Medicines From Plants - Digitalis and Taxol

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.

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.

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 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.

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.

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.

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.