黔南民族师范学院化学化工学院贺银菊讲师|响应面优化紫果西番莲叶多酚超声辅助提取工艺及其抗氧化活性

Passionfruit, also known as Passion fruit and Passiflora edulis, is a popular name given to several species of the genus Passiflora that belongs to Passifloraceae family, which there are more than 500 species distributed in regions of tropical and subtropical climate of the world. Passionfruit mainly has three varieties: yellow, purple and fuchsia. Its fruit has a strong aroma and is reputed as the "king of juice". The flesh, seeds, peel, stems and leaves of Passionfruit contains a variety of active compounds, which have biological activities sach as antioxidant, antibacterial, anti-inflammatory, anti-depressant, anti-fatigue, anti-hypertensive. Studies have found the leaves of Passionfruit have antioxidant, antibacterial, anti-anxiety, neuroprotective, hypoglycemic, etc. And its main active compounds are triterpenoids, flavonoids, alkaloids, and polyphenols. In South America and Europe, Passionfruit leaves are used as medicine to treat nervous tension, migraine, alcoholism, etc. Polyphenols have antibacterial, anti-virus, anti-oxidation, hypolipidemic, anti-tumor, anti-cancer and immune enhancement. There are many polyphenols extraction methods, such as extraction, ultrafiltration, microwave digestion, enzyme, supercritical fluid, and ultrasonic extraction. Ultrasonic-assisted solvent extraction of plant secondary metabolites has been widely used in the fields of medicine, food and chemistry. It is a green extraction technique with a high extraction rate, low energy consumption and a short extraction cycle. In previous studies found that  ultrasound-assisted extraction significantly increased the extraction rate of polyphenols at low ethanol levels, low temperatures and shorter time periods, achieving a more environmentally friendly and less time-consuming method than traditional solvents. The investigation found that the extraction process and antioxidant activity of total flavonoids from Passionfruit leaves were mainly reported at home and abroad, while the extraction of polyphenols from Passionfruit leaves was not reported. In order to study the amount of polyphenols extracted from purple Passionfruit leaves, to optimize the extraction technology and antioxidant activity of polyphenols from purple passionfruit leaves. On the basis of a single factor test, the material to solvent ratio, extraction time, ultrasonic power and ultrasonic temperature were the factors, and the Box-Beheken design(BBD) was applied to optimize the extraction conditions by using the Design-Expert 8.0.6 Trial software. And the amount of polyphenols from purple Passionfruit leaves extracted was determined using the ferrous tartrate method, The antioxidant activity of purple Passionfruit was evaluated by its ability of scavenging 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radicals and hydroxyl radicals, which was expected to provide a theoretical basis for further development of the additional value of purple Passionfruit. The results showed that the quadratic model of response surface analysis was extremely significant and accurate. Four factors, such as the ratio of solvent to material ratio, extraction time , ultrasonic power and ultrasonic temperature, have significant effects on the extraction of polyphenols from purple Passionfruit leaves, the order from largest to smallest is extraction time, solvent to material ratio, ultrasonic power, ultrasonic temperature. The optimal polyphenol extraction conditions were: solvent to material ratio 36:1 mL/g, extraction time 54 min, ultrasonic power 350 W and ultrasonic temperature 70 ℃, At this time, the amount of polyphenols extracted from purple Passionfruit leaves was (13.19 ± 0.17) mg/g. The results of antioxidant activity showed that the polyphenols from purple Passionfruit leaves had good antioxidant activity. When the concentration was 0.2 mg/mL, the scavenging rate of polyphenols to DPPH radicals was 82.25%; When the concentration is 0.8 mg/mL, the scavenging rate of polyphenols to hydroxyl radicals 90.59%, which is equivalent to the scavenging activity of vitamin C that of the reference (90.89%). According to the fitting by Origin8.0 software, the antioxidant activities with 50% inhibitory concentration (IC₅₀ values) of polyphenols in purple Passionfruit leaves for scavenging DPPH radicals and vitamin C that of the reference were 0.058 mg/mL and 0.007 mg/mL respectively. And the antioxidant activities IC50 values of vitamin C those of the reference for scavenging hydroxyl radicals and vitamin C that of the reference were 0.144 mg/mL and 0.282 mg/mL respectively, indicating that the polyphenols in purple Passionfruit leaves have good antioxidant activity, which can be used as a potential source of natural antioxidants in food, medicine, etc.