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Resveratrol, a plant phenolic compound, is found in grapes and red wine, but is not widely distributed in other common food sources. The pathway for resveratrol biosynthesis is well characterized. Metabolic engineering of this compound has been achieved in tomato plants (Lycopersicon esculentum Mill.) in order to improve their nutritional value. Tomato plants synthesizing resveratrol were obtained via the heterologous expression of a grape (Vitis vinifera L.) cDNA encoding for the enzyme stilbene synthase (StSy), under the control of the fruit-specific promoter TomLoxB or the constitutive CaMV 35S promoter. The resulting 35S plants accumulate resveratrol in all the tissues, but in the highest amount in the fruits. While, as expected, LoxS transgenic plants only accumulate it in the fruits, in particular in the skin of the mature fruits. Quantitative analyses carried out on LoxS fruits were compared with those of 35S tomato lines. The LoxS fruits contained levels of trans -resveratrol that were 20-fold lower than those reported for the 35S line. The total antioxidant capability, ascorbate and gluthatione contents were also evaluated. A significant increase in all these antioxidant paramenters was found in the LoxS and 35S lines. These results could explain the higher capability that extract from transgenic fruits have to counteract the pro-inflammatory effects of phorbol ester in monocyte- macrophages via the inhibition of induced cyclo-oxygenase-2 enzyme.

Tomato fruit contains only small amounts of flavonoids, and do not produce any stilbenes. With the aim of generating plants and fruits with increased antioxidant capacity and a wider range of potential health benefits, the tomato flavonoid route was modified through the over-expression of the grape stilbene synthase cDNA. The expression of the StS gene in tomato tissues caused the synthesis of new compounds, not present in either wild type or vector transformed plants, which were identified as trans-resveratrol and trans-resveratrol-glucopyranoside and which have a different tissue specificity, both depending on the promoter used and on the amount of precursors present in the tissues. Since the free radical scavenging capabilities of resveratrol are well known, we wanted to analyse whether its presence in tomato plants and fruit affected the level and/or the metabolism of other antioxidants normally present in tomato. The results here reported indicate that the synthesis of resveratrol affects certain metabolic routes related to primary antioxidants in different ways, according to the levels of resveratrol produced in the tissue.

There is a growing interest in producing food plants with increased amounts of antioxidants because of their potential health benefits. In particular polyphenol, secondary metabolites, such as flavonoids and stilbenes, have a great antioxidant activity, important both for plant physiology and human nutrition. With the aim of generating plants and fruits with increased antioxidant capacity and a wider range of potential health benefits, the tomato flavonoid route was modified through the over-expression of the grape stilbene synthase cDNA under constitutive promoter and a tissue specific, TomLoxB, promoter. The expression of the StS gene in tomato tissues caused the synthesis of new compounds, identified as trans-resveratrol and trans-resveratrol-glucopyranoside which have a different tissue specificity, both depending on the promoter used and on the amount of precursors present in different tissues. In order to verify the metabolic impairment, the amounts of soluble phenolics (i.e. chlorogenic acid) flavonoids (i.e. naringenin) and flavonols (i.e. rutin, and quercetin), in both transgenic and wild type fruits tissues at different stages of maturity, were compared. The results indicate that the stilbenes and the flavonoids found in transgenic plants are present as conjugates. Since the free radical scavenging capabilities of resveratrol are well known, we wanted to analyse whether its presence in tomato fruit affected the level and/or the metabolism of other antioxidants naturally present in tomato. The synthesis of resveratrol affects the other antioxidants in different ways, in particular ascorbate was increased in the transformed tissues. The alteration of ascorbate seem to be proportional to the amount of the resveratrol accumulated in the different tissues. Our results support the view-point that cross-talk between endogenous and introduced pathways is much more complex that the simple competition of enzymes for the same substrates.

SARS-CoV-2 first emerged in China during late 2019 and rapidly spread all over the world. Alterations in the inflammatory cytokines pathway represent a strong signature during SARS-COV-2 infection and correlate with poor prognosis and severity of the illness. The hyper-activation of the immune system results in an acute severe systemic inflammatory response named cytokine release syndrome (CRS). No effective prophylactic or post-exposure treatments are available, although some anti-inflammatory compounds are currently in clinical trials. Studies of plant extracts and natural compounds show that polyphenols can play a beneficial role in the prevention and the progress of chronic diseases related to inflammation. The aim of this manuscript is to review the published background on the possible effectiveness of polyphenols to fight SARS-COV-2 infection, contributing to the reduction of inflammation. Here, some of the anti-inflammatory therapies are discussed and although great progress has been made though this year, there is no proven cytokine blocking agents for COVID currently used in clinical practice. In this regard, bioactive phytochemicals such as polyphenols may become promising tools to be used as adjuvants in the treatment of SARS-CoV-2 infection. Such nutrients, with anti-inflammatory and antioxidant properties, associated to classical anti-inflammatory drugs, could help in reducing the inflammation in patients with COVID-19.