Resveratrol (3,4',5-trihydroxystilbene) belongs to a class of polyphenolic compounds called stilbenes (1). Some types of plants produce resveratrol and other stilbenes in response to stress, injury, fungal infection, or ultraviolet (UV) radiation (2). Resveratrol is a fat-soluble compound that occurs in a trans and a cis configuration (see figure 1).

Both cis- and trans-resveratrol also occur as glucosides (bound to a glucose molecule). Resveratrol-3-O-beta-glucoside is called piceid (3). Scientists became interested in exploring potential health benefits of resveratrol in 1992 when its presence was first reported in red wine (4), leading to speculation that resveratrol might help explain the “French Paradox” (see Cardiovascular Disease below).

More recently, reports on the potential for resveratrol to inhibit the development of cancer (5) and extend lifespan (6) in cell culture and animal models have continued to generate scientific interest.

Metabolism and Bioavailability

Although trans-resveratrol appears to be well-absorbed by humans when taken orally, its bioavailability is relatively low due to its rapid metabolism and elimination (7, 8).

Resveratrol metabolites are primarily detected upon oral exposure to trans-resveratrol. When six healthy men and women took an oral dose of 25 mg of trans-resveratrol, only traces of the unchanged resveratrol were detected in plasma (blood). Plasma concentrations of resveratrol and metabolites peaked around 60 minutes later at concentrations around 2 micromoles/liter (491 micrograms/liter) (7).

A study in 12 healthy men administered an oral dose of 25 mg of trans-resveratrol per 70 kg of body weight reported that serum concentration of resveratrol and metabolites peaked at 30 minutes after administration.

The concentration of total resveratrol (resveratrol and metabolites) ranged from 416 to 471 micrograms/liter, depending on whether resveratrol was administered in wine, vegetable juice, or grape juice (9). Results of another study suggested that the bioavailability of resveratrol from grape juice, which contains mostly glucosides of resveratrol (piceid), may be even lower than that of trans-resveratrol (10).

A recent study reported that bioavailability of trans-resveratrol from red wine did not differ when the wine was consumed with a meal (low- or high-fat) versus on an empty stomach (11).

Information about the bioavailability of resveratrol in humans is important because much of the basic research on resveratrol has been conducted in cultured cells exposed to unmetabolized resveratrol at concentrations that are often 10-100 times greater than peak concentrations observed in human plasma after oral consumption (12).

Although cells that line the digestive tract are exposed to unmetabolized resveratrol, research in humans suggests that other tissues are exposed primarily to resveratrol metabolites. Little is known about the biological activity of resveratrol metabolites, and it is not known whether some tissues are capable of converting resveratrol metabolites back to resveratrol (7).

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