It is an antioxidant (the label says so!)

Willamette Valley Vineyards has succeeded in having TTB approval in including the word "antioxidant" for two of their Pinot noir labels. (Vineyard claims first on wine antioxidant labeling -- Nutraingredients-USA)

Last year scientists at the University of Virginia concluded that resveratrol is the compound primarily responsible for the health benefits of red wine and claimed to have discovered its function in the prevention of cancer - starving cancer cells by inhibiting the action of nuclear factor- kappa B (NF-kB) protein that feeds them.

The vineyard itself has a comment piece on their site for the continued effort to get the antioxidant labeling for their other wines as well.