Abstract
Isothiocyanates, such as sulforaphane and iberin, derived from glucosinolates (GLS) in cruciferous vegetables, are known to prevent and suppress cancer development. GLS can also be converted by bacteria to biologically inert nitriles, such as sulforaphane-nitrile (SFN-NIT) and iberin-nitrile (IBN-NIT), but the role of the gut microbiome in this process is relatively undescribed and SFN-NIT excretion in humans is unknown. An ex vivo fecal incubation model with in vitro digested broccoli sprouts and 16S sequencing was utilized to explore the role of the gut microbiome in SFN- and IBN-NIT production. SFN-NIT excretion was measured among human subjects following broccoli sprout consumption. The fecal culture model showed high inter-individual variability in nitrile production and identified two sub-populations of microbial communities among the fecal cultures, which coincided with a differing abundance of nitriles. The Clostridiaceae family was associated with high levels, while individuals with a low abundance of nitriles were more enriched with taxa from the Enterobacteriaceae family. High levels of inter-individual variation in urine SFN-NIT levels were also observed, with peak excretion of SFN-NIT at 24 h post broccoli sprout consumption. These results suggest that nitrile production from broccoli, as opposed to isothiocyanates, could be influenced by gut microbiome composition, potentially lowering efficacy of cruciferous vegetable interventions.
Highlights
Cruciferous vegetables, including broccoli, brussels sprouts, collard greens, and arugula, ubiquitously contain a class of compounds known as glucosinolates (GLS) [1].Following damage to the cell wall of the vegetable, either the plant enzyme myrosinase converts GLS to bioactive isothiocyanates (ITC) or the epithiospecifier protein can facilitate conversion to nitriles (NIT) [1,2,3,4]
A total of 500 μL of fecal slurry was mixed with 10 mL of brain heart infusion (BHI) broth, with hemin and vitamin K, per the manufacturer’s recommendation, and either 500 μL of filter-sterilized in vitro digested broccoli sprouts (Broc) or a negative control (NC) in vitro digestion
To examine compositional differences between the samples, we examined beta-diversity using a principal coordinate analysis (PCoA)
Summary
Cruciferous vegetables, including broccoli, brussels sprouts, collard greens, and arugula, ubiquitously contain a class of compounds known as glucosinolates (GLS) [1].Following damage to the cell wall of the vegetable, either the plant enzyme myrosinase converts GLS to bioactive isothiocyanates (ITC) or the epithiospecifier protein can facilitate conversion to nitriles (NIT) [1,2,3,4]. Cruciferous vegetables, including broccoli, brussels sprouts, collard greens, and arugula, ubiquitously contain a class of compounds known as glucosinolates (GLS) [1]. Cell culture and animal models have shown that aliphatic ITCs, such as SFN and IBN, have potent anti-cancer properties and can suppress and prevent the formation of cancer [5,6,7,8,9,10,11,12,13,14,15,16]. SFN-NIT excretion in humans following cruciferous vegetable consumption has not been previously described and, the extent that it is present and biologically relevant is unknown
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