Resveratrol (trans-resveratrol) is a produced naturally by several plants when under attack by such as or . Resveratrol has also been produced by chemical synthesis and is sold as a derived primarily from . In mouse and rat experiments, anti-cancer, , blood-sugar-lowering and other beneficial cardiovascular effects of resveratrol have been reported. Most of these results have yet to be replicated in humans. In the only positive human trial, extremely high doses (35 g) of resveratrol in a proprietary formulation have been necessary to significantly lower blood sugar. Resveratrol is found in the skin of red grapes and is a constituent of red wine, but apparently not in sufficient amounts to explain the . Experiments have shown that resveratrol treatment extended the life of fruit flies, nematode worms and short-lived fish but it did not increase the life span of mice.