MSG is not a part of any natural flavoring that Purium has in its product line.  

MSG was discovered and patented in the early 1900s to replicate and enhance the umami flavor profile(savory or meaty flavor) and is not consistent with any Purium flavoring currently in use (apple, berry, caramel, chocolate, vanilla, fruit, etc...).

FDA’s position on MSG and the labeling of MSG is explained in further detail in the following link.  The FDA explicitly states that MSG cannot be listed as spices and flavorings.