Bioactive Components from Morus alba

The root bark of Morus alba L. (Mori Cortex) is used to treat diuresis and diabetes in Chinese traditional medicine. We evaluated different solvent extracts and bioactive components from the root bark of Morus alba L. for their antioxidant, anti-α-glucosidase, antityrosinase, and anti-inflammatory activities. Acetone extract showed potent antioxidant activity, with SC(50) values of 242.33 ± 15.78 and 129.28 ± 10.53 µg/mL in DPPH and ABTS radical scavenging assays, respectively. Acetone and ethyl acetate extracts exhibited the strongest anti-α-glucosidase activity, with IC(50) values of 3.87 ± 1.95 and 5.80 ± 2.29 μg/mL, respectively. In the antityrosinase assay, the acetone extract showed excellent activity, with an IC(50) value of 7.95 ± 1.54 μg/mL. In the anti-inflammatory test, ethyl acetate and acetone extracts showed significant anti-nitric oxide (NO) activity, with IC(50) values of 10.81 ± 1.41 and 12.00 ± 1.32 μg/mL, respectively. The content of the active compounds in the solvent extracts was examined and compared by HPLC analysis. Six active compounds were isolated and evaluated for their antioxidant, anti-α-glucosidase, antityrosinase, and anti-inflammatory properties. Morin (1) and oxyresveratrol (3) exhibited effective antioxidant activities in DPPH and ABTS radical scavenging assays. Additionally, oxyresveratrol (3) and kuwanon H (6) showed the highest antityrosinase and anti-α-glucosidase activities among all isolates. Morusin (2) demonstrated more significant anti-NO and anti-iNOS activities than the positive control, quercetin. Our study suggests that the active extracts and components from root bark of Morus alba should be further investigated as promising candidates for the treatment or prevention of oxidative stress-related diseases, hyperglycemia, and pigmentation disorders.