By Johan Simith
Foxglove leaf and
foxglove leaf extract have long been used as a herbal
remedy to treat heart problems.
Taxol was discovered when scientists
representing the National
Cancer Institute in the United States performed a survey of
plants looking for new
chemotherapy drugs. By destroying so many natural
habitats around the world humans are almost certainly denying themselves the
opportunity to find many new medicines in plants.
Scientists have identified many medicinal chemicals in plants, and there are
probably many more still to be discovered. Digitalis, which strengthens
and slows the heartbeat, is found in foxgloves.
Taxol, which is used as an
anti-cancer drug, is found in yew trees.
Digitalis is obtained from the leaves of the foxglove plant and is a type of
cardiac glycoside. Cardiac glycosides are drugs prescribed to treat atrial
fibrillation and congestive heart failure. Digitalis is generally prescribed in
a form known as
digoxin.
The common foxglove has the scientific name
Digitalis purpurea. Foxgloves
are tall plants with rows of beautiful, tubular flowers ranging in color from
purple to white. The flowers frequently bear spots.
Although digitalis is a helpful drug it must be used in the correct dose.
It’s dangerous if too much is ingested. In addition to digitalis, foxglove
contains other chemicals which are biologically active and are toxic to humans
and animals. The entire foxglove plant is poisonous.
How Does Digitalis Work?
In atrial fibrillation, the heartbeat is rapid and irregular. The
inefficient pumping of the heart increases the risk of a stroke.
Digitalis
helps treat atrial fibrillation by increasing the action of the parasympathetic
nervous system on the heart. One job done by this division of the nervous
system is to slow the heartbeat
In congestive heart failure, the heart is unable to pump enough blood around
the body. As a result, blood may back up in the blood vessels, causing fluid to
leave the blood and enter the tissues. Fluid may build up in the lungs, the
arms and legs, the digestive tract and the liver. This fluid buildup is called
edema. Digitalis increases the amount of calcium in the heart cells. Increased
calcium leads to a stronger heartbeat. Since digitalis strengthens the
contraction of the heart, the heart can pump more blood and edema is reduced.
Digitalis Toxicity
A patient taking digitalis has to be monitored carefully. A dose of
digitalis that can cause digitalis toxicity is not much larger than a
therapeutic dose. Someone suffering from digitalis toxicity may experience loss
of appetite, nausea, vomiting and diarrhea. There may be confusion, an
irregular heartbeat and
vision problems. Vision may be blurred and objects
being viewed may have a yellow tinge, a condition known as
xanthopsia. The
person may also see halos of light around objects. In addition, he or she may
experience depression and hallucinations.
Taxol and Yew Trees
Taxol was discovered in the bark of the Pacific Yew tree in the 1960’s. Its
name is derived from
Taxus brevifolia, the scientific name for the
Pacific Yew. Taxol is most abundant in yew bark but is present in the needles
as well. Recently
taxol has also been found in a number of fungi.
At first the use of taxol was controversial, since removing the bark from
yew trees to extract the taxol kills the trees. In addition, Pacific Yew trees
are slow growing and new trees cannot quickly replace trees killed for taxol
extraction. Nowadays taxol is obtained by a
cell culture method that doesn't
involve killing yew trees.
How Does Taxol Work?
Taxol is used to treat several different cancers, including breast cancer,
ovarian cancer and one type of lung cancer (non-small cell lung cancer). It’s
also used to treat AIDS-related Kaposi’s sarcoma. Taxol, which is also known as
paclitaxel, is used on its own or it is used in combination with other
chemotherapy drugs.
Just before a cell divides its nucleus divides, a process known as mitosis.
Structures called microtubules play an important role in mitosis. Microtubules
form during mitosis, and once mitosis has finished they break down. Taxol stops
microtubule breakdown, thereby interfering with the process of mitosis. When
mitosis is inhibited cell division is inhibited too.
Cancer cells multiply rapidly compared to most body cells and so they have a
high rate of mitosis. Therefore taxol effectively acts as an anti-tumor drug.
Taxol Side Effects
Unfortunately taxol can also prevent the division of normal cells in the
body that divide rapidly, such as the bone marrow cells that produce blood
cells. One of the side effects of taxol may be a low red blood cell count
(resulting in anemia), a low white blood cell count (which can lead to
increased infections) or a low platelet count (which can lead to an increased
risk of bruising and bleeding).
There may be additional side effects, but not everyone will experience them,
or the side effects may be minor. It’s impossible to predict ahead of time how
severe the side effects will be for a particular patient, but quite often
people find taxol treatment less unpleasant than other chemotherapy treatments.
Additional medications can often relieve the side effects that do appear.
The most common side effects of taxol treatment include low blood counts,
nausea, vomiting, diarrhea, temporary hair loss (until the taxol treatment is
topped), mouth sores, muscle or joint pain, numbness and tingling. Other
possible side effects are fluid retention in the feet, ankles or abdomen and
nail darkening.
Some people have an allergic reaction to taxol, but this is usually not due to
the taxol itself but due to the substance used to dissolve the taxol so that it
can enter the bloodstream. Taxol is not water soluble. Doctors generally
prescribe steroids to reduce the chance of an allergic reaction when taxol is
given to a patient.
Mr.
Sheikh Gulzaar is a research writer in
Jammu and Kashmir Medicinal Plants Introduction Centre. More details: http://jkmpic.blogspot.com was established in 1993. The institution also provides planting materils of all herbs, and
Taxus baccata,
Digitalis purpurea, Ginkgo biloba, Podophyllum hexandrum, Lavatera cashmeriana, Origanum vulgare, Phytolacca acinosa, Rheum emodi, Sambucus nigira, Saussurea costs, Solanum nigrum, Hyoscyamus niger.
