【作者】 朱丽娟；

【导师】 熊幼翎；

【作者基本信息】 江南大学 ， 食品科学， 2008， 硕士

【摘要】 国内外研究表明,玉米醇溶蛋白水解物具有良好的体外抗氧化能力以及ACE抑制活性,但是有关玉米醇溶蛋白水解物体内抗氧化及ACE抑制活性的研究较少。本论文主要探讨玉米醇溶蛋白水解物抗氧化及ACE抑制活性的耐消化性,以及抗氧化能力与ACE抑制活性间的相关性。本论文的研究对于促进玉米蛋白在食品加工领域及保健食品领域的应用具有重要的理论和应用价值。本论文首先研究了玉米醇溶蛋白的碱性蛋白酶解产物(ZH)的抗氧化性,利用体外两阶段消化模型(在37 oC,胃蛋白酶作用1 h后由胰蛋白酶继续消化2 h)研究ZH的体内抗氧化特性。以ABTS+·自由基清除能力,DPPH·自由基清除能力,还原能力和Cu2+螯合能力为抗氧化指标,并利用氨基酸自动分析仪和高效凝胶排阻色谱(HPSEC)来测定消化过程中游离氨基酸和分子量分布的变化。结果表明,ZH具有很强的ABTS+·自由基清除能力、Cu2+螯合能力以及还原能力。在5 mg/mL时,ZH的还原能力是0.01 mg/mL Vc的2倍左右,ABTS+·自由基清除能力是0.01 mg/mL Vc的7倍左右,其Cu2+螯合能力比0.1 mg/mL BHA的螯合能力高5倍多(P < 0.05)。经过体外消化,ZH的还原能力几乎提高了一倍,并且保留了原有的ABTS+·自由基清除能力以及Cu2+螯合能力(P < 0.05)。低浓度的ZH消化产物(1 mg/mL)对ABTS+·的清除能力比8 mg/mL的消化产物对DPPH·自由基的清除能力高出近50倍的现象表明,ABTS+·自由基清除能力的测定更适用于水溶性肽抗氧化的评价。论文利用紫外分光光度法测定ZH及其体外消化产物的ACE抑制活性,通过SephadexG-15凝胶柱对ZH消化终产物进行分离,以ABTS+·自由基清除能力,还原能力,Cu2+螯合能力以及ACE抑制率为检测指标,研究了分离组分的抗氧化及ACE抑制活性,并探讨了氨基酸组成和分子量分布对于各组分抗氧化能力以及ACE抑制活性的影响。结果表明,ZH具有很好的ACE抑制活性(8 mg/mL蛋白浓度时抑制率达到80.6±2.67%)。经过体外消化,产物仍然具有良好的ACE抑制活性(83.8±2.03%)。ZH消化终产物经凝胶柱分离后得到四个组分,其中2号组分中分子量在120-568 Da的小肽占77.07%,具有抗氧化能力的氨基酸,碱性氨基酸,支链氨基酸以及疏水性氨基酸含量很高,具有最强的ABTS+·自由基清除能力,还原能力,金属离子螯合能力以及ACE抑制活性。更多还原

【Abstract】 Zein protein hydrolysate showed a strong antioxidant activity and ACE-inhibitory activity, but little is known about the in vivo antioxidant activity and ACE-inhibitory activity. The objective of this study was to assess the survivability of antioxidative activity and ACE-inhibitory activity of Alcalase-treated zein hydrolysate (ZH), and the relationship between antioxidant activity and ACE-inhibitory activity.Firstly, the antioxidative activity of zein hydrolysate treated by Alcalase (ZH) and the antioxidant potential of ZH during a two-stage (1 h pepsin→2 h pancreatin, 37 oC) in vitro digestion was studied. Free Amino acid composition, 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+·) and 1,1-diphenyl-2-picrylhydrazyl (DPPH?) free radical scavenging activity, reducing power, and Cu2+ chelation ability were tested to determine the antioxidant efficacy of ZH. High-performance size exclusion chromatography (HPSEC) was run to evaluate the molecular weight of ZH digests. Results showed that ZH exhibited a strong ABTS+·free radical scavenging activity, reducing power, and Cu2+ chelation ability. The antioxidant activity of ZH (5 mg/mL) was exceeded (P < 0.05) that of 0.01 mg/mL of ascorbic acid and 0.1 mg/mL BHA. After in vitro digestion, the reducing power of ZH increased one-fold (P < 0.05), the ABTS+·free radical scavenging activity and Cu2+ chelation ability were fully recovered when compared with nondigested ZH. The ZH samples tested in the ABTS+·system, though at a lower concentration (1 mg/mL), had a Trolox equivalence of approximately 50 times that of ZH sample (8 mg/mL) tested in the DPPH? system, suggested that the ABTS assay was an appropriate method for the measurement of antioxidant activity of water-soluble proteins and peptides in an aqueous solution.The ACE-inhibitory activity of ZH and it’s digests was determined by Cushman Ultraviolet spectrophotometer. Sephadex G-15 gel filtration was used to separate the final digest of ZH into fractions. ABTS+·free radical scavenging activity, reducing power, Cu2+ chelation ability and ACE-inhibitory activity were tested to determine the antioxidant and ACE-inhibitory efficacy of each fractions, the effect of Amino acid composition and the molecular weight profile was also considered. Results showed that ZH can inhibit ACE activity by 80.6±2.67% at 8 mg/mL, and also exhibited a good ACE-inhibitory activity after in vitro digestion. Four fractions were yielded after Sephadex G-15 gel filtration, of which peptides with MW120-568 Da in fraction 2 representing 70.07% of the total mass, the composition of basic amino acid, branched-chain amino acid, hydrophobic amino acid and the amino acid with antioxidant activity was higher in fraction 2, showed the strongest antioxidant activity and ACE-inhibitory activity.更多还原