Bioavailability of Glucoraphanin and Sulforaphane from High‐Glucoraphanin Broccoli

Abstract

ScopeBroccoli accumulates 4‐methylsulphinylbutyl glucosinolate (glucoraphanin) which is hydrolyzed to the isothiocyanate sulforaphane. Through the introgression of novel alleles of the Myb28 transcription factor from Brassica villosa, broccoli genotypes have been developed that have enhanced levels of glucoraphanin. This study seeks to quantify the exposure of human tissues to glucoraphanin and sulforaphane following consumption of broccoli with contrasting Myb28 genotypes.Methods and resultsTen participants are recruited into a three‐phase, double‐blinded, randomized crossover trial (NCT02300324), with each phase comprising consumption of 300 g of a soup made from broccoli of one of three Myb28 genotypes (Myb28B/B, Myb28B/V, Myb28V/V). Plant myrosinases are intentionally denatured during soup manufacture. Threefold and fivefold higher levels of sulforaphane occur in the circulation following consumption of Myb28V/B and Myb28V/V broccoli soups, respectively. The percentage of sulforaphane excreted in 24 h relative to the amount of glucoraphanin consumed varies among volunteers from 2 to 15%, but does not depend on the broccoli genotype.ConclusionThis is the first study to report the bioavailability of glucoraphanin and sulforaphane from soups made with novel broccoli varieties. The presence of one or two Myb28V alleles results in enhanced delivery of sulforaphane to the systemic circulation.

Accumulation of Dietary S‐Methyl Cysteine Sulfoxide in Human Prostate Tissue

“…The primary aim was to determine whether supplementation of a diet with a broccoli soup would enhance the levels of sulfate and other broccoli‐derived metabolites in the prostate of men scheduled for prostate biopsy. Eighteen men were randomized to either continue their normal diet (non‐supplementation controls) or receive three portions of a glucoraphanin‐rich broccoli soup (300 g) per week for a minimum of 4 weeks manufactured from a broccoli cultivar heterozygous for a Myb28 villosa allele, as previously described . On the study day, samples of whole blood, urine (following a digital rectal prostatic massage), prostate, and peri‐prostatic adipose tissue were collected.…”

“…The analyses of sulforaphane and sulforaphane conjugates in prostate tissue, plasma, and urine was as previously described …”

“…To quantify the amount of SMCSO in plasma and urine from a single portion of soup, samples were analyzed from a previously described acute intervention study (NCT02300324) . In this study, ten volunteers consumed a single portion of the identical soup to that used in the SAP study as described above as part of a three‐phase cross‐over study.…”

“…Despite the reported biological activity of crucifer‐derived metabolites in model systems, it remains challenging to provide a satisfactory mechanistic explanation of how consuming relatively few portions of cruciferous vegetables per week can lead to a reduction in risk of aggressive prostate cancer. Several pharmacokinetic studies have shown that the concentration of glucosinolates and isothiocyanates such as sulforaphane in plasma following a portion of cruciferous vegetables is transient, and significantly lower ( C max < 1 µ m ) than that frequently used in model systems (typical exposure of 5–20 µ m for 24 h) . One explanation may be that there is accumulation of the plant‐derived compounds and/or their biological‐active derivatives in prostate tissue, as has been shown for lycopene derived from tomatoes, resulting in localized exposure of tissue to sufficiently high concentrations to induce changes that may result in reduction in carcinogenesis and growth of cancerous clones.…”

“…In this study, we investigate whether consuming a broccoli soup rich in 4‐methylsulphinybutyl glucosinolate (“glucoraphanin”), the precursor of the isothiocyanate sulforaphane, and SMCSO can result in the accumulation of sulfate, the reported major derivative from SMCSO, and other broccoli‐derived metabolites in human prostate tissue. As we unexpectedly found un‐metabolized SMCSO in prostate and adipose tissues, we additionally quantified SMCSO in tissue samples from prostate from men who had not been involved in a dietary study, and report the level of SMSCO in plasma and urine of volunteers over a 24 h period following consumption of a single portion of the broccoli soup as part of a previously described dietary intervention study to provide further insight to the bioavailability and metabolism of SMCSO.…”