根皮素抑酪氨酸酶活性研究

根皮素从苹果皮中提取分离 ,测定其对酪氨酸酶的活性抑制率。浓度为 0 .3 %时根皮素的抑制率可达 98.2 % ,其IC50 为 0 .0 5 % ,结果优于曲酸和熊果苷。与曲酸和熊果苷复配 ,可使抑制率达到 1 0 0 %。     

根皮苷候选化学对照品的制备及分析研究

目的 研究根皮苷候选化学对照品的制备方法及其质量标准,为含有根皮苷的药材及其相关产品的质量控制提供参考。方法 多穗柯叶片粉碎,用70%的乙醇溶液提取,提取液滤过,浓缩成稠膏,用水稀释,用石油醚（60～90℃）洗涤两次,再用乙酸乙酯提取两次,收集乙酸乙酯部分,采用硅胶柱色谱以二氯甲烷-甲醇系统作为流动相梯度洗脱,收集含有根皮苷的流份,合并,浓缩,再用反相制备高效液相色谱法,以甲醇-水（40:60）为流动相,以紫外光284nm作为检测波长,进行分离纯化,所得的流份经甲醇重结晶得到高纯度根皮苷,通过紫外光谱（UV）、红外光谱(IR)、高分辨质谱(HR-MS)、核磁共振氢谱(1H- NMR)、核磁共振碳谱（13C-NMR）表征鉴定其化学结构。结果 采用高效液相色谱法测定样品色谱纯度,炽灼残渣法测定灰分,以质量平衡法计算根皮苷的含量,制备的根皮苷候选化学对照品经高效液相色谱纯度测定均值为98.59%,炽灼残渣测定均值为0.02%,以质量平衡法计算含量为98.5%。结论 制备得到的高纯度根皮苷对照品符合中药化学对照品技术要求,可作为中药材或其相关产品质量控制的候选对照品;建立的分析方法准确、可靠,可为对照品质量控制提供科学依据。     

Detection of addition of apple juice in purple grape juice

Due to increasing grape juice consumption, quality control is a reality in all countries which produce and consume this product. The most common form of adulteration is by substituting grape juice with apple juice. The adulterated samples can be identified by specific analysis, since apple juice has some compounds that grape has not. There are many studies about the phlorizin and sorbitol content in wines, but in grape juice they are scarce. Therefore, analytical methods to identify the composition of grape juices and determine their authenticity are needed to ensure quality control. The present study aimed to the validation and application of analytical methods for the determination of phlorizin and sorbitol, to detect the addition of apple juice in purple grape juice, by high-performance liquid chromatography. Initially, the methods were validated and tests were conducted by additions of percentages of apple juices in grape juices. Finally, experimental and commercial grape and apple juices were analyzed. Our study found that both methods are effective in detecting the addition of apple juice in grape juice. Four of the 39 commercial grape juices analyzed showed adulteration by the addition of apple juice in grape juice.     

Simultaneous separation and purification of total polyphenols,chlorogenic acid and phlorizin from thinned young apples

An efficient preparative separation of polyphenols from thinned young apples (TYA) has been developed in the present study. X-5 resin was verified to offer the best adsorption capacity and desorption ratio for total polyphenols among the eight macroporous resins investigated. Influential factors, such as pH value and concentration of feeding solution, strippant, and adsorption isotherm to the separation of total polyphenols, were successively investigated on X-5 resin. After one run treatment, the phenolic content was increased 2.12-fold from 35.17% to 74.64%, with a recovery yield of 89.35%. Chlorogenic acid and phlorizin were selectively purified using X-5 and polyamide resins. The contents of chlorogenic acid and phlorizin were 15.20% and 97.52% with recovery yields of 89.16% and 64.95%, respectively. The method developed will provide a potential approach for its wide industrial and pharmaceutical use.     

Evaluation of the anti-inflammatory effects of phloretin and phlorizin in lipopolysaccharide-stimulated mouse macrophages

Many reports suggest that phloretin and phlorizin have antioxidant properties and can inhibit glucose transportation, the anti-inflammatory effects and mechanism of phloretin and phlorizin remain unclear. This study aims to evaluate the anti-inflammatory effects of phloretin and phlorizin in LPS-stimulated murine RAW264.7 macrophages. RAW264.7 cells were pretreated with various concentrations of phloretin or phlorizin (3–100 μM) and cell inflammatory responses were induced with LPS. Pretreated with 10 μM phloretin significantly inhibited the levels of NO, PGE₂, IL-6, TNF-α, iNOS and COX-2. Furthermore, it was demonstrated that phloretin suppressed the nuclear translocation of NF-κB subunit p65 proteins, and decreased phosphorylation in MAPK pathways. Surprisingly, phlorizin did not suppress the inflammatory response in LPS-stimulated RAW264.7 cells. These results suggest that phloretin has an anti-inflammatory effect that reduces levels of proinflammatory cytokines and mediators in RAW264.7 cells.     

Biotransformation of phlorizin by human intestinal flora and inhibition of biotransformation products on tyrosinase activity

Phlorizin (1) was anaerobically incubated with human intestinal bacteria and five biotransformation products (2-6) were obtained. Their structures were elucidated as phloretin (2), phloroglucinol (3), phloretic acid (4), 2,3,4-trihydroxybenzenepropanoic acid (5), and phloretic acid methyl ester (6) on the basis of their spectroscopic data. Using high-performance liquid chromatography equipped with a diode array detector, chromatographic separation of 1-4 was performed on an analytical C₁₈ column. The time course of the biotransformation was studied to probe into the biotransformation mechanism of 1 by human intestinal flora. The abilities of isolated strains to transform 1 were also investigated in order to find an optimal transformation strain. In addition, the inhibitory activity of parent compound 1 and its three main biotransformation products 2-4 on mushroom tyrosinase was estimated. The result showed that 2 has better inhibitory effect on tyrosinase activity than 1.