(WSJ) - Scientists on opposite sides of the globe appear to be getting closer to harnessing one of red wine’s most elusive health-giving ingredients and putting it into a pill.

The ingredient, resveratrol, has been touted for years for its ostensible powersto prolong life and protect against a range of ailments including heart disease, diabetes and Alzheimer’s disease. Studies pointing to those benefits have been performed in laboratories on yeast, worms, fruit flies and mice, among other organisms.

Testing those benefits in humans has proved more complex. Resveratrol occurs naturally in red wine at such low concentrations, and in combination with so many other substances, that studying its health benefits among wine drinkers isn’t practical. And purified resveratrol is broken down in the liver so quickly that it must be given at very high concentrations to prove effective.

A recent human study that suggested resveratrol could slow the progression of Alzheimer’s used a daily dose equivalent to the amount in about 1,000 bottles of red wine, says Scott Turner, director of the Memory Disorders Program at Georgetown University Medical Center, who led the study. Such high doses can lead to side effects such as nausea, vomiting and diarrhea.

Such side effects have caused past efforts to tap the health benefits of resveratrol to founder. GlaxoSmithKlinePLC shelved a project to develop a resveratrol-based pill in 2010 after some clinical-trial patients developed kidney problems. The company, which had hoped to develop the drug as a treatment for a type of blood cancer, concluded that while resveratrol didn’t directly cause those problems, its side effects led to dehydration, which could exacerbate underlying kidney issues.