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Mistletoe (Phoradendron leucarpum)

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BIOLOGY

Mistletoes are a group of vascular, flowering plants that parasitize stems of trees and shrubs. There are 700-1400 species (depending who you ask) of mistletoe worldwide found in the Viscaceae and Loranthaceae families, located mainly in tropical and subtropical regions of the world. Even the family has several synonyms. Renamed by our own Dr. James Reveal as Phoradendron leucarpum (Johnston and Reveal), American mistletoe was previously know as P. serotinum, P. flavescens. Phoradendron has a wide geographic distribution and is found in the US from New Jersey to Florida to Texas. It has a broad host range and parasitizes mostly hardwoods.

The plant is able to produce its own chlorophyll (a hemiparasite), but depends on out-competing its host for nutrients from the host xylem tissue . The flower structure is reduced and primitive in appearance. It uses an endophytic system to penetrate through the cambial region of its host. Birds eat the fruit, dispersing the seeds to other tree limbs. A sticky viscin layer on the seed allows it to adhere to the branch. The seed germinates and develops an adhesive disk. As the haustorium (root like structure) develops in the host cambium, the aerial portions of the plant grow slowly. Shoots are usually visible the second year. Once the endophytic system becomes established, the plant grows quickly. Since the leaves stay green all year, once leaf fall takes place, it is easy to spot balls of mistletoe high up in hardwoods.

HISTORICAL PLANT USE

Druids and many cultures in the British Isles, France and Germany used mistletoe medicinally for convulsions, delirium, hysteria, neuralgia, and heart conditions. This is certainly in keeping with the believe with its ability to protect and to open other worlds for the user. It was known at the time that if children ingested the berries they often experienced convulsions, considered a homeopathic indicator for its use. Anthrposophical medicine introduced Iscador, a remedy used in Germany to this day for patients suffering from cancer. It was believed to be tumor inhibiting, and to increase the number of killer cells of the immune system.

Native American use of Phoradendron was similar to the Druid use of Viscum. Cherokee tribes used a "Tea ooze" to bathe the head for a headache, an infusion of the plant for high blood pressure, and lung problems, the dried, powdered plant, particular from the oak, for epilepsy, and to cure "love sickness", an infusion was taken after four days of vomiting. Houma tribes used the decoction of the plant for debility and paralytic weakness, and as a general panacea (Moerman).

PHARMACOGNOSY

Today compounds have been isolated and identified as having specific biological activity:

Phoratoxin

Several investigators have studied the effect of mistletoe crude extracts on blood circulation. A protein was isolated, viscotoxin from Viscum alba, or European mistletoe, and phoratoxin from Phoradendron serotinum. One main protein and small amounts of two other proteins, all given the name Phoratoxin, decreased the contractile force of the heart and produced bradycardia (slow heart rate). It took larger doses of Phoratoxin to have the same effect as Viscotoxin (Rosell & Samuelson, 1966).

Galactose-Specific Lectin

Recent research on human patients, proved that a mistletoe plant extract---a small nontoxic dose of galactose-specific lectin activated non-specific immune defense responses and increased the plasma B-endorphin levels, improving quality of life for patients undergoing chemo and radiation therapy.

A RECENT EXPERIMENT

Methods:

Two German investigators (Heiny & Beuth, 1994), enrolled 68 patients with histologically verified breast carcinoma (TNM stages III-IV) that had been surgically treated and hospitalized for chemotherapy. Using standardized galactoside-specific mistletoe (ML-1) lectin isolated from the European mistletoe Viscum alba, subcutaneous treatments were administered for twelve weeks. Peripheral blood was drawn from cubital veins to analyze Beta- endorphin plasma levels, lymphocyte subpopulations, and to investigate the in vitro cytokine release at one week before, six weeks and twelve weeks after ML-1 treatment. Comprable intervals were used for control group chemotherapy patients.

Results:

In the control group Beta-endorphin levels were less than before the ML-1 treatment began after both six and twelve week intervals. Among the responders of those treated with ML-1 (app. 70%), Beta- endorphin levels were almost twice as high as before treatment after six weeks and increased slightly from there after twelve weeks.

Generally, in the control group, plasma lymphocyte counts were lower after six weeks, and lower still after twelve weeks. The responders in the treatment regimen showed a drop after six weeks and a slight rise to above six week levels after twelve weeks. The final count after twelve weeks was higher in the ML-1 treatment group than the control.

The cytokine measurement showed a slight decrease in the control group and an increase in the responders of the ML-1 treatment group that was larger in relative size than the decrease of the control group.

References:

Heint BM, Beuth J: Mistletoe Extract Standardized for the Galactoside-Specific Lectin (ML-1) Induces Beta-Endorphin Release and Immunopotentiation in Breast Cancer Patients.

Anticancer Research 14: 1339-1342 (1994).

Rosell S, Samuelsson G: Effect of Mistletoe Viscotoxin and Phoratoxin On Blood Circulation

Toxicon 4: 107-110 (1966).

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