Angiotensin-converting enzyme I inhibitory activity of phlorotannins from Ecklonia stolonifera

ABSTRACT:   As part of our study of the isolation of antihypertensive agents derived from natural marine products, the bioactivity of 10 edible Korean seaweeds were screened by angiotensin converting enzyme (ACE) inhibitory and peroxynitrite assays. Among the crude extracts of selected seaweeds, including five Phaeophyta ( Ecklonia stolonifera , E. cava , Pelvetia siliquosa , Hizikia fusiforme , and Undaria pinnatifida ), four Rhodophyta ( Gigartina tenella , Gelidium amansii , Chondria crassicaulis , and Porphyra tenera ) and one Chlorophyta ( Capsosiphon fulvescens ), the ethanol extracts of E. stolonifera , E. cava , P. siliquosa , U. pinnatifida , and G. tenella exhibited significant inhibitory properties against ACE at more than 50% inhibition at a concentration of 163.93 µg/mL. Phloroglucinol 1 , eckstolonol 2 , eckol 3 , phlorofucofuroeckol A 4 , and dieckol 5 had been isolated previously, and triphlorethol-A 6 and fucosterol 7 were isolated for the first time from E. stolonifera. Also, the ACE inhibitory and peroxynitrite scavenging properties of phlorotannins 1–6 were evaluated, along with fucosterol 7 obtained from E. stolonifera . Among profound peroxynitrite scavenging compounds 1–6 , phlorotannins 3 , 4 and 5 were also determined to manifest marked inhibitory activity against ACE, with 50% inhibition concentration (IC₅₀) values of 70.82 ± 0.25, 12.74 ± 0.15, and 34.25 ± 3.56 µM, respectively.     

Inhibitory activity of Ecklonia stolonifera and its isolated phlorotannins against Cu2+-induced low-density lipoprotein oxidation

Since the oxidation of low-density lipoprotein (LDL) is one of the main causes of atherosclerosis, Cu²⁺-induced LDL oxidation and conjugated diene formation is currently being explored for the development of pharmaceutical drugs or functional foods for the treatment of atherosclerosis. The present work investigated the inhibitory effects on in vitro Cu²⁺-induced human LDL oxidation and conjugated diene formation of the methanol (MeOH) extract of the edible brown alga (Ecklonia stolonifera) and its different solvent-soluble fractions, as well as the phlorotannins isolated from them. The most active ethyl acetate fraction was selected for chromatographic separation to isolate six phlorotannins: phloroglucinol (1), dioxinodehydroeckol (2), eckol (3), phlorofucofuroeckol A (4), dieckol (5), and 7-phloroeckol (6). Compounds 3?C6 showed potent inhibitory activity against Cu²⁺-induced LDL oxidation as compared with probucol, a well-known clinical therapeutic agent for hypercholesterolemia. Moreover, when compound 5 (at levels of 9 and 4.5???M) was used in combination with probucol (4.5???M), they additively inhibited Cu²⁺-induced LDL oxidation. In addition, 3?C5 significantly prolonged the lag time of conjugated diene formation at 10???M. These results suggest that the potent antiatherosclerotic effects of E. stolonifera and its isolated phlorotannins may be partly attributed to the inhibition of Cu²⁺-induced LDL oxidation and conjugated diene formation.     

褐藻多酚的生物活性及提取技术研究进展

本文对不同褐藻中的褐藻多酚存在的形式进行了分析,综述了褐藻多酚抗菌、抗氧化、抗凝血、抗肿瘤以及化学防御等生物活性的研究进展,并比较了有机溶剂浸提、超声波辅助提取、微波辅助提取以及有机溶剂萃取纯化等方法的提取效果,旨在为褐藻多酚的进一步研究和利用提供参考依据.     

Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming

Juvenile sporophytes and gametophytes of Ecklonia stolonifera were incubated in combinations of three pCO₂ levels (360, 720 and 980 ppmv) and two temperatures (10 and 15°C for sporophytes; 15 and 20°C for gametophytes) to examine potential effects of climate change on photosynthesis and growth. Sporophytes had significantly higher maximum quantum yields (F_v/F_m) and maximum relative electron transport rates (rETR_max) at 720 ppmv than 360 and 980 ppmv. Also, these parameters were significantly lower at higher temperature of 15°C than at 10°C. Growth of female gametophytes was maximal at 360 ppmv rather than enriched pCO₂ levels. Female gametophytes had significantly lower growth at higher temperature of 20°C than at 15°C. These results indicate effects of elevated pCO₂ varied between generations: stimulating sporophytic photosynthesis and inhibiting gametophytic growth. Ocean acidification and warming would constitute a grave threat to seedling cultivation of E. stolonifera caused by growth inhibition of gametophytes at high pCO₂ levels and temperatures.     

Application of Two-Level Full Factorial Design for the Extraction of Fucoxanthin and Antioxidant Activities from Sargassum siliquosum and Sargassum polycystum

Two-level full factorial design was employed to identify the extraction parameters that can improve the derivation of fucoxanthin content (FC), total carotenoid content (TCC), and antioxidant from two brown seaweeds, Sargassum siliquosum (SS) and Sargassum polycystum (SP). These parameters included temperature (A: 4–45°C), time (B: 30–1,440 min), and solvent-to-solid ratio (C: 10–50 ml/g). Antioxidant activities were determined as trolox equivalent antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, and ferric-reducing antioxidant power (FRAP). Results showed that all three factors were significant (p < 0.05) in providing higher FC in both species. These factors were also significant in obtaining higher TCC in SS; whereas in SP, TCC was only affected by solvent-to-solid ratio. Only temperature was found to contribute significantly to a higher TEAC in both species. However, none of the factors improved DPPH for SS, except temperature and time for SP. For SS, only time was significant in obtaining higher FRAP; whereas temperature and time were significant for SP. Hence, results indicate that a simple modification in the extraction temperature, time, and solvent-to-solid ratio will be able to improve the derivation of fucoxanthin, carotenoids, and antioxidant activities.     

Evaluation of Biochemical and Nutritional Potential of Seaweeds from Lakshadweep Archipelago

The variation of the proximate composition and mineral content of nine seaweeds available in the Lakshadweep group of islands were studied to evaluate their nutritional quality. The proximate composition and the mineral contents were determined as per standard methodologies. The nutritional quality was found to be comparable with common vegetables and fruits. Hansen’s nutritional quality index has shown the seaweeds U. lactuca, H. valentea, and H. muciformis, in particular, to be safe for their versatile use and that they can contribute to a healthy balanced diet.     

4种海藻膳食纤维对Cd2+、Pb2+、Hg2+的吸附作用

采用模拟胃和小肠环境进行体外实验,同时对大白鼠进行体内实验,研究了4种海藻膳食纤维对Cd2 、Pb2 、Hg2 的体内、体外清除效果,并与麦麸(Wheat bran)膳食纤维进行了比较研究。结果表明:(1)在体外模拟实验中,4种海藻和麦麸膳食纤维对Cd2 、Pb2 、Hg2 的吸附效果与pH、纤维种类有关。在小肠环境下较胃环境吸附强烈,海带(Lamiraria japonica)吸附最强,其次为麒麟菜(Eucheuma)、麦麸和江蓠(Gracilaria),马尾藻(Sargassum)最差。各种膳食纤维对Pb2 吸附最强,对Hg2 最弱。(2)在动物体内实验中,各膳食纤维对大鼠体内重金属排出量(率)均显著大于空白对照组(P<0.05),各膳食纤维对重金属的排出能力由大到小依次为:麒麟菜、海带、麦麸、江蓠、马尾藻。结论认为,海藻膳食纤维具有清除重金属的效果,因此在降低重金属对人体蓄积毒性方面具有应用价值。[中国水产科学,2007,14(1):132-138]     

Identification of bacteria from the normal flora of perch, Perca fluviatilis L., and evaluation of their inhibitory potential towards Aeromonas species

Pathogenic Aeromonas sobria has been identified as a causative agent of ulcerative disease in farmed European perch, Perca fluviatilis L. To study the effect of the normal intestinal bacterial flora of perch against A. sobria, we sampled 193 bacterial isolates from the perch digestive tract. The isolates were identified by sequence analysis of the 16S rRNA gene and their inhibitory potential against A. sobria was evaluated in vitro. Nineteen of the strains isolated showed inhibition and were also tested against other aeromonad and non-aeromonad fish pathogens including Yersinia ruckeri and Vibrio anguillarum. Isolates showing inhibition were primarily Pseudomonas spp.; however, inhibitory Shewanella spp., and Delftia sp. were also identified. A Pseudomonas chlororaphis isolate showed inhibition against all fish pathogens tested.     

Growth performance and feed utilization of Haliotis tuberculata coccinea (Reeve) juveniles from the Azores (north-eastern Atlantic Ocean): An assay of three mono algae diets

We assessed the dietary value of available seaweeds (Ulva lactuca, Ulva intestinalis, and Sargassum vulgare) as food for juvenile abalone Haliotis tuberculata coccinea. During the 6 weeks that the experiment lasted, initial shell length and weight increased from 13.95 ± 0.32 mm to 15.30 ± 0.30 mm and from 0.39 ± 0.02 g to 0.47 ± 0.03 g. Ulva lactuca diet resulted in higher shell growth rate (58.47 ± 16.76 μm day^?1), SGR (1.15 ± 0.47%.day^?1), weight gain (65.5% ± 33.3), and PER (1.56 ± 0.31), possibly thanks to its higher crude protein content. Both green algae (U. lactuca, U. intestinalis) prove to support the growth of H. tuberculata coccinea. However, they might not be appropriate for an optimal intensive aquaculture production; further research should be conducted to find more efficient diets for juvenile abalone.     

鳄鱼血蛋白酶解产物抗氧化特性和血管紧张素转化酶抑制活性研究

研究了鳄鱼血蛋白酶解产物的抗氧化特性和对血管紧张素转化酶（ ACE）的抑制活性。利用木瓜蛋白酶酶解鳄鱼血浆蛋白和血球蛋白,用分光光度法测定了酶解产物的抗氧化能力和用高效液相色谱（ HPLC）测定其ACE的抑制率。结果显示：鳄鱼血浆和血球蛋白酶解产物的亚铁离子螯合能力差异性不显著（ P＞0．05）;在0～5 mg/mL的浓度范围内,血球蛋白酶解产物清除ABTS自由基的能力大于血浆蛋白酶解产物,且在浓度为1 mg/mL时,两者清除ABTS自由基的能力差异性极显著（ P＜0．01）;血浆蛋白酶解产物清除DPPH自由基的能力在0～5 mg/mL的浓度范围内随着蛋白浓度的增加而升高,血球蛋白酶解产物在蛋白浓度为4 mg/mL处达到最大清除率,之后下降;在0～20 mg/mL的浓度范围内,两种酶解产物的还原力随着蛋白浓度的提高显著升高,但两者还原力的差异性不显著（ P＞0．05）;鳄鱼血浆和血球蛋白酶解产物对ACE具有良好的抑制力,其最大抑制率可分别达到75．56％和86．42％。研究表明,鳄鱼血蛋白酶解产物在体外具有抗氧化和抑制ACE的活性。     

The inhibitory activities and antiviral mechanism of Viola philippica aqueous extracts against grouper iridovirus infection in vitro and in vivo

Grouper iridovirus (GIV) is one of the most serious pathogens in mariculture and causes high mortality rates in cultured groupers; then, effective medicines for controlling GIV infections are urgently needed. Viola philippica is a well‐known medicinal plant, and the application of V. philippica aqueous extracts against GIV infection was assessed by different methods in this study. The results showed that the working concentration of V. philippica aqueous extracts was 10 mg/ml. V. philippica aqueous extracts below 10 mg/ml have no significant cytotoxic effects on cell viability, while extracts over 15 mg/ml decreased cell viability and showed cytotoxic activity. V. philippica aqueous extracts had excellent inhibitory effects against GIV infection in vitro and in vivo. The possible antiviral mechanism of V. philippica was further analysed, which indicated that V. philippica did no damages to GIV particles, but it could disturb GIV binding, entry and replication in host cells. V. philippica had the best inhibitory effects against GIV during viral infection stage of binding and replication in host cells. Overall, the results suggest that appropriate concentration of V. philippica aqueous extracts has great antiviral effects, making it an interesting candidate for developing effective medicines for preventing and controlling GIV infection in farmed groupers.     

蜈蚣藻多糖降血糖及降血脂活性的研究

本文通过建立四氧嘧啶高血糖小鼠模型和高脂饲料高血脂小鼠模型,进行摄入不同剂量的蜈蚣藻多糖的动物实验,以测定的小鼠空腹血糖值、大鼠血脂水平[胆固醇（TC）、甘油三酯（TG）、高密度脂蛋白胆固醇（HDL—C）、低密度脂蛋白胆固醇（LDL—C）]以及肝脏的生化指标值,探讨蜈蚣藻多糖的降血糖、降血脂活性效果。结果表明蜈蚣藻多糖能显著降低高血糖小鼠的空腹血糖值及高血脂小鼠的TC,TG,LDL—C含量,提高HDL—C含量。蜈蚣藻多糖具有降血糖、降血脂等功效。     

Identification of angiotensin I-converting enzyme inhibitory peptides derived from salmon muscle and their antihypertensive effect

ABSTRACT:   The salmon peptide digested from salmon muscle showed a strong inhibitory activity against the angiotensin I-converting enzyme (ACE). The antihypertensive effect of the salmon peptide on spontaneously hypertensive rats (SHR) was examined. After the single intravenous administration of the salmon peptide at a dose of 30 mg/kg body weight, the systolic blood pressure (SBP) was significantly reduced against the control. Further, a double-blind, placebo-controlled, parallel-group study determined the efficacy of the salmon peptide in mild hypertensive subjects. The SBP, after a 1.0 g of salmon peptide intake, was significantly reduced at 4 weeks after the intake, and 2 weeks after the intake finished, compared to the value before ingestion. Bioassay-guided separation of the salmon peptide, using a combination of column chromatographic techniques, led to the identification of 20 active di- and tri-peptides, including Ile-Val-Phe and Phe-Ile-Ala as two new ACE inhibitory tripeptides. Ile-Trp had the strongest ACE inhibitory activity (IC₅₀ = 1.2 μM) in vitro , and contributed 5.2% to the total ACE inhibitory activity. The salmon peptide and Ile-Trp showed a digestive resistance by in vitro assay, which mimicked the digestive organ, and had no affinity for factors related to blood pressure regulation, except for the ACE inhibitory activity.     

血管紧张素转化酶抑制肽研究进展

为研究鳗鱼加工副产物的综合利用,以鳗鱼骨胶原蛋白为原料,采用酶解法制备血管紧张素转化酶 (Angiotensin-converting enzyme, ACE) 抑制肽。以ACE抑制活性和水解度为评价指标,通过单因素和响应面试验确定最佳的酶解制备条件,并分析酶解产物的分子质量分布和氨基酸组成。结果显示,碱性蛋白酶为最适水解酶,最佳酶解条件为：温度50 ℃,质量浓度15 g·L^–1,酶解时间5.25 h,加酶量3.1% (质量分数),pH 9.2。在此条件下,鳗鱼胶原蛋白肽的ACE抑制活性为70.33%,与预测值接近;酶解产物中分子质量小于1 kD的肽占57.02%,1~3 kD的肽占36.55%;氨基酸组成分析表明,酶解产物中与ACE抑制活性有关的疏水性氨基酸 (如脯氨酸、缬氨酸、异亮氨酸、亮氨酸、苯丙氨酸) 含量增加。     

Antioxidant and Angiotensin-Converting Enzyme Inhibitory Activities of Protein Hydrolysates Prepared from Threadfin Bream (Nemipterus spp.) Surimi By-products

Solid wastes from threadfin bream (Nemipterus spp.) surimi production composed of head and frame were hydrolyzed by various commercial proteases (Alcalase, Flavourzyme, Neutrase, Protamex, papain, and pepsin) to produce protein hydrolysates with bioactive properties. An Alcalase-hydrolyzed sample at 24.4% degree of hydrolysis (DH) displayed the highest antioxidant activity based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP) assay, and potassium ferricyanide method. In addition, it showed an inhibitory activity toward angiotensin-converting enzyme (ACE) of 25.5%. Antioxidant activity of threadfin bream by-product hydrolysates increased with hydrolysis time and reached the highest DPPH activity after 6 h, while that hydrolyzed for 3 h showed the highest reducing power based on FRAP and potassium ferricyanide assays. In addition, ACE inhibitory activity was found to be at an optimum after 3 h of hydrolysis. The hydrolysates (1 mg/mL) also retarded oxidation of a linoleic acid emulsion system to a similar extent as 0.1 mg/mL 3-tert-butyl-4-hydroxy anisole (BHA), indicating a potential use in the food system. Protein hydrolysates from threadfin bream surimi by-products could be tailor-made to possess both antioxidant and ACE inhibitory activity through controlling DH of Alcalase-catalyzed reactions.