Benefits of Thin Layer Chromatography for the
Isolating Biologically Active Materials in
Indigenous Medicinal Plants
Dr. Gary Witman, Dr. Mark Moskovitz
Thin layer chromatography (TLC) offers a rapid,
inexpensive and reproducible method for screening of
medicinal plant materials. There is such a plethora
of plant material to still evaluate and test for
biological activity and hopefully useful medicinal
properties. Such plant material continues to play a
role in the identification of lead compounds for the
pharmaceutical industry. As the drug pipelines in
pharmaceutical companies begin to “run dry” of
patent protected blockbuster compounds there is once
again a move back to plant medicinal chemistry for
leads in novel structure chemistries.
Newer compounds must be found for the treatment of
bacterial infections which have developed methods
for genetic resistance to virtually all antibiotic
chemotherapy. Vaccines have been effective against
some bacterial antigens, but no vaccines have yet
been found against any of the major parasitic
infections. The rush is on once again for evaluating
medicinal plant chemistry.
One place which is suddenly receiving much attention
is sub Saharan Africa. This region of Africa
contains 60,000 plant species, which is roughly ¼ of
the world’s species of plants. People have lived
longer in sub Saharan Africa than anywhere else on
the continent. Over millions of years hominid
species through trial and error identified medicinal
plants with remarkable biological activity. Due to
language and cultural barriers the experience with
these remarkable plants has been ignored. Newer
chemistry techniques allow for the rapid
identification of potentially useful medical
compounds. . TLC is the ideal tool for finding these
compounds especially the use of aluminas.
An example of a native medicinal plant being studied
in Africa is Siphonochiles aethiopicum. This is also
known as African ginger, or wild ginger. It is
widely distributed in tropical Africa, from South
Africa northwards to Zambia, Malawi, Ethiopia, West
Africa and Gambia. The plant part used is the
rhizome and the flesh roots. The product is
available from commercial plantations and rapid
scale up in plant production is possible.
Utilization of DAI preparative TLC and then the use
of DAI Dry Column Chromatography for rapid scale up
speeds up the process. The rhizomes and roots are
harvested at the end of the growing season when the
plants start to go dormant. In traditional medicine
a small piece of the rhizome is chewed. In Malawi
traditional medicine belief is that the plant is
useful in the treatment of coughs, colds and asthma.
The main traditional use of the rhizome by the Zulu
people has been in the treatment of malaria and
vulvovaginal, and mucocutaneous candidiasis.
Extracts of the rhizome have proven to have
significant antibacterial activity against gram
positive bacteria, but have demonstrated no
anti-viral activity. The produce is rich in
essential oil and contains more than 70
monoterpenoids and sesquiterpenoids, including 1.8
cineole, cis-alloocinemene, alpha-terpineol and
gemacrene B. The main furanoterpenoid,
siphonochilone, represents at least 20% of the oil.
To identify the biologically important compounds the
rhizome material is ground and then extracted using
water, ethanol and acetone. The solvents separate
the compounds into polar, intermediate and non polar
compounds. Then fingerprints are established of
biologically active compounds using TLC technology.
Ideally it is suggested to first use two dimensional
TLC for separation of compounds. The chemical
fingerprint of TLC has been demonstrated to be an
identification tool for traditional medicines.
To date, there is little in the way of toxicity
data. The LD50 brine shrimp toxicity assay is
greater than 2000 ug/ml, and the Vero cell line LD50
is 0.409 ug/ml.
It is hoped that recent experience with this
compound will help to stimulate interest in many
other important medical plants utilized by
indigenous people and which have heretofore not been
fully examined or explored.
Similar use of TLC, (see DAI TLC applications), to
create fingerprints for biologically important
compounds is being achieved with indigenous plant
materials from South America, Europe and Asia.
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