IMMUNE-STIMULANT ACTION OF UNCARIA TOMENTOSA
("CAT'S CLAW")
Federico R. León, Ph.D. y Fernando Cabieses, MD, Dr. Biol., F.A.C.S

Uncaria tomentosa, a plant used by traditional medicine of the Peruvian Amazon, stands out for the diversity of its therapeutic applications.

The Plant and its Uses

This rubiacea, better known as "Cat's claw", has little toxicity even in massive doses and is believed to differ from other rubiacea in its higher antiinflam-matory action. The ashaninka indians of Peru boil the stem's bark in water for an hour and drink the extract, approx-imately a litre a day, until symptoms dissapear. This and other forms in which the product is presented (micro-pulverized bark, freeze-dried extract) have gained recent popularity in Peru, Europe, and the United States. Figure 1 shows a list of the plant's current medicinal applications. The diversity of its uses surpasses that of traditional remedies recognized for their benefits (pau d'arco, echinacea, golden seal, milk vetch, Artemisia annua, ginseng, various fungus).

Explanatory Hypotheses

How can one explain the diversity of U. tomentosa's therapeutic applications? Of course, there may be an excess of en-thusiasm on the part of consumers and therapists that consider Cat's claw as a prodigy of nature. The plant's medicinal attributes directly documented with clinical cases and in biomedical investigations in vitro and in vivo only include (a) a powerful antiinflammatory effect (León & Cabieses, 1995a) and (b) promissory antimutagenic and antitumoral actions (León & Cabieses, 1995b). Yet, the fact that other clinical effects have not yet been evaluated is not proof of its non-existence. Maxwell (1990) proposed an interesting idea: if Cat's claw has a powerful and wide ranged stimulant action on the immune system, it can show effects in diverse clinical areas. If this were true, the variety of uses would be justified. This article reviews the scientific evidences pertaining to the immunologic hypothesis.

Non-specific Stimulation

The immune system includes highly organized elements that intercept and destroy invading substances (toxines, bacteria, virus, tumoral cells, allergens, dead tissue, clots, waste). The phagocytes (neutrophils, eosinophils, monocytes) are leucocytes that respond to invasion in a non-specific manner, engulfing and devouring any strange element present in blood or interstitial fluids (phagocytosis). Monocytes, on activating, grow into macrophagues.

Wagner et al. (1985) presented in vitro experiments proving that U. tomentosa, either as a total extract or through specific alkaloids isolated from it, had a strong action on the phagocytotic function of blood neutrophils and macrophagues. The average increases in the Brand-Tympner granulocyte test and the Allen chemical luminescence test reached 30% to 40%.Another set of findings, based on Biozzi's carbon clarification test, is particularly relevant to this article since it stems from an in vivo test and demonstrates the virtues of the total extract (i.e., a preparation that, like the ashaninka medicine, is purported to take advantage of all the bark components). The Biozzi test evaluated the phagocytotic activity of tissue macrophagues of the endothelial-reticular system on carbon particles injected intravenously in animals. As shown in Figure 2, the U. tomentosa alkaloids and catequine presented neutral or negative effects. On the other hand, both their combination (Alkaloids + Catequine) and the total Cat's claw extract activated the phagocytosis substantially. As Aquino et al. (1991) would demonstrate later with respect to U. tomentosa's antiinflammatory effect, Wagner et al. (1985) showed that the total extract was a more efficient stimulant of the immune system than the isolated compounds. Thus, scientific evidences showing the non-specific immune-stimulant action of Cat's claw do exist.

Specific Effects

Lymphocytes are leukocytes that travel through blood vessels and lymphatic tissue developing actions oriented towards specific objectives. B lymphocytes produce antibodies called immunoglobulines. T lymphocytes include "killer" cells that attack specific antigens, "helper" cells that activate B lymphocytes and phagocytes, and "suppressor" cells that balance the system. There are scientific evidences that U. tomentosa has specific immune-stimulant effects.

In an in vitro study of effects on four bacteria, Blais (1992) compared a combined Allium sativum (garlic) and U. tomentosa freeze-dried extract to an extract of A. sativum alone. It can be observed in Figure 3 that the combination strongly inhibited the growth of Echerichia coli (90%) and only moderately (50%) the growth of the other organisms (Salmonella typhimurium, Listeria innocua, Listeria monocytogenes); A. sativum alone was inactive.

Aquino et al.(1989), studying quinovic acid glycosides isolated from U. tomentosa, showed their inhibitory effect against the infection caused by the vesicular stomatitis virus; yet, most glycosides were inactive against the type 1B rhinovirus.

Keplinger (1982) reported that U. tomentosa increases the level of immuno-globuline in cancer patients. On the other hand, Huber (1985) studied the influence of an U. tomentosa freeze-dried extract on the spontaneous proliferation of human hemopoietic tumors and found dose-dependent inhibitory effects on some tumors (K562 leukemia), but not in others (Rajj lymphome, U266 plasmocytome).

These findings represent qualified support to the hypothesis of U. tomentosa's wide immunologic range. It seems that the plant activates the immune system efficiently against some bacteria, some virus, and some tumors; its efficiency against other bacteria, virus, and tumors may be low or non-existent.

Comment

The reviewed studies partially support Maxwell's explanation (1990) for (a) they suggest that, owing to a wide immunologic action, Cat's claw may have therapeutic effects on several diseases, yet (b) they also show that the range is not unlimited. It is improbable that the immunologic action on its own can account for all the alleged medicinal benefits of the plant. Nevertheless, this does not neccessarily contradict the therapeutical applications mentioned by Jones (1994) and Steinberg (1994). Nearly 70 U. tomentosa phytocomponents have been quoted by Duke (1992a, 1992b, 1994); considering their demonstrated biological properties, one must recognize the possibility that the plant really has many of the medicinal virtues attributed to it. The credibility of these attributions, however, will decrease to the extent that time passes and positive clinical evidences are not rigurously reported syndrome by syndrome.

References

Aquino, R., De Simone, F., Pizza, C., Conti, C., y Stein, M. L. (1989). Plant metabolites, structure and antiviral activity of quinovic acid glycosides from Uncaria tomentosa and Guettarda platypoda. Journal of Natural Products 52, 679-685.

Aquino, R., De Feo, V., De Simone, F., Pizza, C., y Cirino, G. (1991). Plant metabolites, new compounds, and antiinflammatory activity of Uncaria tomentosa. Journal of Natural Products 54, 453-459.

Blais, B. W. (1992). "Algunos experimentos preliminares de las propiedades antibacteriales del extracto acuoso de Uncaria tomentosa (uña de gato) y de Allium sativum (ajo)." Ottawa, Canada Department of Agriculture. (Draft)

Duke, J. A. Ed. (1992a). CRC handbook of biologically active phytochemicals and their bioactivities. Boca Raton, FL: CRC Press.

Duke, J. A. Ed. (1992b). CRC handbook of phytochemical constituents in GRAS herbs, plant foods and medicinal plants. Boca Raton, FL: CRC Press.

Duke, J. A. (1994). "Uña de gato (uncaria spp.): Possible alternative to coca?". Washington, DC: US Department of Agriculture. (Draft)

Huber, C. (1985). "La influencia de los extractos de Uncaria en algunas funciones linfocíticas, en la fagocitosis de granulocitos y en el crecimiento in vitro de tumores hemopoiéticos humanos." Innsbruck, Austria: Tesis, Departamento de Inmunobiología Clínica, Clínica Universitaria. (Spanish translation.)

Jones, Kenneth. (1994) Uña de Gato: Life-giving vine of Peru. The American Herb Association Quarterly Newsletter, Vol. X, Issue 3, p. 4.

Keplinger, K. (1982) Cytostatic, contraceptive, and antiinflamatory agents from Uncaria tomentosa. PTC Int. Appl. WO 82 01 130, Austria.

León, F. R., y Cabieses, F. (1995a). Efecto antiinflamatorio de la Uncaria tomentosa ("Uña de Gato"). Boletín del Instituto Nacional de Medicina Tradicional (Ministerio de Salud del Perú), Mayo.

León, F. R., y Cabieses, F. (1995b). Relevancia de la Uncaria tomentosa ("Uña de Gato") para la prevención y trata- miento del cáncer. Boletín del Instituto Nacional de Medicina Tradicional (Ministerio de Salud del Perú), Abril.

Maxwell, N. (1990). Witch-doctor's apprentice: Hunting for medicinal plants in the Amazonian, 3rd. ed. New York: Citadel Press.

Steinberg, P. N. (1994) Uncaria tomentosa ("cat's claw"). Wonder herb from the Amazon. New Editions Health World, 40-45.

Wagner, H., Kreutzkamp, B., y Jurcic, K. (1985). Die Alkaloide von Uncaria tomentosa und ihre Phagozytose- steigernde Wirkung. Planta Medica, 419-423.