Abstract
Dietary R-sulforaphane is a highly potent inducer of the Keap1/Nrf2/ARE pathway. Furthermore, sulforaphane is currently being used in clinical trials to assess its effects against different tumour processes. This study reports an efficient preparation of enantiopure R-sulforaphane based on the enzymatic hydrolysis of its natural precursor glucoraphanin. As an alternative to broccoli seeds, we have exploited Tuscan black kale seeds as a suitable source for gram-scale production of glucoraphanin. The defatted seed meal contained 5.1% (w/w) of glucoraphanin that was first isolated through an anion exchange chromatographic process, and then purified by gel filtration. The availability of glucoraphanin (purity ≈ 95%, weight basis) has allowed us to develop a novel simple hydrolytic process involving myrosinase (EC 3.2.1.147) in a biphasic system to directly produce R-sulforaphane. In a typical experiment, 1.09 g of enantiopure R-sulforaphane was obtained from 150 g of defatted Tuscan black kale seed meal.
Highlights
Since dietary sulforaphane (4R-1-isothiocyanato-4-(methylsulfinyl)butane; R-sulforaphane; CAS RN [142825-10-3]) was isolated from broccoli [1], several hundred papers have focused on this isothiocyanate (ITC), which is one of the most potent naturally occurring inducers of theKeap1/Nrf2/ARE pathway [2]
Several methods for the purification of natural R-sulforaphane are based on the separation of the compound from complex mixtures of ITCs present in water extracts of broccoli seed or seed meal after myrosinase hydrolysis
Those methods are based on low-pressure column chromatography [12], solid phase extraction coupled with preparative HPLC [13] and macroporous resin [14], but generally, the yield and/or purity of the obtained R-sulforaphane were limited
Summary
Since dietary sulforaphane (4R-1-isothiocyanato-4-(methylsulfinyl)butane; R-sulforaphane; CAS RN [142825-10-3]) was isolated from broccoli [1], several hundred papers have focused on this isothiocyanate (ITC), which is one of the most potent naturally occurring inducers of the. Several methods for the purification of natural R-sulforaphane are based on the separation of the compound from complex mixtures of ITCs present in water extracts of broccoli seed or seed meal after myrosinase hydrolysis. Those methods are based on low-pressure column chromatography [12], solid phase extraction coupled with preparative HPLC [13] and macroporous resin [14], but generally, the yield and/or purity of the obtained R-sulforaphane were limited. The gram-scale availability of purified GRA has allowed us to develop a novel hydrolytic process involving myrosinase in a biphasic system (Scheme 1) to produce enantiopure R-sulforaphane as a single product in 99% yield without the need of any further chromatographic steps
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