Polyphenolic compounds in artichoke varieties and regulation of their synthesis in artichoke

Polyphenols are widespread constituents of plants that have been used in the treatment of diseases for centuries. The current growing interest in dietary plants has led to renewed attention on artichoke, because of its high polyphenolic content. Polyphenolic artichoke extracts have surprising pharmacological and biochemical effects, such as a marked antioxidative potential and cancer chemopreventive properties. Hence, there is considerable interest in improving our understanding of polyphenol biosynthesis and its regulation in artichoke, to enhance the levels of these bioactive molecules in plants used as food, starting from the evaluation of phenolic content of different genotypes. A combination of genetic and biochemical analyses was used to help identifying genes involved in the accumulation of polyphenols and characterizing different artichoke varietal types diffused in the Mediterranean region by polyphenolic content. Six traditionally cultivated varieties of artichoke (Mola, Tondo di Paestum, Sant'Erasmo, Bianco di Ostuni, Blanca de Tudela and Violet de Provence) were selected, and qualitative and quantitative evaluations of phenolic profile were carried out on different artichoke tissues (three bract orders and receptacle of flower heads and leaves) in several developmental stages, by HPLC and mass spectrometry analyses. Our results show that polyphenols content mainly depend on the genotype and part of the plants. Total polyphenols were more abundant in leaves than in heads, while cynarin and chlorogenic acid (CGA) were the most abundant hydroxycinnammates (mainly in capitula). The fine regulation of biosynthetic pathway leading to the accumulation of phenylpropanoids is achieved by combinatorial actions of transcription factors (TF) belonging to various classes, among which MYB TF. Two putative MYB TF genes were isolated from artichoke (Tondo di Paestum and Locale di Mola), which showed a high similarity to MYB12 TF of other plant species (e.g. Arabidopsis, tomato). These genes were over-expressed under UV-light stress conditions. Total polyphenols content will be measured in artichoke tissues to possibly confirm correlation of the artichoke MYB factors with accumulation of these compounds. Heterologous expression in bacteria and quantitative real-time PCR are being performed to gain insights into the molecular mechanism of polyphenols regulation in this edible plant, contributing to future progress in the study of polyphenols accumulation.