Epiallopregnanolone

Epiallopregnanolone is allopregnanolone with the 3-hydroxyl flipped to β, and that flip matters more than usual: the 3β epimer largely loses the strong GABA-A activity that makes allopregnanolone a drug. So it inherits the pregnane-neurosteroid family name without the headline mechanism — which is exactly what an honest entry needs to make clear.

What it is, structurally

Epiallopregnanolone is 3β-hydroxy-5α-pregnan-20-one, also called isoallopregnanolone: the 3β epimer of allopregnanolone . Same C21 pregnane skeleton, same 20-ketone, hydroxyl on the opposite face. In neurosteroids that 3α-versus-3β orientation is the difference between potentiating the GABA-A receptor and not — the 3α alcohols are the active ones.

CAS number and chemistry

The CAS Registry Number for epiallopregnanolone is 516-55-2. PubChem CID 92787, molecular formula C21H34O2, molar mass 318.5 g/mol, systematic name 3β-hydroxy-5α-pregnan-20-one. A firmly registered identity, adjacent to allopregnanolone's.

Why the epimer is different

The 3β orientation is not just cosmetic. Epiallopregnanolone (as isoallopregnanolone/sepranolone) does not potentiate GABA-A the way allopregnanolone does; in fact it is studied as a modulator that can counter allopregnanolone's effect. So where allopregnanolone has a strong, drug-grade calming action, its 3β epimer has a muted or even opposing one. That undercuts the main reason a pregnane neurosteroid would be added for “calm” in the first place.

What wearers report, and the evidence

Field reports specific to epiallopregnanolone are thin, and it lacks both the chemosignal case of the androstenes and the strong neurosteroid action of its 3α sibling. It rides on the list mostly as a structural family member. Honesty means saying the basis for a worn effect here is weaker than for almost anything else in the pregnane group — no volatile-signal role, and a muted internal one.

Does any pheromone product use it?

Rarely as a headline ingredient. Where it appears it is a minor pregnane-family component rather than a molecule a formula is built around.

The honest read

Epiallopregnanolone is a well-identified epimer of allopregnanolone that largely lacks the very activity that makes its sibling interesting. It is real and registered, but as a worn molecule it has neither a chemosignal case nor a strong neurosteroid one. Understand it as context for allopregnanolone ; do not expect much from it on its own.

The 3α/3β rule in neurosteroids

Epiallopregnanolone is a clean illustration of a rule that runs through this whole family: in pregnane neurosteroids, the 3α-hydroxyl forms are the GABA-A-active ones, and flipping to 3β generally switches that activity off. That is why allopregnanolone (3α) is a drug and epiallopregnanolone (3β) is not — a single stereochemical flip, a large difference in effect.

More than just inactive, the 3β epimer is studied as a functional antagonist. Under the name isoallopregnanolone (sepranolone) it has been investigated for its ability to block allopregnanolone's action, for instance in premenstrual dysphoric disorder. So if anything, epiallopregnanolone leans against the calming effect that would be the whole point of adding a pregnane neurosteroid to a blend — which makes its pheromone-list presence essentially structural.

Isoallopregnanolone and the PMDD research

Under the name isoallopregnanolone (sepranolone), the 3β epimer has genuine clinical interest — but as a modulator that blocks allopregnanolone , investigated for premenstrual dysphoric disorder. That is a real and interesting pharmacology, and it runs opposite to the calming effect you would want from a pregnane neurosteroid, which is why epiallopregnanolone is a weak entry as a worn “calm” molecule.

FAQ

What is epiallopregnanolone?

The 3β epimer of allopregnanolone, 3β-hydroxy-5α-pregnan-20-one (CAS 516-55-2), also called isoallopregnanolone.

Is it as calming as allopregnanolone?

No — the 3β orientation largely loses the GABA-A potentiation that gives allopregnanolone its effect, and the epimer can even oppose it.

Is epiallopregnanolone a pheromone?

There is no chemosignal case for it and only a muted neurosteroid one. Its presence on a molecule list is essentially structural.

Why is epiallopregnanolone so much weaker than allopregnanolone?

Because of the 3α-to-3β flip. The 3α orientation is what lets allopregnanolone potentiate the GABA-A receptor; the 3β epimer largely loses that and can even oppose it.

Does epiallopregnanolone do anything worn?

There is no chemosignal case and only a muted, possibly oppositional neurosteroid one. It is on molecule lists as a family member, not for a demonstrated effect.

Is epiallopregnanolone the same as isoallopregnanolone?

Yes — isoallopregnanolone (sepranolone) is the same 3β epimer, studied as an allopregnanolone antagonist. The pheromone-list name and the pharmacology name refer to one molecule.

How do you even get epiallopregnanolone?

Almost always as a research chemical rather than a finished consumer product — it is not a molecule mainstream pheromone brands build around. That obscurity, plus its muted activity, is why it functions more as a completeness entry on a molecule index than as something to buy.

Is it worth including in a blend?

There is no strong case for it. It lacks a chemosignal role and largely lacks the calming neurosteroid action of allopregnanolone , so it brings little a formulator would actually want.

Further reading

PubChem. Epiallopregnanolone, CID 92787 (CAS 516-55-2).