Antioxidant activities of Thai pigmented rice cultivars and application in sunflower oil

An analytical comparison for active chemical compounds and their antioxidant activities between three representative pigmented Thai rice cultivars was performed. It was revealed that the darkest purple‐red cultivar (Kum Doi Musur, KDM) contained the highest total phenolic content of 1164.6 mg gallic acid equivalent per100 g (dry basis, db) and the highest total monomeric anthocyanin content of 381.7 mg per100 g (db), when compared with the purple cultivar (Riceberry) and the red cultivar (Sungyod). Its 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity and ferric reducing antioxidant power were also the highest. When applied in sunflower oil, the KDM crude extract was efficiently capable of retarding lipid peroxidation as assessed by peroxide value, p‐anisidine value, totox value and the Rancimat method. Results show this specific pigmented rice to be a potent antioxidant for stabilisation of sunflower oil.     

Isolation and characterisation of a novel angiotensin I‐converting enzyme‐inhibitory peptide derived from douchi,a traditional Chinese fermented soybean food

BACKGROUND: Douchi, a traditional fermented soybean food, has recently attracted a great deal of attention owing to its superior physiological activity. In the present study the angiotensin I‐converting enzyme (ACE)‐inhibitory activity of typical douchi procured from various regions of China was analysed. An ACE‐inhibitory peptide derived from the most potent douchi was also isolated and characterised. The pattern of ACE inhibition and resistance to hydrolysis by gastrointestinal proteases of this peptide are described. RESULTS: ACE‐inhibitory activities were detected in all douchi samples, with IC₅₀ values ranging from 0.204 to 2.011 mg mL^?1. Among the douchi samples, a Mucor‐type douchi exhibited the most potent ACE‐inhibitory activity (IC₅₀ = 0.204 mg mL^?1). A novel ACE‐inhibitory peptide was then isolated from this Mucor‐type douchi using ultrafiltration followed by Sephadex G‐25 column chromatography and reverse phase high‐performance liquid chromatography. The amino acid sequence of the purified peptide was identified by Edman degradation as His‐Leu‐Pro (IC₅₀ = 2.37 µmol L^?1). The peptide is a competitive inhibitor and maintained its inhibitory activity even after incubation with some gastrointestinal proteases. CONCLUSION: The present study shows that peptides derived from soybean fermentation during douchi processing could be the main contributor to the ACE‐inhibitory activity observed. Copyright © 2009 Society of Chemical Industry     

Industrial clarification of anthocyanin‐rich grape pomace extracts by crossflow membrane filtration

A comparative study on the clarification of anthocyanin‐rich grape pomace extracts was carried out by tubular, hollow fibre and spiral wound industrial crossflow membrane units. Three polysulfone membranes were tested: a 500‐kDa molecular mass cut‐off (MMCO), and a 0.2‐ and 0.6‐μm pore size cut‐offs (PSCO). The 500‐ kDa MMCO and the 0.2‐μm PSCO membranes produced particle‐free extracts, while the 0.6‐μm membrane showed deficient clarification. The 500‐kDa MMCO membrane produced up to 3.7% loss of most of the individual anthocyanins, while the 0.6‐ and 0.2‐μm PSCO membranes produced up to 2% only of some of the anthocyanins with higher molecular masses. Permeate steady fluxes of up to 53 L h^?1 m^?2 were obtained. Particles with sizes of 0.5–1.5 μm and the macromolecular anthocyanin–tannin complexes had a major impact on membrane performance. The obtained results are scalable to industrial installations.     

Grass carp peptides hydrolysed by the combination of Alcalase and Neutrase: Angiotensin‐I converting enzyme (ACE) inhibitory activity,antioxidant activities and physicochemical profiles

In this study, grass carp peptides were prepared by enzymatic hydrolysis of grass carp protein using the combination of Alcalase and Neutrase, and angiotensin‐I converting enzyme (ACE) inhibitory activity in vitro, antihypertensive activity in vivo, antioxidant activities, and physicochemical properties of peptides achieved from grass carp protein were characterised after ultrafiltration and desalted processes using mixed ion exchange resins. The purified peptides exhibited strong ACE inhibitory activity (IC₅₀ = 105 μg mL^?1), antihypertensive activity with the maximal drop for systolic blood pressure (SBP) of 43 mmHg at a dosage of 100 mg per kg body weight in spontaneously hypertensive rat (SHR), and antioxidant activities indicated by thiobarbituric acid‐reactive substance values in a liposome‐oxidising system, radical‐scavenging activity and chelation of metal ions (Fe²⁺). The molecular weight of peptides was <1000 Da. Compared to grass carp protein, the peptides separated from enzymatic hydrolysates possessed similar amino acid compositions, but contained higher concentrations of essential amino acids. Moreover, the peptides exhibited excellent solubility at a wide range of pH values from 2 to 10, and lower apparent viscosity than the protein. The peptides separated from enzymatic hydrolysates might be used as a promising ingredient in antihypertensive functional foods and nutraceuticals.     

玉米蛋白制备降血压肽的研究

本实验以我国来源丰富且价格低廉的玉米蛋白为原料,选用嗜热菌蛋白酶、胰凝乳蛋白酶、胰蛋白酶和碱性蛋白酶等4种酶来水解玉米蛋白制备降血压肽。选用马尿酰-组氨酰-亮氨酸(HHL)为血管紧张素转化酶(ACE)的模拟底物,利用反相高效液相色谱(RHPLC)检测ACE催化反应生成的马尿酸(Hip)的量,确定水解产物的ACE抑制活性从而来对酶进行筛选。研究结果表明,碱性蛋白酶的水解能力最强,碱性蛋白酶和嗜热菌蛋白酶的水解产物都达到了很好的ACE抑制活性(90%左右)。     

具ACE抑制活性的大豆肽的制备及精制研究

采用酶解技术制备具ACE抑制活性的大豆肽混合物。选择了最佳水解用酶,优化了反应条件。确定碱性蛋白酶解最佳条件为:pH9.0,温度50℃,底物浓度6%,酶用量([E]/[S])3%,作用时间4h。选择D3520型大孔树脂对水解产物进行脱盐精制,脱盐率91.2%,肽回收率89.3%,ACE抑制活性提高了28.5%,大豆分离蛋白ACE抑制肽混合物分子质量主要分布为200-720,在pH3-10,溶解性达98.1%以上,且稳定性好。     

食物源ACE抑制肽的生产及构效关系研究进展

生物活性肽是蛋白质中隐藏着的可在体内发挥一定生理功能的活性肽段。目前已从食物蛋白中获得了具有免疫调节、抑菌、抗病毒、抗肿瘤、抗血栓形成、抗高血压等功能的多肽,其中血管紧张素转化酶(ACE)抑制肽是研究热点之一。ACE通过产具有升压作用的血管紧张素Ⅱ和降解扩张血管的舒缓激肽在调节血压中发挥着重要作用。ACE抑制肽可通过消化道水解、发酵和熟化过程、体外酶解和遗传重组方法而获得,并可作为功能因子添加到功能食品中,相关产品已上市或研发中。本文对ACE抑制肽的生产及其构效关系研究进展等进行综述。     

大鲵肌肉ACE抑制肽的制备及其稳定性

以大鲵肌肉为原料,以血管紧张素转化酶(ACE)抑制率为评价指标,通过单因素试验筛选得到3种效果较佳的单酶。在此基础上,借助混料试验,对三酶复合的配比进行优化。当风味蛋白酶、中性蛋白酶与菠萝蛋白酶质量比为0.54︰0.23︰0.23时,产物具有最高的ACE抑制率,IC50值为0.55 mg/mL。探究金属离子和体外模拟胃肠消化道酶系对对产物ACE抑制率稳定性的影响,结果显示,Zn^2+、Al^3+、Fe^2+离子能显著降低大鲵多肽的ACE抑制率,胃蛋白酶系对大鲵多肽的ACE抑制率影响较小,但胰蛋白酶系能显著降低ACE抑制率。     

分步酶解法制备菜籽肽及其分子量分布与抑制ACE活性关系研究

选取胰蛋白酶和Flavourzyme风味蛋白酶,采用超声波辅助分步酶解法制备菜籽肽;测试不同条件下的水解度、混合肽分子量分布和ACE活性抑制率。结果显示随着酶解液的水解度提高,混合肽中小分子量(3ku以下)的可溶性肽含量不断提高,ACE活性抑制率也不断升高,也说明使用该方法制备的菜籽肽具有ACE活性抑制作用。同时,这一结果有助于菜籽蛋白的开发将更加广泛。     

Proximate composition and sensory evaluation of anthocyanin‐rich purple sweet potato (Ipomoea batatas L.) wine

Purple sweet potato (PSP) is a special type of sweet potato having high anthocyanin pigment in the root. The starch contents of PSP (root/water homogenised in 1:1 ratio) were enzymatically saccharified [using commercial thermostable enzymes Termamyl^® (0.2%) and Dextrozyme^®GA (1%)] to fermentable sugars, and the filtrate was ameliorated with cane sugar to achieve 20° Brix, for subsequent fermentation into a red wine using 2% yeast (Saccharomyces cerevisiae) as starter culture. The wine had the following proximate compositions: total soluble sugar (TSS), 2.25° Brix; starch, 0.15 g per 100 mL; total sugar, 1.35 g per 100 mL; TA, 1.34 g tartaric acid per 100 mL; phenol, 0.36 g (caffeic acid equivalent) per 100 mL; anthocyanin, 55.09 mg per 100 mL; tannin, 0.64 mg per 100 mL; lactic acid, 1.14 mg per 100 mL; ethanol, 9.33%(v/v); and pH, 3.61. 2, 2‐Diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity of the wine was 58.95% at a dose of 250 μg mL^?1. Principal component analysis reduced the eleven original analytical and proximate variables (TSS, starch, total sugar, TA, phenol, anthocyanin, tannin, lactic acid, ethanol, pH, DPPH) to four independent components, which accounted for 76.65% variations. Sensory evaluation was carried out by sixteen trained panellists on various attributes such as clarity, colour, viscosity, odour, flavour, spritz and finish. Independent ‘t’ test confirmed that all the sensory attributes of the PSP wine scored closely (within 10% variation) to that of a commercial grape wine. The red wine produced contains essential antioxidants and acceptable sensory qualities.     

Physicochemical and structural characteristics of starches from Chinese hull‐less barley cultivars

Fourteen hull‐less barley cultivars, collected from four major cultivated areas in China, were employed to investigate the structural and physicochemical properties of their starches in this study. Relatively wide variations in physicochemical properties of the starches were observed. Amylose content ranged from 23.1% to 30.0%, swelling power and water solubility index ranged from 12.8 to 19.9 g g^?1 and 12.7% to 23.7% respectively. Peak viscosity was from 170 to 346 Rapid Visco Unit (RVU), peak temperature (T_p) of starch gelatinisation was from 55.6 to 61.8 °C and enthalpy of starch retrogradation ranged from 0.3 to 3.1 J g^?1. Weight‐based chain‐length proportions of fa, fb₁, fb₂ and fb₃ in amylopectins ranged from 21.65% to 24.95%, 44.48% to 49.44%, 15.56% to 17.19% and 9.83% to 16.66% respectively. Correlation analyses showed that amylose content was inversely related to pasting parameters and enthalpy of gelatinisation. Pasting properties and amylopectin structures were the most important parameters to differentiate starch properties among different hull‐less barley cultivars in this study. This work will be useful for exploring applications of Chinese hull‐less barley starches in food and non‐food industries.     

酪蛋白水解物中ACE抑制肽分离及氨基酸序列分析

以牛乳酪蛋白为底物,先经胃蛋白酶水解,再经胰蛋白酶水解,从水解物中分离获得血管紧张素转化酶（angiotensin converting enzyme,ACE）抑制肽并确定其氨基酸序列。酪蛋白的双酶水解物经超滤和葡聚糖凝胶色谱分离,分离得到3 个组分,收集高ACE活性抑制效果组分Ⅱ和Ⅲ。采用离子色谱法分析水解片段的氨基酸组成,液相色谱-质谱法分析水解片段的氨基酸序列,采用固相合成法制备获得的短肽片段,用分光光度法检测ACE活性抑制效果。结果表明,组分Ⅱ包含缬氨酸、丝氨酸、脯氨酸、亮氨酸、苯丙氨酸、谷氨酸、天冬氨酸、酪氨酸,共8 种氨基酸,组分Ⅲ包含痕量的丝氨酸和酪氨酸;将组分Ⅱ和Ⅲ经液相色谱-质谱分析,获得8 个片段,其中,αs2-f（56～57）∶YS、αs2-f（98～107）∶YQKFPQYLQY和κ-f（52～61）∶INNQFLPYPY具有ACE活性抑制作用,其IC50值分别为11.89、11.75 μg/mL和421 μg/mL。     

降血压肽的生理活性及应用

来源于食物蛋白的降血压肽对血管紧张素转化酶（ACE）的活性具有抑制作用。本介绍降血压肽的作用机制,生理效果,研究进展并展望其应用前景 。     

纳豆菌蛋白酶水解玉米醇溶蛋白制备血管紧张素转化酶抑制肽

利用纳豆菌固态发酵产酶酶解玉米醇溶蛋白,酶解物经SephadexG-25分离纯化,对产物及其组分血管紧张素转化酶(ACE)抑制活性进行检测。结果表明,酶解血管紧张素转化酶的抑制活性为77.83%,经分离后组分3的抑制效果最好,可达89.4%。     

酶解-膜分离组合制备ACE抑制肽

测试了膜分离操作压力、温度、pH值、料液体积浓度等操作参数对酶活力、血管紧张素转换酶(ACE)抑制肽分离的影响,并建立分段酶解、分级膜分离组合模式实现从扇贝裙边酶解产物中分离ACE抑制肽.结果表明:膜分离操作操作参数对酶活力、ACE抑制肽分离均有较大影响;二段酶解-二级膜分离组合模式制备及分离ACE抑制肽的得率最高,为5.73%,其IC50为0.088mg/ml;一段酶解-二级膜分离组合模式制备及分离ACE抑制肽的得率为3.19%,其IC50为0.081mg/ml;一段酶解-单级膜分离组合模式制备及分离ACE抑制肽的得率只有2.31%,其IC50为0.078mg/ml.