Centrifugal partition chromatography applied to the isolation of oak wood aroma precursors

Flavours extracted from oak wood during barrel ageing contribute to the organoleptic character of wines and spirits. The aim of this work was to identify the glycosidic precursors of the key volatile compounds responsible for oak wood aroma. Oak extract is a very complex matrix and, furthermore, precursors are present in very small quantities. Preparative centrifugal partition chromatography (CPC) is a promising solution for purifying the oak extract. The solvent system was selected on the basis of the partition coefficient of glycosidase enzyme activity (K_ca). Thanks to the efficacy of CPC separation, three glucoside gallates were subsequently isolated by HPLC chromatography. Vanillin-(6′-O-galloyl)-O-β-d-glucopyranoside, 3,4,5-trimethoxyphenyl-(6′-O-galloyl)-O-β-d-glucopyranoside, and (6R,9R)-3-oxo-α-ionol-9-O-(6′-O-galloyl)-β-glucopyranoside (macarangioside E) were isolated and identified. This was the first time that vanillin-(6′-O-galloyl)-O-β-d-glucopyranoside was identified and the first time that macarangioside E was isolated from oak wood. Heating macarangioside E resulted in the formation of megastigmatrienone, which has an aroma reminiscent of tobacco.     

五种中草药水溶性多糖对α-葡萄糖苷酶活性的影响

从山茱萸、知母、甘草、地榆及诃子中提取水溶性多糖,并通过酶抑制动力学反应考察其对α-葡萄糖苷酶活性的影响。酶动力学反应结果表明:地榆多糖对α-葡萄糖苷酶有激活作用;知母多糖对α-葡萄糖苷酶的活性随时间的变化先激活后抑制;山茱萸多糖、甘草多糖及诃子多糖均对α-葡萄糖苷酶有抑制活性,其中抑制活性最好的是甘草多糖,其抑制率为72.5%;其各自的影响机理还有待进一步研究。     

The methionine precursor dl-2-hydroxy-(4-methylthio)butanoic acid protects intestinal epithelial barrier function

dl-2-hydroxy-(4-methylthio)butanoic acid (HMTBA) is a source of dietary methionine (Met) that is widely used in poultry nutrition. We have previously shown that HMTBA is preferentially diverted to the transsulfuration pathway, which gives antioxidant metabolites such as taurine and glutathione. Therefore, here we hypothesize that this Met source can protect epithelial barrier function in an in vitro model of intestinal inflammation of Caco-2 cells. The results show that HMTBA prevents the increase in paracellular permeability induced by H₂O₂ or tumour necrosis factor-α. This effect can be attributed to the increased production of taurine and reduced glutathione. Similar results were obtained for dl-Met, although the protective role of the amino acid was less pronounced than that of the hydroxy analogue. In conclusion, the diversion to the transsulfuration pathway means that this Met precursor is of greater value than previously thought, due to its capacity to improve intestinal homeostasis and the quality of poultry products destined for human consumption.     

芭蕉的α-葡萄糖苷酶抑制活性

利用体外α-葡萄糖苷酶抑制模型对芭蕉花与根提取物进行活性评价,并与阳性对照Acarbose比较,发现芭蕉花与根提取物均能抑制α-葡萄糖苷酶活性。除芭蕉花的乙酸乙酯和正丁醇提取物外,其他提取物活性均远大于阳性对照Acarbose(IC50=1103.01μg·mL-1)。其中,芭蕉根和花的石油醚提取物的活性最高(IC50=32.03μg·mL-1和49.37μg·mL-1)。不同部位比较,芭蕉根的α-葡萄糖苷酶抑制活性好于花;同一部位不同溶剂的提取物比较,石油醚提取物α-葡萄糖苷酶抑制活性高于乙酸乙酯和正丁醇提取物。     

云南野生香薷油对子代小鼠学习记忆功能的影响

本研究旨在探讨云南野生香薷油对子代小鼠学习记忆功能的影响。将昆明种小鼠从受孕第1d开始分为空白对照、阳性对照、低、中、高剂量5个组,用云南野生香薷油灌胃至断乳,断乳d小鼠按孕鼠剂量灌胃至出生49d后做Morris水迷宫实验,之后测定小鼠脑组织神经递质和肝、脑组织的脂肪酸。结果表明,与空白对照组比较,定位航行实验的第5d各组均有统计学意义（P〈0．01）。空间探索实验的阳性对照组有统计学意义（P〈0．05）。脑神经递质TPro、NO、AchE：阳性、中、高剂量组均有统计学意义（P〈0．05）。肝脂肪酸结果中阳性和高剂量组的ALA有统计学意义（P〈0．05）;脑组织脂肪酸结果：高剂量组的油酸和ALA有统计学意义（P〈0．05）。可见,富含α-亚麻酸的香薷油具有部分改善子代小鼠学习记忆的功能,其作用可能与喂养此香薷油使脑组织的TPro升高,NO、AchE降低;肝和脑组织的α-亚麻酸升高有关。     

枳椇籽油a-亚麻酸的富集纯化工艺研究

本文研究了枳椇籽油中α-亚麻酸的富集纯化及工艺.通过正交试验确定了最佳的皂化工艺条件:以乙醇为皂化介质,皂化比例为1∶6.0,皂化温度为45℃,皂化时间为30 min.采用尿素包合法对枳椇籽油中α-亚麻酸的富集纯化及工艺条件进行了研究,结果表明:以丙酮为尿包介质、尿包比例为1∶4、尿包温度为0℃、尿包时间为10h,枳椇...     

透明颤菌vgb基因在地衣芽孢杆菌中表达用于改良α-淀粉酶生产菌株

地衣芽孢杆菌高温α-淀粉酶是淀粉加工与食品发酵工业上关键酶制剂之一。为了降低高温α-淀粉酶生产过程中所需要的高溶氧水平对设备的要求,进一步提高α-淀粉酶的生产性能,本研究构建同源整合载体pAX01-sacB-vgb,在地衣芽孢杆菌(B.licheniforms)CICC 10181染色体中表达增强摄氧的透明颤菌血红蛋白基因(Vitreoscilla hemoglobin gene,vgb)。发酵实验结果表明,在同等溶氧条件下,重组菌比野生菌生物量提高了45.8%,高温α-淀粉酶酶活提高了116.7%,具有良好的工业应用前景。     

α-亚麻酸研究进展

α-亚麻酸属于n-3系列多不饱和脂肪酸,分子结构为△9,12,15-18:3,主要来源于陆地植物, 如杜仲、藿香、亚麻、紫苏等。在体内代谢过程中,它主要作为EPA和DHA前体物质,并具有降低胆固醇、血脂,预防心血管疾病、保护视力和抑制过敏反应等功能。该文主要介绍α-亚麻酸的来源、分离提取方法进展及生理功能,并对α-亚麻酸发展前景进行展望。     

Thermotoga neapolitana α-葡萄糖苷酶基因克隆及表达

本文拟克隆新阿波罗栖热袍菌(Thermotoga neapolitana DSM 4359)的一种α-葡萄糖苷酶基因(TNAG),其GenBank注册号为lcl27401。首先以T.neapolitana DSM 4359基因组DNA为模板,通过PCR扩增目的基因并完成T克隆,在NCBI数据库中比对结果表明:目的基因与Thermotoqa sp.RQ2等氨基酸序列相似度高于99%。再将目的基因连接至表达载体pET-32a(+),并导入大肠杆菌Rosetta中用IPTG诱导表达。SDS-PAGE显示表达蛋白的大小约为72KDa。热纯化后酶液测活反应的最适温度为80℃,最适pH在5.0左右。     

桐油酶水解制备桐酸的工艺研究

为探索利用桐油酶水解制备桐酸的合理工艺,采用单因素实验考察了水解温度、水添加量和酶添加量对桐油水解率的影响,在此基础上以桐油水解率和α-桐酸保留率为指标,运用响应面法对桐油酶水解工艺条件进行优化。结果表明:桐油酶水解制备桐酸的最佳工艺条件为水解温度45℃、水添加量22%、酶添加量0.5%,在此条件下桐油水解率为90.15%,α-桐酸保留率为98.26%。