What Are Glucosinolates? How Broccoli, Glucoraphanin, I3C and Sulforaphane Fit Together
A head of broccoli does not come with an ingredient list. Yet once you start reading about broccoli sprouts, you meet names such as glucosinolates, glucoraphanin, sulforaphane and I3C. Are they all different names for the same thing?
No. What are glucosinolates? They are a family of naturally occurring plant compounds that contain sulfur and nitrogen. You find them especially in broccoli, cabbage, kale and other cruciferous vegetables. Glucoraphanin and glucobrassicin belong to this family. Sulforaphane and indole-3-carbinol (I3C) are examples of substances that can form when particular glucosinolates break down.
Knowing which compounds start in the plant makes broccoli sprout science much easier to follow.
What Are Glucosinolates? They're Already Inside the Plant
Broccoli makes glucosinolates itself. They are not added ingredients or one substance hiding behind a complicated name. Each member of this family has its own chemical structure.
They are involved in plant defence. When tissue is damaged, glucosinolates can form substances that help the plant respond to challenges such as insects.
Broccoli is not alone. Brussels sprouts, cabbage, kale, cauliflower, radish and mustard plants all contain glucosinolates. These are familiar examples of glucosinolate-rich foods, although the particular compounds and their amounts are not the same in every vegetable.
The compounds in the plant and the substances formed after breakdown are not always the same. That distinction is more useful than memorising every name.
Broccoli Has More Than One Glucosinolate
Glucoraphanin is one of the best-known glucosinolates in broccoli. Scientists place it in a group called aliphatic glucosinolates, but the important part is easier to remember: glucoraphanin is a natural starting compound that can give rise to sulforaphane. Young broccoli sprouts have drawn particular interest because of their glucoraphanin content.
Broccoli also contains glucobrassicin, an indole glucosinolate. Its breakdown can produce indole-3-carbinol, or I3C. Glucoraphanin and glucobrassicin share a family name, but are different molecules.
Broccoli can contain other glucosinolates too, including glucoerucin.
This is also why we talk about glucoraphanin when introducing our NZ-grown Broccoli Sprout Capsules. Our broccoli sprout material contains naturally occurring glucoraphanin together with active myrosinase, an enzyme that helps explain what happens next.
Why the Names Change When Broccoli Is Chopped or Chewed
In an intact broccoli plant, glucosinolates and an enzyme called myrosinase can be kept apart within the tissue. When you cut, crush or chew that tissue, they can come into contact. Myrosinase then helps break down the glucosinolates.
The products can include isothiocyanates, indoles and nitriles, depending on the starting glucosinolate and conditions. Some contribute to the taste and aroma of cruciferous vegetables.
Myrosinase is an enzyme, not a glucosinolate. And breakdown is not a promise that every molecule of a starting compound will turn into one chosen final substance. Conditions matter, so two foods containing glucoraphanin need not form identical amounts of sulforaphane.
This helps explain why scientific articles mention both glucosinolates and their breakdown products.
Glucoraphanin, Sulforaphane and I3C Are Not All the Same Kind of Compound
Broccoli can contain glucoraphanin, produce sulforaphane and be associated with I3C. These words describe different things.
Glucoraphanin is a glucosinolate present in the plant. Sulforaphane is an isothiocyanate, a different kind of compound that can form when glucoraphanin breaks down with help from myrosinase under suitable conditions. So sulforaphane itself is not a glucosinolate.
I3C has a different starting point. It is a breakdown product of glucobrassicin, another glucosinolate. I3C is not a glucosinolate either. In the acidic environment of the stomach, I3C can form further substances, including DIM. If you are curious about that extra name, we explain how sulforaphane and DIM differ in a separate article.
Here is the detail worth keeping: glucosinolates are the starting family. Glucoraphanin is one member. Sulforaphane and I3C are examples of compounds that can form after different glucosinolates break down.
Sharing a vegetable source does not make these names interchangeable.
Does Every Broccoli Plant Have the Same Glucosinolates?
No. The mix and amount can change with the broccoli variety, the age of the plant and the part you are looking at. Growing conditions matter too, as do storage and preparation after harvest.
In a well-known 1997 study, researchers found that young broccoli sprouts and mature broccoli from the plants they tested had different glucosinolate profiles. The young sprouts stood out for glucoraphanin-related compounds, while the mature samples contained a larger share of certain indole glucosinolates.
That does not mean every young sprout has an identical make-up, or that mature broccoli lacks glucoraphanin. It means plant age can change the balance. A sprout is more than a miniature broccoli head.
We have explored why the three-day broccoli sprout stage matters if you would like to learn more about this part of the plant's growth.
Why We Talk About Glucoraphanin in Our NZ-Grown Sprouts
At Kiwi Superfoods, we choose 100% NZ-grown, lightly milled broccoli sprouts for our capsules. We like being able to offer a distinctive plant ingredient in a format that is easy to take at home, at work or when travelling.
We believe you should know more than the word broccoli on a label. Glucoraphanin is the natural starting compound associated with sulforaphane formation. Active myrosinase tells you that the enzyme involved in breakdown is present in our finished sprout material.
We check our finished material to confirm myrosinase remains active. We want you to understand both the starting compound and the enzyme, not just see their names on a label.
Our capsules are not formulated or standardised as an isolated I3C or DIM supplement. We do not present them as a measured source of every glucosinolate or claim that all the plant's compounds remain unchanged. What we focus on is our NZ-grown sprout ingredient, its naturally occurring glucoraphanin and its active myrosinase.
For us, that is a good reason to look more closely at our Broccoli Sprout Capsules: a simple way to include this interesting part of broccoli in your day, without having to grow and prepare fresh sprouts yourself.
What This Means If You Prefer Broccoli Sprout Capsules
We keep our capsules straightforward. Each bottle contains 60 capsules, and each capsule supplies 600 mg of NZ-grown broccoli sprout material. The labelled daily serving is two capsules, which you can take with or without food. Our listed formulation is gluten free and vegan-friendly.
If fresh sprouts aren't always in your fridge, our capsules offer a convenient way to include broccoli sprout material in your day. They complement a varied diet rather than replacing vegetables.
For more on our ingredients and how to take the capsules, you can read our broccoli sprout ingredient and capsule FAQs.
A quick safety note: if you are pregnant or breastfeeding, or have a thyroid condition, check with your doctor before using the capsules. If you take regular medication or are thinking about a separate I3C or DIM supplement, check suitability with a qualified health professional. Always follow the product label.
Common Questions About Glucosinolates
Are glucosinolates the same as sulforaphane?
No. Glucosinolates are a family of natural plant compounds. Sulforaphane is an isothiocyanate that can form when one specific glucosinolate, glucoraphanin, breaks down under suitable conditions. They are closely connected in broccoli chemistry, but they are not different names for the same compound.
Is glucoraphanin a glucosinolate?
Yes. Glucoraphanin is a particular glucosinolate naturally found in broccoli and broccoli sprouts. It is well known as the starting compound associated with sulforaphane formation. Myrosinase can help break it down, but the amount of sulforaphane formed depends on the conditions.
Is indole-3-carbinol, or I3C, a glucosinolate?
No. Indole-3-carbinol, or I3C, is a breakdown product that can form from glucobrassicin. Glucobrassicin is the indole glucosinolate present in cruciferous plants; I3C is a different compound formed after that starting material is broken down.
Which vegetables naturally contain glucosinolates?
Glucosinolates occur in cruciferous vegetables, including broccoli, broccoli sprouts, cabbage, kale, Brussels sprouts, cauliflower, radish and mustard plants. Each contains its own mix of glucosinolates, and the amounts can vary with variety, growing conditions, plant age and preparation.
The Broccoli Detail Worth Remembering
Broccoli contains a whole family of natural plant compounds called glucosinolates. Glucoraphanin is one of them. With help from myrosinase, glucoraphanin can form sulforaphane. Other glucosinolates, including glucobrassicin, can lead to different compounds such as I3C.
That is why we are pleased to offer our NZ-grown Broccoli Sprout Capsules with naturally occurring glucoraphanin and active myrosinase. If this is the part of broccoli that has caught your interest, we would love you to explore our capsules and see how easily they can fit into your day.
References
- National Cancer Institute. Cruciferous Vegetables and Cancer Prevention.
- Linus Pauling Institute, Oregon State University. Isothiocyanates.
- Linus Pauling Institute, Oregon State University. Indole-3-Carbinol.
- Fahey JW, Zhang Y, Talalay P (1997). Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens.
- Ilahy R et al. (2020). Pre- and Post-harvest Factors Affecting Glucosinolate Content in Broccoli.
