Maybe it's the
flavonoids, maybe it's the
terpenes. Maybe both. In fact, I would put money that it's the
whole cocktail of compounds that gives it sedative efficacy - any one of them on their own is probably not as effective as the whole chamomile flower.
Apigenin is not a very good drug,
pharmacokinetically speaking. It has erratic oral
bioavailibility and undergoes metabolism in the liver to a variety of other compounds, depending on a bunch of things like personal genetics, other drugs being taken that induce or inhibit liver enzymes, set and setting etc.
Apiin is a compound of apigenin with two sugars, a prodrug of sorts, found in
parsley. It only has an oral BA of about 0.22% (+/- 0.16%), which is pretty low and highly variable. But at least a small portion is absorbed.
[ref] That could change if you take enough of it or you have other terpenes inhibiting metabolism.
Apigenin and the like can't be smoked because they will be destroyed rapidly, and can't really be injected either because they are not very water soluble. So the best method to get them into your body may indeed be as a tea mixed with other terpenes and the like to make sure at least a little bit of everything gets to your brain.
However, apigenin and its glycosides* (sugar compounds) have been
demonstrated to bind to the same site that benzodiazepines do; so presumably this is why it exerts its sedative and calming effects.
What is clear is that chamomile tea is a good sedative; it's been used traditionally for hundreds of years with great success. Medically related plants like
lavender (contains
linalool and other terpenes/flavones) and
hops (contains sesquiterpenes like
humulene,
caryophyllene, and hop
alpha acids like
humulone etc) are observed to have a
strong sedative effect presumably mediated through some sort of GABAergic, glutamate, or cannabinoid-mediated pathways. People picking hops have been known to fall asleep on top of ladders and hurt themselves, it's that
powerful as a sedative, just from smelling it.
There is actually quite a lot of research on the sedative properties of
linalool from lavender, for instance, that suggests it works by acting as a serotonin
5HT1a agonist to reduce anxiety - like
cannabidiol. And caryophyllene is a
CB2 receptor agonist (also like CBD) that is present in many plants, herbs, and spices.
I don't think anyone has become dependent on chamomile tea to sleep either. But I wouldn't be surprised if chamomile withdrawal was a thing that could happen, given what we know about it an its constituent chemicals. It probably takes a lot of chamomile
It would be interesting to see if chamomile tea substitutes for, or helps out with chronic benzodiazepine usage. Both treat the same sort of set of symptoms and hit the same receptor, so it's worth a try!
Plants are wonderful, and we have the tools and technology to figure out exactly what all their magical compounds are (like
HPLC,
NMR, all that stuff), and do (
radioligands for cell assays, binding simulations, high throughput screening) these days. We are living in a golden age of pharmacy.
* On glycosides:
Glycosides are compounds made from binding a sugar molecule to another molecule. They're abundant in nature, because sugar molecules are very polar and make compounds more water soluble. It's a good way for cells to excrete molecules as waste, or for defense. Your body does this with drugs like codeine, morphine, acetaminophen, all sorts of things.
Salicin from willow bark is a glycoside that breaks down into
salicylic acid - the painkiller drug that is a precursor to
aspirin.
I could keep writing, but I'll stop now.
