Several species from the Brassica genus are very important agricultural crops in different parts of the world and are also known to be heavy metal accumulators. There have been a large number of studies regarding the tolerance, uptake and defense mechanism in several of these species, notably Brassica juncea and B. napus, against the stress induced by heavy metals. Numerous studies have also been published about the capacity of these species to be used for phytoremediation purposes but with mixed results. This review will focus on the latest developments in the study of the uptake capacity, oxidative damage and biochemical and physiological tolerance and defense mechanisms to heavy metal toxicity on six economically important species: B. juncea, B. napus, B. oleracea, B. carinata, B. rapa and B. nigra.

In this study, the lipophilic and hydrophilic phenol composition of virgin olive oils (VOO) obtained from olives from two of the most important Portuguese cultivars ('Galega Vulgar' and 'Cobrançosa'), harvested at different ripening stages and under two irrigation schemes (rain fed and irrigated), was evaluated. Phenolic alcohols (hydroxytyrosol and tyrosol), phenolic acids and derivatives and flavonoids (luteolin and apigenin), as well as tocopherols were quantified. Lipophilic (>300mgkg(-1)) and hydrophilic phenols (>600mgkg(-1)) were present in high contents in both VOO, for early ripening stages. Gamma-tocopherol content is higher in 'Galega Vulgar' VOO. Total phenols showed a decrease between ripening index 2.5 and 3.5. The dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), also known as oleacein, was the major phenolic compound identified in both oils. The concentration of free hydroxytyrosol and tyrosol in both VOO is very low while their esterified derivatives, like 3,4-DHPEA-EDA and p-HPEA-EDA, are much more abundant.

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acid in olive oils were observed. The ripening stage of fruits showed to be a key factor on the amount and profile of bioactive compounds of olive oil.

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Tobacco (Nicotiana tabacum L.) is a tolerant species that accumulates cadmium. We studied the effect of Cd (0, 10, 25, 50, 100 lM) on growth parameters, chlorophyll and proline contents, enzymatic antioxidative response and lipid peroxidation of tobacco plants grown in hydroponic culture for 11 days to clarify the strategy of plant response against oxidative stress caused by this heavy metal. Cadmium accumulated more in roots than in shoots. Plant growth was not significantly affected by the cadmium concentrations used. Young leaves were more affected, showing visible chlorosis and a significant decrease in chlorophyll content at high Cd concentrations. Dry weight of both leaves and roots increased indicating a lower capacity for roots to absorb water. An increase in malondialdehyde levels was observed, indicating that lipid peroxidation occurred as a result of ROS formation. The activity of guaiacol peroxidase in leaves increased, indicating that it was very important in the scavenging of H 2 O 2 , while superoxide dismutase activity only increased in old leaves. Ascorbate peroxidase showed constant activity levels in tobacco leaves, suggesting that the ascorbate-glutathione pathway was less important as a defense mechanism.