Enzymolysis-ultrasonic assisted extraction of flavanoid from Cyclocarya paliurus (Batal) Iljinskaja:HPLC profile, antimicrobial and antioxidant activity

This study aimed to describe Enzymolysis-ultrasonic assisted extraction of flavanoid from Cyclocarya paliurus (Batal) Iljinskaja: HPLC profile, antimicrobial and antioxidant activity. An enzymolysis-ultrasonic assisted extraction (EUAE) method was developed and optimized for the extraction of Cyclocarya paliurus flavonoids in liquid form (CPF). The key factor influencing the extraction yield of Cyclocarya paliurus flavonoids was identified by two-level Plackett-Burman Design (PBD) with eight factors. Plackett-Burman Design determined the following four key factors as significant for the extraction yield of Cyclocarya paliurus flavonoids viz. Enzymatic temperature, enzymatic pH, complex enzyme concentration and ultrasonic power. The Box-Behnken Design (BBD) was subsequently applied to optimize the four key factors identified from Box-Behnken Design. Chemical composition of Cyclocarya paliurus flavonoids was investigated by high performance liquid chromatography (HPLC). Antimicrobial activity was carried out with the disc diffusion method. Antioxidant activities were investigated by DPPH assays, O2·− assays, ABTS+ assays and the reducing power. The optimal extraction conditions were as follow: enzymatic temperature of 50.71 °C, enzymatic pH of 5.08, complex enzyme concentration of 3.23% and ultrasonic power of 108.03 W. Under the optimal extraction conditions, the extraction yield of Cyclocarya paliurus flavonoids was 34.24 ± 0.32 mg/g, which was well-matched with the predicted value (34.47 mg/g). Isoquercetin, quercetin-3-O-α-l-rhamnoside, kaempferol-3-O-α-l-rhamnoside, quercetin and kaempferol were identified from Cyclocarya paliurus flavonoids with the content of 2.37%, 1.94%, 15.77%, 4.86% and 2.64%, respectively. The inhibition zones diameters of Cyclocarya paliurus flavonoids at the concentration of 80 μg/mL against Staphylococcus aureus, Salmonella and Escherichia coli were 21.5 ± 0.45, 17.5 ± 0.35 and 13.5 ± 0.25 mm, respectively. Results also showed a dose dependent scavenging activity as evidenced by IC50 values for superoxide (0.152 mg/mL) and ABTS+ (0.185 mg/mL) radicals. These results indicated that Cyclocarya paliurus flavonoids could be used as antimicrobial and antioxidant agents applying in pharmaceutical, functional foods and natural cosmetics.