Sulforaphane vs Glucoraphanin: Conversion, Myrosinase & Labels

Sulforaphane and glucoraphanin are not interchangeable names for the same ingredient. Glucoraphanin is a relatively stable glucosinolate precursor. Sulforaphane is the more reactive isothiocyanate generated when glucoraphanin is hydrolyzed—most efficiently by the enzyme myrosinase.

That distinction changes how you read research, compare doses and evaluate supplement labels.

Sulforaphane vs glucoraphanin at a glance

What exactly happens during conversion?

In intact broccoli tissue, glucoraphanin and myrosinase are physically separated. Chopping, chewing, crushing or otherwise damaging plant cells allows enzyme and precursor to meet. Myrosinase hydrolyzes glucoraphanin, and sulforaphane can be generated.

If active plant myrosinase is absent, some conversion can still occur through gut microbial activity—but human exposure is generally lower and more variable.

Human studies show why the distinction matters

A label can provide plenty of precursor while the body receives relatively little sulforaphane. Several human studies show the gap.

Precursor-rich vs pre-hydrolyzed preparation

A crossover trial found average urinary sulforaphane bioavailability of about 70% from a pre-hydrolyzed sulforaphane-rich beverage versus about 5% from a glucoraphanin-rich beverage.^[1]

Fresh sprouts vs a myrosinase-inactivated supplement

Fresh broccoli sprouts generated substantially higher and earlier sulforaphane and erucin metabolite exposure than the tested broccoli supplement lacking active plant myrosinase.^[2]

Glucoraphanin with vs without added myrosinase

In 2026, adding mustard-seed myrosinase to a glucoraphanin-rich broccoli seed extract increased average sulforaphane bioavailability from 18.6% to 39.8%.^[3]

Raw vs cooked broccoli

Even the same food amount can behave differently. In a small human crossover trial, estimated sulforaphane bioavailability was about 37% after raw broccoli versus 3.4% after cooked broccoli.^[4] Cooking can inactivate native myrosinase while leaving some glucoraphanin precursor intact.

Why glucoraphanin-only products are more variable

A glucoraphanin-only product relies more heavily on microbial conversion in the gut. That route can work, but conversion differs among people and can vary over time. This makes the administered precursor dose a weak stand-in for the amount of sulforaphane that reaches circulation.

That is not an argument that glucoraphanin is a poor ingredient. It is an argument that precursor dose and delivered active exposure are different measurements.

Why add active myrosinase?

Pairing glucoraphanin with active myrosinase is a rational way to solve the conversion problem while retaining the precursor's relative stability. Human studies consistently show better conversion when functional enzyme is present.

But “contains myrosinase” is not the whole formulation story. A human pilot using an active-myrosinase broccoli extract found that gastric acidity and enteric coating influenced conversion.^[5] Enzyme activity has to survive the relevant processing and gastrointestinal environment.

What about preformed or stabilized sulforaphane?

Supplying sulforaphane directly bypasses glucoraphanin conversion. That can make the administered dose easier to define, but sulforaphane is reactive and historically harder to stabilize.

Modern stabilized formulations can deliver defined direct doses. A 2025 Phase I study of enteric-coated stabilized sulforaphane demonstrated measurable pharmacokinetics at 46.2–92.4 mg/day direct sulforaphane exposures, while also showing that tolerability becomes increasingly relevant at pharmacologic dosing.^[6]

So the choice is not “active compound good, precursor bad.” Both strategies can be rational when properly designed.

How to decode a supplement label

Can you convert glucoraphanin mg into sulforaphane mg?

Not with a simple one-to-one calculation. Glucoraphanin and sulforaphane have different molecular weights, and the biological conversion is not 100%. Real-world yield depends on enzyme activity, preparation and individual physiology.

This is why our dosage guide keeps precursor dose, nominal sulforaphane dose and internal exposure separate.

Which form should you choose?

There is no universally superior chemical form. A practical evidence-based hierarchy is:

1. A transparent direct/stabilized sulforaphane product can provide the clearest nominal active dose if stability is credible.
2. Glucoraphanin plus active myrosinase is a strong precursor-based strategy supported by human bioavailability evidence.
3. Glucoraphanin without active myrosinase can still generate sulforaphane, but exposure is generally more variable.
4. Generic broccoli-extract milligrams without precursor or enzyme information are the hardest to connect to human studies.

This hierarchy describes dose transparency and delivery logic, not guaranteed clinical outcomes.

Bottom line

Glucoraphanin is the precursor; sulforaphane is the conversion product. Human studies repeatedly show that the distance between those two compounds is not trivial: active myrosinase, cooking, gut conversion and delivery design can change systemic exposure several-fold.

When comparing products, stop asking whether the bottle says “broccoli.” Ask what compound is quantified, how conversion is achieved, and what evidence supports the finished formulation. For the enzyme itself, read our myrosinase guide; for the full product framework, see the sulforaphane supplement guide.