Phosphonic and Phosphinic Acid Derivatives as Novel Tyrosinase Inhibitors: Kinetic Studies and Molecular Docking

A dozen of phosphonic and phosphinic acid derivatives containing pyridine moiety were synthesized and its inhibitory activity toward mushroom tyrosinase was investigated. Moreover, molecular docking of these compounds to the active site of the enzyme was performed. All the compounds ( 1 – 10 ) demonstrated the inhibitory effect with the IC₅₀ and inhibition constants ranging millimolar concentrations. The obtained results indicate that the compounds show different types of inhibition (competitive, noncompetitive, mixed), but all of them are reversible inhibitors. The obtained outcomes allowed to make the structure–activity relationship (SAR) analysis. Compound 4 ([(benzylamino)(pyridin‐2‐yl)methyl]phenylphosphinic acid) revealed the lowest IC₅₀ value of 0.3 mm and inhibitory constant of K_i 0.076 mm , with noncompetitive type and reversible mechanism of inhibition. According to SAR analysis, introducing bulky phenyl moieties to phosphonic and amino groups plays an important role in the inhibitory potency on activity of mushroom tyrosinase and could be useful in design and development of a new class of potent organophosphorus inhibitors of tyrosinase. Combined results of molecular docking and SAR analysis can be helpful in designing novel tyrosinase inhibitors of desired properties. They may have broad application in food industry and cosmetology.     

The effect of fucoidan on tyrosinase: computational molecular dynamics integrating inhibition kinetics

Fucoidan is a complex sulfated polysaccharide extracted from brown seaweed and has a wide variety of biological activities. In this study, we investigated the inhibitory effect of fucoidan on tyrosinase via a combination of inhibition kinetics and computational simulations. Fucoidan reversibly inhibited tyrosinase in a mixed-type manner. Time-interval kinetics showed that the inhibition was processed as first order with biphasic processes. For further insight, we simulated dockings with various sizes of molecular models (monomer to decamer) of fucoidan and showed that the best binding energy change results were obtained from the pentamer (?1.89?kcal/mol) and the hexamer (?1.97?kcal/mol) models of AutoDock Vina. The molecular dynamics simulation confirmed the binding mechanisms between tyrosinase and fucoidan and suggested that fucoidan mostly interacts with several residues including copper ions located in the active site. Our study suggests that fucoidan might be a potential natural antipigment agent.     

血尿酸水平与冠状动脉病变程度的关系探讨

目的:探讨血尿酸(SUA)水平与冠状动脉病变程度的关系。方法:将268例疑似冠心病(CHD)患者,经冠状动脉造影分为冠心病组198例和非冠心病组70例;冠心病组又分为单支病变组80例,双支病变组56例,三支病变组62例。分别检测各组研究对象血尿酸含量,同时记录年龄、性别、吸烟、高血压、糖尿病、血尿酸及冠状动脉造影结果,分析血尿酸与已知冠心病主要危险因素、冠状动脉病变程度的相关性。结果:冠心病组血尿酸水平(395.35±84.40)μmol/L,显著高于非冠心病组(282.20±66.68)μmol/L(P<0.05)。单支病变组(338.48±77.36)μmol/L、双支病变组(399.62±84.36)μmol/L、三支病变组(445.16±92.20)μmol/L,血尿酸水平呈递增趋势,各组之间的差异有统计学意义。结论:血尿酸水平可反映冠状动脉病变严重程度。降尿酸治疗有望成为心血管疾病防治的一种新途径。     

2型糖尿病患者颈动脉粥样硬化与血尿酸水平的相关性研究

目的：探讨2型糖尿病（T2DM）患者颈动脉粥样硬化与血尿酸水平的相关性。方法：测定214例T2DM患者血清尿酸、血脂、糖化血红蛋白水平及颈动脉中层内膜厚度（IMT）,按颈动脉IMT分为4组：A组：无动脉粥样硬化组;B组：动脉粥样硬化组,C组：斑块形成组,D组：管腔狭窄组。比较各组生化指标,并分析颈动脉粥样硬化与血清尿酸水平的相关性。结果：各组性别、年龄、TC、HDL、LDL无显著差异;C组血清TG水平较A组低（P=0.02）,D组血清HbA1c水平较A组（P=0.038）及B组（P=0.015）显著降低。D组血清尿酸水平与A组相比显著升高（P=0.001）,但D组与B、C组及A组与B、C组间差异均无统计学意义;相关分析显示颈动脉粥样硬化程度与血清尿酸水平呈显著正相关（P=0.002）,相关系数为0.201。结论：高血清尿酸水平可能是导致T2DM患者颈动脉粥样硬化的危险因素之一,需慎重处理T2DM患者高尿酸血症问题。     

Antioxidation and Tyrosinase Inhibition of Polyphenolic Curcumin Analogs

A series of polyphenolic curcumin analogs were synthesized and their inhibitory effects on mushroom tyrosinase and the inhibition of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical formation were evaluated. The results indictated that the analogs possessing m-diphenols and o-diphenols exhibited more potent inhibitory activity on tyrosinase than reference compound rojic acid, and that the analogs with o-diphenols exhibited more potent inhibitory activity of DPPH free-radical formation than reference compound vitamin C. The inhibition kinetics, analyzed by Lineweaver–Burk plots, revealed that compounds B₂ and C₂ bearing o-diphenols were non-competitive inhibitors, while compounds B₁₁ and C₁₁ bearing m-diphenols were competitive inhibitors. In particular, representative compounds C₂ and B₁₁ showed no side effects at a dose of 2,000 mg/kg in a preliminary evaluation of acute toxicity in mice. These results suggest that such polyphenolic curcumin analogs might serve as lead compounds for further design of new potential tyrosinase inhibitors.     

Altered Circadian Relationship Between Serum Nitric Oxide,Carbon Dioxide,and Uric Acid in Multiple Sclerosis

The free radical nitric oxide (NO^·) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO^?), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO^? and CO₂, is generally low in MS patients. We investigated the relationship between serum ONOO^?, CO₂, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO^· metabolites nitrite/nitrate (NO), CO₂, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO₂, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24 h pattern in serum ONOO^? formation and UA may either contribute to or reflect the disease processes in MS.     

Altered Circadian Relationship Between Serum Nitric Oxide, Carbon Dioxide, and Uric Acid in Multiple Sclerosis

The free radical nitric oxide (NO^·) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO^-), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO^- and CO₂, is generally low in MS patients. We investigated the relationship between serum ONOO^-, CO₂, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO^· metabolites nitrite/nitrate (NO), CO₂, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO₂, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24 h pattern in serum ONOO^- formation and UA may either contribute to or reflect the disease processes in MS.     

Inhibitory effects of hinokitiol on tyrosinase activity and melanin biosynthesis and its antimicrobial activities

The inhibitory effects of hinokitiol, a constituent of the woody oils isolated from Cupressaceae heartwood, on mushroom tyrosinase and melanin formation in B16 melanoma cells as well as its antimicrobial activity were investigated. Our results showed that hinokitiol could strongly inhibit both monophenolase activity and diphenolase activity of the enzyme and the inhibition was reversible. The IC₅₀ values were estimated as 9.67?μM for monophenolase activity and 0.21?μM for diphenolase activity. The lag time of the monophenolase activity was not obviously lengthened by the compound. Kinetic analyses showed that the inhibition mechanism of hinokitiol was a mixed-type inhibition of the diphenolase activity. Hinokitiol effectively inhibited both cellular tyrosinase activity and melanin biosynthesis in B16 melanoma cells with significant cytotoxicity. Furthermore, it was found that hinokitiol could inhibit the proliferation of Salmonella enteritidis, Escherichia coli, Bacillus subtilis, Staphyloccocus aureus, Klebsiella pneumoniae, and Ralstonia solanacearum to different extents. This research may widen the use of hinokitiol in the fields of food preservation, depigmentation, and insecticide use.     

脑小血管病患者血清尿酸水平和步态障碍之间的相关性

目的:探讨脑小血管病(Cerebral small vessel disease,CSVD)患者血清尿酸(Uric acid,UA)水平和步态障碍之间的相关性。方法:将我院自2018年1月至2019年1月收治的CSVD患者172例作为研究对象,根据患者血清尿酸水平分为研究组87例,对照组85例。收集和比较两组的临床资料,使用Logistic回归分析血清尿酸和CSVD患者脑室旁、深部白质高信号、步态障碍之间的相关性。结果:两组的年龄、性别、体质指数、血糖指标、血脂指标水平,合并高血压、糖尿病病史和吸烟情况比较差异无统计学意义(P0.05)。研究组血清尿酸水平、饮酒患者比例明显高于对照组(P0.05),脑室旁高信号和深部白质高信号中重度比例均明显高于对照组(P0.05);将步态障碍、脑室旁高信号与深部白质高信号作为影响因素带入相关分析,结果显示血清尿酸水平与步态障碍、脑室旁高信号与深部白质高信号比较存在正相关(P0.05)。结论:CSVD患者血清高尿酸水平与脑室旁、深部白质高信号病变程度呈明显的正相关性,也是患者步态障碍的影响因素。     

一株人肠源性高效尿酸降解菌的分离、鉴定及降尿酸条件优化

摘要 目的：肠道作为人体的重要消化器官,其内定植的微生物在尿酸合成和代谢过程中发挥着重要作用,本研究利用含尿酸靶向培养基筛选正常人群肠道内具有降尿酸功能的细菌并鉴定。方法：依据尿酸的摩尔质量制备含不同浓度尿酸的BHI培养基,液体培养基扩增并驯化肠道粪便微生物,固体培养基分离和纯化具有尿酸降解功能的细菌。挑取固体培养基上形态一致的单个菌落进行革兰氏染色和镜检,筛选出已纯化菌株,在需氧和厌氧培养条件下测定尿酸降解率,选取降解率≥50%以上的菌株为高效尿酸降解菌的候选菌株,再测定不同温度和pH值条件下的尿酸降解率,进行降尿酸条件优化。利用16S rDNA序列测定法对尿酸降解菌进行鉴定,药敏实验测定该菌对抗生素的敏感性。结果：正常人群粪便微生物中分离获得一株高效尿酸降解菌B5C,第5天需氧条件下的尿酸降解率均>50%,与初始尿酸浓度相比具有统计学意义（P＜0.05）。优化降尿酸条件后,在37℃、pH7.0时,降解率可达88.7%,经鉴定为粪肠球菌,对常见的抗生素如阿莫西林、氨苄西林和青霉素G等具有较高的敏感性。结论：本研究利用含不同尿酸浓度的靶向培养基驯化、分离和鉴定出一株人肠源性细菌,在需氧条件下也具有较高的尿酸降解率,可为今后临床降尿酸微生物制剂的开发和利用提供新的菌种资源。     

血清尿酸水平与老年轻度高血压患者的内皮功能相关性分析

目的:探讨血清尿酸水平与老年轻度高血压患者的内皮功能相关性。方法:选取我院2020年1月到2020年12月共收治的200例老年轻度高血压患者作为研究对象,所有患者均为未使用过降压药物治疗,将其分为轻度高血压组。另选取同期收治的200例高血压常规药物治疗患者作为重度高血压组与200名健康者作为对照组,对比三组患者血清尿酸水平与血管内皮功能。对观察组所有患者依照血清尿酸水平进行分组,将血清尿酸水平208-360μmol/L的患者分为低尿酸组,共计136例,将血清尿酸水平≥360μmol/L的患者分为高尿酸组,共计64例。对比两组患者的一般临床指标、血管内皮功能与氧化应激指标,并分析血清尿酸水平与老年轻度高血压患者的内皮功能相关性。结果:重度、轻度高血压组与对照组患者NO、ET-1、SUA水平对比差异显著,具有统计学意义(P<0.05);高尿酸组与低尿酸组患者TG、TC、DBP、SBP水平对比无明显差异(P>0.05),高尿酸组患者Cr水平高于低尿酸组,组间对比,差异具有统计学意义(P<0.05);高尿酸组与低尿酸组患者T-AOC、GSH-Px、LHP、MDA、NO、ET-1水平对比差异显著,高尿酸组患者LHP、MDA和ET-1水平明显高于低尿酸组,高尿酸组患者T-AOC、GSH-Px、NO水平明显低于低尿酸组,组间对比,差异具有统计学意义(P>0.05);Spearman相关分析结果显示:TG、TC、Cr、DBP、SBP与血尿酸水平无明显相关性(P>0.05),T-AOC、GSH-Px、NO与血清尿酸水平呈负相关(P<0.05),LHP、MDA、ET-1与血清尿酸水平呈正相关(P<0.05)。结论:血清尿酸水平与老年轻度高血压患者的内皮功能具有明显相关性,而且证明血尿酸水平的升高可能由患者氧化应激导致,因此氧化应激水平也是引起血管内皮功能障碍的一种潜在机制,希望本研究结果能够为高血压患者的疾病控制提供参考意见。     

绝经后女性高尿酸血症患者性激素结合球蛋白与血尿酸的相关研究

目的：研究绝经后女性高尿酸血症患者血浆中性激素结合球蛋白（sexhormonebindingglobulin,SHBG）水平与血尿酸水平的相关性。方法：选取绝经后女性404例,其中高尿酸血症组204例,正常对照组200例,测量所有研究对象体重、身高、腰围、臀围、收缩压（SBP）、舒张压（DBP）,并计算体重指数（BMI）和腰臀比（WHR）,检测血尿酸（UA）、空腹血糖（FBG）、总胆固醇（TG）、甘油三酯（TC）低密度脂蛋白（LDL）、高密度脂蛋白（HDL）、雌激素（E2）、雄激素（T）、空腹胰岛素（INS）及SHBG,并计算胰岛素抵抗指数（Homa-IR）。结果：与绝经后女性尿酸正常者相比,高尿酸血症的患者UA,WHR,TC,FBG,INS,Homa-IR明显升高（P〈0．01）,DBP,WAIST和LDL升高（P〈0．05）,SHBG水平明显下降（P〈0．01）;SHBG与INs、uA、TG呈显著负相关（P〈0．05）,SHBG与E2呈显著正相关P〈0．01）。结论：绝经后女性中高尿酸血症患者的低血浆SHBG水平与高血尿酸水平显著相关,血浆SHBG水平下降与胰岛素抵抗可能高度相关,低sHBG可能作为绝经后女性患高尿酸血症的高危因素。     

A Series of Benzylidenes Linked to Hydrazine‐1‐carbothioamide as Tyrosinase Inhibitors: Synthesis,Biological Evaluation and Structure−Activity Relationship

Tyrosinase is a type 3 copper enzyme responsible for skin pigmentation disorders, skin cancer, and enzymatic browning of vegetables and fruits. In the present article, 12 small molecules of 2‐benzylidenehydrazine‐1‐carbothioamide were designed, synthesized and evaluated for their anti‐tyrosinase activities followed by molecular docking and pharmacophore‐based screening. Among synthesized thiosemicarbazone derivatives, one compound, (2E)‐2‐[(4‐nitrophenyl)methylidene]hydrazine‐1‐carbothioamide, is the strongest inhibitor of mushroom tyrosinase with IC₅₀ of 0.05 μM which demonstrated a 128‐fold increase in potency compared to the positive control. Kinetic studies also revealed mix type inhibition by this compound. Docking studies confirmed the complete fitting of the synthesized compounds into the tyrosinase active site. The results underline the potential of 2‐benzylidenehydrazine‐1‐carbothioamides as potent pharmacophore to extend the tyrosinase inhibition in drug discovery.     

饮食和生活习惯与胃癌的相关性研究进展

胃癌是起源于胃粘膜上皮细胞的恶性肿瘤。近年来,虽然大部分国家胃癌发生率呈下降趋势,但我国胃癌的发病率和死亡率仍居高不下。胃癌的发生是多因素共同参与的复杂过程,如与种族、遗传、年龄、性别、幽门螺旋杆菌感染、饮食等因素相关,其中饮食及生活习惯被认为与胃癌的发生关系密切。而且早期胃癌的预后相对良好,降低发生率是防治胃癌的一项关键措施。因此,通过了解饮食及生活习惯因素与胃癌之间的关系,可以加强胃癌的一级预防,从而改善胃癌患者预后。本文就高盐、高脂饮食,蛋白质、蔬菜水果摄入以及吸烟、饮酒等因素与胃癌关系的研究进展进行综述,以期对胃癌的预防奠定一定基础。     

The Influence of Dietary Molybdenum and Copper Supplementation on the Contents of Serum Uric Acid and Some Trace Elements in Cocks

The effect of molybdenum (Mo) and copper (Cu) supplementation on some blood parameters and trace elements of tissues of cocks was investigated. The animals were fed with commercial poultry feed and water ad libitum and the experimental groups received peroral supplementation of different amounts of Mo or Cu during 4 weeks. Lowered values of serum uric acid were established in animals receiving 400 µg supplementation of either Mo or Cu. In contrast, the cocks receiving 100 µg supplementation of Cu displayed elevated concentrations of uric acid in the serum. A very significant statistical difference was noted between the uric acid levels of the animals receiving either moderate (group IV) or excess (group V) supplementation of Cu. The cocks with an excess of Cu displayed lowered hemoglobin and hematocrit values but no signs of Cu-intoxication were found in macro- and microscopical studies. Atomic absorption spectrophotometry was employed in the determinations of the content of Mo, Cu, Zn, Mn, Fe and & in the liver and kidneys of the cocks. The authors suggest that the results of the trace element analyses presented are to be considered as preliminary values. Furthermore, the effect of Mo and Cu on uric acid metabolism should be additionally clarified by applying histochemical studies on xanthine oxidase in different tissues of cocks in order to make conclusions on the significance of Mo and Cu in the etiology of avian gout.     

The inhibitory effect of benzenethiol on the cresolase and catecholase activities of mushroom tyrosinase

The inhibitory effect of benzenethiol on the cresolase and catecholase activities of mushroom tyrosinase (MT) have been investigated at two temperatures of 20 and 30°C in 10 mM phosphate buffer solution, pHs 5.3 and 6.8. The results show that benzenethiol can inhibit both activities of mushroom tyrosinase competitively. The inhibitory effect of benzenethiol on the cresolase activity is more than the catecholase activity of MT. The inhibition constant (K_i) value at pH 5.3 is smaller than that at pH 6.8 for both enzyme activities. However, the K_i value increases in cresolase activity and decreases in catecholase activity due to the increase of temperature from 20 to 30°C at both pHs. Moreover, the effect of temperature on K_i value is more at pH 6.8 for both cresolase and catecholase activities. The type of binding process is different in the two types of MT activities. The binding process for catecholase inhibition is only entropy driven, which means that the predominant interaction in the active site of the enzyme is hydrophobic, meanwhile the electrostatic interaction can be important for cresolase inhibition due to the enthalpy driven binding process. Fluorescence and circular studies also show a minor change in the tertiary structure, without any change in the secondary structure, of the enzyme due to the electrostatic interaction in cresolase inhibition by benzenethiol at acidic pH.     

Modeling the interaction between the N‐terminal domain of the tumor suppressor p53 and azurin

It is known that the half life of the tumor suppressor p53 can be increased by the interaction with the bacterial protein azurin, resulting in an enhanced anti‐tumoral activity. The understanding of the molecular mechanisms on the basis of this phenomenon can open the way to new anti‐cancer strategies. Some experimental works have given evidence of an interaction between p53 and azurin (AZ); however the binding regions of the proteins are still unknown. Recently, fluorescence studies have shown that p53 partakes in the binding with the bacterial protein by its N‐terminal (NT) domain. Here we have used a computational method to get insight into this interacting mode. The model that we propose for the best complex between AZ and p53 has been obtained from a rigid‐body docking, coupled with a molecular dynamics (MD) simulation, a free energy calculation, and validated by mutagenesis analysis. We have found a high degree of geometric fit between the two proteins that are kept together by several hydrophobic interactions and numerous hydrogen bonds. Interestingly, it has emerged that AZ binds essentially to the helices H_I and H_III of the p53 NT domain, which are also interacting regions for the foremost inhibitor of p53, MDM2. Copyright © 2009 John Wiley & Sons, Ltd.