Sulforaphane & Brassica Isothiocyanates: Role in the Body, Sources & Which Microgreens Have It

Broccoli sprouts have built an entire reputation around one compound: sulforaphane, usually mentioned in the same breath as cancer-prevention headlines. That reputation is real. It's also not shared equally by every microgreen in this post's own title.

Sulforaphane, specifically, isn't a compound found in Mustard, Turnip, or Kohlrabi microgreens. It's produced from a precursor called glucoraphanin, which is specific to broccoli. Mustard, Turnip, and Kohlrabi each produce their own chemically distinct isothiocyanates instead, from their own separate glucosinolate pathways. Broccoli, the actual sulforaphane source, is covered here directly too, alongside Mustard, Turnip, Kale, Bok Choy, and Kohlrabi.

What It Is

Isothiocyanates are a family of sulfur-containing plant compounds formed when glucosinolates (their inert storage form) are broken down by the enzyme myrosinase, released when plant tissue is chewed or cut. Different Brassica species and varieties store different specific glucosinolates, which is why the resulting isothiocyanate differs from one variety to the next, even within the same plant family. Sulforaphane specifically comes from glucoraphanin, the glucosinolate broccoli specialises in. Mustard's glucosinolate, sinigrin, breaks down into allyl isothiocyanate instead, a different compound with a different structure. This is why “Brassica isothiocyanates” is a more accurate umbrella term for this post than “sulforaphane” alone, even though sulforaphane is the most widely discussed member of the family.

Role in the Body

The Keap1-Nrf2-ARE pathway: how isothiocyanates work

Under normal, unstressed conditions, a protein called Keap1 binds to a transcription factor called Nrf2 in the cell's cytoplasm and continuously marks it for degradation, keeping Nrf2 levels low. Isothiocyanates, including sulforaphane, are chemically reactive toward specific cysteine residues on Keap1; when an isothiocyanate modifies those residues, Keap1 releases Nrf2 instead of degrading it. Free Nrf2 then moves into the cell nucleus, pairs with a partner protein, and binds to a DNA sequence called the antioxidant response element (ARE) in the promoter region of a large battery of genes, switching on the transcription of the body's own detoxification and antioxidant enzymes (including glutathione S-transferases, NAD(P)H:quinone oxidoreductase, and heme oxygenase-1). This is a well-documented mechanism at the cellular and molecular level: isothiocyanates don't act as antioxidants themselves so much as trigger the body to upregulate its own antioxidant enzyme production.

Food Sources (General)

Broccoli and broccoli sprouts are the primary dietary source of glucoraphanin and, by extension, sulforaphane. Mustard greens, horseradish, and wasabi are rich in allyl isothiocyanate. Watercress, radish, and cabbage contribute their own distinct isothiocyanate profiles.

Which Microgreens Have It

This post links Mustard, Turnip, Kohlrabi, Broccoli, Kale, and Bok Choy. Each produces a genuinely different isothiocyanate profile. Broccoli is the standout entry: a 2023 human feeding study using broccoli microgreens specifically (not sprouts), Bouranis et al. (2023), published in Foods, confirmed broccoli microgreens deliver bioavailable sulforaphane in real people, measured directly in urine and stool, at levels comparable to broccoli sprouts. That's a stronger form of evidence than a simple lab concentration, since it confirms the compound survives digestion and actually reaches the body. Mustard has a real, direct concentration measurement, genuinely rich in allyl isothiocyanate. Turnip and Kohlrabi are both anchored to mature-plant compound identity, since no microgreen-specific quantification exists for either. Kale and Bok Choy are qualitative. Both are Brassica microgreens with a real, plausible isothiocyanate contribution, but no study was found isolating either one's specific compound profile at the microgreen stage.

Frequently Asked Questions

Do Mustard, Turnip, or Kohlrabi microgreens contain sulforaphane?

No, not specifically. Sulforaphane comes from glucoraphanin, a glucosinolate specific to broccoli. Mustard, Turnip, and Kohlrabi each produce their own distinct isothiocyanates from different glucosinolate precursors, related in family but chemically different compounds, each with their own Keap1-modifying reactivity.

Which AgriZen microgreen actually contains sulforaphane?

Broccoli, and it's linked directly in this post. A 2023 human feeding study using fresh broccoli microgreens specifically confirmed bioavailable sulforaphane in participants' urine and stool, at levels comparable to broccoli sprouts, real evidence that the compound survives digestion and reaches the body.

Is allyl isothiocyanate (from mustard) as well studied as sulforaphane?

Sulforaphane has a larger, more mature body of human clinical research behind it. Allyl isothiocyanate has its own documented biological activity and is well characterised chemically, but with comparatively fewer human studies.

Why does the heat in mustard microgreens matter here?

The same enzymatic breakdown (myrosinase acting on sinigrin) that releases allyl isothiocyanate when mustard tissue is cut or chewed is what produces its characteristic pungent, peppery flavour. The heat and the bioactive compound come from the same chemical event.

A Note on This Information

Everything above describes documented nutritional biochemistry and published research, not medical advice. Nothing on this page is a claim that any AgriZen microgreen treats, prevents, cures, or manages a medical condition. If you're managing a health condition, taking medication, pregnant, or have specific dietary needs, please check with a doctor or registered dietitian before making significant changes to your diet.