龙须菜ACE抑制肽的体外稳定性和抗氧化活性研究

以龙须菜为原料，通过酶解法制备分子量<1 kDa的龙须菜蛋白，分别以冷冻干燥和喷雾干燥收集多肽组分(GLP-F、GLP-S)，研究其在体外环境的活性保留率和抗氧化能力。通过血管紧张素转化酶(Angiotensin Ⅰ converting enzyme, ACE)活性抑制、总抗氧化能力、DPPH·清除能力、羟自由基清除能力、超氧阴离子清除能力等实验测定多肽抗氧化能力及体外稳定性。结果表明，通过ACE抑制活性为指标，两多肽在ACE抑制活性均有较好的IC₅₀值(0.62、0.70 mg/mL)，金属离子Zn2+和Cu2+促进两个多肽ACE活性的保留，Al3+、K+、Fe3+等离子均能较好保留两多肽的ACE抑制活性，Ca2+的加入则降低了多肽的ACE抑制活性。随着NaCl浓度的升高，GLP-F和GLP-S的ACE抑制活性降低；高糖浓度下GLP-F的ACE抑制活性较好保留，GLP-S的ACE抑制活性显著增加（P<0.05）。GLP-F在强酸强碱环境下ACE抑制活性略降低5%，GLP-S的ACE抑制活性不受酸碱pH环境的影响；在低于40 ℃的温度条件下，GLP-F和GLP-S的ACE抑制活性得到保留。在模拟体外胃肠消化系统可知:GLP-F为前体型抑制肽，GLP-S为真抑制型抑制肽。?20 ℃条件下两者活性都能保持稳定，而GLP-F在4 ℃贮藏至14 d活性保留降至40.67%。体外抗氧化试验表明，GLP-S在总抗氧化能力、DPPH·、·OH和O₂?·清除能力方面均优于GLP-F。因此，GLP-F多肽体外降血压活性稳定性上更优于较GLP-S，而GLP-S在抗氧化方面效用高于GLP-F，此为龙须菜多肽开发为天然降血压肽和抗氧化肽提供理论参考。

Study on in Vitro Stability and Antioxidant Activity of ACE Inhibitory Peptide from Gracilaria lemaneiformis

Gracilaria lemaneiformis were prepared by enzymatic hydrolysis with molecular weight <1 kDa, collecting peptide components by freeze drying and spray drying, measuring the activity retention rate and antioxidant capacity of ACE inhibitory peptides in the in vitro environment. The antioxidant capacity and in vitro stability of peptides were determined by experiments of inhibition of angiotensin converting enzyme activity, total antioxidant capacity, DPPH· scavenging capacity, hydroxyl free radical scavenging capacity and superoxide anion scavenging capacity. The results showed that by using ACE inhibitory activity as indicators, both had good IC₅₀ values (0.62, 0.70 mg/mL) in ACE inhibitory activity. The addition of metal ions (Zn2+、Cu2+) were both promoted inhibitory activity retention, (Al3+、K+、Fe3+) were retained the ACE inhibitory activity of GLP-F and GLP-S, Ca2+reduced the ACE inhibitory activity of both. With the increase of NaCl concentration, the ACE inhibitory activity was reduced of GLP-F and GLP-S; under high sugar concentration, GLP-F was better retained, and GLP-S activity was significantly increased(P<0.05). With strong acid and alkali, GLP-F activity retention decreased by 5%, GLP-S inhibitory activity remained unchanged with pH 4~10. Below 40 ℃, the ACE inhibitory activity was stabled of GLP-F and GLP-S. Simulation the digestion of gastrointestinal tract, GLP-F belonged to pro-drug type, GLP-S belonged to true inhibitor type. GLP-F and GLP-S suited for storage at ?20 °C, GLP-F activity retention decreased to 40.67% stored at 4 ℃ until 14 d. The results of above antioxidant tests indicated that GLP-S had superior in terms of total antioxidant activities, DPPH· free radicals, ·OH and O₂?· than GLP-F. Therefore, the stability of GLP-F polypeptide in lowering blood pressure activity in vitro had better than that of GLP-S, and GLP-S had more effective than GLP-F in anti-oxidation. Gracilaria lemaneiformis polypeptide providing theoretical reference for the development of natural antihypertensive peptides and antioxidant peptides.