超声波及微波提取豆粕中总黄酮的工艺优化

对超声波及微波提取异黄酮的工艺进行优化．超声波提取最佳条件：60％乙醇、60℃、功率400W、提取30min,微波法提取最佳条件：微波功率560W,料液比为1：30g／mL,微波处理4min溶剂浸提40min．结果表明,超声波及微波处理能有效缩短提取时间,提高提取率．     

Original article: Thermal dynamic properties of isoflavones during dry heating

Thermal stabilities of major soya isoflavones at different dry‐heating temperatures were determined in this study. The conversion of glucoside isoflavones to aglycone isoflavones was monitored as well. The thermal degradation of the isoflavones: glucoside form daidzin, glycitin, and genistin and aglycone form daidzein, glycitein, and genistein followed first‐order reaction kinetics at heating temperatures 100, 150, and 200 °C. The degradation rate constants of the six isoflavones were not significantly different at 100 °C. However, the constants increased with increasing heating temperature. The half‐life for the glucoside and aglycone isoflavones was from 144 to 169 min and 139 to 176 min at 100 °C, respectively. They decreased rapidly to 15.7–54.7 and 36.0–90.7 min when temperature increased to 150 °C. When heated at 200 °C, they further decreased to 5.8–6.0 and 15.7–21.2 min, respectively. The order of thermal stability from lowest to highest was glycitin < genistin < daidzin < glycitein < genistein < daidzein at temperature below 150 °C. However, their thermal stabilities were not different at 200 °C. The conjugated glucosides were cleaved from the isoflavones to produce their corresponding aglycones when heated at 150 °C or higher. The production of glycitein increased constantly and was the highest among the three aglycone isoflavones.     

Anti-photoaging effects of soy isoflavone extract (aglycone and acetylglucoside form) from soybean cake

Soy isoflavones, found in soybean and soybean products, have been reported to possess many physiological activities such as antioxidant activity, inhibition of cancer cell proliferation, reduction of cardiovascular risk, prevention of osteoporosis and alleviation of postmenopausal syndrome. In our previous study, soy isoflavone extract ISO-1 (containing 12 soy isoflavones) from soybean cake was demonstrated to prevent skin damage caused by UVB exposure. In this study, soy isoflavone extract from soybean cake was further purified and evaluated for the protective effects on UVB-induced damage. The results revealed that Fraction 3, which contains the aglycone group (daidzein, genistein and glycitein) and acetylglucoside group (acetyldaidzin, acetylgenistin and acetylglycitin) of soy isoflavones, could inhibit UVB-induced death of human keratinocytes and reduce the level of desquamation, transepidermal water loss (TEWL), erythema and epidermal thickness in mouse skin. Furthermore, topical application of Fraction 3 increased the activity of catalase and suppressed cyclooxygenase-2 (COX-2) and proliferating cell nuclear antigen (PCNA) expression in mice exposed to UVB. In addition, in comparison with ISO-1 and genistein, the Fraction 3 possessed much greater protective effects on both UVB-induced oxidative stress and keratinocyte death than other fractions. Therefore, the soy isoflavone extract Fraction 3 from soybean cake is a desirable anti-photoaging agent for skin care.     

Enhancement of Biological Properties of Soymilk by Fermentation

Soymilk has attracted much interest in the food industry because of its health- promoting properties. Fermentation with lactic acid bacteria is known to provide value addition to soymilk by reducing the beany flavor and content of indigestible oligosaccharides and by enhancing the bioavailability of isoflavones, resulting in a nutritious probiotic food product. In the present study, Soymilk fermentation was studied using Lactobacillus acidophilus strain isolated from ragi, and effect of soymilk supplementation on the fermentation characteristics was also investigated. Viable count of 1.99 × 10⁹ CFU/mL sample and 630.1 U/g of β-glucosidase activity were determined in soymilk after 12 h of fermentation. Soymilk supplementation with skimmed milk powder at 5% level gave best results with viable counts of 22.9 × 10⁹ CFU/ml sample or 212.9 × 10⁹ CFU/g solids; 764 U/g of β-glucosidase activity, 1.44% la titratable acidity and pH of 3.9. Daidzein and genistein profile in fermented soymilk showed that 45.8% and 57.5% of respective isoflavones existing as aglycone form, indicating enhancement of the biological property of soymilk through improvement of health-relevant bioactive forms.     

用大孔吸附树脂分离大豆糖蜜中异黄酮的研究

选择6种大孔吸附树脂分离大豆糖蜜中的异黄酮,考察大孔吸附树脂对大豆糖蜜中异黄酮的吸附能力,并以糖蜜中异黄酮浓度、吸附液流速、吸附液pH值为参数进行单因素试验.结果表明:最佳树脂为LS-800,其静态吸附率为64.12％,静态解吸率为69.39％;动态吸附条件为:吸附液中异黄酮质量浓度1.23 mg/mL,吸附液流速1 mL/nin,吸附液pH值4.0,吸附率为89.50％;动态解吸条件为:解吸液为体积分数为80％乙醇水溶液,解吸液流速1 mL/min,解吸率为86.22％.经大孔树脂分离纯化后,产品中的异黄酮含量为56.03％,回收率为68.82％.     

响应面法优选银杏果中异黄酮提取工艺研究

以银杏果为原料,通过对索氏提取时间、固液比、乙醇体积分数、提取温度单因素试验确定最佳单因素水平并做响应面优化实验,确定了以乙醇为提取剂提取银杏果中异黄酮化合物的最佳工艺条件．然后采用紫外分光光度法测定异黄酮质量分数．结果表明,最佳提取工艺为：索氏提取时间5 h ,固液比1∶30,乙醇体积分数80％,提取温度97．45℃．在最佳条件提取后采取紫外分光光度计测定,回收率为98．15％,精密度为3．391％,银杏果异黄酮质量分数为2．255 m g／g ．     

酱油中黄酮类物质的分离与鉴定

采用真空浓缩干燥酱油、乙酸乙酯热回流抽取酱油中黄酮类物质 ,并使用薄层层析法 (TLC)进行分离纯化。研究表明 ,理想的方法是用硅胶GF2 54 做吸附剂 (薄层板厚度约为0 3mm) ,用三氯甲烷∶甲醇 =6∶1的混合展开系统。从提取物中分离出 3种样品 ,Rf 值分别为 0 70、0 50、0 4 0。把TLC法分离制备的样品进行结构检测 ,经过紫外光谱和TLC鉴定 ,判定酱油中的主要异黄酮为大豆素、染料木素和 6 ,7,4’ -三羟异黄酮     

大豆及其有效成分体外抗蛋白非酶糖化作用

为探讨豆浆的抗蛋白非酶糖化作用及其有效成分,将20g/L的牛血清白蛋白(BSA)与80mmol/LD-葡萄糖体外孵育,与此同时分别加入不同浓度豆浆、大豆异黄酮和染料木素,糖化系统建立90d时,测定各反应体系荧光值。结果表明,100mg/ml豆浆和0.1mg/ml大豆异黄酮体外能明显抑制非酶糖化反应,且随浓度升高,抑制作用明显增强;与等浓度豆浆比较,大豆异黄酮抑制作用明显较强。1μg/ml染料木素能明显抑制牛血清蛋白的非酶糖化作用,且与阳性对照氨基胍无明显差异。该研究表明豆浆具有抗蛋白非酶糖化作用,其中的有效成分可能与大豆异黄酮有关,大豆异黄酮中的有效成分与染料木素有关。     

大豆中的功能性成分

论述了大豆异黄酮及大豆皂甙的研究进展，并对前景进行了展望。