Health Promoting Effects of Plant Antioxidants: Molecular Mechanisms Underlies the Biological Activities of Phytochemicals

The health benefit of plant-derived foods is established and new researches are identifying active plant derived molecules among the thousands phytochemicals. Some phytochemicals are antioxidants and have been proposed as effective anticancer agents. Among them, polyphenols and carotenoids, present in different foods and beverages, have retained attention in recent years. Polyphenols from grape seed extracts (GSE) possess a broad spectrum of chemo-protective properties and lycopene, found in tomatoes and other fruits, has been proposed to modulate hormonal and immune systems, metabolic pathways, and gap junction intercellular communication (GJIC). In animal cells, GJIC has been implicated in the cell growth control via adaptive responses: differentiation, proliferation and apoptosis. GJIC is deficient in many human tumors and its restoration or upregulation is associated with decreased cell proliferation. In the carcinogenesis process, the reversible inhibition of GJIC has been hypothesized to be involved in the tumor promotion phase. Some innovative, safe and environmentally-friendly processes, based on supercritical carbon dioxide (S-CO2) extraction and on subcritical water extraction (SWE) is developing for the production of antioxidants from plant matrices. GSE and new S-CO2-extracted oleoresins obtained from tomato and tomato added with grape seeds were analysed for antioxidant activities and biological properties on human keratinocytes and human breast cancer cell (MCF-7) cultures. Plant extracts showed the ability to enhance the GJIC and connexin 43 expression in human cell cultures, and were able to completely overcome the GJIC inhibition induced by the tumor promoter HgCl2. The knowledge of molecular mechanisms underlies the phytochemical effect and the availability of products with potentially healthy properties obtained from natural sources (e.g., tomato berries and waste winery by-products), by environmentally friendly methods, could lay new basis for preventive nutrition.