IT IS A UNIQUE PATHWAY
Alpha-monolaurin is used in the human and animal industry as a strong natural antibacterial and antiviral additive. Alpha-monolaurin is composed of a lauric acid linked to a glycerol via an ester bond (Figure 1). It is made of lauric acid that is a natural ingredient found in the coconut. We call it alpha-monolaurin as the lauric acid binds the glycerol in the position alpha. Some other combinations (Figure 2) are possible but the alpha-monoglycerides gets some specific properties.
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 monoglycerides self emulsifying in water. Consequently they are active in four different environments: water, feed, stomach, and the intestinal tract and even in the blood.
The monoglycerides with a bond in position alpha are less prone to be broken down by lipases and esterases and will therefore maintain their functions all along its biological life in all parts of the gut (stomach, duodenum, colon) and even in the blood. As illustration, tributyrin (three butyric acids bound to one molecule of glycerol) will be decomposed by lipase in the duodenum. The lipase will break the beta and gamma links to release 2 free butyric acids into the intestine but the alpha position will not be degraded. After releasing butyric acid, the rest of tributyrin will become a alpha-monobutyrin. This transformation will increase its amphilic properties and provide it new functions in the intestine.
Alpha-monolaurin is used in the Animal industry for its antibacterial properties. It has mainly effects against gram positive bacteria as it disrupts their outside lipid membranes, but also seem to have antiviral properties on fat-enveloped virus. Due to its amphiphilic nature, it forms micelles, which provide them with the ability to get incorporated into the lipid membrane of these microorganisms, thereby altering the permeability. Alpha-monolaurin disrupts the cell membrane of these bacteria and the fat envelop of viruses which makes the pathogens leaky (Figure 2 & 3).
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. Furthermore, it is thought that interference of alpha-monolaurin with the membrane modifies the transmembrane signal transduction which results in inhibition of harmful exoproteins.
The table below from a study of Pr Thormar demonstrated the antiviral effect of several alpha-monoglycerides. Among these 6 components tested, alpha-monolaurin has the strongest effect on the reduction of virus titer. That can be explained by its stronger amphiphilic effect. Monoglycerides of C8 and C10 behind more hydrophilic and monoglycerides of C18 behind too lipophilic. The size of lauric acid (12 carbons) gives the alpha-monolaurin the proper lipophilic / hydrophilic balance for an optimal effect on bacteria and virus.
As all these modes of action are physical and do not require a chemical recognition like for most antibiotics, it is very difficult for the bacteria and virus to develop mechanism of resistance. Up to now, we did not find any resistance to alpha-monolaurin bactericidal and virucidal effect.
But research has proven that alpha-monolaurin have a much stronger antibacterial effect compared to their corresponding free fatty acids. The table below compares the MIC of lauric acid to the one of alpha-monolaurin (cf figure 6). That superior effect is explained here again by the amphiphilic properties given by the combination with glycerol.
Moreover, it is suggested that lipophilic molecules like alpha-monolaurin have more tendency to be transported from the enterocytes to the lymphatic system (the fat channel) instead of going via the portal vein to the liver. By going through the lymph vessel, it will avoid to be degraded by the liver and can have a systemic action. Studies show that when administering alpha-monolaurin in the diet, we can identify it in the lymph, in the blood and in the milk.
Alpha-monolaurin is actually found naturally in the milk of mammals up to 500 ppm. We all have been fed with alpha-monolaurin when we were breast-fed by our mothers. It serves for generations as a defense mechanism of infants protected through the milk of their mothers. For that reason, among all feed additives used in our industry, alpha-monolaurin is the only one that can have an effect on suckling piglets through the treatment of the sows. That would actually be the first treatment that piglets would receive together with colostrum. Alpha-monolaurin is therefore an efficient solution to help fighting against viral and bacterial systemic disease. In Swine, Alpha-monolaurin is used for the prevention of streptococcus in piglets and it can help us to limit development of PRRS. For Poultry, it is recommended to limit effect of Necrotis Enteritis but it can help as well against viral disease as Newcastle disease or Infectious Bronchitis.