核桃青皮提取物的多酚含量、体外抗氧化和抗菌活性的评价

本研究测定了核桃青皮乙醇提取物中多酚的组成及含量，分析了该提取物的体外抗氧化能力、抗菌活性及潜在抑菌机理。结果表明，核桃青皮提取物中总酚含量为（21.71±0.98）mg/g，总黄酮含量为（22.16±0.45）mg/g。通过超高效液相色谱/串联质谱和高效液相色谱鉴定出9种主要化合物，分别为槲皮苷、扁蓄苷、紫云英苷、金丝桃苷、异槲皮素、槲皮素、咖啡酸、阿魏酸和胡桃醌。核桃青皮提取物对偶氮二异丁脒盐酸盐（2,2’-azobis-2-methylpropanimidamide dihhydrochloride,AAPH）诱导的生物大分子氧化损伤具有保护作用。1 mg/mL核桃青皮提取物对牛血清白蛋白氧化损伤有明显的保护作用；0.5 mg/mL核桃青皮提取物能保护质粒DNA免受氧化损伤。核桃青皮提取物对大肠杆菌具有抑制作用，其通过增加细菌细胞膜的通透性，破坏细菌完整性，进而导致细胞内核酸和蛋白质泄漏。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果表明，核桃青皮提取物对细菌蛋白合成的损伤是其可能的抗菌机制。此外，核桃青皮提取物抑制了大肠杆菌的呼吸，核桃青皮提取物和磷酸三钠的呼吸叠加抑制率最低，明显降低...

Evaluation of Phenolic Content and in Vitro Antioxidant and Antibacterial Activity of Extract from Green Walnut Husks

In this study, the total phenol and flavonoid contents of the ethanol extract of green walnut husks were determined as (21.71 ± 0.98) and (22.16 ± 0.45) mg/g, respectively. Using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) and high performance liquid chromatography (HPLC), nine major compounds in the extract were identified including quercitrin, avicularin, astragalin, hyperoside, isoquercetin, quercetin, caffeic acid, ferulic acid and juglone. The extract had a protective effect against 2,2’-azobis-2-methyl-propanimidamide dihhydrochloride (AAPH)-induced oxidative damage to biological macromolecules. The extract at 1 mg/mL had a significant protective effect against oxidative damage to bovine serum albumin (BSA), and at 0.5 mg/mL, it could protect plasmid DNA from oxidative damage. The extracts had antibacterial activity against Escherichia coli, which could increase the permeability of the bacterial cell membrane and destroy its integrity, thereby resulting in the leakage of intracellular nucleic acid and proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the damage to cellular proteins could be another antibacterial mechanism of the extract. In addition, the extract inhibited the respiration of E. coli, and the percent increase in respiration rate with the extract alone compared to that with its combination with trisodium phosphate was the lowest. The extract significantly reduced the activity of glucose-6-phosphate dehydrogenase. Therefore, it can be inferred that the extract exerts an antibacterial effect mainly by participating in regulating the respiratory metabolism of the pentose phosphate pathway.