What is the enzyme in broccoli that creates sulforaphane?

January 2, 2026 •

4 min read

Researchers have consistently found that diets rich in cruciferous vegetables like broccoli are associated with a reduced risk of certain chronic diseases. The remarkable health benefits of this vegetable are unlocked by a specific enzyme in broccoli called myrosinase, which converts a precursor compound into the powerful bioactive chemical, sulforaphane. This article explores the science behind this conversion and how you can maximize the benefits of eating broccoli.

Quick Summary

The enzyme responsible for producing the powerful compound sulforaphane in broccoli is myrosinase. This enzyme reacts with glucoraphanin when the vegetable is chopped or chewed. Cooking methods, especially high heat, can destroy myrosinase, impacting sulforaphane bioavailability. Learn how to prepare broccoli to maximize its beneficial effects.

Key Points

Myrosinase is the Key Enzyme: The enzyme myrosinase, found in broccoli, converts a precursor chemical into the beneficial compound sulforaphane.
Damage Activates the Enzyme: Myrosinase is activated when the plant's cells are damaged through chewing, chopping, or blending, allowing it to react with glucoraphanin.
Heat Destroys Myrosinase: High-heat cooking methods, such as boiling or microwaving, can inactivate the heat-sensitive myrosinase enzyme, reducing sulforaphane production.
Maximize Sulforaphane with Preparation: To get the most sulforaphane, chop broccoli and wait at least 40 minutes before cooking, eat it raw, or steam it lightly.
Boost Cooked Broccoli with Mustard Seed: Adding a source of active myrosinase, like mustard seed powder, to cooked broccoli can restore the conversion process.
Gut Bacteria Provide a Backup: If myrosinase is destroyed by cooking, gut microbes can still convert some glucoraphanin into sulforaphane, though less efficiently.

Understanding the Myrosinase-Glucoraphanin System

Broccoli and other cruciferous vegetables do not naturally contain high levels of sulforaphane. Instead, they store a precursor compound called glucoraphanin. The magic happens when the plant's cell walls are damaged, such as through chewing, chopping, or blending. This action brings the glucoraphanin into contact with the enzyme myrosinase, which catalyzes a reaction that produces sulforaphane.

The Chemical Reaction Explained

The conversion process is a fascinating aspect of plant biology and nutrition. Myrosinase, a thioglucosidase enzyme, hydrolyzes glucoraphanin (a type of glucosinolate) to produce an unstable intermediate compound. This intermediate then rearranges to form the final product: sulforaphane. This sophisticated defense mechanism evolved to protect the plant from pests, but it offers significant health benefits for humans who consume it.

Myrosinase and Sulforaphane: Key Benefits

Antioxidant and Anti-inflammatory Properties: Sulforaphane's primary health benefit is its ability to activate the Nrf2 pathway in human cells. This pathway regulates the expression of a wide array of cytoprotective genes, including antioxidant and phase II detoxification enzymes. By inducing these enzymes, sulforaphane helps combat oxidative stress and inflammation, two key drivers of aging and chronic diseases.

Anticancer Effects: Numerous studies have investigated sulforaphane's potential in cancer prevention. It has been shown to induce apoptosis (programmed cell death) in cancer cells and inhibit the growth of various types of cancer cells in lab and animal studies. Research suggests that regularly consuming cruciferous vegetables can significantly reduce the risk of certain cancers, such as prostate, breast, and colon cancer.

Other Health Advantages: Beyond its well-documented anticancer effects, sulforaphane has been linked to other potential health improvements. These include supporting heart health by reducing inflammation, helping manage blood sugar levels in type 2 diabetes, and protecting against sun damage when applied topically.

Maximizing Sulforaphane Production

Since myrosinase is a heat-sensitive enzyme, how broccoli is prepared plays a crucial role in the amount of sulforaphane available. Cooking at high temperatures, like boiling or microwaving for an extended period, can inactivate the enzyme, effectively halting the conversion process.

Practical Tips for Preparation

Chop and Wait: Cut your broccoli and let it sit for at least 40 minutes before cooking. This pre-chopping allows the myrosinase and glucoraphanin to mix and produce sulforaphane before the heat can inactivate the enzyme. It is recommended to chop vegetables finely to maximize this effect.
Steam Lightly: Steaming broccoli for a short duration (1-3 minutes) is a highly effective method for maximizing sulforaphane levels, preserving both the enzyme and glucosinolates.
Eat it Raw: Raw broccoli, including sprouts, contains the highest levels of both myrosinase and glucoraphanin, offering the most potent source of sulforaphane.
The Mustard Seed Trick: If you prefer your broccoli well-cooked, you can still boost sulforaphane production. Adding a source of exogenous myrosinase, such as powdered brown mustard seeds, to cooked broccoli has been shown to increase sulforaphane bioavailability significantly.

Comparison of Sulforaphane Bioavailability by Cooking Method


Preparation Method	Myrosinase Activity	Sulforaphane Bioavailability	Notes
Raw	High	Highest	Excellent for maximum benefit. Chewing is the activating step.
Lightly Steamed (1-3 mins)	Good	High	Optimal for retaining most nutrients and activating the enzyme.
Stir-fried/Sautéed	Moderate to Low	Moderate	Depends on heat level and duration. Pre-chopping helps.
Boiled	Very Low	Very Low	High heat quickly inactivates the enzyme and leaches out water-soluble compounds.
Microwaved	Very Low	Very Low	Similar to boiling; high heat can rapidly destroy the enzyme.
Cooked + Mustard Seed Powder	High (exogenous)	Significantly Increased	External myrosinase restores sulforaphane production.

The Role of Gut Microbes

Even if the myrosinase enzyme is destroyed during cooking, the glucoraphanin that survives can still be converted into sulforaphane by the bacteria in your gut. While this process is generally less efficient than the activation by the plant's native myrosinase, it still contributes to overall sulforaphane levels. This highlights the importance of a healthy gut microbiome for nutrient absorption.

Conclusion: Eat Your Broccoli Wisely

The enzyme myrosinase is the critical component in broccoli that unlocks the potent, bioactive compound sulforaphane. This conversion, which occurs when the vegetable's cells are broken, is the foundation of many of broccoli's anti-inflammatory, antioxidant, and anticancer properties. By understanding how preparation methods like cooking affect this delicate enzyme, you can make informed choices to maximize the nutritional benefits of your food. Simple strategies such as chopping and waiting, eating it raw, or adding a sprinkle of mustard seed powder to cooked broccoli can significantly increase the bioavailability of sulforaphane, helping you get the most out of this nutrient-dense vegetable. A balanced and varied diet, including both raw and gently cooked cruciferous vegetables, is an excellent way to support long-term health and wellness.

Frequently Asked Questions

The primary enzyme in broccoli that is responsible for its powerful health benefits is myrosinase. This enzyme, stored separately within the plant's cells, triggers a chemical reaction when the cells are damaged.

Sulforaphane is created when the enzyme myrosinase reacts with its precursor compound, glucoraphanin. This reaction happens when broccoli is chopped, chewed, or otherwise damaged, which allows the two compounds to mix.

Yes, high-heat cooking methods like boiling or microwaving for an extended period can denature, or destroy, the myrosinase enzyme. This prevents the conversion of glucoraphanin to sulforaphane.

To maximize sulforaphane, it is best to eat broccoli raw or to chop it and let it sit for at least 40 minutes before cooking. Lightly steaming for a few minutes is also an effective preparation method.

Yes, you can still increase sulforaphane bioavailability from cooked broccoli by adding an external source of myrosinase after cooking. Good sources include mustard seed powder, radishes, or other raw cruciferous vegetables.

Sulforaphane has numerous health benefits, including powerful antioxidant and anti-inflammatory properties, activation of detoxification enzymes, and potential anticancer effects that may reduce the risk of certain cancers.

Yes, broccoli sprouts typically contain a much higher concentration of glucoraphanin and active myrosinase compared to mature broccoli, making them a more potent source of sulforaphane.