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Myrosinase-dependent and -independent formation and control of isothiocyanate products of glucosinolate hydrolysis.

Angelino D, Dosz EB, Sun J, Hoeflinger JL, Van Tassell ML, Chen P, Harnly JM, Miller MJ, Jeffery EH - Front Plant Sci (2015)

Bottom Line: Because humans typically cook their brassica vegetables, destroying myrosinase, there is a great interest in determining how human microbiota can hydrolyze glucosinolates and release them, to provide the health benefits of ITC.We found that addition of excess thiols released protein-thiol-bound ITC, but that the microbiome supports only poor hydrolysis unless exposed to dietary glucosinolates for a period of days.These findings explain why 3-5 servings a week of brassica vegetables may provide health effects, even if they are cooked.

View Article: PubMed Central - PubMed

Affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.

ABSTRACT
Brassicales contain a myrosinase enzyme that hydrolyzes glucosinolates to form toxic isothiocyanates (ITC), as a defense against bacteria, fungi, insects and herbivores including man. Low levels of ITC trigger a host defense system in mammals that protects them against chronic diseases. Because humans typically cook their brassica vegetables, destroying myrosinase, there is a great interest in determining how human microbiota can hydrolyze glucosinolates and release them, to provide the health benefits of ITC. ITC are highly reactive electrophiles, binding reversibly to thiols, but accumulating and causing damage when free thiols are not available. We found that addition of excess thiols released protein-thiol-bound ITC, but that the microbiome supports only poor hydrolysis unless exposed to dietary glucosinolates for a period of days. These findings explain why 3-5 servings a week of brassica vegetables may provide health effects, even if they are cooked.

No MeSH data available.


Related in: MedlinePlus

Cyclocondensation products generated by ex vivo gut luminal microbiota hydrolysis of Glucoraphanin. (A) Microbiota hydrolysis products from rats fed with 10% broccoli powder diet up to two weeks, in comparison to control diet. (B) Hydrolysis of glucoraphanin after incubation with luminal microbiota of rats that received 10% broccoli powder diet or 10% glucosinolate (GSL)-free broccoli powder diet. Results are the mean ± SD of three independent experiments. Each measurement is significantly different from control.
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Figure 1: Cyclocondensation products generated by ex vivo gut luminal microbiota hydrolysis of Glucoraphanin. (A) Microbiota hydrolysis products from rats fed with 10% broccoli powder diet up to two weeks, in comparison to control diet. (B) Hydrolysis of glucoraphanin after incubation with luminal microbiota of rats that received 10% broccoli powder diet or 10% glucosinolate (GSL)-free broccoli powder diet. Results are the mean ± SD of three independent experiments. Each measurement is significantly different from control.

Mentions: We fed rats (adult, male Fisher 344) an AIN93G-based diet containing 10% freeze-dried broccoli for 0, 1, or 2 weeks, before removing the caecal microbiota anaerobically to incubate them in broth in an anaerobic chamber. Separate incubates were removed from the chamber at 5 min to 6 h, treated with benzene dithiol and appearance of 1,3-benzodithiole-2-thione estimated by HPLC (Figure 1A). Because broccoli is rich in fiber, which can act as a prebiotic altering the microbiome, we repeated the study heating the broccoli powder in water at 80 °C overnight (glucosinolate-free broccoli, Figure 1B). Results clearly show that 1,3-benzodithiole-2-thione was formed in a time-dependent manner and that the formation was far greater after 1 week feeding glucosinolates. We detected no compound at time 0, showing there was no contamination from diet. A further week’s feeding made no significant difference from 1 week’s feeding. Furthermore, feeding a broccoli diet free of glucosinolates for a week had no impact, showing that the glucosinolates were the effective component. However, because we had used benzene dithiol to estimate product, we were unable to identify specific product(s).


Myrosinase-dependent and -independent formation and control of isothiocyanate products of glucosinolate hydrolysis.

Angelino D, Dosz EB, Sun J, Hoeflinger JL, Van Tassell ML, Chen P, Harnly JM, Miller MJ, Jeffery EH - Front Plant Sci (2015)

Cyclocondensation products generated by ex vivo gut luminal microbiota hydrolysis of Glucoraphanin. (A) Microbiota hydrolysis products from rats fed with 10% broccoli powder diet up to two weeks, in comparison to control diet. (B) Hydrolysis of glucoraphanin after incubation with luminal microbiota of rats that received 10% broccoli powder diet or 10% glucosinolate (GSL)-free broccoli powder diet. Results are the mean ± SD of three independent experiments. Each measurement is significantly different from control.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593958&req=5

Figure 1: Cyclocondensation products generated by ex vivo gut luminal microbiota hydrolysis of Glucoraphanin. (A) Microbiota hydrolysis products from rats fed with 10% broccoli powder diet up to two weeks, in comparison to control diet. (B) Hydrolysis of glucoraphanin after incubation with luminal microbiota of rats that received 10% broccoli powder diet or 10% glucosinolate (GSL)-free broccoli powder diet. Results are the mean ± SD of three independent experiments. Each measurement is significantly different from control.
Mentions: We fed rats (adult, male Fisher 344) an AIN93G-based diet containing 10% freeze-dried broccoli for 0, 1, or 2 weeks, before removing the caecal microbiota anaerobically to incubate them in broth in an anaerobic chamber. Separate incubates were removed from the chamber at 5 min to 6 h, treated with benzene dithiol and appearance of 1,3-benzodithiole-2-thione estimated by HPLC (Figure 1A). Because broccoli is rich in fiber, which can act as a prebiotic altering the microbiome, we repeated the study heating the broccoli powder in water at 80 °C overnight (glucosinolate-free broccoli, Figure 1B). Results clearly show that 1,3-benzodithiole-2-thione was formed in a time-dependent manner and that the formation was far greater after 1 week feeding glucosinolates. We detected no compound at time 0, showing there was no contamination from diet. A further week’s feeding made no significant difference from 1 week’s feeding. Furthermore, feeding a broccoli diet free of glucosinolates for a week had no impact, showing that the glucosinolates were the effective component. However, because we had used benzene dithiol to estimate product, we were unable to identify specific product(s).

Bottom Line: Because humans typically cook their brassica vegetables, destroying myrosinase, there is a great interest in determining how human microbiota can hydrolyze glucosinolates and release them, to provide the health benefits of ITC.We found that addition of excess thiols released protein-thiol-bound ITC, but that the microbiome supports only poor hydrolysis unless exposed to dietary glucosinolates for a period of days.These findings explain why 3-5 servings a week of brassica vegetables may provide health effects, even if they are cooked.

View Article: PubMed Central - PubMed

Affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.

ABSTRACT
Brassicales contain a myrosinase enzyme that hydrolyzes glucosinolates to form toxic isothiocyanates (ITC), as a defense against bacteria, fungi, insects and herbivores including man. Low levels of ITC trigger a host defense system in mammals that protects them against chronic diseases. Because humans typically cook their brassica vegetables, destroying myrosinase, there is a great interest in determining how human microbiota can hydrolyze glucosinolates and release them, to provide the health benefits of ITC. ITC are highly reactive electrophiles, binding reversibly to thiols, but accumulating and causing damage when free thiols are not available. We found that addition of excess thiols released protein-thiol-bound ITC, but that the microbiome supports only poor hydrolysis unless exposed to dietary glucosinolates for a period of days. These findings explain why 3-5 servings a week of brassica vegetables may provide health effects, even if they are cooked.

No MeSH data available.


Related in: MedlinePlus