Anti Aging Compound or Controversial UV Blocker? Molecular Discrimination

Two chemical substances have been appearing in the news in recent months, one associated with beneficial effects, the other possibly with negative effects. These compounds have the same chemical constitution yet very different properties and applications.

Resveratrol is a constituent of red wine that has been observed to have some possibly beneficial effects on animals, including reducing the effects of aging in certain tests. Indeed, there has been speculation that resveratrol is responsible for the so called French Paradox, the observation that people in France do not suffer as much as the rest of the world from a high fat diet. The other topical molecule is oxybenzone, a constituent of sun screens, that helps block ultraviolet light induced skin damage. Although sun screens definitely help to prevent skin cancers, there is some concern, unsupported by the FDA, that compounds such as oxybenzone may be deleterious to your health.

So we have two molecules, one which has entered the popular press as a possible magic bullet to ward off the effects of aging and the other a possible threat to health. When you examine these molecules you see that they have exactly the same number of carbon, oxygen and hydrogen atoms. They each have fourteen carbon atoms, twelve hydrogen atoms and three oxygen atoms, or C₁₄H₁₂O₃, to be precise. They are chemical anagrams of one another and chemists would say that they are isomers. In fact, if you look at the chemical structures (in the first diagram) you will see that resveratrol and oxybenzone have similarities, two ring structures and three oxygen atoms. Looking beyond the chemical structure to the three dimensional structure of the molecules (the second diagram) you will, however, see differences. Resveratrol is a longer molecule with its oxygen atoms (shown in red) spread out on the outside of the molecule. Oxybenzone is more compact and its oxygen atoms are clustered on one side of the molecule.

Living tissues see the molecules in three dimensions and do not see these molecules as being similar in any way. The proteins and nucleic acids with which resveratrol and oxybenzone interact are highly selective. Although resveratrol and oxybenzone have the same number of atoms, have the same atomic constituents and some of the same chemistry, proteins molecules, cells, scientists, journalists and the media have no trouble whatsoever in understanding that they have different effects, because their three dimensional shapes are different. At the molecular level, we implicitly know that small differences are significant. Thank goodness for molecular discrimination, and vive la difference!