Antioxidants in Italian Head Lettuce (Lactuca sativa var. capitata L.) Grown in Organic and Conventional Systems under Greenhouse Conditions

Lettuce belongs to the Asteraceae family and it is native of the Mediterranean region. In our research, the effect of cultivation practices (organic versus conventional) on antioxidants in Italian head lettuce (Lactuca sativa var. capitataL.) grown in greenhouse was investigated. Bioactive molecule levels, antioxidant properties and the cytotoxicity of polyphenolic extracts from the edible part of head lettuce in Caco-2 cells were determined. FRAP values are 5.33±0.35 and 6.35±0.08mmol/kg in organic products and 4.83±0.16 and 1.80±0.04mmol/kg in conventional products. FRAP values differ significantly (P<0.001) between organic and conventional lettuces harvested in September. Significant differences are found between organic and conventional extracts in some target compounds such as quercetin, rutin, lutein, β-carotene and vitamin C. No difference in biological effect is observed between organic and conventional products harvested in July and in September, whereas a major cytotoxicity is found for polyphenol extracts derived from organic and conventional lettuces harvested in September

Structure–Activity Relationship of Resveratrol and Its Analogue 4,4'-Dihydroxy-Trans-Stilbene Toward the Endothelin Axis in Human Endothelial Cells

Resveratrol inhibits endothelin-1, a vascular tension regulator. We synthesized the resveratrol analogue 4,4’dihydroxy-trans-stilbene with 2 hydroxyl groups in the 4 and 4’ position to obtain a molecule more active than resveratrol (3,4’,5-trihydroxy-trans-stilbene). The results demonstrate that 4,4’-dihydroxy-trans-stilbene led to a significant decrease in total endothelin-1 secretion and in endothelin-1 messenger RNA (mRNA) levels in human endothelial cells. In addition, resveratrol and its analogue decreased endothelin-converting enzyme-1 mRNA levels and further reduced the activity of the enzyme. 4,4’-dihydroxy-trans-stilbene was more active than resveratrol because the new molecule exerted greater activity at the level of endothelin synthesis and conversion, even at a lower concentration. Although 4,4’-dihydroxy-trans-stilbene and resveratrol inhibited formation of reactive oxygen species and lipid peroxidation, the treatment of cells with different oxidant agents did not modify the endothelin-1 release. This finding suggests that the inhibition of endothelin-1 secretion is independent of the antioxidant properties of the 2 compounds. On the basis of these results, the resveratrol analogue 4,4’- dihydroxy-trans-stilbene could be a promising chemopreventive agent against cardiovascular disease