Glucobrassicin — I3G (Indolic Glucosinolate · I3C/DIM Precursor · Oestrogen Metabolism)
| Compound | Glucobrassicin (I3G) |
| Chemical class | Glucosinolate — Indolic (3-Indolylmethyl glucosinolate) |
| CAS | 4356-52-9 |
| Primary source | Brassica oleracea var. italica (broccoli buds/sprouts), Brussels sprouts, cabbage |
| Key applications | I3C/DIM precursor, oestrogen metabolism modulation, chemopreventive, hormone balance |
| Claim strength | High (via I3C/DIM metabolites) |
| Typical form | Broccoli extract (glucobrassicin co-constituent); Brussels sprout extract |
| Buy from Herbuno |
Name origin: From Brassica (the genus) + -in (glucosinolate suffix). Glucobrassicin (indole-3-ylmethyl glucosinolate, I3G) is the most abundant indolic glucosinolate in cruciferous vegetables and the primary precursor to indole-3-carbinol (I3C), which subsequently condensates to diindolylmethane (DIM) under acidic gastric conditions. The indole ring system distinguishes glucobrassicin from aliphatic glucosinolates and gives its hydrolysis products distinct pharmacology. Traditional use: Cabbage, Brussels sprouts, and broccoli have documented traditional therapeutic use across European phytomedicine — particularly cabbage for gastric ulcer healing (documented in the 1950s by Garnett Cheney, who identified the anti-ulcer factor in raw cabbage juice, later understood to involve glucobrassicin and its hydrolysis products). Research trajectory: Glucobrassicin’s significance lies primarily in generating I3C and then DIM — compounds with well-documented oestrogen metabolism modulation, anti-oestrogenic, anti-androgenic, and chemopreventive activities. Multiple human RCTs have been conducted with I3C and DIM derived from glucobrassicin hydrolysis. Glucobrassicin itself also generates indole-3-acetonitrile (IAN), indole-3-carbaldehyde, and ascorbigen on hydrolysis — a complex metabolic fate. Commercial source: Broccoli Liquid Extract and Broccoli Powder from Herbuno deliver glucobrassicin as a co-constituent. See sourcing options below.
Evidence for Glucobrassicin Applications
Oestrogen metabolism modulation (via I3C/DIM): Human clinical studies with I3C (300–400 mg/day, equivalent to glucobrassicin intake from 300–400 g cruciferous vegetables) demonstrate significant shifts in urinary oestrogen metabolite ratios — increasing the “good” 2-hydroxyoestrone (2-OHE1) fraction relative to the “bad” 16α-hydroxyoestrone (16α-OHE1). This metabolite shift is associated with reduced breast cancer risk in epidemiological studies. Claim strength: High (via I3C; glucobrassicin as precursor).
Chemopreventive — cervical dysplasia: A human RCT (Bell et al. 2000) with I3C (200–400 mg/day) in women with CIN 2/3 (cervical intraepithelial neoplasia) showed complete regression in 50% of treated women versus 0% placebo over 12 weeks. This is one of the strongest direct clinical outcomes for an I3C/glucobrassicin application. Claim strength: Moderate (single RCT; not reproduced at scale).
Hormonal balance and anti-androgenic: I3C and DIM modulate androgen receptor signalling (competitive AR binding, reduced DHT-mediated transcription), relevant for PCOS, prostate health, and male hormonal balance formulations. Human pilot data support DIM’s hormonal modulation in healthy men and women. Claim strength: Moderate.
Nrf2 activation: Indole-3-carbinol and its metabolites activate Nrf2, inducing Phase-II detoxification enzymes. This pathway is complementary to (but distinct from) sulforaphane’s Nrf2 activation, as the two act through different Nrf2 binding domains. Claim strength: Moderate.
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Dosage & Formulator Specification
Clinical I3C dose (from glucobrassicin hydrolysis): 200–400 mg/day I3C for hormonal and chemopreventive applications. This requires significant glucobrassicin intake — approximately 300–500 g cruciferous vegetables/day or a concentrated broccoli/Brussels sprout extract standardised to glucobrassicin + I3C content. For DIM-focused formulations (more stable than I3C), 100–300 mg/day DIM is the studied range. Broccoli extract from Herbuno delivers glucobrassicin alongside glucoraphanin — request full glucosinolate profile by HPLC on CoA to quantify indolic vs aliphatic fractions.
Processing note: steaming preserves glucobrassicin more than boiling (which leaches water-soluble glucosinolates). Myrosinase from gut microbiota converts glucobrassicin to I3C with variable efficiency. I3C is unstable in acid (spontaneously condensates to DIM in the stomach) — this means glucobrassicin, I3C, and DIM are all precursors in the same metabolic cascade, with DIM being the most pharmacologically relevant endpoint.
Frequently Asked Questions — Glucobrassicin
What is the metabolic cascade: glucobrassicin → I3C → DIM?
Glucobrassicin is hydrolysed by myrosinase to unstable indole-3-carbinol (I3C) + glucose + sulfate. In the acidic gastric environment, I3C spontaneously condenses: two molecules form DIM (diindolylmethane), three form CTet (cyclic trimer), and other oligomers form. DIM is the primary pharmacologically active metabolite reaching systemic circulation. This is why DIM supplements (delivering the endpoint metabolite directly) are more predictable than glucobrassicin or I3C supplements where acid conversion efficiency varies.
Why does glucobrassicin affect oestrogen metabolism?
DIM (formed from glucobrassicin → I3C → DIM cascade) is a partial agonist/antagonist of oestrogen receptors (ERα and ERβ) with cell-type specific effects. More importantly, DIM induces CYP1A1 and CYP1A2 enzymes, shifting oestradiol metabolism toward 2-hydroxylation (producing the less active 2-OHE1) and away from 16α-hydroxylation (producing the more proliferative 16α-OHE1). The 2-OHE1/16α-OHE1 ratio (the “oestrogen metabolite ratio”) is the primary biomarker used in I3C/DIM clinical studies.
Should formulators use glucobrassicin, I3C, or DIM for hormonal health supplements?
Each has different formulation advantages: Glucobrassicin (in broccoli extract) requires myrosinase for bioactivation — most variable, least targeted. I3C is more bioactive than glucobrassicin but is unstable (condenses to DIM in stomach) — conversion efficiency varies with gastric pH. DIM is the most pharmacologically characterised endpoint metabolite with the most predictable absorption and activity — preferred for targeted hormonal balance formulations. For general Brassica wellness positioning, broccoli extract (glucobrassicin-containing) is appropriate; for specific hormonal balance claims, DIM is the preferred form.
Is glucobrassicin safe for oestrogen-sensitive conditions?
The oestrogen-modulating activity of I3C/DIM is complex — it is anti-oestrogenic in some contexts (reduces 16α-OHE1, reduces ERα signalling) and potentially mildly oestrogenic in others (ERβ agonism at high concentrations). For women with oestrogen-positive breast cancer or on tamoxifen, the interaction with hormonal milieu requires medical supervision. Standard advisory language for oestrogen-sensitive conditions applies. At dietary cruciferous vegetable intake levels (300–500 g/day), epidemiological data support cancer-protective rather than cancer-promoting effects.
Related compounds: Glucoraphanin, Indole-3-Carbinol, Diindolylmethane, Sulforaphane
Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.
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