Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides

To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.     

大豆中异黄酮类化学成分的研究

用w(C2H5OH)=70%的工业乙醇从脱脂大豆饼中提取大豆异黄酮,并依次用乙酸乙酯、正丁醇萃取,乙酸乙酯萃取部分经硅胶柱和SephadexLH-20柱层析,用V(CHCl3)∶V(CH3OH)=(12～4)∶1梯度洗脱。分离得到4种化合物,通过理化常数和光谱分析鉴定其化学结构,分别为大豆甙元(daidzein)、染料木素(genistein)、大豆甙(daidzin)、染料木甙(genistin)。     

纳豆制备过程中大豆异黄酮的转化条件

使用日本古法制备纳豆,从纳豆中分离筛选出高活性的纳豆菌为实验菌株。研究了纳豆制备过程中大豆异黄酮的转化情况,发酵液中的大豆异黄酮在大豆异黄酮糖苷酶的水解作用下水解掉侧链糖基,转化为活性更高的大豆异黄酮苷元。根据薄层层析法确定了大豆异黄酮转化为大豆异黄酮苷元的最佳培养条件:培养温度为37℃,培养时间2 d,pH 7.0,含水质量分数60%。发酵液中大部分的大豆异黄酮苷转化为大豆异黄酮苷元,从而得到更利于人体吸收的大豆异黄酮苷含量较高的纳豆制品。     

7-羟基-4’-甲基-异黄酮的合成

以对甲基苯乙酸、间苯二酚为原料,经合成脱氧安息香中间体,环合成7-羟基-4'-甲基-异黄酮.在脱氧安息香增碳环合的反应中,探索了3种不同的增碳环合试剂对反应的影响,较理想的环合试剂为BF3·Et2O-DMF-PCl5.该工艺路线条件温和,产率达到72%.     

大豆异黄酮的功能与应用

大豆异黄酮是大豆生长过程中形成的一类次生代谢产物。大量研究表明大豆异黄酮在防癌抗癌、防治心血管疾病、预防骨质疏松症等方面有重要作用、本文综述了大豆导黄酮的结构、组成、生理功能以及在国内外的应用。     

Ripening temperature affects the content and distribution of isoflavones in sufu,a fermented soybean curd

Sufu, a fermented soybean curd, was prepared by ripening the salted tofu cubes in the Aspergillus oryzae‐fermented rice–soybean koji mash at 25, 35 or 45 °C for a period of 16 days. It showed that the 16‐day ripened sufu contains less total isoflavone content (629.29–739.68 μg g^?1 dried matter) than the salted tofu before ripening (942.59 μg g^?1 dried matter). Regardless of ripening temperature, ripening causes a major reduction in the content of β‐glucoside and malonylglucoside isoflavones along with a significant increase of aglycone isoflavone content. These changes were enhanced as the ripening period extended. Among the various treatments examined, sufu ripened at 45 °C showed the greatest increase in aglycone content coupled with the greatest decrease in malonylglucosides. The distribution of malonylglucosides decreased from an initial 40.32% in the tofu cube to 9.78% after 16 days of ripening at 45 °C. Meanwhile, the distribution of aglycone increased from 13.17% to 39.88%.     

乙醇/磷酸氢二钾双水相体系分离大豆异黄酮

利用乙醇/磷酸氢二钾双水相体系浸提大豆异黄酮固体,并采用四因素四水平正交试验,考察了乙醇质量分数、磷酸氢二钾质量分数、温度、时间对大豆异黄酮的分配系数和萃取收率的影响。结果发现,影响大豆异黄酮萃取收率的因素为:时间磷酸氢二钾质量分数乙醇质量分数温度。最佳提取条件为:25%乙醇/25%磷酸氢二钾双水相体系,室温(20℃)浸提30 min。大豆异黄酮几乎全部分配在上相,其上相收率为97.0%。     

Antioxidant Properties of Genistein in a Model Edible Oil System

ABSTRACT:  Antioxidant properties of genistein were tested during the low temperature oxidation of linseed oil. Four linseed oil solutions were prepared: linseed oil, linseed oil containing 2 μmol added genistein/g oil, linseed oil containing 4 μmol added genistein/g oil, and linseed oil containing 200 ppm butylated hydroxyanisole (BHA). Dimethyl sulfoxide (DMSO) (1.7%) was added to all solutions to allow for the solubilization of genistein. Antioxidant activities were analyzed using 2 techniques: (i) the oven stability test carried out at 60 °C with periodic determination of peroxide values (PV); and (ii) oxidation on a heated (60 °C) FTIR-ATR crystal with periodic scanning and collection of infrared spectra. Induction points (IP) for each solution were determined. A strong correlation ( r = 0.91) was noted between the 2 analytical methods used. Three significantly ( P < 0.10) different levels of IP were generally observed. The shortest IP (17 h for PV, 36.9 h for FTIR) was found for the linseed oil. Intermediate IP's were obtained for the 2 μmol added genistein/g oil (32.4 h for PV, 43.5 h for FTIR) and 4 μmol added genistein/g oil (33.9 h for PV, 44.2 h for FTIR) samples. The longest IP (39.9 h for PV, 54.2 h for FTIR) was obtained for the 200 ppm BHA containing solution. Although genestein was not as effective as BHT in retarding oxidation, the results clearly demonstrate that it is able to act as an antioxidant in a bulk oil system.     

大豆异黄酮的研究进展

介绍了大豆异黄酮的成分及结构，并对大豆异黄酮多种生理功能及其研究进展做了重点阐述。     

大豆低温脱溶粕中两种异黄酮单体分离与结构鉴定

以大孔树脂柱色谱、制备薄层色谱从大豆粕乙醇提取物中分离出二种异黄酮单体,经HPLC,UV,IR,ESI／MS,和1H NMR,13C NMR,DEPT NMR,HQSC NMR分析确证其结构是大豆甙(daidzin)和染料木素(genistein)。