Preparation of isoflavones enriched soy protein isolate from defatted soy hypocotyls by supercritical CO2

Soy hypocotyls, the byproduct from soy protein industry, rich in isoflavones, was attempted to develop into a value-added functional food, soy protein isolate (SPI). Soy hypocotyls were defatted by supercritical CO₂ (SC-CO₂) under the following conditions as 35 MPa, 2 h, 45 °C with a constant flow rate of CO₂ at 5 l/min, fed from the bottom of the extraction vessel. Via extraction, the oil contents were lowered from 10.5 g/100 g in original soy hypocotyls to 0.2 g/100 g in defatted soy hypocotyls (DSH) with a Protein Dispersibility Index (PDI) value of 91.2 that contained about 2.18 g/100 g of isoflavones and 63.6 g/100 g of proteins. SPI was then extracted from DSH under the optimized conditions including: the pH of water solution at 6, the ratio of DSH to water solution as 1:10 and the extraction temperature at 30 °C with the extraction time of 30 min. The freeze-dried SPI contained 92.46 g/100 g of the proteins and 640 mg/100 g of isoflavones, where the three major β-glycosides, glycitin, daidzin and genistin accounted for about 83.7% of the total isoflavones. The yields of SPI and isoflavones were about 48% and 30% in terms of their respective total contents in DSH.     

豆制品生产中高浓度废水的检测与分析

为了深入探讨豆制品生产废水的再资源化价值,文中对豆腐和大豆分离蛋白生产过程中所排放高浓废水的成分和水质进行了检测与分析。结果显示,高浓乳清废水的COD、BOD远远高于国家规定的排放标准,其主要成分为糖、乳清蛋白、脂肪以及含量相对丰富的生物活性成分。在豆腐生产所排放的黄浆水中含有的大豆皂苷占大豆原料中皂苷原含量的58%、大豆异黄酮的50%,功能性低聚糖———水苏糖和棉籽糖分别占83%和94%;蛋白质占17%,脂肪占17%。一步碱溶酸沉法生产大豆分离蛋白时所排放的乳清废水中含有的大豆皂苷、异黄酮、水苏糖、棉籽糖、蛋白质、脂肪分别占豆粕中的38%、34%、87%、65%、8%、28%。说明豆制品生产废水中的大豆皂苷、大豆异黄酮以及大豆低聚糖等生物活性成分的含量颇高、具有回收价值。     

Isoflavones reduce inflammation in 3T3-L1 adipocytes

Isoflavones are widely consumed and they have been attributed beneficial effects. We have explored how genistein, daidzein and equol affect the adipocyte functions of glucose uptake and the secretion of inflammatory molecules in 3T3-L1 adipocytes inflamed with TNF-α.     

Soluble phenolics and antioxidant properties of soybean (Glycine max L.) cultivars with varying seed coat colours

This research was the first to investigate nutritional components, including soluble phenolics (isoflavones and anthocyanins), protein, oil, and fatty acid as well as antioxidant activities in different coloured seed coat soybeans (yellow, black, brown, and green) for two crop years. The soluble phenolics differed significantly with cultivars, crop years, and seed coat colours, while protein, oil, and fatty acid exhibited only slight variations. Especially, malonylgenistin and cyanidin-3-O-glucoside compositions had the most remarkable variations. Green soybeans had the highest average isoflavone content (3079.42 μg/g), followed by yellow (2393.41 μg/g), and black soybeans (2373.97 μg/g), with brown soybeans showing the lowest value (1821.82 μg/g). Anthocyanins showed only in black soybeans, with the average contents of the primary anthocyanins, cyanidin-3-O-glucoside, delphinidine-3-O-glucoside, and petunidin-3-O-glucoside, quantified at 11.046, 1.971, and 0.557 mg/g, respectively. Additionally, Nogchae of green soybean and Geomjeongkong 2 of black soybean may be recommended as potential cultivars owing to the highest average isoflavone (4411.10 μg/g) and anthocyanin (21.537 mg/g) contents. The scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals also differed remarkably, depending upon isoflavone and anthocyanin contents, with black soybeans exhibiting the highest antioxidant effects.     

Anti-inflammatory and anti-hyperalgesic evaluation of the condiment laurel (Litsea guatemalensis Mez.) and its chemical composition

Litsea guatemalensis Mez., a native plant of Mexico and Central America, is widely used as a food condiment, in the same manner as Laurus nobilis L. In folk medicine, it is used to treat several diseases such as respiratory and gastrointestinal complaints. We report here the anti-inflammatory and anti-hyperalgesic properties of ethanolic extract and the compound 5,7,3′,4′-tetrahydroxy-isoflavone (3), which was isolated in addition to pinocembrin (1), and scopoletin (2). The results confirm that both the ethanolic extract and Compound 3 showed anti-inflammatory activity, by inhibiting paw oedema induced by carrageenan, and also reduced the influx of leucocytes, particularly neutrophils, to the pleural cavity and consequently anti-hyperalgesic activity, when assessed in the model of persistent pain induced by partial sciatic nerve ligation.     

Effects of fermentation on the phytochemical composition and antioxidant properties of soy germ

Soy germ is a remarkable source of bioactive phytochemicals offering an interesting alternative as starting ingredient for fermented food. This work aimed to determine whether lactic acid bacteria fermentation of soy germ induces changes on its phytochemical composition. The antioxidant properties of fermented soy germ samples periodically taken during the fermentation process were evaluated and correlated with the concentration and structural modifications of isoflavones, saponins, phytosterols and tocopherols. Fermented soy germ extracts exhibited a higher inhibition effect against the superoxide anion radical, and lesser but significant ferric-reducing and DPPH radical scavenging effects compared with raw soy germ. By comparison to the traditional whole seed-based products, soy germ exhibits higher levels of isoflavones, saponins, phytosterols and tocopherols. All these phytochemicals contributed to the antioxidant capacity of soy germ and were conserved under lactic acid bacteria fermentation.     

Mushroom tyrosinase inhibitory effects of isoflavones isolated from soygerm koji fermented with Aspergillus oryzae BCRC 32288

The inhibition of mushroom tyrosinase in soygerm koji, fermented with Aspergillus oryzae BCRC 32288, was investigated. A methanol extract of the soygerm koji was partitioned into hexane, ethyl acetate and water. The ethyl acetate extract showed potent anti-tyrosinase activity with an IC₅₀ value of 0.19 mg/ml. The active compounds were isolated by activity-guided silica gel column chromatography and high-performance liquid chromatography (HPLC) methods. Seven tyrosinase inhibitors were purified and identified as 6,7,4′-trihydroxyisoflavone, 7,8,4′-trihydroxyisoflavone, 5,7,8,4′-tetrahydroxyisoflavone, 7,4′-dihydroxyisoflavone (daidzein), 6-methoxy-7,4′-dihydroxyisoflavone (glycitein), 4′-hydroxyisoflavone-7-O-glucoside (daidzin), and 5,4′-dihydroxyisoflavone-7-O-glucoside (genistin) by comparing their mass, ¹H NMR, and ¹³C NMR spectral data with those in the literature. The purified seven isoflavones from fermented soygerm koji were divided into two groups, based on their inhibitory effects on mushroom tyrosinase. Five isolated isoflavones showed inhibitory activity against monophenolase activity of mushroom tyrosinase only, with IC₅₀ values of 0.009 ± 0.001 (6,7,4′-trihydroxyisoflavone), 0.203 ± 0.018 (daidzein), 0.218 ± 0.007 (glycitein), 0.267 ± 0.008 (daidzin), and 0.343 ± 0.013 (genistin) mM. The kinetic study indicated that the five inhibitors significantly lengthened the lag time of the monophenolase activity of tyrosinase and acted competitively for the l-tyrosine binding site of the enzyme. So, the five isoflavones were competitive inhibitors for the monophenolase activity of tyrosinase. The other two isoflavones, 7,8,4′-trihydroxyisoflavone and 5,7,8,4′-tetrahydroxyisoflavone, inhibited both monophenolase and diphenolase activities of tyrosinase. Moreover, pre-incubation of each of the two isoflavones with tyrosinase resulted in total irreversible inhibition of the enzyme activity, even at concentrations as low as of 10 μM. Hence, 7,8,4′-trihydroxyisoflavone and 5,7,8,4′-tetrahydroxyisoflavone were irreversible inhibitors of mushroom tyrosinase.     

绿豆萌芽期功能性营养成份的测定和分析

对绿豆(phaseolusradiatuslinn)在不同萌芽期蛋白质、氨基酸、总糖、还原糖、矿质元素、异黄酮和皂甙的含量进行了分析,结果表明,除总糖外其余物质含量在萌发期均较对照增加。在萌芽13h后,还原糖含量达到最大值,较对照增加172.7%;萌发26h后,蛋白质与氨基酸含量达到最大值,分别较对照增加9.2%和15.9%;萌发39h后,异黄酮和皂甙的含量出现最大值,分别较对照增加54.8%和138%。在绿豆萌发后矿质元素增加较显著的有Fe、Ca、Cu和Zn。萌发达13h时,Fe含量出现最大值,分别较对照增加65.9%;萌发达39h时Ca、Zn、Cu含量出现最大值,分别较对照增加39.6%、27.7%和117.6%。结论:食用绿豆芽或对绿豆芽进行加工可获得更多的营养物质。     

Relative antioxidant activity of soybean isoflavones and their glycosides

The present study compared the antioxidant potency of genistein and daidzein with their corresponding glycosides isolated from soybean seeds. The antioxidant activity was assessed using three methods, namely human low-density lipoprotein (LDL) oxidation, the ferric reducing-antioxidant power (FRAP) and the anti-DPPH free radical assays. It was found that soybean was rich in genistein and daidzein but they were present mainly in form of glycosides. Both the FRAP and the anti-DPPH assays demonstrated that these glycosides, as well as genistin, daidzein, glycitin, malonyl glycitin and malonyl genistein possessed similar antioxidant activities to their corresponding aglycones, genistein and daidzein. In contrast, the antioxidant potency of these glycosides was much weaker than their corresponding aglycones, genistein and daidzein, in the LDL oxidation assay. The present results demonstrate that genistein and daidzein were less effective, as antioxiants in the three assays, than two well-defined antioxidants, green tea epicatechin and -tocopherol. It is concluded that soybean isoflavones and their glycosides possess antioxidant activity but they are ineffective antioxidants compared with tea epicatechins and -tocopherol.     

Skim milk powder supplementation affects lactose utilization, microbial survival and biotransformation of isoflavone glycosides to isoflavone aglycones in soymilk by Lactobacillus

Four probiotic bacteria, Lactobacillus acidophilus 4461, L. acidophilus 4962, Lactobacillus casei 290 and L. casei 2607, were used for fermentation of soymilk (SM) prepared from soy protein isolate (SPI) supplemented with skim milk powder (SMP) (SSM). Soymilk and reconstituted skim milk (RSM) were used as controls. Lactose utilization in SSM by these probiotic organisms ranged from 14.97 to 18.15mg/ml, compared to 14.12-16.06mg/ml for RSM. The pH in SSM dropped to 4.07-4.29 compared to 6.15-6.36 for SM and 4.10-4.96 for RSM. The microbial viable counts were also significantly enhanced by up to 0.98logCFU/ml by the supplementation of SMP to SM. The biotransformation level of isoflavone glycosides (IG) to isoflavone aglycones (IA) in SSM ranged from 81.4% to 85.1%, which was 13.9-19.0% higher than that for SM, after 24h of incubation. Most of IG in SSM was completely converted to IA, except malonyl glycitin and malonyl genistin. At the end of the incubation, IA comprised up to 76.8% of total isoflavones in SSM.