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什么是α-单脂肪酸甘油酯?

时间:2019-05-10 10:37来源:未知 作者:admin 点击:

什么是α-单脂肪酸甘油酯?


One

α-单脂肪酸甘油酯是一类甘油酯,其由通过甘油的sn1-位与脂肪酸连接的形成酯键,并且因其强抗微生物作用而闻名。 图1给出了酯化反应的示意图,以获得这种α-单脂肪酸甘油酯。 脂肪酸的氢原子(H)与甘油分子的羟基(OH)反应,导致水分子(H2O)的形成,并在脂肪酸的氧原子与碳原子之间产生共价键。 

Alpha-monoglycerides are a class of glycerides that are composed of a fatty acid linked to the sn1-position of glycerol via an ester bond and are known for their strong antimicrobial effects. Figure 1 gives a schematic overview of the esterification reaction to obtain such an α-monoglyceride. The hydrogen atom (H) of the fatty acid reacts with the  hydroxyl  group  (OH) of the glycerol molecule resulting in the formation of a water  molecule  (H2O)  and  creating  a  covalent  bond  between the oxygen atom of the fatty acid and the carbon atom of the glycerol molecule.

图一(Figure 1)

 

(A)脂肪酸和甘油的酯化反应形成α-单脂肪酸甘油酯

(A)   Esterification reaction of a fatty acids and glycerol to form an α-monoglyceride.

 

(B)丁酸和甘油酯化后形成α-单丁酸甘油酯。

(B)   Formation of α-monobutyrin after esterification of butyric acid and glycerol.


Two

α-单脂肪酸甘油酯、α-甘油二酯和α-甘油三酯的分子结构的差异如图2所示。当一种脂肪酸与甘油的第一个碳原子(sn1-位置)结合时,该分子称为α-单脂肪酸甘油酯。当一种脂肪酸与甘油分子的第二个碳原子结合时,形成β-单脂肪酸甘油酯。重要的是要知道只有α-单脂肪酸甘油酯有抗菌作用。甘油三酯是一种脂肪,在正常的消化过程中分解,是能量的来源。

The difference between the molecular structure of α-monoglyceride, α-diglyceride and α- triglyceride is shown in Figure 2.When one fatty acid is bound to the first carbon atom (sn1- position) of glycerol, the molecule is termed an α-monoglyceride. A β-monoglyceride is formed when one fatty acid is bound to the second carbon atom of the glycerol molecule. It is important to know that only the α-monoglycerides have antimicrobial effects. A triglyceride is a fat, which is broken down during normal digestion processes and is a source of energy.

图二(Figure 2.)

α-单脂肪酸甘油酯、甘油二酯和甘油三酯的示意图概述

Schematic overview of α-monoglyceride, diglyceride and triglyceride

 

Three

根据脂肪酸的链长,可以产生不同的α-单脂肪酸甘油酯(图3)。短链α-单脂肪酸甘油酯(SCFA)和中链α-单脂肪酸甘油酯(MCFA)具有不同的特性,短链的Alpha-单脂肪酸甘油酯像α-单丙酸甘油酯和单丁酸甘油酯,丙酸和丁酸的α-单甘油酯分别对革兰氏阴性菌有抑制作用。

Depending on the chain length of the fatty acid, different α-monoglycerides can be produced (Figure 3). A distinction can be made between α-monoglycerides of short chain fatty acids (SCFA) and α-monoglycerides of medium chain fatty acids (MCFA), which have  different  characteristics. Alpha-monoglycerides of SCFA such as α-monopropionin and α-monobutyrin, the α-monoglycerides of propionic acid and butyric acid respectively, are mainly active against gram negative bacteria.

图三(Figure 3.)

FRAmelco的五种常用的α-单脂肪酸甘油酯

Overview of the five commonly produced α-monoglycerides by FRAmelco.


多重优势

与游离脂肪酸相比,α-单脂肪酸甘油酯的强共价键具有多重优势(表1)。α-单甘油酯不依赖于酸碱度,因此不会离解。在饲料加工过程中不挥发、不腐蚀、热稳定。此外,单脂肪酸甘酯具有中性的味道和气味,但更重要的是,研究表明,α-单脂肪酸甘酯与其相对应的游离脂肪酸相比,具有更强的抗菌作用。

The strong covalent bond of α-monoglycerides results in multiple benefits compared to free fatty acids (Table 1). Alpha-monoglycerides are pH independent and consequently do not dissociate. They are non-volatile, non-corrosive and heat stable during feed processing. Furthermore, monoglycerides have a neutral taste and odor, but more important, research has shown that α-monoglycerides have a much stronger antimicrobial effect compared to their corresponding free fatty acids.

此外,α-单脂肪酸甘油酯是两亲性化合物,具有亲脂性,因为它们的脂肪酸尾部和亲水性性,由于其亲水性主干(甘油)。这使得α-单脂肪酸甘油酯在水中自乳化。因此,它们在四种不同的环境中活动:水、饲料、胃和肠道。Framelco的α-单脂肪酸甘油酯基产品有干燥和液体两种形式,有些还通过饮用水使用的。

Moreover, α-monoglycerides are amphiphilic compounds possessing both lipophilic (fat-loving) properties, due to their fatty acid tail and hydrophilic (water-loving) properties, due to their hydrophilic backbone (glycerol). This makes α-monoglycerides self emulsifying in water. Consequently they are active in four different environments: water, feed, stomach, and the intestinal tract. FRAmelco’s α-monoglycerides based products are available in dry and liquid form and some are applied also via drinking water.

表1(Table 1)

比较游离脂肪酸和α-单脂肪酸甘油酯之间的差异

Comparison between free fatty acids and α-monoglycerides.
 

抗菌作用

与游离脂肪酸相比,α-单脂肪酸甘油酯的强共价键具有多重优势(表1)。α-单甘油酯不依赖于酸碱度,因此不会离解。在饲料加工过程中不挥发、不腐蚀、热稳定。此外,单脂肪酸甘酯具有中性的味道和气味,但更重要的是,研究表明,α-单脂肪酸甘酯与其相对应的游离脂肪酸相比,具有更强的抗菌作用。

The strong covalent bond of α-monoglycerides results in multiple benefits compared to free fatty acids (Table 1). Alpha-monoglycerides are pH independent and consequently do not dissociate. They are non-volatile, non-corrosive and heat stable during feed processing. Furthermore, monoglycerides have a neutral taste and odor, but more important, research has shown that α-monoglycerides have a much stronger antimicrobial effect compared to their corresponding free fatty acids.

此外,α-单脂肪酸甘油酯是两亲性化合物,具有亲脂性,因为它们的脂肪酸尾部和亲水性性,由于其亲水性主干(甘油)。这使得α-单脂肪酸甘油酯在水中自乳化。因此,它们在四种不同的环境中活动:水、饲料、胃和肠道。Framelco的α-单脂肪酸甘油酯基产品有干燥和液体两种形式,有些还通过饮用水使用的。

Moreover, α-monoglycerides are amphiphilic compounds possessing both lipophilic (fat-loving) properties, due to their fatty acid tail and hydrophilic (water-loving) properties, due to their hydrophilic backbone (glycerol). This makes α-monoglycerides self emulsifying in water. Consequently they are active in four different environments: water, feed, stomach, and the intestinal tract. FRAmelco’s α-monoglycerides based products are available in dry and liquid form and some are applied also via drinking water.

表1(Table 1)

比较游离脂肪酸和α-单脂肪酸甘油酯之间的差异

Comparison between free fatty acids and α-monoglycerides.


作用部位

有机酸只在酸性环境中有活性,这意味着消化系统的第一部分。这可以用它们的pka值来解释。pka值是50%的有机酸离解后失去杀菌性能的pH值(图4A)。但是,为了获得最佳的肠道健康和性能,这些添加剂在肠道环境中也具有活性是很重要的(图4B)。由于单脂肪酸甘油酯是稳定且不依赖于酸碱度的分子,因此它们在整个胃肠道中都很活跃。

Organic acids are only active in an acidic environment, meaning the first part of the digestive system. This can be explained by their pKa value. The pKa-value is the pH at which 50% of the organic acid is dissociated, losing the bactericidal properties (Figure 4A).However, for optimal gut health and performance, it is important that these additives are also active in the intestinal environment (Figure 4B). As α-monoglycerides are stable and pH independent molecules, they are active in the entire gastro-intestinal tract.

图四(Figure 4)

(A)五种有机酸的pka值。

(A)pKa value of five organic acids.

(B)家禽胃肠道有机酸和单脂肪酸甘油酯作用部位的比较

(B)Comparison between the site of action of organic acids and α-monoglycerides in the gastrointestinal tract of poultry

 


作用方式
中链α-单脂肪酸甘油酯

中链的α-单脂肪酸甘油酯主要对革兰氏阳性细菌有作用,但似乎也具有抗病毒的特性。由于这些α-单脂肪酸甘油酯的两亲性,它们形成胶束,使它们能够融入这些微生物的脂质膜,从而改变渗透性。中链的α-单脂肪酸甘油酯甚至可能破坏这些细菌的细胞膜和使病原体病毒的囊膜泄漏(图6)。此外,革兰氏阳性菌和囊膜病毒没有完整的膜,不能有效的粘附侵入宿主细胞,从而不能感染和繁殖。

Alpha-monoglycerides of MCFA have mainly effects against gram positive bacteria, but also seem to have antiviral properties. Due to the amphiphilic nature of these α-monoglycerides they form micelles, which may provide them with the ability to get incorporated into the lipid membrane of these microorganisms, thereby altering the permeability. Alpha-monoglycerides of MCFA may even disrupt the cell membrane of these bacteria and the fat envelop of viruses which makes  the  pathogen leaky (Figure 6). Furthermore, gram positive bacteria and fat enveloped viruses can not properly adhere to, and invade, a host cell without an intact membrane. In this way infection and multiplication will not be possible.

此外,还认为α-单脂肪酸甘油酯对膜的干扰会改变跨膜信号转导,从而抑制有害的外显蛋白。而且,更多的亲脂性分子,如中链的α-单脂肪酸甘油酯,更倾向于从肠细胞向淋巴系统转运,而不是通过门静脉到肝脏。这样一来,除了肠道中的直接抗菌作用外,这些α-单脂肪酸甘油酯还具有系统性作用,因为它们被完整地运输到身体的其他器官,在那里它们可以帮助抵御感染

Furthermore, it is thought that interference of α-monoglycerides with the membrane modifies the transmembrane signal transduction which results in inhibition of harmful exoproteins. Moreover, it is suggested that more lipophilic molecules like α-monoglycerides of MCFA have more tendency to be transported from the enterocytes to the lymphatic system instead of going via the portal vein to the liver. In this way, besides the immediate antimicrobial effect in the intestine, these α-monoglycerides have a systemic effect as they are transported intact to other organs of the body where they can help fighting infections.

 

总之中链α-单脂肪酸甘油酯如:α-单辛酸甘油酯、α-单葵酸甘油酯、α-单月桂酸甘油酯对革兰氏阳性军更有效。进行了多项研究,已经证明了α-单脂肪酸甘油酯在体外和体内的均有抗菌作用,很多科学文献表明,中链的α-单脂肪酸甘油酯,尤其是α-单月桂酸甘油酯,具有抗病毒的特性。

In contrast,α-monoglycerides of MCFA like α-monocaprylin, α-monocaprin and α-monolaurin are more efficient against gram positive bacteria. Multiple studies have been conducted which prove the antibacterial effect of α-monoglycerides in vitro and in vivo. In addition, scientific literature  is  suggesting  α-monoglycerides of MCFA, and more particularly α-monolaurin, have antiviral properties.

图五(Figure 5).

中链α-单脂肪酸甘油酯甘油酯对细菌的作用方式。

The mode of action of α-monoglycerides of MCFA’s on bacteria

短链α-单脂肪酸甘油酯

短链的α-单脂肪酸甘油酯和中链的单甘油酯的作用方式略有不同。

The mode of action of α-monoglycerides of SCFA and-monoglycerides of MCFA are slightly different.

短链的α-单脂肪酸甘油酯主要对革兰氏阴性菌有作用。人们认为没有一种作用方式,但是这些α-单脂肪酸甘油酯有几种作用方式可以影响细菌。细菌需要甘油来维持其重要功能和膜的形成。甘油是由细菌通过专门的蛋白质通道(水甘油三酯)从环境中吸收的。短链的α-单脂肪酸甘油酯可被认为是甘油,并通过这些通道被动转运。在细菌内部,酶分解单脂肪酸甘油酯,释放脂肪酸,降低细菌内部的酸碱度。或者,这些蛋白通道也可能被α-单脂肪酸甘油酯阻断,因为它们的分子结构比甘油大。结果,细菌不再能够吸收甘油,并将死亡。此外,脂肪酸还可以通过在转录水平下调基因来改变DNA,并抑制参与宿主细胞入侵的蛋白质生成(TTSS复合物)。

Alpha-monoglycerides of SCFA have mainly an effect against gram negative bacteria. It is thought that there is not one mode of action, but that there are several ways these α-monoglycerides can affect bacteria. Bacteria need glycerol for vital functions and to build up their membrane. Glycerol is taken up from the environment by the bacteria through specialized protein channels (aquaglyceroporin). The α-monoglycerides of SCFA may be recognized as glycerol and passively be transported through these channels. Inside the bacteria enzymes break down the _-monoglycerides and the fatty acid is released which lowers the internal pH of the bacteria. Alternatively, these protein channels may also be blocked by α-monoglycerides, since their molecular structure is larger compared to glycerol. As a result bacteria are no longer able to take up glycerol and will die. In addition, the fatty acid can alter DNA by down regulation of the genes at transcription level and inhibit the protein production involved in invasion of host cells (TTSS Complex).

图六(Figure 6).

短链α-单脂肪酸甘油酯对细菌的作用模式

The mode of action of α-monoglycerides of SCFAs on bacteria

 

 

来源:荷兰FRAmelco/佰高威盛公司

声明:本文为“华康动物健康服务平台”所有,未经许可,禁止转载!谢谢合作

 


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