Flavonoids from Morus alba L. Leaves: Optimization of Extraction by Response Surface Methodology and Comprehensive Evaluation of Their Antioxidant, Antimicrobial, and Inhibition of α-Amylase Activities through Analytical Hierarchy Process

To explore the flavonoids from Morus alba L. leaves (MLF), the process of extracting was optimized by a response surface methodology and the antimicrobial and antioxidant activities were evaluated in vitro. The yield of flavonoids reached 50.52 mg g(−1) under the optimized extraction conditions (i.e., extraction temperature, 70.85 °C; solvent concentration, 39.30%; extraction time, 120.18 min; and liquid/solid ratio, 34.60:1). The total flavonoids were extracted in organic solvents with various polarities, including petroleum ether (MLF(p)), ethyl acetate (MLF(e)), and n-butanol (MLF(b)). In vitro, the four MLF samples exhibited good antioxidant activities for scavenging of 2, 2′-azinobis-(3-ethylbenz-thiazoline-6-sulphonate) radical, 1, 1-diphenyl-2-picrylhydrazyl radical, and total reducing power. Regarding antimicrobial efficacy, the MLF samples suppressed the development of Staphylococcus aureus, Bacillus subtilis, and Bacillus pumilus. The MLF samples inhibited α-amylase activity to a certain extent. The analytical hierarchy process (AHP) was used to evaluate comprehensively the bioactivities of the MLF samples. The AHP results revealed that the bioactivity comprehensive score (78.83 μg mL(−1)) of MLF(e) was optimal among the four MLF samples. Morus alba L. leaves also exhibited non-hemolytic properties. All bioactivities suggested the potential of MLF(e) as a candidate resource in the food and drug industries.