understanding chirality

When a patient comes into your practice and asks if the products you carry are chirally correct, what do you say? You may know your product line is formulated with chirally correct ingredients, but do you really understand what that means? Our patients are becoming more and more savvy when it comes to purchasing products, and it is up to us to educate them and give them the right information with regard to product formulation.

Chiral is the Greek term for “hand,” and in chemistry, chirality usually refers to molecules. Two mirror images of a chiral molecule are called enantiomers or optical isomers. These pairs of isomers are often designated as right- and left-handed: D for “Dextro” (right side) and L for “Levo” (left side). An Isomer is defined as “Any of two or more substances that are composed of the same elements in the same proportions but differ in properties because of differences in the arrangement of atoms.”

Our own hands are one of the best and widely used examples of chirality, in that no matter how you configure your hands, one side cannot be exactly the same as the other. This becomes obvious when you shake someone’s left hand with your right hand or try to put a left-handed glove on your right hand. But not everything in nature is the same as a pair of hands. A water glass, for example, does not have a right or left side. That being said, our hands are chiral and a water glass is achiral.

image courtesy of Wikipedia.com

The L and D isomers have different effects upon your body. For many years products and medications were formulated with molecules with both isomers present at the same time. When this happens, there are three possible effects upon the body:

1. The body will recognize and use one side, considering the other side to be waste and disposing of it.

2. They will cancel each other out and there will be no effect.

3. The side that is not compatible will cause harm and be considered toxic by the body and could lead to increased

free radical production.

One example is vitamin C. The ascorbic acid molecule exists as two isomers: L-ascorbic acid and D-ascorbic acid.  The L side has all of the benefits of vitamin C, such as collagen production, UV protection and antioxidant properties, whereas the D side leads to increased dryness, itching and free radical production. Skin care products that are formulated with both sides together, rather than with the isolated ‘L’ side, can lead to one of the three scenarios listed above. Another and more extreme example of what can happen if both isomers are present in a formulation at the same time is the devastating birth defects associated with the drug thalidomide. Thalidomide was given to pregnant women during the 1950’s to help curb morning sickness, and subsequently caused devastating birth defects in children born to mothers that took thalidomide. In 1979 it was discovered that although the D-isomer was recognized and used by the body as intended, it was the L-isomer that was responsible for the birth defects.

As skin care clinicians, we do not have to worry about isolating the correct side of a chiral molecule. Science has advanced in the skin care industry and most products are now formulated chirally correctly. For over 20 years PCA SKIN has been formulated with chirally correct ingredients, and we will continue to formulate products backed by science and rigorous research.


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