Allylbenzene and related compounds are NOT alkaloids.  That is why it's so hard to get them to work.  Either they become an alkaloid in the body, or there is some kind of receptor as yet unknown in the body that interacts with them.  It's possible that it won't become an alkaloid - look at THC, no nitrogen group but it still can be psychedelic at the CB1 receptor.

But no, just extracting the myristicin/elemicin/safrole and ingesting won't work as well as in the context of nutmeg.  The other parts of nutmeg do something to your body that makes it work.  This is why just drinking nutmeg essential oil doesn't get everyone high (in fact not most people).