酿酒酵母对葡萄酒中白藜芦醇含量的影响研究

为了检测酵母菌对于葡萄酒中白藜芦醇含量的影响,以天津产区的不同葡萄品种为原料,分别用两种筛选出的本土酵母CS18、GS10和商用酵母QA23进行红、白葡萄酒的发酵。采用高效液相色谱(HPLC)对酒中的四种白藜芦醇异构体进行了检测分析。结果表明:由本室筛选的具有β-葡萄糖苷酶活力的CS18菌株酿造的葡萄酒白藜芦醇含量最高。     

酶解法提取虎杖中白藜芦醇、白藜芦醇苷、大黄素

用纤维素酶对虎杖进行了酶解,提高了虎杖中白藜芦醇的提取率,同时提取出白藜芦醇苷和大黄素。通过单因素实验考察了酶解温度、pH、酶解时间、酶用量对目标物提取率的影响,得出较佳的酶解工艺条件为:酶用量2mg/g虎杖,pH=3.0,在40℃酶解1h。酶解后用m(虎杖):m[φ(乙醇)=60%]=1:20,50℃提取2h。w(白藜芦醇)=1.50%,w(白藜芦醇苷)=0.38%,w(大黄素)=0.78%。酶解法较直接提取法更有利于虎杖中有效成分白藜芦醇、大黄素的提取。     

Supercritical CO2 extraction of resveratrol and its glycoside piceid from Chinese traditional medicinal herb Polygonum cuspidatum

Resveratrol (3,5,4′‐trihydroxystilbene) and its glycoside piceid are phenolic compounds found to be beneficial to health. In this paper, resveratrol and piceid were successfully extracted from the Chinese traditional medicinal herb Polygonum cuspidatum (Hu Zhang in Chinese), with supercritical CO₂ plus ethanol modifier. The effects of ethanol content, pressure and temperature on the yields of resveratrol and piceid were investigated. Results showed that the extraction pressure was the main factor for the effective extraction of the two substances in the presence of ethanol modifier, especially for piceid. The optimal extraction condition was obtained: 30 MPa, 50 °C, (100 ml l^?1), ethanol and 20 kg h^?1 of CO₂, at which the yields of resveratrol and piceid were 7.1 g kg^?1 and 16.0 g kg^?1, respectively. The yields obtained by supercritical fluid extraction (SFE) was comparable with those obtained by traditional organic solvent methods, indicating that SFE is an alternative method for extraction of the two compounds. Copyright © 2004 Society of Chemical Industry     

Enzymatic Synthesis of α‐Glucosides of Resveratrol with Surfactant Activity

We report the synthesis of a series of α‐glucosyl derivatives of resveratrol (3,5,4′‐trihydroxystilbene) by a transglycosylation reaction catalyzed by the enzyme cyclodextrin glucanotransferase (CGTase) using starch as glucosyl donor. Several reaction parameters (temperature, solvent composition, enzyme concentration and starch/resveratrol ratio) were optimized. The yield of α‐glucosylated products reached 50% in 24 h. The structures of the derivatives were determined by a combination of amyloglucosidase‐hydrolysis tests, MS and 2D‐NMR. Three families of products were obtained: glucosylated at 3‐OH, at 4′‐OH and at both 3‐OH and 4′‐OH. The bonds between glucoses were basically α(1→4). Interestingly, the water solubilities of the α‐glucosylated derivatives were at least 65‐ and 5‐fold higher than those of resveratrol and the natural β‐glucosylated derivative (piceid), respectively. In contrast with piceid, the synthesized α‐glucosylated compounds exhibited surfactant activity, with critical micelle concentration (CMC) values in the range 0.5–3.6 mM. Although the incorporation of a glucosyl moiety caused a loss of antioxidant activity (more pronounced in the position 3‐OH compared with 4′‐OH), the fact that the glycosides need to be converted into the aglycones before they are absorbed minimizes such an effect. In contrast, the modification of physicochemical properties such as solubility and partition coefficient by glycosylation could exert a positive influence on the bioavailability of resveratrol.     

虎杖中白藜芦醇、白藜芦醇苷、大黄素等有效成分的提取

对虎杖中的有效成分白藜芦醇、白藜芦醇苷、大黄素等进行了提取,提取液经有机溶剂萃取分离后,用紫外分光光度法测定吸光度,确定了各有效成分的含量.考察了乙醇体积分数、提取温度、提取时间,物料比对各有效成分提取率的影响,通过正交实验确定最佳工艺为:乙醇浓度80%,提取温度70℃,料液比1:20,提取时间2 h.提取得率白藜芦醇为5.57%,白藜芦醇苷为10.74%、大黄素为2.67%、未知物1为8.87%、未知物2为7.13%.使用邻苯三酚自氧化法,对各有效成分的抗氧化性进行了测定.     

顺,反-白藜芦醇甙和顺,反-白藜芦醇高效液相色谱分离研究

研究利用高效液相色谱分离顺,反-白藜芦醇甙和顺。反-白藜芦醇。结果显示,以 ACN和H2O为流动相,采用梯度洗脱。在25min内有效分离顺,反-白藜芦醇甙和顺,反-白藜芦醇。     

Effect of yeast strain selection on the concentration of cis- and trans-resveratrol and resveratrol glucoside isomers in wine

The influence of four fermentative yeast strains belonging to the Saccharomyces cerevisiae species, on the content of cis‐ and trans‐resveratrol and resveratrol glucoside isomers in Vitis vinifera L. cv. Shiraz grape musts during alcoholic fermentation was studied by reverse phase high performance liquid chromatographic (RP‐HPLC) analysis. During vinification an increase in both the free and the glucosidic forms was observed up to day three/five (cis‐ resveratrol/piceid) or day four (trans‐ isomers) after which varible yeast, β‐glucosidase activity was noted until dryness where a general increase in free forms of resveratrol was accompanied by a decrease in the corresponding glucoside. In the finished wines ready for bottling or aging, the total amount of all resveratrol forms reflected (P < 0.05) the manufacturers polyphenol extraction ratings for the strains. Relative extraction of total phenolics in red wine amongst different yeast strains was demonstrated to mimic relative stilbene content.     

Influence of pressing method on juice stilbene content in muscadine and bunch grapes

ABSTRACT:  Juice stilbene contents of 2 muscadine ( Vitis rotundifolia) cultivars, Noble and Carlos, and 2 bunch grape ( Vitis labrusca) cultivars, Mid South and Miss Blanc were evaluated after crushing and pressing. Four commercial pressing methods were used to produce juice: (1) cold press of fresh berries (CP); (2) hot press of fresh berries (HP); (3) cold press of frozen and thawed berries (FCP); and (4) cold press of pectolytic enzyme treated berries (ECP). Free run juice (FRJ) from the crusher without pressing was also tested. An HPLC with a UV detector was used to verify the presence and quantity of resveratrol, piceid, and their isomers. For the muscadine juices, total stilbenes were greater for HP and FCP than for FRJ and CP treatments. Trans -resveratrol was only detected in HP juices of the muscadines at levels near the detection limits. The bunch grape cultivars behaved similar to the muscadines in the processing treatments. HP juice had the greatest total stilbene levels and was significantly greater than FRJ, CP, and FCP. Total stilbene levels in juices from the 2 bunch grape cultivars, were higher (up to 5 times greater depending on pressing method) than for the muscadine grape cultivars. Total stilbene levels in muscadine juices treated with pectinase before pressing (ECP) were similar to those of the FCP samples. Juice from FCP and ECP treated Noble muscadine had total stilbene levels greater than FRJ and CP but less than HP levels. Juices from HP-, ECP-, and FCP-treated Carlos muscadine had total stilbene levels greater than for FRJ and CP juices.