何首乌提取物对脂肪酸合酶的抑制作用

目的:分析何首乌提取物对脂肪酸合酶的抑制作用。方法:以反应体系测定实验室制得的FAS活性,取何首乌萃取液样品,加入测定FAS活性反应之中,在进行反应,计算剩余活性,绘制抑制作用曲线;分别以乙酰辅酶、丙二酸单酰辅酶为底物,取不同浓度何首乌提取物,进行FAS全反应;取Wistar大鼠,随机分为对照组与观察组各30只,观察组给予配有何首乌提取物水液样品,对照组灌注三蒸谁,20d后,击昏大鼠,取大鼠肝脏,离心,取上清液,测定FAS活性,并进行对比。结果:40%乙醇为最佳提取剂;何首乌提取物在FAS全反应、FAS酮酰还原反应中IC50分别为(0.62±0.02)μg/m L、(2.13±0.11)μg/ml;何首乌根块提取物与乙酰辅酶、丙二酸单酰辅酶均呈非竞争性关系;以对照组活性为对照数值,则为(1.0±0.8),高于观察组肝脏FAS活性为(0.82±0.11),差异具有统计学意义(P0.05)。结论:何首乌提取物对脂肪酸合酶具有抑制效果,且与乙酰辅酶、丙二酸单酰辅酶不存在竞争关系,确实可抑制大鼠肝脏FAS活性。     

银杏叶丙酮提取物对动物脂肪酸合酶的抑制

银杏叶丙酮提取物(AEGL)对动物脂肪酸合酶(FAS)有强抑制作用。选定的萃取条件是室温下用60%丙酮搅拌萃取30~60min。该萃取液IC50值为4.66μg/mL,抑制能力明显强于已知的FAS抑制剂,有效物的初步分离显示,对FAS有抑制作用的成分可能存在于黄酮组分中。酶学动力学研究表明,抑制包含可逆抑制和不可逆抑制两部分。推测酮酰还原功能域(KR)的NADPH结合部位是其作用部位之一。标准银杏叶提取物EGb761对FAS的可逆抑制和不可逆抑制都明显比银杏叶的60%丙酮萃取液弱,后者对NADPH呈现比较明显的竞争性,不同于EGb761,这表明银杏叶还具有新的应用开发领域。     

鸭肝脂酸合成酶的NADPH底物抑制及作用动力学

已知动物脂肪酸合成酶的底物乙酰辅酶Ａ和丙二酰辅酶Ａ具有竞争性双底物抑制的乒乓机制。实验发现鸭肝脂肪酸合成酶的第三个底物ＮＡＤＰＨ也具有底物抑制,并研究了它的规律及与ＮＡＤＰＨ有关的稳态动力学。发现对于该酶的全反应,增加丙二酰辅酶Ａ浓度,降低环境盐浓度,均使ＮＡＤＰＨ底物抑制减少。但以ＮＡＤＰＨ作底物的酮酰还原和烯酰还原二步单独反应以及包含四步单独反应的乙酰乙酰辅酶Ａ还原反应都无ＮＡＤＰＨ底物抑制现     

鸭肝脂肪酸合成酶的NADPH底物抑制及作用动力学

己知动物脂肪酸合成酶的底物乙酰辅酶Ａ和丙二酰辅酶Ａ具有竞争性双底物抑制的乒乓机制。实验发现鸭肝脂肪酸合成酶的第三个底物ＮＡＤＰＨ也具有底物抑制,并研究了它的规律及与ＮＡＤＰＨ有关的稳态动力学。发现对于该酶的全反应,增加丙二酰辅酶Ａ浓度,降低环境盐浓度,均使ＮＡＤＰＨ底物抑制减少。但以ＮＡＤＰＨ作底物的酮酰还原和烯酰还原二步单独反应以及包含四步单独反应的乙酰乙酰辅酶Ａ还原反应都无ＮＡＤＰＨ底物抑制现象。ＮＡＤＰＨ底物抑制对丙二酰辅酶Ａ为竞争性,丙二酰辅酶Ａ底物抑制对ＮＡＤＰＨ为非竞争性。在全反应中ＮＡＤＰＨ和丙二酰辅酶Ａ之间发现为乒乓机制,在乙酰乙酰辅酶Ａ还原反应中,两个底物ＮＡＤＰＨ和乙酰乙酰辅酶Ａ之间则表现为序列反应机制。降低环境盐浓度使ＮＡＤＰＨ和丙二酰辅酶Ａ之间的乒乓机制向序列机制转化。在全反应中,ＮＡＤＰ产物抑制相对ＮＡＤＰ为竞争性,对丙二酰辅酶Ａ为非竞争性。     

中药提取物中α-葡萄糖苷酶抑制剂的筛选

目的：从中药中筛选α-葡萄糖苷酶抑制剂。方法：采用α-葡萄糖苷酶、淀粉酶以及蔗糖酶活性测定方法,对126种经水煮醇沉提取的常用中药进行α-葡萄糖苷酶抑制活性筛选。结果：在0．28mg／ml反应体系下,24种中药提取物显著抑制α-葡萄糖苷酶活性;在0．1mg／ml反应体系下,5种中药提取物抑制α-淀粉酶活性。大黄、山茱萸、赤芍、五倍子对α-葡萄糖苷酶、α-淀粉酶以及转化酶活性均有抑制作用,与阳性药物拜唐苹比较,这4种中药抑制α-淀粉酶的活性较低,但抑制α-葡萄糖计酶和转化酶的活性明显强于拜唐苹。结论：某些中药提取物能显著抑制α-葡萄糖苷酶活性,如果对其进一步分离、纯化并提取活性部位,可望获得抑制活性更强的中药α-葡萄糖苷酶抑制剂。     

来源于中药和功能性食品的脂肪酸合酶抑制剂（英文）

肥胖症及其相关疾病已成为迫切需要解决的公共卫生问题。脂肪酸合酶（fatty acid synthase,FAS）是一种多功能复合酶,对长链脂肪酸的生物合成发挥至关重要的作用,是治疗肥胖、2型糖尿病、癌症、炎症和心血管疾病等的潜在靶点。在过去的30年里,FAS抑制剂的研究受到越来越多的关注。在中国,传统中药和功能性食品广泛被应用于慢性疾病的预防和治疗,其中有多种天然产物对FAS的活性表现出很强的抑制作用。本文综述了来源于中药和功能性食品中的FAS抑制剂结构和活性特点,为天然来源的FAS抑制剂治疗肥胖症和相关疾病提供了依据。     

用HPLC法从中药中筛选血管紧张素转化酶抑制剂

本文发展了一种从中药中筛选血管紧张素转化酶(ACE)抑制剂的高效液相色谱法.以马尿酰-组氨酰-亮氨酸为反应底物,人体血浆中内生的ACE作为反应用酶,反应所生成的马尿酸为检测指标,未加酶抑制剂的反应为空白对照.用阳性药物卡托普利对本方法进行了验证.应用本方法对中药提取物进行了ACE抑制活性的筛选,其中地龙的ACE抑制活性最强,其IC50值为2.57 mg/mL.用HPLC法筛选中药ACEI且有很好的精密度和准确性.     

中药提取物对钙调磷酸酶-活化T细胞核因子通路的抑制作用

通过研究多种具有清热解毒、除湿功效的中草药提取物对钙调磷酸酶-活化T细胞核因子(Ca N-NFAT)信号通路的抑制作用发现天然的Ca N-NFAT通路抑制剂。采用荧光素酶报告基因方法,检测多种中药提取物对Ca N-NFAT信号通路影响;采用CCK8法检测中药提取物的非特异性细胞毒性。实验发现:多种中药提取物在1 mg/m L浓度时对PMA/A23187刺激的K562细胞内Ca N-NFAT通路具有抑制作用,并且没有显著的细胞毒作用;其中部分中药提取物在0.25~1 mg/m L剂量范围内对Ca N-NFAT通路具有剂量依赖性的抑制作用,结果提示这些中药提取物中可能含有能够有效抑制Ca N-NFAT信号通路的活性成分。     

氨基葡萄糖对酪氨酸酶的抑制作用

通过对酪氨酸酶催化底物L-DOPA反应速率的观察测定,研究了氨基葡萄糖（G-NH2）对酪氨酸酶的抑制作用。在反应液中加入50μL浓度为2.2 mg/mL G-NH2时（体系中G-NH2终浓度为36μg/mL）,酶抑制率为50%。GNH2对酪氨酸酶的抑制作用是个复杂的过程,酶反应呈先促进后抑制。分析酶抑制曲线Lineweaver-Burk双倒数图,得出G-NH2为混合抑制剂,进一步研究发现多巴醌生产量会减少,抑制类型是不可逆抑制。     

姜半夏乙醇提取物对人胃癌SGC7901细胞增殖和凋亡的影响

目的：观察姜半夏乙醇提取物对人胃癌SGC7901细胞增殖和凋亡的影响。方法：不同浓度姜半夏乙醇提取物（终浓度为1mg／ml,0．5mg／ml,0．25mg／ml,0．125mg／ml）处理SGC7901细胞后,倒置相差显微镜下观察细胞的形态学变化;通过甲基噻唑基四唑法检测细胞增殖状况、描绘生长曲线,使用紫外分光光度法观察药物干预后细胞ATP酶活力;AnnexinV．异硫氰酸荧光素（fluorescein isothiocyanate,FITC）／碘化丙啶（propidium iodide,PI）双标记法流式细胞术检测姜半夏乙醇提取物对SGC7901细胞诱导凋亡的情况。结果：不同浓度姜半夏乙醇提取物均能不同程度地抑制人胃癌SGC7901细胞的增殖;在姜半夏乙醇提取物诱导细胞后细胞发生了边缘毛刺、体积缩小等形态学变化,同时可见细胞折光度和贴壁能力下降;Annexin V-F／TC／PI双标记法检测显示姜半夏乙醇提取物可诱导细胞发生凋亡;细胞总ATP酶活力在药物干预72小时后出现明显下降;并且随着药物浓度增加细胞凋亡率、细胞形态异常改变以及ATP酶活力抑制作用均呈上升趋势。结论：姜半夏乙醇提取物可抑制人胃癌SGC7901细胞的增殖,促进其凋亡,抑制细胞ATP酶活力。     

The extract of leaves of Acer truncatum Bunge: A natural inhibitor of fatty acid synthase with antitumor activity

Fatty acid synthase (FAS) has been identified as a potential antitumor target. The extract from the leaves of Acer truncatum Bunge (Extr) was prepared to assay its inhibitory activity against FAS, which was isolated from duck liver, and the correlated antitumor bioactivity. Its inhibition of FAS is composed of reversible fast-binding inhibition, IC50 = 0.7 microg/ml, and irreversible slow-binding inhibition following saturation kinetics with a dissociation constant of 0.68 microg/ml and a limiting rate constant of 0.0288 min(-1). The Extr exhibited different type of inhibitions against the three substrates in the FAS overall reaction. Compared with EGCG in inhibition constant and IC50 value, the Extr appeared to be a more efficient inhibitor, and exhibited a considerable inhibition against the growth of four kinds of cancer cells (patent application number 200510068054.2). It was infered that the inhibitory activity is likely attributable to the co-operative effect of the components.     

Suppression of fatty acid synthase, differentiation and lipid accumulation in adipocytes by curcumin

Curcumin is a well-known component of the cook seasoning and traditional herb turmeric (Curcuma longa), which has been reported to prevent obesity. However, the mechanism still remains to be determined. In this study, curcumin is found to be an effective inhibitor of fatty acid synthase (FAS), and its effects on adipocytes are further evaluated. Curcumin shows both fast-binding and slow-binding inhibitions to FAS. Curcumin inhibits FAS with an IC?? value of 26.8 μM, noncompetitively with respect to NADPH, and partially competitively against both substrates acetyl-CoA and malonyl-CoA. This suggests that the malonyl/acetyl transferase domain of FAS possibly is the main target of curcumin. The time-dependent inactivation shows that curcumin inactivates FAS with two-step irreversible inhibition, a specific reversible binding followed by an irreversible modification by curcumin. Like other classic FAS inhibitors, curcumin prevents the differentiation of 3T3-L1 cells, and thus represses lipid accumulation. In the meantime, curcumin decreases the expression of FAS, down-regulates the mRNA level of PPARγ and CD36 during adipocyte differentiation. Curcumin is reported here as a novel FAS inhibitor, and it suppresses adipocyte differentiation and lipid accumulation, which is associated with its inhibition of FAS. Hence, curcumin is considered to be having potential application in the prevention of obesity.     

Evaluation of inhibition of fatty acid synthase by ursolic acid: Positive cooperation mechanism

The inhibitory effect of ursolic acid (UA) on fatty acid synthase (FAS, EC 2.3.1.85) was investigated. We found that UA potently inhibited the activity of FAS with a half-inhibitory concentration value (IC₅₀) of 6.0 μg/ml. The inhibition kinetic results showed that the inhibition of FAS by UA was competitive against acetyl-CoA and malonyl-CoA, but uncompetitive to NADPH. UA at low concentration slowly inactivated FAS, but FAS was fast inactivated by high concentration of UA in a positive cooperative manner. Moreover, NADPH significantly enhanced the inactivation of FAS by low concentration of UA, but NADPH slightly decreased the inactivation of FAS by high concentration of UA. Taken together, the results suggest that ursolic acid decreases the FAS activity through inactivation of acetyl/malonyl transferase. The combination of NADPH and KR domain promotes the inhibitory effect of UA on FAS.     

Antimicrobial effect by extracts of rhizome of Alpinia officinarum Hance may relate to its inhibition of beta-ketoacyl-ACP reductase

Inhibitory effects on bacterial growth showed that 40% ethanol extract of galangal (rhizome of Alpinia officinarum Hance) can inhibit Staphylococcus aureus, alpha-Hemolytic streptococcus, beta-Hemolytic streptococcus and Streptococcus pneumoniae. beta-ketoacyl-ACP reductase (FabG, EC.1.1.1.100) is a key enzyme in type II fatty acid synthase system in bacteria and catalyzes beta-ketoacyl-ACP reduction. The galangal extracts inhibited FabG with an IC(50) value of only 4.47 +/- 0.10 microg/mL and is more potent than other previously published inhibitors. Kinetics studies showed that the inhibition consisted of both reversible and irreversible inhibition. The extracts of galangal inhibit FabG in a competitive pattern against NADPH. So far, no inhibitor has been reported to exhibit irreversible inhibition of FabG, whereas the galangal ethanol extract can inhibit FabG irreversibly. The irreversible inhibition presented two phases. It is probable that the galangal extract inhibit FabG, thereby displaying antibacterial ability.     

The extract of leaves of Acer truncatum Bunge: A natural inhibitor of fatty acid synthase with antitumor activity

Fatty acid synthase (FAS) has been identified as a potential antitumor target. The extract from the leaves of Acer truncatum Bunge (Extr) was prepared to assay its inhibitory activity against FAS, which was isolated from duck liver, and the correlated antitumor bioactivity. Its inhibition of FAS is composed of reversible fast-binding inhibition, IC₅₀ = 0.7 μg/ml, and irreversible slow-binding inhibition following saturation kinetics with a dissociation constant of 0.68 μg/ml and a limiting rate constant of 0.0288 min^{? 1}. The Extr exhibited different type of inhibitions against the three substrates in the FAS overall reaction. Compared with EGCG in inhibition constant and IC₅₀ value, the Extr appeared to be a more efficient inhibitor, and exhibited a considerable inhibition against the growth of four kinds of cancer cells (patent application number 200510068054.2). It was infered that the inhibitory activity is likely attributable to the co-operative effect of the components.     

The novel inhibitory effect of Pangdahai on fatty acid synthase

Recently, animal fatty acid synthase (FASN) is reported as a potential therapeutic target for obesity and cancer. Considerable interest has been developed in searching for novel inhibitors of this enzyme. An extract from Pangdahai has been found to inhibit FASN in both reversible and irreversible manners, with an IC(50) of 3.5 microg/ml and an apparent inactivation rate constant of k(obs) of 2.2 x 10(-3)/min. The kinetic study showed that the Pangdahai extract inhibited the overall FASN reaction uncompetitively with acetyl-CoA, but it presented in a mixed manner both with NADPH and with malonyl-CoA. Its major reacting site on this enzyme, as compared between two IC(50) values, is not in the beta-ketoacyl reduction domain. A weight reducing experiment in rats showed that the extract significantly reduced the adipose and food intake, but in view of statistics (P < 0.05), a correlation between the reductions in the adipose and in the food consumption and the inhibition of hepatic FASN could not be established. Three known flavonoid compounds were isolated from the extract and the structure-activity relationship was discussed.     

α-Mangostin induces apoptosis and suppresses differentiation of 3T3-L1 cells via inhibiting fatty acid synthase

α-Mangostin, isolated from the hulls of Garcinia mangostana L., was found to have in vitro cytotoxicity against 3T3-L1 cells as well as inhibiting fatty acid synthase (FAS, EC 2.3.1.85). Our studies showed that the cytotoxicity of α-mangostin with IC(50) value of 20 μM was incomplicated in apoptotic events including increase of cell membrane permeability, nuclear chromatin condensation and mitochondrial membrane potential (ΔΨm) loss. This cytotoxicity was accompanied by the reduction of FAS activity in cells and could be rescued by 50 μM or 100 μM exogenous palmitic acids, which suggested that the apoptosis of 3T3-L1 preadipocytes induced by α-mangostin was via inhibition of FAS. Futhermore, α-mangostin could suppress intracellular lipid accumulation in the differentiating adipocytes and stimulated lipolysis in mature adipocytes, which was also related to its inhibition of FAS. In addition, 3T3-L1 preadipocytes were more susceptible to the cytotoxic effect of α-mangostin than mature adipocytes. Further studies showed that α-mangostin inhibited FAS probably by stronger action on the ketoacyl synthase domain and weaker action on the acetyl/malonyl transferase domain. These findings suggested that α-mangostin might be useful for preventing or treating obesity.     

Potent inhibition of fatty acid synthase by parasitic loranthus [Taxillus chinensis (dc.) danser] and its constituent avicularin

The medicinal herb parasitic loranthus in a screen was found to inhibit fatty acid synthase (EC 2.3.1.85, FAS) and reduce body weight of rats in our previous study. Now we have determined the inhibitory characteristics and kinetic parameters of extracts of parasitic loranthus [Taxillus chinensis (DC.) Danser]. The parasitic loranthus extracts (PLE) inhibits FAS reversibly and irreversibly and with an IC50 value of 0.48 microg/ml, appears to be the most potent inhibitor reported to date. PLE contains various potent inhibitors and may react with different sites on FAS. The irreversible inhibition exhibits a time-dependent biphasic process including a speedy fast-phase during the initial several minutes. The fast-phase inhibition seems to be caused by some potent but low-concentration component(s) in the extracts. In addition, we have found that avicularin existing in this herb can potently inhibit FAS. This glycosylated flavonoid and quercetin play an effective role in inhibiting FAS by parasitic loranthus.     

Evaluation of the inhibitory activities of aceraceous plants on fatty acid synthase

Fatty acid synthase (FAS) is a very significant lipogenic enzyme participating in energy metabolism in vivo and has been reported as a potential new therapeutic target for cancer treatment. The extracts from sixteen Aceraceae were prepared to assay their inhibitory activities against duck liver FAS and their correlated antitumor bioactivity. Their inhibition of FAS was composed of a reversible fast-binding inhibition, by which 0.41 microg/mL of the A. campestre extract inhibits 50% FAS activity, and an irreversible slow-binding inhibition with inactivation rate constants, k(obs), ranging between 1.5 x 10(-3) and 10.6 x 10(-3) min(-1). Three Aceraceae extracts were selected from their smaller IC50 values to study different type of inhibitions against the three substrates in the FAS overall reaction. As compared with other reported FAS inhibitors including EGCG with regard to inhibition constant and IC50 value, the extracts appeared to be more efficient inhibitors, and exhibited a considerable inhibition against the growth of five types of cancer cells (China patent application number 200610088901.6), which may be related to the inhibition of lipogenesis in these cells.