Impatiens is a genus of plants in the family Balsaminaceae commonly referred to as jewelweed or touch-me-not. One common species found in Northeastern United States is I. capensis. Another common species is I. pallida, but these plants may also be known as I. balsimina, and I. biflora. These plants tend to grow in wet shady soils along stream banks. Traditionally, the plant has been crushed and the extract applied to poison ivy rash (Lipton 1958, Long et. al. 1997). In addition, Native Americans used the plant to treat stomach cramps (Jiasuey &Allaire). This seems odd since when eaten jewelweed can cause vomiting, catharsis, and act as a diuretic (Lipton 1958). Thus, teas made from jewelweed to treat poison ivy may cause digestive upset. More recently, compounds contained in various parts of the plant have been shown to be useful in treating various types of cancer as well as have many other uses (Kamei et. al. 1998, Villasenor & Domingo 2000, Isgiguro et. al. 2000, Trump et. al. 2001, Suzuki et. al. 2001).
The most common folk use of jewelweed is to treat rashes caused by poison ivy. Despite its widespread use for this purpose, little research has been done on its efficacy. Lipton (1958) did a clinical study where he determined that 108 of 115 patients who presented with existing poison ivy rashes that he treated with jewelweed preparations "responded most dramatically to the topical application of [jewelweed]". He later did a patch test on himself and again concluded that jewelweed extract was the most effective course of treatment. In 1980, two researchers tested the idea that perhaps it was not the jewelweed extract but the water in which it was mixed that actually worked to fight the poison ivy. They used a quantitative patch test in themselves treating two exposed areas to water, two to jewelweed, and two with nothing. They determined that jewelweed does nothing to prevent the rash and that plain water may be slightly beneficial (Guin & Reynolds 1980). Further supporting these findings, a group of researchers performed a randomized, double blinded, paired comparison investigation of ten volunteers. The volunteers were exposed to urushiol, the active agent in poison ivy, then treated with stem extract from jewelweed on one site and water on the other. The results of this study showed no difference in the resulting poison ivy rash, thus concluding that jewelweed was an ineffective treatment (Long et. al. 1997). Thus more research is needed before a definite conclusion on jewelweed's efficacy can be drawn.
Perhaps the reason for the varying investigative results lies in what part of the plant is used. Researchers in Japan showed that the pericarp of Impatiens balsamina contained three dinaphthofuran-7,12-dione derivatives (Ishiguro et .al. 1998). These three compounds all had significant anti-itching activity. However two of the three studies described above used stem extracts (Guin & Reynolds 1980, Long et. al. 1997), while only one used the entire plant (Lipton 1958). Also these compounds only serve to reduce itching, not the rash. This may, however, be significant since poison ivy rash can be spread by itching.
Root cultures of jewelweed were shown to contain the naphthoquinone, lawsone (Panichayupakanant et. al. 1995). This compound is also found in henna, which is used in the Middle East to treat dermatitis and fungal infections (Devecioglu 2001). Lawsone along with anthraquinone, another compound found in root cultures (Panichayupakanant et. al. 1995) have both been shown to be inhibitory to human colon carcinoma cell growth in cultures. These compounds along with other related compounds block cell division in the S phase (Kamei et. al. 1998).
Another compound found in the same root culture study was spinasterol (Panichayupakaranant 1995). This compound when isolated from squash flowers was shown to have great anticarcinogenicity potential when tested using the mouse skin tumor assay. It is already known to be an antimutagen (Villasenor & Domingo 2000). This same compound was also shown to inhibit cholesterol absorption, and the production of bile acids in laboratory mice (Uchida et. al. 1983).
A coumarin derivative, scopoletin, also isolated from root cultures (Panichayupakaranant 1995) was shown to enhance eosinophil activation causing the to release hydrogen peroxide. A second coumarin derivative, isofraxidin, (Panichayupakaranant 1995) acts as a sedative (Chen & Liu 1991).
The seeds of Impatiens balsamina have been shown to contain four cysteine rich compounds with marked antimicrobial properties. These proteins, labeled Ib-AMP 1 through 4, were shown to inhibit the growth of a wide range of fungi and bacteria without harming human cells. (Tailor et. al. 1997). Subsequent structural studies of Ib-AMP 1 suggested that the protein interacts with membrane bound receptors, though the exact mechanism is not yet determined (Patel et. al 1998).
More recently jewelweed has taken on significance for its potential in treating breast and testicular cancer. Researchers in Japan discovered that the aerial parts of Impatiens balsamina contain a testosterone 5alpha-reductase inhibitor. The compound was named impatienol 1. This compound has been previously synthesized but this is the first time it was isolated from a natural source (Ishiguro et. al. 2000). Other studies on 5alpha-reductase inhibitors have shown that these compounds block the intracellular metabolism of testosterone and inhibit the growth of the prostate. It is thought that this activity may prevent prostate cancer from even developing, though results of a long term study are not yet complete (Trump et. al. 2001). This same group of compounds is also under investigation for their potential role in inhibiting cell proliferation in hormone dependent human breast carcinoma (Suzuki et. al. 2001).
As can be seen jewelweed contains many useful compounds even if it is not effective against poison ivy. More research is needed to see if any of the other compounds found in this plant have medicinal uses and whether jewelweed is a feasible source of the compounds for therapeutic uses.
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Suzuki, T., A.D. Darnel, J.I. Akahira, N. Ariga, S. Ogawa, C. Kaneko, J. Takeyama, T. Moriya, & H. Sasano. 2001. 5alpha-reductases in human breast carcinoma: possible Modulator of in situ and androgenic actions. Journal of Clinical Endocrinology and Metabolism 86:2250-2257.
Tailor, R.H., D.P. Acland, S. Attenborough, B.P. Cammue, I.J. Evans, R.W. Osborn,, J.A. Ray, S.B. Rees, W.F. Broekaert. 1997.A novel family of small cysteine-rich antimicrobial peptides from seed of Impatiens balsamina is derived from a single precursor protein. Journal of Biology and Chemistry 272:24480-24487.
Trump, D.L., J.A. Waldstreicher, G. Kolvenbag, P.S. Wissel, B.L Neubauer. 2001. Androgen antagonists: Potential role in prostate cancer prevention. Urology 57:64-67.
Uchida, K., H. Mizuno, K. Hirota, K. Takeda, N. Taheuchi, Y. Ishikawa. 1983. Effects of spinasterol and sitosterol on plasma and liver cholesterol levels and biliary and fecal sterol and bile acid excretions in mice. Japanese Journal of Pharmacology. 33:103-112.
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