Micellar electrokinetic capillary chromatography (MECC) was used to follow the myrosinase (β-thioglucoside glucohydrolase EC 3.2.3.1)-catalyzed transformation of glucobrassicin (indol-3-ylmethylglucosinolate, 1a) and neoglucobrassicin (N-methoxyglucobrassicin, 1b) into nitriles, ascorbigens, and other products. The influence of pH, ascorbic acid, and Fe(II) ions was investigated. In the presence of ascorbic acid, (5 mM), thiocyanate ion and ascorbigens were the dominating products from 1a and 1b. In the presence of Fe(II) ions (2.5 mM), nitriles were the dominating products between pH 4 and 6−7. During hydrolysis of 1b in neutral or weakly basic solution, an unstable intermediate was detected by MECC. Comparisons of the rate of ascorbigen formation from 1a, 1b, and indol-3-ylcarbinol showed that ascorbigens were formed directly from ascorbate and unstable products of the hydrolysis of indole glucosinolates and that indol-3-ylcarbinols were not important intermediates. Structures of 1a, 1b, and products of 1b were confirmed by 1H NMR, MS, and UV spectroscopy. Keywords: Indole glucosinolate; myrosinase; ascorbigen; isothiocyanate; nitrile

Content of total and individual glucosinolates were determined in, `Marathon' broccoli florets (Brassica olerucea L. var. italica stored 7 days at 10C under air, 0.5% O2, 0.5% O2 + 20% CO2 or 20% CO2 atmosphere, followed by transfer to air for 2 days. `Marathon' broccoli contained glucoraphanin, glucobrassicin, neoglucobrassicin, glucoiberin, 4-methoxyglucobrassicin, progoitrin, glucoalyssin, and gluconasturtiin. The methylssulfinylalkylglucosinolates (glucoiberin and glucoraphanin) and the indol-3-ylmethylglucosinolates (glucobrassicin, neoglucobrassicin and 4-methoxyglucobrassicin) accounted for 78% and 20% of the total content, respectively, in freshly harvested broccoli. CA treatment and storage time had no significant effect on the relative content of these two groups of glucosinolates. Freshly harvested broccoli contained 47 μmol glucosinolate/g dry weight. The total glucosinolate content increased 42% and 21% during 7 days storage under air and 0.5% O2 + 20% CO2, respectively, as compared to freshly harvested broccoli, and decreased 15% in broccoli stored under 20% CO2. Treatment with 20% CO2 in the absence of 0, resulted in visible CO, injury and water soaking of the tissue. Aeration had no significant effect on total glucosinolate content but reduced the glucobrassicin content 35% in broccoli stored 7 days under 0.5% O2 + 20% CO2 or 20% CO2 atmosphere. In contrast, the 4-methoxyglucobrassicin content increased during storage under low O2 atmosphere and increased further after transfer to air.

Consumption of plants of the species Brassica oleracea is related to a decreased incidence of certain cancer forms in humans, and this has been linked to the presence of glucosinolates in those vegetables. After ripe seeds, sprouts of some brassicaceous plants contain the highest concentration of these compounds and are therefore a good source of glucosinolates for chemoprotection. In the present experiments, the content and distribution of glucosinolates was determined in ripe seeds and sprouts (seedlings) of five varieties of B. oleracea (white cabbage, red cabbage, Savoy cabbage, broccoli and cauliflower) by high performance liquid chromatography. The type and concentration of individual glucosinolates varied according to variety of B. oleracea, plant parts in which they occurred and the sprouting period of the seed. Concentration of alkyl glucosinolates decreased whereas that of indol-3-ylmethylglucosinolates increased throughout the sprouting period. Roots had the highest glucosinolate concentration in four and seven day old sprouts whereas at both sprouting times, cotyledons had the highest concentration of alkylthio-and alkylsulphinylglucosinolates. #

The potato cyst nematode (Globodera rostochiensis cv. Woll) is responsible for large yield losses in the potato crop, and opportunities for reducing the attack of these plant nematode species are, therefore, important. This study has been devoted to the testing of the in vitro effects on the potato cyst nematode of eight glucosinolates [prop-2-enyl-, but-3-enyl-, (R)-4-methylsulfinylbut-3-enyl-, benzyl-, phenethyl-, 4-hydroxybenzyl-, (2S)-2-hydroxybut-3-enyl-, and (2R)-2-hydroxy-2-phenylethylglucosinolate] as well as the effects of the products of this myrosinase-catalyzed hydrolysis. The glucosinolates were used at three concentrations, 0.05, 0.3, and 1.0 mg/mL, in the presence or absence of the enzyme myrosinase. The effects of the compounds on the mortality were monitored every 8 h for a 72 h period. No effects were found for any of the intact glucosinolates. However, when active myrosinase was included with 1 mg/mL phenethylglucosinolate at pH 6.5, 100% mortality was observed within just 16 h. A similar effect was achieved at the same concentration of benzyl- and prop-2-enylglucosinolates in the myrosinase-containing solutions, although longer exposures were required (24 and 40 h, respectively). The main aglucone products released from the glucosinolates with pronounced effects on the nematodes were shown to be the corresponding isothiocyanates. The results suggest that mixtures of these specific glucosinolates and active myrosinase or autolysis of plant materials containing these enzymes and glucosinolates might be used to control the potato cyst nematode in the soil.

Glucosinolates are amino acid derived allelochemicals present in all plants of the order Capparales. These compounds are degraded by myrosinase isoenzymes, releasing a series of biologically active products defined by the parent glucosinolate and the reaction conditions. Species within the Brassicaceae are found to differ in their glucosinolate profile and glucosinolate concentrations. Different tissues within a single plant also show such variations, which are further influenced by the growth stage and environmental conditions. In the experiments described in this paper, four Brassica species of the U-triangle (B. carinata, B. nigra, B. juncea and B. rapa) were compared with respect to their glucosinolate profiles in roots, stems, leaves and reproductive organs at different developmental stages. The glucosinolate profile of corresponding ripe seeds was also determined. Prop-2-enylglucosinolate was identified as the major glucosinolate in the three mustards, where it represented over 90% of the total glucosinolate concentration of ripe seeds and over 50% of green tissues. The relative concentration of this glucosinolate increased in all tissues during plant growth. Brassica rapa showed a different glucosinolate profile than the three mustards, with higher concentrations of but-3-enylglucosinolate, 2-hydroxybut-3-enylglucosinolate and 2-hydroxypent-4-enylglucosinolate. The concentration of indol-3-ylmethylglucosinolates was also higher in B. rapa than in the mustard plants, with 4-hydroxyglucobrassicin representing 30% of the total glucosinolate concentration in ripe seeds. The total glucosinolate concentration of the species studied varied with growth stage and the mustards achieved a maximum towards the end of the period monitored. Glucosinolate concentration decreased in roots and leaves but increased in reproductive tissues. The determined glucosinolate profiles are an initial step in assessing the biofumigation potential of these species of the Brassicaceae family.

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