Unlocking the secrets of Chinese herbal medicine
If you were suffering from a
stomachache, and you lived in China 2000 years ago, you might visit a
practitioner of traditional medicine. After an examination, the healer would
probably prescribe several herbs or plants to treat your stomach pain. In
modern-day China, if you were to visit one of the still-popular practitioners
of traditional medicine, you would likely receive the same treatment for your
stomachache.
For thousands of years, herbal
medicine has been used to treat illness in Asia and in other parts of the
world. Today, even in the United States, a visit to most drug stores and any
health food store reveals an ever-growing number of herbal and plant-based
products lining the shelves. Prudent shoppers want to know what these natural
materials actually contain and how they counteract symptoms and illnesses.
The problem with traditional
analysis of traditional medicines
Of course, prudent shoppers
aren't the only ones who are curious. Doctors and scientists also want to
identify the active substances in these natural remedies. The usual methods for
discovering the compounds that are found in a plant sample are high performance
liquid chromatography (HPLC) with mass spectrometry or ultraviolet (UV)
detection. Using these techniques, the compounds that compose a plant sample
are identified by the length of time they take to pass through a column packed
with synthetic material, similar to silica, and by either their UV-light
absorption characteristics or their atomic weight. Unfortunately for
scientists, samples of natural materials often contain numerous components, and
they may even contain extraneous "dirty" compounds. These unwanted components
can contaminate the packed tubing used for chromatography, sometimes making it
impossible to continue testing.
Honey I shrunk the column
Researchers at Agilent have
pioneered a better way to analyze natural materials. It's called capillary
electrophoresis (CE), and it solves the problem of contaminated packing by
using an open tube. In CE, components of a sample separate as they migrate
through the column in response to an electric field. Similar to HPLC,
individual compounds are identified by the length of time they take to navigate
their way through the column. However, there is an important difference between
HPLC and capillary electrophoresis. Capillary electrophoresis has higher
resolution because it uses open tubing that is a fraction of the size of
standard HPLC columns. Using these smaller columns yields several
advantages:
- Minimal amounts of
material are required for analysis.
- High resolution
capability makes separating numerous compounds easier.
- Analysis time is
shortened because samples travel through the capillary tube much more
quickly.
- CE is very tolerant of
complex and "dirty" samples.
As with HPLC, capillary
electrophoresis can be coupled with mass spectrometry or UV detection to verify
the identification of a sample's components.
Putting CE to the test 
Chemists at Agilent teamed
with students and professors at Peking University, Beijing, to analyze several
samples of traditional medicines that are based on natural materials. The first
sample, Mahuang, is often used to treat asthma and respiratory infections. It
is known to contain ephedrine, a stimulant to the central nervous system.
Capillary electrophoresis was used to analyze Mahuang for ephedrine (see Figure
1). The expected ephedrine peak is found traversing the column at 5 minutes;
however, several other components are also visible as peaks on the graph. The
presence of ephedrine was confirmed by comparing the UV absorbance spectra of
the peak at 5 minutes on the Mahuang graph with that from a peak produced by a
pure ephedrine sample, (see Figure 2). One of the Mahuang peaks matches the
known peak for ephedrine perfectly, verifying that Mahuang contains
ephedrine.
Another natural material
sample, Mahonia stem, was also analyzed using capillary electrophoresis. Many
species of the Mahonia plant are used in traditional Chinese medicine for their
antibacterial, antioxidant, and antifungal properties, among others. CE testing
on two species, M. japonica and M. fortunei, shows that even though they share
some compounds, each species has varying amounts of them. There are also some
compounds unique to each of the Mahonia species, possibly giving them different
therapeutic qualities.
Agilent's work with Peking
University helps quantify what practitioners of traditional Chinese medicine
have known for millennia, that herbal remedies are serious medicine. Consumers
need to know that, like the modern pharmaceuticals of today, herbal remedies
can have side effects and interactions. Capillary electrophoresis is a key to
unlocking those properties -- and the ancient secrets -- of herbal medicine.
For more information
Agilent's Chemical Analysis Group provides solutions
for identifying, quantifying and analyzing the chemical properties of thousands of
substances. To learn more about other capillary electrophoresis solutions, visit our
Capillary Electrophoresis
section of Agilent.com.
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