Anticancer effects of sweet potato protein on human colorectal cancer cells

AIM: To investigate the effects of proteins purified from sweet potato storage roots on human colorectal cancer cell lines. METHODS: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Hoechst 33258 nuclear staining and Boyden transwell chamber methods were used to determine whether purified sweet potato protein (SPP) from fresh sweet potato roots affected proliferation, migration and invasion, respectively, of human colorectal cancer SW480 cells in vitro . The inhibitory effects of SPP on growth of human colorectal cancer HCT-8 cells intraperitoneally xenografted in nude mice and spontaneous lung metastasis of murine Lewis lung carcinoma 3LL cells subcutaneously transplanted in C57 BL/6 mice were also investigated in vivo . RESULTS: SPP inhibited the proliferation of SW480 cells in a dose-dependent manner, with an IC 50 value of 38.732 μmol/L (r2 = 0.980, P = 0.003) in the MTT assay. Hoechst 33258 nuclear staining further revealed inhibition of cell viability and induction of apoptosis by SPP. The transwell assay disclosed significant reduction in migrated cells/field by 8 μmol/L SPP (8.4 ± 2.6 vs 23.3 ± 5.4, P = 0.031) and invaded cells/field through the ECMatrix by 0.8 μmol/L SPP, compared with the control (25.2 ± 5.2 vs 34.8 ± 6.1, P = 0.038). Both intraperitoneal (ip) and intragastric (ig) administration of SPP led to significant suppression of growth of intraperitoneally inoculated HCT-8 cells in nude mice to 58.0% ± 5.9% (P = 0.037) and 43.5% ± 7.1% (P = 0.004) of the controls, respectively, after 9 d treatment. Bloody ascites additionally disappeared after ip injection of trypsin inhibitor. Notably, ig and ip administration of SPP induced a significant decrease in spontaneous pulmonary metastatic nodule formation in C57 BL/6 mice (21.0 ± 12.3 and 27.3 ± 12.7 nodules/lung vs 42.5 ± 4.5 nodules/lung in controls, respectively, P < 0.05) after 25 d treatment. Moreover, the average weight of primary tumor nodules in the hind leg of mice decreased from 8.2 ± 1.3 g/mice in the control to 6.1 ± 1.4 g/mice in the ip group (P = 0.035). CONCLUSION: SPP exerts significant antiproliferative and antimetastatic effects on human colorectal cancer cell lines, both in vitro and in vivo .

Relationship Between Soluble Protein,Chlorophyll and ATP in Drought-Resistant Sweet Potato Under Water Stress

Some indices concerning the metabolism of substance and energy in sweet potato leaves under water stress were studied. The results showed an obvious increase in soluble protein content. Compared with control, Chl a, Chl b, total Chl contents and the ratio of Chl a to Chl b all decreased to some extent. ATP content increased in some varieties and decreased in others, but the stronger the drought resistance of the variety , the higher the ATP content. The correlation coefficient(r)of the soluble protein content, ratio of Chl a to Chl b and ATP content as a percentage of the drought-resistant sweet potato control variety are 0. 8968, - 0. 8509 and 0. 8200, respectively, P<0. 01. So these indices can be used to evaluate the drought resistance of different sweet potato varieties.

Nutritional and Functional Characteristics of Protein-Fortified Pasta from Sweet Potato

Despite being a healthy low glycaemic index food, the production and consumption of sweet potatoes are decreasing globally. The global production trends indicated a decline from 130.47 million tonnes (MT) in 2004 to 107.64 MT in 2009, while the production in China, having the largest share towards world production of sweet potatoes, witnessed a decrease from 105.84 MT in 2004 to 81.21 MT in 2009. There is an interest in increasing consumption of healthy low glycaeimic index foods, especially in the context of a projected alarming rise in the diabetic population in the developing world by 2025. The objective of this study was to enhance the utilization of sweet potato as a low glycaemic food, mainly through its use in the development of high protein pasta. Among three protein sources, whey protein concentrate (WPC), defatted soy flour (DSF), and fish powder (FP), WPC gave high quality pasta with strong starch-protein network formation, as evidenced from scanning electron microscopic studies and low in vitro starch digestibility. Protein nutritional quality was also high for WPC-fortified sweet potato pasta, with very high scores for lysine and leucine as well as high essential amino acid index and calculated protein efficiency ratio. Fractionation of starch showed that the WPC-fortified sweet potato pasta had the lowest rapidly digested starch (RDS) and the highest resistant starch (RS) content, indicating its potential as a low glycaemic food.

Sweet Potato Leaf Curl Virus: Coat Protein Gene Expression in <i>Escherichia coli</i>and Product Identification by Mass Spectrometry

Sweet potato is one of the first natural GMOs, genetically modified 8000 years ago by Agrobacterium rhizogenes as reported recently by Kyndt et al. A section of 10 kbp long DNA (Transferred- DNA or T-DNA) of the Ri (Root-inducing) plasmid was transferred to the plant genome by A. rhizo-genes and has been maintained in all 291 hexaploid sweet potato cultivars of the world. The maintenance in the sweet potato genome and expression of two T-DNA genes for tryptophan-2-monooxygenease (iaaM) and for indole-3-acetamide hydrolase (iaaH) are likely to be physiologically significant since these enzymes convert tryptophan to indole-3-acetic acid, a major plant growth hormone auxin. Sweet potato (Ipomoea batatas (L.) Lam) is ranked the third most important root crop after potato and cassava, and the seventh in global food crop production with more than 126 million metric tons. Although sweet potato originated in Central or South America, China currently produces over 86% of world production with 109 million metric tons. In the United States, North Carolina is the leading producer with 38.5% of the 2007 sweet potato production, followed by California, Mississippi, and Louisiana with 23%, 19%, and 15.9%, respectively. Leaf curl virus diseases have been reported in sweet potato throughout the world. One of the causal agents is Sweet potato leaf curl virus (SPLCV) belonging to the genus Begomovirus (family Geminiviridae). Although SPLCV does not cause symptoms on Beauregard, one of the most predominant sweet potato cultivars in the US, it can reduce the yield up to 26%. Serological detection of SPLCV is not currently available due to the difficulties in obtaining purified virions that can be used as antigen for antiserum production. In attempts to obtain the coat protein (CP) of SPLCV for antibody production, primers were designed to amplify the CP gene. This gene was cloned into the expression vector pMAL-c2E as a fusion protein with maltose-binding protein, and transformed into Escherichia coli strain XL1-Blue. After gene induction, a fusion protein of 72 kDa was purified by amylose affinity chromatography. The yield of the purified fusion protein was approximately 200 μg/liter of bacterial culture. Digestion with enterokinase cleaved the fusion protein into a 42.5 kDa maltosebinding protein and a 29.4 kDa protein. The latter protein was identified by mass spectrometry analysis as the coat protein of SPLCV based on the fact that the mass spectrometry elucidated the sequences corresponding to 37% of amino acid positions of the SPLCV coat protein.

不同富硒方式对甘薯叶蛋白抗氧化活性的影响

以甘薯叶为研究对象,分别对叶面与土壤进行富硒处理,通过分析甘薯叶中硒含量及甘薯叶蛋白的抗氧化活性的变化,研究不同富硒方式对甘薯叶蛋白抗氧化活性的影响。结果显示叶面富硒与土壤富硒都能提高甘薯叶蛋白的硒含量,在1.6 mg/mL的富硒质量浓度条件下两种富硒处理组蛋白硒含量分别达到了20.10 mg/g与1.68 mg/g。富硒对甘薯叶蛋白的抗氧化活性有一定的提升作用,其中,叶面富硒可使甘薯叶蛋白超氧阴离子自由基清除率提升19.17%。根据相关性分析可知,除硒含量对抗氧化活性有较大影响外,样品中总酚与总黄酮含量也在一定程度上影响着样品的抗氧化活性。经对比可知,叶面富硒能更好地提高甘薯叶蛋白中的硒含量,是较佳的富硒方式。

不同复热方式对添加甘薯蛋白水解物的冷冻预烤制面包品质的影响

前期研究表明,添加甘薯蛋白水解物(SPPH)能有效改善冷冻面团的品质。本研究在此基础上,以面包的损失率、含水量、硬度和色差为考察指标,在解冻或非解冻的条件下,探究微波、蒸汽和烘烤3种复热方式下SPPH对冷冻预烤制面包品质的影响。结果表明,与解冻组相比,非解冻复热后的面包品质均显著高于进行解冻前处理的面包。在相同复热条件下,SPPH组的冷冻预烤制面包具有更低的复热损失率,更高的含水量和更小的硬度,其中蒸汽复热组的品质最好,复热后的损失率仅降低了4.29%,水分质量分数由36.98%增加至39.38%,面包皮的硬度仅增加了0.27%。从色泽上看,烘烤复热组的面包表皮深褐色加深最为明显。综合各项指标,非解冻处理SPPH组的蒸汽复热方式复热效果最佳。SPPH的添加能够改善冷冻预烤制面包及其复热后的品质。

酶法改性对甘薯蛋白质结构及理化性质的影响

为研究酶解处理后甘薯蛋白质(sweet potato protein,SPP)结构及理化性质的变化,选用5种蛋白酶(碱性蛋白酶、中性蛋白酶、木瓜蛋白酶、胰蛋白酶和胃蛋白酶)对SPP进行酶解处理,分析蛋白酶酶解产物结构变化,测定其水解度、溶解度、持水性、乳化性等理化指标。结果表明:木瓜蛋白酶和碱性蛋白酶处理后SPP水解度较其他3种蛋白酶处理后更高;SDS-PAGE凝胶电泳图谱显示,经酶解后SPP中处于高分子量的条带被降解为25 ku的低分子量条带;FTIR光谱分析表明,在5种蛋白酶酶解产物的二级结构中α-螺旋和β-转角是其主要结构;木瓜蛋白酶和胰蛋白酶处理后SPP溶解度较高;碱性蛋白酶、木瓜蛋白酶和中性蛋白酶酶解产物持油性、乳化性及起泡性优于其他蛋白酶酶解产物,而胰蛋白酶酶解产物持水性较佳。综上,这一研究可为SPP活性研究及新产品开发提供理论基础。

不同品种甘薯组成成分比较分析

甘薯作为我国第四大粮食作物,不仅在解决人们温饱方面发挥了重要作用,而且作为一种营养丰富的食材也广受青睐。甘薯的经济价值主要取决于其产量和营养品质,营养品质的评定主要包括淀粉、还原糖、蛋白质、膳食纤维、矿质元素等方面。为了探究适合在邢台地区种植的甘薯品种,选取河北省邢台市柏乡县甘薯产业园试验田规范种植的11个甘薯品种,测定其产量、水分、干物质、蛋白质、粗脂肪、还原糖、淀粉和粗灰分8个指标。实验结果表明:徐薯22、大开花和秦五这三个品种的干物质含量和淀粉含量较好,口感粉面;济薯26、商19、烟薯25、西瓜红、紫薯的蛋白质含量较好,营养品质较高;秦五、烟薯25、秦八的还原糖含量较高,口感香甜;徐薯32、徐薯22、玛沙利的粗脂肪含量较高。

紫薯低聚糖3种脱蛋白方法的比较分析

以低聚糖损失率和蛋白质脱除率为衡量指标,选用Sevag法、三氯乙酸法和酶法对紫薯低聚糖进行脱蛋白处理。结果表明:Sevag法、三氯乙酸法和酶法的蛋白质脱除率分别为40.34%、71.50%、82.95%,低聚糖损失率分别为40.22%、55.63%、13.05%。酶法是脱除紫薯低聚糖提取液中蛋白质较为理想的方法。

甘薯蛋白研究进展

甘薯蛋白不仅具有重要的营养功能,还具有潜在的医疗保健作用,它是宝贵的蛋白资源。本文从开发利用蛋白质的角度,介绍了近年来国内外在甘薯蛋白结构、营养及开发方面的研究进展,以期推动我国甘薯研究的进一步发展,加快我国甘薯资源的开发利用。

甘薯可溶性蛋白、叶绿素及ATP含量变化与品种抗旱性关系的研究

对水分胁迫下甘薯叶片部分物质和能量代谢指标的研究结果表明 ,水分胁迫下叶片中可溶性蛋白含量明显增加 ;叶绿素a、叶绿素b、总叶绿素含量及叶绿素a/b比值与对照相比均有所下降 ;ATP含量有增有减 ,但品种抗旱性愈强 ,ATP含量愈高。叶片中可溶性蛋白含量、叶绿素a/b比值、ATP含量占对照百分率与品种抗旱性间的相关系数r分别为 0 .896 8、- 0 .85 0 9和 0 .82 0 0 ,P <0 .0 1。因此 。

不同肉色甘薯蛋白质营养价值评估

随机选取甘薯品种资源中红肉色、黄肉色、紫肉色品种各10份,利用国际通用的蛋白质氨基酸营养价值评价体系对其氨基酸组成模式及蛋白质营养价值进行评估、比较。结果表明,3种肉色甘薯必需氨基酸总含量均高于FAO/WHO,低于鸡蛋模式,富含酪氨酸,甲硫氨酸为第1限制氨基酸。不同肉色甘薯蛋白质及氨基酸含量高低为紫色>红色>黄色,必需氨基酸组成模式平衡性为黄色>红色>紫色。

四种甘薯蛋白粉品质比较

通过测定“台农”,“京6”,“55-2”和“红冬”四种甘薯品种所提取蛋白粉各组分(粗蛋白、粗纤维、粗脂肪、水分、灰分、总糖、金属元素)的含量、分析氨基酸组成、蛋白构成成分和色泽等项指标的差异,对四种甘薯蛋白粉品质进行了比较研究。结果表明,甘薯“55-2”所提取的蛋白粉纯度最高,其蛋白含量达到86.89%,且蛋白粉色泽好,金属元素含量少。

国内甘薯糖蛋白研究进展

介绍了国内近年来在甘薯糖蛋白结构、生理活性及提取分离方面的研究进展，以期推动我国甘薯研究的进一步发展，加快我国甘薯资源的开发利用。

紫薯花青素提取条件优化及淀粉等产物的制备

以‘紫罗兰’紫薯为原料,研究同步提取紫薯花青素以及制备紫薯淀粉、纤维素和紫薯蛋白的工艺及参数。紫薯与酸乙醇(p H 2)混合破碎、过滤、沉淀分离淀粉;将滤渣和分离淀粉后上清液混合,用微波辅助法提取花青素并优化提取条件;花青素提取液沉淀分离紫薯蛋白;提取花青素的滤渣制备紫薯纤维素。结果表明:微波辅助提取紫薯中花青素的最佳工艺条件为微波时间4 min、微波温度52℃、料液比1∶22.40(g/m L)、乙醇体积分数62%(p H 2),在此条件下紫薯花青素的提取率(93.64±0.69)%、粗提物中花青素含量(9.58±0.20)mg/g。制备的紫薯淀粉质量分数(95.77±0.41)%、得率(占总淀粉质量分数)(73.06±1.03)%;滤渣粉中纤维素含量(117.11±2.69) mg/g;制备的紫薯蛋白中蛋白质含量(524.78±24.84) mg/g。该制备方法能够提高紫薯的利用率,降低生产成本。

甘薯蛋白对DMH/DSS诱导的肥胖小鼠炎症相关结肠癌的抑制作用

目的采用1,2-二甲肼(1,2-dimethylhydrazine,DMH)/右旋葡聚糖苷钠(dextran sodium sulfate,DSS)诱导雄性肥胖ICR小鼠建立炎症相关结肠癌模型,观察甘薯蛋白(sweet potatoprotein,SPP)的抑制作用及机制。方法在腹腔注射15 mg/kg的DMH,1周后给予小鼠1周的2%DSS饮水,间隔1周后再次给予1周DSS饮水,循环3次。在给予DMH后第3 d开始灌胃给予不同剂量SPP(0.02、0.2及1 g/kg·bw)至21周。结果各SPP干预组肿瘤数及恶性腺瘤率较DMH/DSS模型组均降低,SPP干预组癌组织中β-catenin,IGF-1及血管内皮生长因子(vascular endothelial growth factor,VEGF)蛋白表达显著降低。结论 SPP对化学致癌剂/致炎剂诱导的炎性相关性结直肠癌具有显著抑制作用,其机制与SPP下调癌组织中β-catenin,IGF-1及VEGF蛋白表达有关。

紫薯花色苷-蛋白复合物的制备及结构表征

采用硫酸铵沉淀法制备紫薯花色苷-蛋白复合物,经二乙氨基乙基纤维素52和Sephadex G-75葡聚糖凝胶纯化得紫薯纯蛋白,利用聚丙烯酰胺凝胶电泳测定紫薯蛋白及紫薯花色苷-蛋白复合物的分子质量,运用紫外、荧光、红外和圆二色谱多种光谱方法对紫薯蛋白及紫薯花色苷-蛋白复合物进行结构表征。结果表明:紫薯蛋白及花色苷-蛋白复合物的分子质量无明显差异,均存在4种不同的分子质量分布:58、24、18 k D和14 k D。紫薯蛋白紫外最大吸收峰位于200 nm波长处,复合物的紫外光谱略有红移且吸收增强。紫薯蛋白荧光光谱的最大发射波长是340 nm,而复合物的荧光强度几乎完全猝灭。紫薯蛋白的红外光谱图具有酰胺带特征吸收,复合物的红外光谱峰形和吸收强度发生明显变化。圆二色谱图显示紫薯蛋白二级结构以β-折叠(43.6%)和无规卷曲(45.7%)为主,β-转角(10.6%)次之,而复合物以β-折叠(72.2%)为主,无规卷曲(27.8%)含量降低,β-转角消失。

超高压下酶解处理对甘薯蛋白乳化特性的影响

为研究在超高压下酶解处理后甘薯蛋白酶解产物乳化特性的变化,选用蛋白酶K(Proreinase.K)、碱性蛋白酶(Alcalase)、中性蛋白酶AS1.398、中性蛋白酶Neutrase和木瓜蛋白酶(Papain)5种酶,在4种压力(100、200、300和400 MPa)及最适酶活温度和pH下处理5种酶与甘薯蛋白的混合液4min后,取上清液并测定其水解度、乳化液的微观结构、乳化活性指数(EAI)、乳化稳定性指数(ESI)。结果表明,与常压下相比,超高压下5种酶解产物的水解度均显著增加,超乳化液颗粒除Alcalse外,其余4种均变得更为细小均一,且4种产物的EAI显著提高,其中Papain在300MPa下处理的酶解产物EAI最佳,为101.59m^2·g^(-1)。而经超高压下酶解处理后5种酶解产物的ESI均比常压下提高,Neutrase在300MPa下处理后的ESI最好,达到75.80min。此外,选用Papain(p H值7,55℃)在300MPa(EAI最佳的条件)下处理6min,酶解产物的EAI和ESI均达到最大值,分别为129.58m2·g-1和21.98min。本研究为甘薯蛋白作为乳化剂在食品工业中的应用提供了基础理论支撑。

甘薯叶片可溶性蛋白提取方法探索及其成分分析

探索了甘著叶片可溶性蛋白质的浸提方法,确定了蛋白质的沉淀方法,并分析了叶片可溶性蛋白粉中粗蛋白含量、粗纤维、粗脂肪和蛋白质中的氨基酸组成。结果表明,甘薯叶片主要含有一种分子量为53000Da的可溶性蛋白质,用pH为6．5～7．5的1％亚硫酸氢钠溶液浸提甘薯叶片粉末可较好地提取甘薯叶片中的可溶性蛋白质。经浸提、沉淀、透析、冻干处理获得的台农叶片蛋白粉中含有62．6％粗蛋白、0．18％粗纤维和0．51％粗脂肪。台农叶片可溶性蛋白质含有各种人体所需要的氨基酸,主要氨基酸是赖氨酸(99．88mg/g蛋白质)、亮氨酸(12026mg/g蛋白质)和天门冬氨酸(140 74mg/g蛋白质),并且必需氨基酸含量高于非必需氨基酸的含量,其比值为1．04,第一限制性氨基酸为色氨酸,氨基酸分数为75．9。

紫甘薯花色苷生产中紫薯蛋白的分离与富集

为了将紫甘薯色素提取液中的花色苷与蛋白分离,选择不同型号的大孔吸附树脂对紫甘薯色素提取液进行了吸附与解吸实验,筛选出特异性吸附提取液中色素的树脂。并利用大孔吸附树脂对流出液中紫甘薯蛋白进行富集。实验结果表明:ADS-7型树脂能有效将提取液中的花色苷与蛋白分离,分离程度达70%以上;流出液以1 BV/h、2 mg/mL流经树脂D3520,以pH值为3.0,浓度80%,4倍柱床体积的乙醇为洗脱剂,洗脱流速0.8 BV/h,紫甘薯蛋白得率在60%以上。