Exogenous myrosinase from mustard seed increases bioavailability of sulforaphane from a glucoraphanin-rich broccoli seed extract in a randomized clinical study.

Inactive glucoraphanin (GR) in broccoli is converted to the antioxidant, anti-inflammatory, and anti-bacterial sulforaphane (SF) by cruciferous vegetable enzyme myrosinase (Myr), or similar enzymes from specific gut bacteria; both sources have variable efficiency. The effects of exogenous Myr on the conversion efficiency of GR to SF was compared to gut microbial Myr-like activity. In a randomized, double-blind, crossover study, sixteen subjects (9 F: 7 M) received a single oral dose of GR in broccoli seed extract with Myr-containing mustard seed powder, or broccoli seed extract alone, both with ascorbic acid. GR + Myr, on average, doubled the bioavailability of SF (39.8 ± 3.1%) compared to GR alone (18.6 ± 3.1%), and increased the conversion rate in the first 8 h (25.4% ± 2.7%) compared to GR alone (8.0% ± 2.7) based on measurement of urinary metabolites. There were no differences in fecal bacterial communities after the single dose; however, four bacterial GR-converting genes significantly correlated with GR conversion (p < 0.0155). To our knowledge, this is the first human study to simultaneously investigate (1) a well-defined Myr source, (2) broccoli seeds as source of GR, (3) prediction of gut microbial responsiveness to GR.