The bioavailability and biological activity of sulphur-containing compounds from broccoli

The bioavailability of the broccoli-derived sulphur-containing compounds, glucoraphanin (GR), S-methyl-L-cysteine sulfoxide (SMCSO) and sulforaphane (SF), were quantified through a dietary intervention study in humans with the use of soups made with three broccoli genotypes that differed in their Myb28 alleles. One genotype was homozygous for the normal broccoli Myb28B allele while the other two were either heterozygous or homozygous for a Myb28V allele introgressed from the wild species Brassica villosa. Phytochemical analysis of the soups confirmed that the presence of one or more Myb28V alleles led to higher levels of GR. A randomised, double-blinded, three-phase, crossover study was employed to quantify the pharmacokinetics of GR, SF and SMCSO following consumption of the soups. A significantly higher plasma concentration and urinary excretion of GR, SMCSO and SF and metabolites occurred following consumption of broccoli soup derived from the Myb28B/V and Myb28V/V genotypes compared to Myb28B/B genotype. There was considerable inter-individual variation in the excretion of these metabolites following consumption of the soups, with certain volunteers having consistently higher plasma levels of SF and higher levels of SF excretion for each of the different phases of the study. However, there was no correlation between plasma and urine levels of SF with SMCSO or GR. The use of in vitro models indicated that intact GR and SMCSO may either require a transporter to diffuse across the enterocytes or diffuse paracellularly to reach the systemic circulation. As an initial investigation to explore the biological activity of SMCSO, experiments were undertaken to investigate whether SMCSO could induce nrf2-regulated genes within human and mouse liver cells, with the use of SF as a positive control. No gene induction was observed with SMCSO and it was concluded that the biological activity of SMCSO was likely to reside in its microbial degradation products

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

Scope: Observational studies have associated consumption of cruciferous vegetables with reduced risk of prostate cancer. This effect has been associated with the degradation products of glucosinolates—thioglycosides that accumulate within crucifers. The possible role of S-methyl cysteine sulfoxide, a metabolite that also accumulates in cruciferous vegetables, and its derivatives, in cancer prevention is relatively unexplored compared to glucosinolate derivatives. The hypothesis that consuming a broccoli soup results in the accumulation of sulfate (a SMCSO derivative) and other broccoli-derived metabolites in prostate tissue is tested. Methods and results: Eighteen men scheduled for transperineal prostate biopsy were recruited into a 4-week parallel single blinded diet supplementation study (NCT02821728). Nine men supplemented their diet with three 300 mL portions of a broccoli soup each week for four weeks prior to surgery. Analyses of prostate biopsy tissues reveal no detectable levels of glucosinolates and derivatives. In contrast, SMCSO is detected in prostate tissues of the participants, with significantly higher levels in tissue of men in the supplementation arm. SMCSO was also found in blood and urine samples from a previous intervention study with the identical broccoli soup. Conclusion: The consequences of SMCSO accumulation in prostate tissues and its potential role in prevention of prostate cancer remains to be investigated