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Prepared
by: Dr. Charlene DeHaven, Clinical Director
CHIRAL COMPOUNDS©
Chiral Compounds
Recent cosmetic literature contains a fair amount of discus-
sion about “chirality” of compounds. Many of these writings
are unclear, confusing and even misleading. Extensive
research of the medical literature base yielded the following
information and conclusions.
First of all, we should explain chirality. This term simply
refers to the rotation of a compound composed of a long
string of molecules about an axis. These long and winding
strings of molecules may be rotated, in some instances, to
the right and, in others, to the left. The sum of carbon,
oxygen, hydrogen and other molecules within two chiral
compounds is the same, although these identical number of
molecules are arranged slightly differently in space; these
compounds are called “enantiomers” of each other, meaning
they have the same number of each type of molecules but
are configured in a slightly different way in space. Most
simply stated, chiral compounds are not symmetrical. They
cannot be superimposed directly upon their own mirror
image. A simple illustration of chirality is right and left-
handedness. The right and left hands of any given
individual are not exactly alike, each containing unique
patterns, lines, and tissue prominences, and, if laid on top of
one another, do not fit within the same image. Yet, even
though different and, certainly, not exact matches, they are
both useful to individual functioning. Likewise, many other
body parts are not symmetrical.
Considering rotational axis of biochemical compounds within
the body, amino acids (the building blocks of proteins)
are, in general, of L-chirality or rotated to the left.
Here, “L” or “levo” refers to left. Sugars, on the other
hand, which are used to build the genetic code of DNA,
are of D-chirality or rotated to the right. “D” refers
to “dextro” or right. Most chemicals (for example, enzymes)
synthesized within the body are of L-rotation. This L-rotation
has been speculated to occur as a relationship to the
earth’s rotation when early life began and also to relate
to the rotation of groups of serine, an amino acid. However,
biological systems, includ- ing humans, recognize and
use compounds with varying chirality. This probably relates
to the efficiency of life’s survival mechanisms and the
ability of organisms to utilize a variety of substances
in their environments.
Within organisms, occasionally a receptor site (for example, a
receptor site for a specific molecule in the intestine) will recog-
nize either the D form or the L form more efficiently. Occa-
sionally, a drug is slightly more efficient if it possesses only
one of these chiralities. These, however, are very minor
differences and sometimes so academic they make no practi-
cal difference in the real world of biochemical functioning.
Since organisms on earth tend to synthesize more of the L-
rotated compounds, a skin product obtained from plant source-
will contain the vast majority of its compounds in L-form.
Another fact to realize is that there is always some shift
back and forth in nature between the L-form and D-form; it
is nearly impossible to keep only one rotation in solution at
any given time. This means that, even if a substance is
advertised as being “chirally pure”, it cannot be since
nature causes some of it to constantly shift back and forth
between its own enantiomers.
Thus, it is not necessary to have a “chirally pure” skin
product. Furthermore, nature will make it impossible for
such a product to exist for even a nanosecond. A “racemic”
or chirally mixed substance is not harmful. Biochemical
systems are able to use and recognize a variety of enantio-
mers because of survival efficiency.
 References
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Relations in Large Random Supramolecular Structures”,
O Katzenelson, D Avnir; Chemistry. 2000 Apr 14;6(8):1346-54.
“Effect of Earth’s Orbital
Chirality on Elementary Particles and Unification of
Chiral Asymmetries in Life on Different Levels”,
YJ He, F Qi, SC Qi; Med Hypothesis. 2000 May;54(5):783-5.
“Chirality and Handedness:
the Ruch “Shoe-Potatoe” Dichotomy in the Right-Left Classification
Problem”,
RB King; Ann N Y Acad Sci. 2003 May;988:158-70 .
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of Metoprolol: Enantioselectivity of Alpha- Hydroxymetoprolol
in Plasma and Urine”,
PM Cerqueira, EJ Cesarino, C Bertucci, PS Bonato, VL Lanchote;
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of Biological Molecules”,
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Epub 2003. |
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