Damage to the Membrane Permeability and Cell Death of Vibrio parahaemolyticus Caused by Phlorotannins with Low Molecular Weight from Sargassum thunbergii

ABSTRACT

To understand the mode of action of low molecular weight phlorotannins (LMPs) from Sargassum thunbergii against Vibrio parahaemolyticus, effects of LMPs on the growth curve and the content changes of some substances in culture media were investigated, and those on morphological and ultramicrostructure were also observed by scanning electron microscope and transmission electron microscopy. The results showed that LMPs inhibited thalli growth at logarithmic phase and damaged the cell membrane and cell wall of tested bacteria which led to the leakage of cytoplasm and the deconstruction of membrane permeability. The present study indicates that LMPs as natural products in seaweeds deserve further investigation for food safety control and aquacultural drugs.     

海带抗氧化多酚的制备及活性研究

用1：1的氯仿：甲醇超声提取海带成分,并用石油醚、乙酸乙酯和正丁醇依次进行萃取,利用DPPH法、邻二氮菲-Fe^2＋氧化法、铁氰化钾还原法和邻苯三酚自氧化进行抗氧化实验,同时与抗氧化剂2,6-二叔丁基对甲酚（BHT）和没食子酸（GA）进行对照。结果显示海带提取物与各萃取组分均具有较强的抗氧化能力,其中乙酸乙酯提取物（EA）抗氧化活性最强。在50μg／mL浓度时,EA清除DPPH自由基、羟自由基、超氧阴离子自由基的能力和还原能力均高于抗氧化剂BHT,且清除超氧阴离子自由基的能力也高于CA;另外,Aqueous组分在所有测定浓度下清除羟自由基能力均高于GA,清除O2的能力也高于BHT。海带各提取物总酚含量的分析表明总酚含量与抗氧化活性之间具有一定的相关性,总酚含量高其抗氧化能力也相应提高,表明多酚是提取物中重要的抗氧化成分。4种抗氧化方法的比较表明DPPH法的相关系数最高（R=0．987）,是海带体外抗氧化实验最有效的方法。     

重金属镉对铜藻生长及其生物活性成分积累的影响

为研究水体重金属污染对经济海藻的生长和品质造成的严重影响,以经济褐藻铜藻Sargassum horneri为研究对象,在温度为15℃的条件下,研究了由Cd Cl2·2.5H2O配制不同浓度(0、0.1、0.5、1.0、5.0 mg/L)的重金属镉胁迫对铜藻生长、光合色素、可溶性糖、可溶性蛋白等生理生化指标,以及对生物活性成分(岩藻黄素、褐藻胶和褐藻多酚)积累的影响。结果表明:对照组藻体的特定生长率(SGR)在15 d内持续升高,0.1、0.5 mg/L Cd处理组的SGR在试验前10 d内逐渐升高,然后保持稳定至第15天,1.0 mg/L处理组的SGR随着培养时间的延长呈波动变化状态,而5.0 mg/L处理组的SGR呈先升高后降低的趋势;藻体的各项生理生化指标随胁迫时间呈不同的变化趋势,但在试验第15天时,各胁迫组藻体的叶绿素a、类胡萝卜素和可溶性蛋白含量均显著低于对照组(P0.05),而可溶性糖含量则显著高于对照组(P0.05);铜藻的岩藻黄素和褐藻多酚含量在不同浓度的Cd胁迫下均有极大程度的下降,且Cd胁迫浓度越高,降幅越大,而褐藻胶含量在Cd浓度≤0.5 mg/L胁迫下未有显著变化(P0.05),在Cd≥1.0mg/L时显著下降(P0.05)。研究表明,在铜藻产业化开发应用过程中,其养殖海域的重金属污染是需要考虑的重要因素。     

Phlorotannins from Alaskan Seaweed Inhibit Carbolytic Enzyme Activity

Global incidence of type 2 diabetes has escalated over the past few decades, necessitating a continued search for natural sources of enzyme inhibitors to offset postprandial hyperglycemia. The objective of this study was to evaluate coastal Alaskan seaweed inhibition of α-glucosidase and α-amylase, two carbolytic enzymes involved in serum glucose regulation. Of the six species initially screened, the brown seaweeds Fucus distichus and Alaria marginata possessed the strongest inhibitory effects. F. distichus fractions were potent mixed-mode inhibitors of α-glucosidase and α-amylase, with IC₅₀ values of 0.89 and 13.9 μg/mL, respectively; significantly more efficacious than the pharmaceutical acarbose (IC₅₀ of 112.0 and 137.8 μg/mL, respectively). The activity of F. distichus fractions was associated with phlorotannin oligomers. Normal-phase liquid chromatography-mass spectrometry (NPLC-MS) was employed to characterize individual oligomers. Accurate masses and fragmentation patterns confirmed the presence of fucophloroethol structures with degrees of polymerization from 3 to 18 monomer units. These findings suggest that coastal Alaskan seaweeds are sources of α-glucosidase and α-amylase inhibitory phlorotannins, and thus have potential to limit the release of sugar from carbohydrates and thus alleviate postprandial hyperglycemia.     

Mixture of Phlorotannin and Fucoidan from Ecklonia cava Prevents the Aβ-Induced Cognitive Decline with Mitochondrial and Cholinergic Activation

The anti-amnesic effect of a mixture (4:6 = phlorotannin:fucoidan from Ecklonia cava, P4F6) was evaluated on amyloid-beta peptide (Aβ)-induced cognitive deficit mice. The cognitive function was examined by Y-maze, passive avoidance, and Morris water maze tests, and the intake of the mixture (P4F6) showed an ameliorating effect on Aβ-induced learning and memory impairment. After the behavioral tests, superoxide dismutase (SOD) activity and thiobarbituric acid-reactive substances (TBARS) contents were confirmed in brain tissue, and in the results, the mixture (P4F6) attenuated Aβ-induced oxidative stress. In addition, mitochondrial activity was evaluated by mitochondrial reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content, and mitochondria-mediated apoptotic signaling pathway, and the mixture (P4F6) enhanced mitochondrial function. Furthermore, the mixture (P4F6) effectively regulated tau hyperphosphorylation by regulating the protein kinase B (Akt) pathway, and promoted brain-derived neurotrophic factor (BDNF) in brain tissue. Moreover, in the cholinergic system, the mixture (P4F6) ameliorated acetylcholine (ACh) content by regulating acetylcholinesterase (AChE) activity and choline acetyltransferase (ChAT) expression in brain tissue. Based on these results, we suggest that this mixture of phlorotannin and fucoidan (P4F6) might be a substance for improving cognitive function by effectively regulating cognition-related molecules.