Phenolic compounds are a large group of phytochemicals widespread in the plant kingdom. Depending on their structure they can be classified into simple phenols, phenolic acids, hydroxycinnamic acid derivatives and flavonoids. Phenolic compounds have received considerable attention for being potentially protective factors against cancer and heart diseases, in part because of their potent antioxidative properties and their ubiquity in a wide range of commonly consumed foods of plant origin. The Brassicaceae family includes a wide range of horticultural crops, some of them with economic significance and extensively used in the diet throughout the world. The phenolic composition of Brassica vegetables has been recently investigated and, nowadays, the profile of different Brassica species is well established. Here, we review the significance of phenolic compounds as a source of beneficial compounds for human health and the influence of environmental conditions and processing mechanisms on the phenolic composition of Brassica vegetables.

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Glucosinolates are sulphur compounds that are prevalent in Brassica genus. This includes crops cultivated as vegetables, spices and sources of oil. Since 1970s glucosinolates and their breakdown products, have been widely studied by their beneficial and prejudicial biological effects on human and animal nutrition. They have also been found to be partly responsible for the characteristic flavor of Brassica vegetables. In recent years, considerable attention has been paid to cancer prevention by means of natural products. The cancer-protective properties of Brassica intake are mediated through glucosinolates. Isothyocianate and indole products formed from glucosinolates may regulate cancer cell development by regulating target enzymes, controlling apoptosis and blocking the cell cycle. Nevertheless, variation in content of both glucosinolates and their bioactive hydrolysis products depends on both genetics and the environment, including crop management practices, harvest and storage, processing and meal preparation. Here, we review the significance of glucosinolates as source of bioactive isothiocyanates for human nutrition and health and the influence of environmental conditions and processing mechanisms on the content of glucosinolate concentration in Brassica vegetables. Currently, this area is only partially understood. Further research is needed to understand the mechanisms by which the environment and processing affect glucosinolates content of Brassica vegetables. This will allow us to know the genetic control of these variables, what will result in the development of high quality Brassica products with a healthpromoting activity.

Kales (Brassica oleracea acephala group) are important vegetable crops in traditional farming systems in the Iberian Peninsula. They are grown throughout the year to harvest their leaves and flower buds. The glucosinolate content of kales is dependent upon the environmental factors, plant part examined, phenological stage of plant growth, and level of insect damage. The objectives of this study were to evaluate the changes in the total and individual glucosinolate concentrations during plant development and to determine if significant variation of glucosinolate levels can be explained by insect pests attack and other environmental factors in four locations in northwestern Spain. The total glucosinolate concentration in leaves of B. oleracea increased with plant age from seedling to early flowering stages. At that stage, the aliphatic glucosinolate content in leaves of B. oleracea declined drastically over time as the content in the flower buds increased. The highest contents of indolyl glucosinolate (glucobrassicin) and of the aromatic glucosinolate occurred in leaves harvested at the optimum consumption stage while flower buds contained the highest concentration of aliphatic glucosinolates, especially sinigrin. Sinigrin is reported to have anticarcinogenic properties. There appears to be a loss of total and individual glucosinolate concentrations related to pest attack. Leaves damaged by lepidopterous pests contained a lower total glucosinolate content (25.8 micromol g-1 dw) than undamaged leaves (41 micromol g-1 dw). The amounts of sinigrin, glucoiberin, and glucobrassicin were also lowest in insect-damaged leaves. Environmental factors such as soil properties and temperature appear to influence the glucosinolate content in leaves although more research on this subject is needed.

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Introduction – Brassica vegetables have been related to the prevention of cancer and degenerative diseases, owing to their glucosinolate and phenolic content.Objective – Identification of glucosinolates, flavonoids and hydroxycinnamic acids in representative varieties of kale, cabbage and leaf rape.Methodology – One local variety of each crop was evaluated in this study using a multi‐purpose chromatographic method that simultaneously separates glucosinolates and phenolics. Chromatograms were recorded at 330 nm for flavonoid glycosides and acylated derivatives and 227 nm for glucosinolates.Results – Eight glucosinolates were identified in kale and cabbage, which exhibited the same glucosinolate profile, and 11 glucosinolates were identified in leaf rape. Furthermore, 20 flavonoids and 10 hydroxycinnamic acids were detected in kale and cabbage, while 17 flavonoids and eight hydroxycinnamic acids were found in leaf rape.Conclusions – This study has provided a deeper and comprehensive identification of health‐promoting compounds in kale, cabbage and leaf rape, thus showing that they are a good source of glucosinolates and phenolic antioxidants. Copyright © 2011 John Wiley & Sons, Ltd.

18Cooking Brassica vegetables as a domestic processing method has a great 19 impact on health-promoting bioactive compounds: glucosinolates (GLS), flavonoids, 20 hydroxycinnamic acids, and vitamin C. In Galicia (NorthWestern Spain), one of the 21 most consumed horticultural crops is Brassica rapa, by using the leaves (turnip greens) 22 and the young sprouting shoots (turnip tops) in different culinary preparations. In order 23to determine the effect of cooking, on turnip greens and turnip tops, bioactive GLS, 24 flavonoids, hydroxycinnamic acids and vitamin C were analysed and simultaneously 25 determined. The level of retention of each individual compound after cooking 26 procedures was evaluated in the edible organs, and we also in the cooking water, in 27 order to compare their composition to a fresh uncooked control. Steaming, conventional 28 boiling, and high-pressure cooking, traditional processing methods of this kind of 29 vegetables, were the three domestic processing methods used in this work. Results 30 showed that total GLS and phenolics were significantly affected by the cooking 31 procedure and the loss rate varied among individual compounds. Steaming was the 32 method that better preserved GLS and phenolic compounds. Conventional boiling and 33 high-pressure cooking methods presented similar rate of losses of total GLS content 34 (64%) and total phenolic content (more than 70%). Degradation among glucosinolate 35 classes, aliphatic or indolic, was similar. The total flavonoids lost in turnip greens were 36 64% and 67% for conventional boiling and high-pressure, respectively. The main losses 37 were caused by leaching into the cooking water. The concentration of vitamin C 38 suffered a drastic loss in the process of sample handling and after cooking. Despite the 39 fact that any cooking procedure affected negatively the nutritional composition of the 40 turnip greens and tops, our results showed high retentions of individual compounds in 41 steaming, and the lowest retentions were obtained in the traditional high-pressure 42 ACCEPTED MANUSCRIPT 3 cooking. High retention of health-promoting compounds in the cooking water should be 43 considered for increasing the intake of properties of Brassica rapa. 44