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Vinblastine, Vincristine, and L-dopa: Interesting Plant Chemicals

Linda Crampton has an honors degree in biology. She is very interested in plant chemicals and their actions and benefits in the human body.

The Madagascar periwinkle, or Catharanthus roseus, contains chemicals that are used in chemotherapy to treat cancer.

The Madagascar periwinkle, or Catharanthus roseus, contains chemicals that are used in chemotherapy to treat cancer.

Interesting Chemicals From Plants

The Madagascar periwinkle is an attractive flowering plant that contains vinblastine and vincristine. When formulated correctly, these chemicals are used as chemotherapy drugs. The pods of the velvet bean are covered by soft hairs, which gives the plant its name. The beans contain L-dopa, which is a helpful chemical in the treatment of Parkinson’s disease.

The Madagascar periwinkle and the velvet bean are just two of the large number of plants that have been found to contain useful chemicals with respect to human health. There are almost certainly many more plants in nature that have undiscovered benefits, which is a powerful argument in support of their protection.

Plants containing desirable chemicals are sometimes grown as crops. The chemicals are obtained by an extraction process and concentrated to make a drug. In other cases, scientists investigate plant chemicals to discover their structure and then produce synthetic chemicals that are identical to the natural ones. Sometimes researchers are able to improve the properties of natural chemicals and make them more effective. In all of these situations, a plant species is essential for the development of a new medicine.

A purple version of the Madagascar periwinkle

A purple version of the Madagascar periwinkle

The Madagascar Periwinkle

The Madagascar periwinkle is native to Madagascar and India but is now grown in many countries as a garden plant. It has also escaped from gardens and grows as a weed. The red, purple, pink, or white flowers often have a center that is a different color from the rest of the flower. Madagascar periwinkles have glossy green leaves and may grow up to a meter tall.

The sap of the plant has a milky appearance and is poisonous. It contains vinblastine, vincristine, and many other alkaloids. Researchers are discovering that many of these alkaloids are biologically active inside the human body.

Vinblastine and vincristine are both used to treat cancer. The medications are extracted from Madagascar periwinkles, but the yield is quite low. Researchers are exploring ways to increase the amount of medicinal chemicals made by the plant. They are also investigating efficient methods to make the drugs synthetically.

Vinblastine, Vincristine, and Cancer

Vinblastine and vincristine have very similar chemical structures. Although they work in the same general way, their abilities aren't identical. Each is helpful for specific types of cancers.

Vinblastine is used to treat disorders such as Hodgkin’s disease (or Hodgkin's lymphoma), non-Hodgkin's lymphoma, and testicular cancer. It's also used to treat a condition called Langerhans cell histiocytosis, or LCH. Langerhans cells are part of the immune system and help the body to fight infections. In LCH, too many immature Langerhans cells are made. As the cells collect, they form tumors and damage organs.

Vincristine is used in the treatment of several types of leukemia (cancer of the white blood cells) and lymphoma (cancer of the lymph cells, or lymphocytes). It's also used to treat Wilms' tumor, which is a type of kidney cancer, as well as some kinds of brain cancer.

Microtubules are made of molecules of a globular protein called tubulin. Both alpha (blue) and beta (orange) tubulin are found in microtubules. "Vinca" used to be the first part of the scientific name for the Madagascar periwinkle.

Microtubules are made of molecules of a globular protein called tubulin. Both alpha (blue) and beta (orange) tubulin are found in microtubules. "Vinca" used to be the first part of the scientific name for the Madagascar periwinkle.

How Do Vinblastine and Vincristine Work?

Microtubules

Cells contain a supporting network of protein tubules, which are known as microtubules. Microtubules also play a vital role in the movement of cell parts and in the process of cell division.

Chromosome Replication

The nucleus of a cell contains chromosomes. Each chromosome is made of a DNA molecule attached to protein. DNA is the genetic material of cells. Before a cell divides, every chromosome in the nucleus is replicated, enabling each daughter cell to have an identical set of chromosomes.

Mitosis

At first, the two copies of each chromosome are joined together. During a process called mitosis, spindle fibers made of microtubules separate the paired chromosomes and pull the former partners to opposite ends of the cell. Once the chromosomes have reached their destination, the cell divides down the middle.

Effect of Vinblastine and Vincristine on Mitosis

Vinblastine and vincristine stop microtubule formation during mitosis. This prevents mitosis and cell division from taking place. This effect is strongest in cells that have a high rate of division, such as cancer cells. Therefore vinblastine and vincristine can act as chemotherapy drugs.

Each chromosome is replicated before cell division. The paired chromosomes are separated as microtubules (or spindle fibers) pull them to opposite poles of the cell.

Each chromosome is replicated before cell division. The paired chromosomes are separated as microtubules (or spindle fibers) pull them to opposite poles of the cell.

Possible Side Effects of Vinblastine and Vincristine

Unfortunately, in addition to affecting cancer cells, vinblastine and vincristine may affect other cells that have a high rate of cell division. These include cells in the lining of the intestine, the cells in the bone marrow that produce blood cells, and the cells in the hair follicles. Interference with these cells can produce side effects of the cancer treatment.

Possible vinblastine or vincristine side effects include:

  • constipation and other gastrointestinal problems
  • hair loss
  • a low platelet count, which can cause increased bleeding
  • a low white blood cell count, which can lead to an increased incidence of infections
  • a low red blood cell count, resulting in anemia.

The drugs may occasionally cause nerve damage, possibly due to their effect on the microtubules in the nerve cells. Vincristine is more likely to cause nerve damage than vinblastine.

Velvet Beans

The velvet bean is a climbing plant that is native to tropical areas in the Caribbean, Africa, and India and is cultivated in various parts of the world. It’s a member of the legume family, a plant group that contains beans and peas. Its scientific name is Mucuna pruriens. It's sometimes known as cowhage, the hell fire bean, or another name.

Velvet beans are very variable in appearance. The flowers range from white to purple in color. The pods that contains the seeds (or beans) are covered with orange, brown, grey, white, or black hairs. These hairs can produce a severe itch when human skin touches them. The seeds inside the pods are shiny and may be black, brown, maroon, or white. They may also have a mixture of colors and appear mottled.

Like many other beans, velvet beans are a good source of protein, but they are potentially toxic. If they are used for food, they have to be soaked for a long time. In addition, the boiling water has to be changed several times during the cooking process to remove the toxins. In some parts of Central America, the beans are roasted and then ground to use as a coffee substitute.

L-Dopa and Parkinson's Disease

In people with Parkinson’s disease, brain cells that make a chemical called dopamine are damaged and destroyed. The amount of dopamine in the brain therefore decreases. As a result, the affected person can't control or coordinate their muscle movements properly.

At the moment we don’t know for certain why dopamine-producing cells are damaged in people suffering from Parkinson’s disease. Dopamine administered to patients is unable to relieve their symptoms because the chemical is unable to cross the blood-brain barrier. L-dopa, which the body converts into dopamine, can penetrate the blood-brain barrier, however.

Synthetic L-dopa is a standard medication for treating Parkinson’s disease and improving the patient’s quality of life. It's also known as levodopa. It's usually administered with a helper medicine called carbidopa. Carbidopa prevents levodopa from breaking down in the body before it gets to the brain and therefore reduces the required dose. This may in turn reduce nausea, a possible side effect of levodopa administration.

These are also velvet beans. The flowers, pods and seeds of velvet bean plants have a variable appearance.

These are also velvet beans. The flowers, pods and seeds of velvet bean plants have a variable appearance.

L-Dopa in Velvet Beans

Velvet beans contain L-dopa. The chemical is sometimes present in large amounts. The amount of L-dopa in velvet beans depends not only on the cultivar of bean but also on the environmental conditions in which the bean plants are grown.

Unlike the Madagascar periwinkle, velvet beans can be eaten. In addition, the potentially medicinal chemical may be concentrated enough to be helpful. A big problem with using velvet beans to obtain L-dopa is that the amount of L-dopa in the beans varies, however. A person doesn’t know how many beans to eat in order to obtain an effective or a safe dose of L-dopa or how much of the chemical he or she is actually ingesting.

Velvet Beans and Parkinson's Disease

Velvet beans have traditionally been used for Parkinson's disease—or at least for symptoms resembling those of the disease—in some cultures. There hasn't been much scientific research related to the benefits of the beans, however.

In 2004, the result of one investigation involving velvet beans and Parkinson's disease patients was published in the British Medical Journal. Only eight patients took part in the investigation. The researchers compared the medicinal effects of a synthetic L-dopa/carbidopa mixture with a velvet bean powder in a double blind experiment. In this type of experiment, neither the test subject nor the person administering a substance knows whether the substance is the medication or a placebo. The researchers discovered that the bean powder started to work faster (34.6 minutes versus 68.5 minutes) and worked for 37 minutes longer than the L-dopa/carbidopa treatment.

The results of the experiment are very interesting. Clinical trials with much larger sample sizes and bean powders containing different doses of L-dopa are needed in order to confirm and clarify the results, however. If the bean powder is helpful, it would be interesting to identify the chemical in the bean that serves the same function as carbidopa. Unfortunately, as far as I know, no recent investigations related to the effect of velvet beans on Parkinson's disease have been performed.

Fava beans or broad beans also contain L-dopa.

Fava beans or broad beans also contain L-dopa.

Fava or Broad Beans and L-Dopa

Fava beans are also called broad beans. They contain L-dopa, although in a much lower quantity than velvet beans. It would still be a good idea for a patient taking prescribed L-dopa supplements to ask their doctor about the advisability of eating fava beans. The bean sprouts, pods, stems, and leaves reportedly contain more L-dopa than the unsprouted beans.

Some people suffer from a genetic problem called favism and can't eat fava beans. These people are unable to make enough of an enzyme called glucose-6-phosphate dehydrogenase. The disorder is therefore sometimes called glucose-6-phosphate dehydrogenase deficiency, or G6PD deficiency. In this disorder the red blood cells burst when exposed to certain stimuli, including (in some people with the disorder) the ingestion of fava beans.

The inflorescence of a velvet bean plant

The inflorescence of a velvet bean plant

Precautions When Using Plant Chemicals

Medicines are often discovered in plants, analyzed, and then synthesized in a laboratory later. Destruction of the Earth’s plant species will decrease our chances of discovering new medicines.

Some plant chemicals can be useful in disease treatment. The amount of the chemical that's ingested is often unknown when plant parts are eaten, however, unless a chemical analysis is performed. Another potential problem is that plant parts or extracts may contain toxins in addition to a beneficial substance.

Like synthetic medicines, chemicals from plants can cause side effects, interact negatively with medications inside a person’s body, or be dangerous for people with additional medical problems besides the one being treated. Therefore it’s very important to follow a doctor’s advice before and during the use of plant chemicals for a health problem.

References

  • The U.S. National Library of Medicine contains vinblastine information.
  • The Cancer Research UK website has more information about vinblastine.
  • The U.S. National Library of Medicine contains facts about vincristine injections.
  • Information about vincristine can also be found at the Mayo Clinic website.
  • The University of California, San Francisco, describes Parkinson's disease medications, including L-dopa.
  • Mucuna pruriens in relation to Parkinson's disease is described in the Journal of Neurology, Neurosurgery and Psychiatry (a publication of the British Medical Journal)

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Questions & Answers

Question: How long can you live with leukemia?

Answer: This is impossible for me to say. Only a doctor familiar with a patient’s particular condition can give an answer, and even they can’t answer with certainty. There are many variables involved in determining lifespan, including the type of leukemia that a person has. In some cases, treatment has enabled people to live for a long time after their diagnosis.

© 2011 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on July 18, 2011:

Thank you for the visit and the comment, jamterrell!

jamterrell on July 18, 2011:

Very interesting hub. Lots of information article.

Linda Crampton (author) from British Columbia, Canada on March 06, 2011:

Hi, CMHypno. Thanks for commenting. Yes, there's so much more to be learned!

CMHypno from Other Side of the Sun on March 06, 2011:

Fascinating stuff Alicia. We still have so much to learn about plants and their medicinal properties.

Linda Crampton (author) from British Columbia, Canada on February 27, 2011:

Hi, Fossillady. Yes, the possibility of more great but undiscovered medicines in plants is exciting. I hope scientists find them quickly. Thanks for the comment.

Kathi from Saugatuck Michigan on February 27, 2011:

Quite interesting and you explained the technical aspects for the us laymen very well, Wow, nice work. Continued discoveries give as a ray of hope