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Horopito: A Unique New Zealand Medicinal Herb

Campbell Berry-Kilgour, BSc (Hons.)

The Maori people of New Zealand accumulated a vast storehouse of knowledge about indigenous flora.

This is evident in the myriad of spiritual and practical uses that intertwine with the medicinal use of the 200 or so plants used by the Maori for ritual or herbal purposes. Maori believe plants and man have a common origin, both being offspring of Tane, in his capacity as controller of the forests, and of fertilization. In plants, Maori saw living life forms that are senior in status to man, because Tane created plant life before mankind.1

This article provides some insight into the traditional medicinal uses of one such New Zealand plant, horopito (Pseudowintera colorata), and how such use is now corroborated by almost two decades of scientific research.

Ethnobotanical Profile

Horopito also is known as New Zealand pepper tree, winter's bark, or red horopito. Pseudowintera is so named because early taxonomists recognized the similarity between horopito and the South American Drimys winteri that provided the herbal remedy "winter's bark." They are both members of the Winteraceae family, which are mainly found on the land masses that once made up the great southern continent of Gondwana - South America, Australia, New Zealand and New Guinea. The reproductive parts of the Winteraceae family are primitive, reflecting their origin among the first flowering plants. In New Zealand, horopito appears in the fossil record for more than 65 million years.2

Horopito is particularly unusual in that its flowers come directly off the older stems rather than from among the leaves. It's not surprising that New Zealand has such unique flora and fauna. Situated at the bottom of the South Pacific, plants were able to evolve in isolation from other landmasses in a climate range from subtropical to glacial.

Historical and Traditional Use

The Maori gave the name "horopito" to all three species of Pseudowintera they found in New Zealand, and this sometimes causes confusion. However, it's only the very hot-tasting Pseudowintera colorata that possesses the extraordinary antifungal properties described in this article.

Maori traditionally used horopito for many complaints, several of which bear some relation to recent scientific discoveries about the plant's properties. Horopito was one of the plants used by the tohunga (expert, learned man, medical expert) to drive away evil spirits. Also, its leaves were "worn" by the souls of the dead as they made their way across country to the astral entrance and underworld portals at Cape Reinga (Te Rerenga Wairua) on the northwestern-most tip of the Aupouri Peninsula, at the northern end of the North Island of New Zealand. Garments of horopito leaves were said to be the attire of dwellers in that other world.1

In Maori lore, the skin was said to come under the control of a being named Toroa. "Tree water" or Wai rakau, was regarded as invaluable in the treatment of skin problems. As far back as 1848, horopito is documented in the treatment of skin diseases such as ringworm, or for venereal diseases. "Leaves bruised and steeped in water; a remedy for the paipai, or skin complaint. The leaves and tender branches of this shrub are bruised and steeped in water, and the lotion used for ringworm; or the bruised leaves are used as a poultice for chaffing of the skin, or to heal wounds, bruises or cuts." Infection due to Candida albicans (Maori – Haha, Haka) is documented as being a major cause of death of Maori babies, due to their being fed an "unsatisfactory diet."3 The leaves of horopito were steeped in water to extract the juice and this decoction was used in the treatment of what we now understand as oral thrush.

Early European settlers to New Zealand also used horopito for medicinal purposes. For internal use, leaves were either chewed or prepared as a tea. "The leaves and bark are aromatic and pungent; the former are occasionally used by settlers suffering from diarrhoeic complaints." A decoction of the leaves was taken for stomachache and was known as "Maori Painkiller" and "Bushman's Painkiller."1

There are accounts of the bark being used in the 19th century as a substitute for quinine: "The stimulating tonic and astringent properties of which are little inferior to winter's bark." A French nun, Mother Aubert, went to live among the Maori at the end of the 19th century, and the native plant remedies she later created became commercially available and widely used throughout the colony of New Zealand. Horopito was one of the two ingredients in her patent medicine, Karana. In a letter to the French Consul, she described it as "superior to Quinquina [quinine] in the treatment of chronic stomach sickness" Mother Aubert used the funds her medicines generated to run one of New Zealand's first homes for ostracized, unwed mothers.

Pharmacology

The main biologically active chemical constituent of horopito is the sesquiterpene dialdehyde polygodial.4 It's known that polygodial is a component of the "hot taste" in peppery spices common in traditional Japanese cuisine.5 Polygodial has been shown to exhibit fungicidal activity against yeasts and filamentous fungi.6 9-Deoxymuxigadial (also a sesquiterpene dialdehyde) also might have pharmacological activity. Other constituents include essential oils such as pinenes, limones, humulene and eugenol, and the flavonoids quercetin, luteolin and proanthocyanidins.7

In 1982, a group from Canterbury University in New Zealand reported they had isolated a substance called polygodial in horopito leaves. The Canterbury University team grew cultures of Candida albicans and measured the zone of inhibition in these cultures produced by discs of polygodial extracted from the leaves of horopito. They found it was very effective at inhibiting Candida. Comparison with the drug amphotericin B (which commonly is used to treat systemic mycoses) found that the Horopito-derived polygodial gave larger zones of inhibition. Polygodial also suppressed Candida colony growth from day one, while amphotericin B required three to four days incubation.3

Polygodial has been shown to possess strong antifungal activity, comparable to amphotericin B, against yeast-like fungi Candida albicans, Candida krusei, Candida utilis, Cryptococcus neoformans, Saccharomyces cerevisiae and also the filamentous fungi Trichophyton mentagraphytes, Trichophyton ruburum and Pencillium marneffe.8 The antifungal activity of polygodial generally was not reduced by several susceptibility-testing conditions such as medium type, incubation temperature, inoculum size and medium pH. However, polygodial's antifungal activity was strongly increased in acidic conditions. Fungal environments in the human host, such as the mouth, vagina and skin, often are acidic, and their colonization usually creates a microenvironment with even lower pH. Under these circumstances, polygodial can be expected to act as an effective antifungal agent.

Studies conducted by the Cawthron Institute in Nelson, New Zealand, show that dried, milled horopito leaf is effective at killing Candida albicans in vitro. When compared to other natural antifungal compounds such as sodium caprylate, pau d'arco or grape seed extract, milled horopito leaf produces a far lower minimum inhibitory concentration (MIC).

MICs are defined as the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation. MICs are used by diagnostic laboratories mainly to confirm resistance, but most often as a research tool to determine the in vitro activity of new antimicrobials, and data from such studies have been used to determine MIC breakpoints.

Many New Zealand native plants exhibit regional variations in genetic make up and, consequently, biological activity. In order to determine the level of any variation across horopito populations, the private research company Forest Herbs Research and the New Zealand government-owned Industrial Research Limited joined forces to conduct the first comprehensive study of all the major populations of horopito. This research demonstrated a fivefold variation between the most active and the least active plant populations. The most active horopito populations evolved in an isolated forest that fortunately survived burning and clearing by the early settlers to New Zealand. Seedlings from this area form the basis of the sustainable horopito plantation that supplies current commercial demand.

Editor's Note: Part two of this article will appear in the February 2007 issue of Naturopathy Digest.

References

  1. Riley, M. Maori Healing and Herbal: New Zealand Ethnobotanical Sourcebook. Paraparaumu, New Zealand: Viking Sevenseas, 1994.
  2. Webb C, Johnson P, Sykes B. Flowering Plants of New Zealand. Christchurch, New Zealand: DSIR Botany, 1990; p. 104.
  3. Pomare M. Report Appendix Journal. Wellington, New Zealand: House of Representatives, 1903, H 31:73.
  4. McCallion RF, Cole AL, Walker JR, Blunt JW, Munro MH. Antibiotic substances from New Zealand plants, II: Polygodial, an anti-Candida agent from Pseudowintera colorata. Planta Medica 1982;44:134-38.
  5. Kubo I, Ganjian L. Insect antifeedant terpenes, hot-tasting to humans. Experientia 1981;37(10):1063-4.
  6. Kubo I, Taniguchi M. Polygodial, an antifungal potentiator. Journal of Natural Products, 1988;51(1):22-9.
  7. Larsen L. A Literature Survey of the Constituents of Pseudowintera colorata. Dunedin, New Zealand: Crop and Food Research, Ltd., 2001.
  8. Lee SH, Lee JR, Lunde C, Kubo I. In vitro antifungal susceptibilities of Candida albicans and other fungal pathogens to polygodial, a sesquiterpene dialdehyde. Planta Medica, 1999;65(3):204-8.

About the Author: Campbell Berry-Kilgour is a graduate of the University of Aberdeen in Scotland with a BSc (Hons.) in Pharmacology. For the past six years, he has been working with Forest Herbs Research of New Zealand, focusing on potential applications of the New Zealand native herb Pseudowintera colorata, or horopito against Candida albicans. He is a dynamic speaker who is passionate about his research into natural medicine, particularly in relation to the use of natural products and digestive well-being.



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Date Last Modified - Friday, 17-Oct-2008 12:11:02 PDT