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.