You can obtain the enumerations list through the MxModelReflection Module so that can do an xpath comparison on the MxObjectEnumValue entity.
This might be a silly question, but why would you want that? An enumeration is predefined so why check if it has a string value in it?
I you want to check the caption i guess you could use the getCaption(<enum>) to get the caption of the enum and then check that caption vs a string.