###### Abstract  
Variations in the concentration of glucoraphanin (GRA) and glucoerucin (GER), as well as the corresponding breakdown products, isothiyanates (ITCs) and nitriles, were investigated during the growth of broccoli sprouts. The concentrations of GRA and GER decreased sharply from 33.66 umol/g to 11.48 umol/g and 12.98 umol/g to 8.23 umol/g, respectively, after seed germination. From the third to the seventh day, both GRA and GER were maintained as relatively stable. The highest concentrations of sulforaphanne (17.16 umol/g) and enucin (12.26 umol/g) were observed on the first day. Hereafter, the concentrations of nitrile hydrolyzed from GRA or GER were higher than those of the corresponding ITCs. Moreover, the ratio of sulforaphanne nitrile decreased from 1.35 to 0.164 from 1 d to 5 d, with a similar trend exhibited for erucin/erucin nitrile after 2 d. RNA-seq analysis showed that _BolMYB28_ and _BolCYP83A1_, involved in aliphatic glucosinolate (GSL) biosynthesis, remained largely unexpressed until the third day. In contrast, the genes operating within the GSL-myrosinase hydrolysis pathway were highly expressed right from the beginning, with their expression levels increasing significantly after the third day. Additionally, we identified two _BolESPs_ and six _BolNPS_ that might play important roles in promoting the production of nitriles during the development of broccoli sprouts. broccoli sprout glucosinolate; RNA-seq; sulforaphanne; erucin +
Footnote †: journal: plants  
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well as their protection against cardiovascular diseases [1; 5]. Sulforaphane, derived from glucoraphanin (GRA) according to TGG hydrolysis, is well known for its chemopreventive and anti-inflammatory properties, in vitro, in vivo, and in preclinical trials [1; 5; 6]. Erucin, another ITC hydrolyzed from glucoerucin (GER), also shows various health benefits [7; 8]. Furthermore, in vivo studies have shown the inter-conversion between sulforaphane and erucin in human subjects [9; 10; 11]. However, simple nitriles and epithionitriles from GSLs have shown limited ability to induce quinone reductase or glutathione \(S\)-transferase or inhibit cancer cell growth [12; 13]. Moreover, some simple nitriles may even have genotoxic effects in HepG2 cells [14]. Notably, some intact GSLs themselves have recently been found to have health-promoting effects. For example, GER possesses good direct as well as indirect antioxidant activity and effectively decomposes hydrogen peroxide and alkyl hydroperoxides [15]. Furthermore, GRA and GER could up-regulate cytochrome P450 and phase II enzyme systems in precision-cut rat lung slices [16]. However, the bioavailability of ITCs from fresh broccoli sprouts is dramatically higher than the broccoli supplements lacking TGFs [9]. Given the varying biological effects of GSL metabolites, we need to clarify the changing patterns of these health-promoting GSL profiles and their breakdown products during broccoli sprouting. GRA and GER are aliphatic GSLs derived from methionine and transplanted from biosynthesis cells to seeds [17; 18]. In plants, GER can be catalyzed by a subclade of flavimonooxygenases into GRA [19]. GRA and GER are the predominant health-promoting GSL profiles and greatly accumulate in broccoli seeds [20; 21]. However, compared to GRA and sulforaphane, GER and erucin in broccoli sprouts have received relatively little attention. Previous studies have reported genetic variation in GSLs and their breakdown products in broccoli seeds [20] and sprouts [22]. Some studies have highlighted the role of BolESPs in promoting the production of nitriles in broccoli florets [12; 13] and sprouts [23], as well as Chinese kale sprouts [24]. However, some research on _Arabidopsis_ has shown that some NSPs also play a role in nitrile production during GSL hydrolysis [25; 26].