Broccoli Glucosinolates

Topic 1. Investigating the effect of food matrix on glucosinolates thermal degradation.

Glucosinolates (GSLs) are secondary plant metabolites that occur in members of the order Brassicales including Brassica crops, such as cabbage, rape, or broccoli. The consumption of Brassica vegetables is thought to be beneficial for human health because of breakdown products of the GSLs, namely isothiocyanates (ITCs). The latter being released enzymatically from GSLs by endogenous myrosinase after tissue disruption. During heat treatments (sterilisation, pasteurization, cooking) GLS are degraded yielding a large array of breakdown products including nitriles, epithionitriles, isothiocyanates and the like. It has been shown that the chemical environment GLS are in affect the rate of GLS thermal degradation which means that the same GLS will be degraded at different rates when occurring in different vegetal matrices. In addition, the relative amount of ITC and nitriles also may change according to the chemical environment.

Aim
In the present study we will investigate the effect of the vegetal matrix on thermal degradation of several GLS.
Proposed approach
In a set of experiments, different vegetables (not containing GLS) are selected, freeze dried and reconstituted with  water and GLS and subjected to heat treatments for different times. In a second set of experiments GLS are dissolved in aqueous/alcoholic extracts from different vegetables and subjected to heat treatment. After heat treatments GLS and ITCs are quantified in the samples and the relative effect of different vegetal matrix compared to the broccoli matrix.

References
Bones AM & Rossiter JT (2006) The enzymic and chemically induced decomposition of glucosinolates. Phytochemistry 67 (2006) 1053–1067.

For more information please contact Edoardo Capuano.

Topic 2. Investigating the effect of food matrix on the conversion of glucosinolates to isothiocyanates.

ITCs are the product of the degradation of glucosinolates catalyzed by myrosinase upon chewing and in general upon disintegration of the vegetal tissues. ITCs are supposed to be anti-carcinogenic. For that reason  the amount of ITCs in the vegetables at the moment of swallowing has a great importance. The conversion of GLS to ITC depends on the chemical environment myrosinase and GLS are in. Supposedly different chemical environment would differently affect myrosinase catalytic activity and the final content in ITCs. It is long known for instance that vitamin C affects myrosinase activity. Analogously it is known that a set of proteins exists in planta which can direct the enzymatic conversion of GLS towards specific breakdown products (nitriles, epithionitriles) rather than ITCs.

Aim
In the present study we will investigate the effect of vegetal matrix in general and vitamin C in particular on the extent of the conversion of GLS to ITCs catalysed by the enzyme myrosinase.
Proposed approach
Different vegetables from cruciferous and brassicaceae are selected and their GLS content and MYR activity is assessed in different part of the plant. After grinding of the vegetable matrix the amount of ITCs produced and the amount of residual GLS are measured. The matrix effect is established by calculating the conversion rate, i.e. the % of GLS hydrolysed (or ITCs produced) per unit of myrosinase activity. In a different set of experiments selected (part of) vegetable will be grounded after addition of variable amount of vitamin C and the conversion rate will be calculated.

References
Bones AM & Rossiter JT (1996) The myrosinase-glucosinolate system, its organisation and biochemistry. Physiologia Plantarum 97, 194–208.
Bones AM & Rossiter JT (2006) The enzymic and chemically induced decomposition of glucosinolates. Phytochemistry 67 (2006) 1053–1067.

For more information please contact Edoardo Capuano.

Topic 3. Effect of meal composition on the formation and bioaccessibility of isothiocyanates from broccoli.

Brassica vegetables are rich in glucosinolates (GLs), phytochemicals that can be hydrolysed by myrosinase (MYR), an endogenous plant enzyme. During mastication, plant cells are damaged and MYR catalyses the GL hydrolysis forming breakdown products including isothiocyanates (ITC), with anticarcinogenic properties.

A few small studies show the effect of different meal composition on ITC bioaccessibility. For instance, proteins may interact with ITC during digestion depending on the amino acid composition and the ITC type, reducing the ITC bioaccessibility. The in vitro digestion can be a useful tool to investigate the ITC formation and availability when eating broccoli along with other food components.

Objectives

The aims of  to investigate the effect of broccoli meal composition (like proteins, fibre, fat) on ITC formation and bioaccessibility by means of in vitro digestion.

The student will work on the in vitro digestion to digest broccoli along with different meal components. GLs (HPLC), and ITC (LC/MS) at different stage of the in vitro digestion will be monitored.

For more information please contact Teresa Oliviero.

Topic 4. Effect of meal composition on the formation and bioavailability of isothiocyanates  from broccoli.

Brassica vegetables are rich in glucosinolates (GLs), phytochemicals that can be hydrolysed by myrosinase (MYR), an endogenous plant enzyme. During mastication, plant cells are damaged and MYR catalyses the GL hydrolysis forming breakdown products including isothiocyanates (ITC), with anticarcinogenic properties.

A few small studies show the effect of different meal composition on ITC bioavailability. For instance, proteins may interact with ITC during digestion depending on the amino acid composition and the ITC type, reducing the ITC bioavailability.
Objectives
The aims of  to investigate the effect of broccoli meal composition (like proteins, fibre, fat) on ITC formation and bioavailability by means of in in vivo digestion.
The student will work on a human intervention study, in which participants will eat different broccoli products (with proteins, fibre, fat)  (GLs analyzed by HPLC) and will collect 24 h spot urines.  The intake on ITC will be analyzed in the urine (LC/MS).

For more information please contact Teresa Oliviero.

Topic 5. Functional pasta enriched with broccoli - In vitro bioaccessibility of isothiocyanate.

Brassica vegetables are rich in glucosinolates (GLs), phytochemicals that can be hydrolysed by myrosinase (MYR), an endogenous plant enzyme. During mastication, plant cells are damaged and MYR catalyses the GL hydrolysis forming breakdown products including isothiocyanates (ITC), with anticarcinogenic properties.

Pasta enriched with broccoli can be a good  strategy to increase the vegetables intake, because (1) pasta is routinely consumed (2) dry pasta is a perfect carrier to stabilize phytochemicals that otherwise are easily degraded. 

Objectives
The aims of  to investigate the effect incorporation of broccoli in functional pasta  on ITC formation and bioaccessibility by means of in vitro digestion.

The student apply the in vitro digestion to digest broccoli pasta. GLs (HPLC), and ITC (LC/MS) at different stages of the in vitro digestion will be monitored.  

For more information please contact Teresa Oliviero.