## 2 Sources and Absorption of Resveratrol  
The primary dietary sources of resveratrol include grapes, wine, apples, peanuts, and soy. Still, since the concentration of resveratrol present in all these food products is highly variable, it would be difficult to accurately estimate the average daily intake. This is related both to the fact that exogenous biological and physical stressors affect the resveratrol content in a specific food or drink and to the fact that endogenous factors interfere with the biosynthesis of resveratrol. Among the many varieties, wines made from grapes of the Pinot Noir and San Laurent showed the highest level of _trans_-resveratrol. Nevertheless, red wines, such as those from Salento, are rich in this natural antioxidant, along with others [41; 42]. The resveratrol content is also influenced by various aspects of the wine-making process, including temperature, pH value, and SO\({}_{2}\) level. However, getting a minimal health-beneficial dose of resveratrol through wine would mean drinking several liters. For this reason, some manufacturers sell pharmaceutically manufactured supplements with exactly specified resveratrol content. Nevertheless, the clinical potential of resveratrol in humans is somewhat difficult to estimate because there is still insufficient information on the optimal dosage, biotransformation, potential side effects, and pharmacokinetic parameters. In fact, resveratrol is characterized by a reduced bioavailability linked to its ability to be rapidly metabolized and subsequently eliminated in the urine and feces [17]. The low availability of this compound is often associated with its low solubility in water (\(\sim\)3 mg/100 mL) and the high permeability of the intestinal membrane. In fact, after oral administration, resveratrol is absorbed in the intestine by passive diffusion or thanks to membrane transporters. It can then be metabolized by glucuronidation and sulfation of the phenolic group (yielding resveratrol-4-O-glucuronwide, resveratrol-3-O-glucuronide, and resveratrol-3-O-sulfate, respectively) or by hydrogenation of the aliphatic double bond and is subsequently released in the bloodstream, as observed in clinical trials [43; 44]. In the bloodstream, resveratrol can bind to proteins such as albumin or to lipoproteins, such as LDL, forming complexes that dissociate when, at the cell membrane level, LDL and albumin interact with specific receptors, allowing the entry of stilbene into the cell [45]. In plasma, the concentration of unmodified free resveratrol is extremely low (around 1% of the ingested amount) and it generally depends on the ingested dose. However, exceptionally high amounts can be associated with a number of side effects, including diarrhea, nausea, and abdominal pain. Since one of the major obstacles related to the administration of this antioxidant compound is its bioavailability, numerous research and studies focus precisely on the improvement of the pharmacokinetic profile of resveratrol [46]. To this aim, different approaches have been proposed, such as those based on the use of emulsions and solid dispersions or on the encapsulation of resveratrol in nanocarriers, such as liposomes, micelles, and polymeric nanoparticles [47; 48; 49]. It is also possible to use a similar compound extracted from the roots of the _Polygonum Cuspidatum_ plant, namely, polydatin, which differs from resveratrol by one molecule of glucose (Figure 2) [50; 51]. The presence of the conjugated carbohydrate makes the molecule more water-soluble, increasing its bioavailability. Other polyphenols present in red wine, such as quercetin, catechins, and gallic acid, could also potentially function as chemoprevertive agents. For example, a mixture of polyphenols extracted from vine shoots showed anti-proliferative activity superior to resveratrol alone in cancer cells due to a synergistic action between the various polyphenols [52; 53].