Penzeys (a spice co.) makes theirs from:
salt, black pepper, paprika, Turkish oregano, cayenne pepper, garlic, celery, Mexican oregano, basil, nutmeg, cumin, marjoram, thyme and rosemary.
No numbers are given, and you probably don't need two kinds of oregano, but I've made it before with a similar list, and it is generally insensitive to precise ratios. I'd start with
2x black pepper, paprika, oregano, cayenne, garlic,
1x basil, cumin, marjoram
1/2x nutmeg, thyme, rosemary
bulk up with salt (store-bought stuff is mostly salt), and experiment from there. You can probably find more on google. Add hotter things or anything you find interesting :)
MSG is the primary ingredient in Accent. The full ingredient list for Accent "original flavor" is as follows:
Monosodium Glutamate, Salt, Chili Pepper, Tricalcium Phosphate (As Anticaking Agent), Spice (Cumin, Oregano), Paprika Extractives(color), Garlic Extractives, Onion Extractives, Yellow No.6 Lake, Yellow No.5 Lake.
Best Answer
My first instinct was no way, remembering that the branches and leaves contain a high amount of thujone, which is a neurotoxin and not without risks, especially if used over a long time or while pregnant. This is the same stuff that caused absinthe to be discredited for decades.
But Thuja oils typically contain 40% α-thujon, sage (salvia officinalis) up to 60%. Thuja's pungent smell would prevent ingesting too much.
So my conclusion would be:
do not use for a long time or when pregnant (most midwives caution against using sage, too, btw.)
use sparingly for health reasons, a limited amount is considered safe by health agencies world wide, see information on absinthe for example.
use very sparingly for culinary reasons, because the taste is quite "pronounced". I had to take a herbal medicine with thuja decades ago and still shudder to think of it. (It did work, though...)
When thinking of potential culinary uses, think of uses for sage or juniper - you will want to use it as a spice in foods that can "handle" the woody, bitter tinge. Dark red meat or even game perhaps? Complement with a generous amount of pepper and perhaps a good red wine.
Another approach that might be worth a try is sweetening it up - like "fir syrup" (is this known in American cuisine?).