## 1 Introduction  
Polyphenols are secondary metabolites produced by plants and also found in many natural products, such as fruit and vegetables, and their derivatives, such as tea, coffee, olive oil, and wine [1, 2, 3]. Polyphenols are well known for their antioxidant properties, which confer to them health-beneficial effects [4, 5, 6, 7]. Among them, resveratrol is probably one of the most investigated molecules. It was first described in 1940 by [PERSON], a Japanese student who was investigating extracts from traditional medicinal plants and called it \"resveratrol\" because the molecule had been extracted from the roots of _Ventrum grandiflora_ (white helebore) and presented the skeleton of resorcinol in its molecular structure [8]. The extract from this plant was exploited for treating several allergic and inflammatory diseases, among others. However, this molecule did not attract much interest until 1997, when [PERSON] and colleagues published an article regarding its cancer chemopre activity [9]. Resveratrol is the common name for 3,54\({}^{\prime}\)-trihydroxy-_trans_-stilbene, a natural photolexin derived from phenylpropanoids, that is synthesized in plants under stress conditions, such as infections or UV exposure. Under UV radiation it rapidly isomerizes to the _cis_ geometric form, but this compound, despite interesting biological activity, has been less investigated because of its lower abundance [10]. Nevertheless, the _trans-cis_ isomerization and fluorescence are the main deactivation pathways, although dependent on the environmental conditions [11, 12]. The _trans_-Resveratrol can be extracted in its free form or as glucoside directly from the plant but grapes are the preferred source due to the ease of extraction. Small concentrationsof _cis_-resveratrol can be also present in wines despite its lack in grapes, suggesting its formation because of yeast isomerases during the fermentation process. Similar to other polyphenols, resveratrol has multiple biological activities and many beneficial effects, such as anti-inflammatory and antioxidant properties, mainly related to its ability to scavenge free radicals, and, as such, it can also have a positive influence on the pathologies developed due or related to oxidative stress, such as cancer (Figure 1) [13,14]. Nevertheless, some controversial results have been published in the literature, especially regarding its in vivo usefulness [15,16]. In fact, only a small portion of the ingested resveratrol reaches the body tissues, despite up to 70% being found in plasma, due to its quick liver metabolism, especially to glucuronide and sulfate conjugates, and excretion [17]. This limits enormously its exploitation, especially considering that the amount normally ingested (e.g., up to 5 mg/L in red wine) can reach plasma concentrations that are much lower than those tested in vitro (e.g., 30-100 \(\upmu\)M). However, the use of novel technological approaches could help overcome this limitation, thus improving resveratrol bioavailability [18]. In addition, this natural compound has the capacity to modulate several biochemical pathways. For example, it has been shown that treatment with resveratrol of Parkin-null fibroblasts, isolated from patients with Parkinson's disease (PD), was able to increase mitochondrial biogenesis, followed by the partial rescue of mitochondrial functions and oxidative stress, through activation of the 5'-adenosine monophosphate-activated protein kinase (AMPK)/sirtu1 (SIRT1)/peroxisome proliferatorator-activated receptor gamma coactivator 1-alpha (PGC-1\(\upalpha\)) pathway [19]. Moreover, Parkin-null primary fibroblasts are characterized by changes in the oxidative balance, and the loss of reduced glutathione (GSH) with an increase of its oxidized form (GSSG) is one of the earliest biochemical changes detectable. Resveratrol treatment of these cells contributes to preservation of  
Figure 1: Chemical structure of _trans_-resveratrol (in the dark-red rectangle) and main biological pathways affected.