A Phytomedical Overview: Wasabia Japonica
Glen Nagel, ND and Brian Oates, PhD
True Japanese Wasabi is one of the world’s most rare perennial crops. Wasabia japonica is a member of the mustard family called the Brassicaceae, formerly Cruciferae. Wasabia is native to Japan and Sakhalin Island north of Japan. It grows naturally in the gravel beds of mountain streams and requires a specific environment to thrive. Wasabia is traditionally cultivated in either water or soil for different tastes. Outside of Japan, Wasabi is usually identified as the spicy green paste served with sushi. However, typical Wasabi paste is in fact horseradish root (Armoracia rusticana) and coloring, and has little if any true Wasabia root. Pure Wasabi (called Wasabia to differentiate it from common horseradish sushi wasabi) is more costly and considered a rare delicacy. It is traditionally grated fresh onto food, since it can lose its flavor in as little as 10-15 minutes. In Japan, Wasabia has not only been considered a food delicacy that adds a pungent flavor to food, but it is also believed to have powerful medicinal action. Like many aspects of a healthy traditional Japanese diet, regular use of Wasabia may be partially responsible for the longevity and health of the Japanese people. Currently, scientific research is beginning to help us understand why Wasabia is both a super food and a powerful herbal medicine.
Fresh Wasabia contains protein, fiber, vitamins B6 and C, and the minerals calcium, magnesium, potassium and manganese. Wasabia is similar to many plants in the mustard family in that it contains a group of compounds called glucosinolates. These components are enzymatically converted to the bioactive isothiocyanates (ITCs) in an aqueous medium when the cells are disrupted by being chewed or ground up. Wasabia differs from other crucifers in that it has higher concentrations of ITCs, especially long-chain ITCs. These long-chain ITCs (6-methylsulfinylhexyl isothiocyanate or 6-MITC, 7-methylsulfinylheptyl isothiocyanate and 8-methylsulfinyloctyl isothiocyanate) also give Wasabia its unique flavor, termed its “green note.” The enzyme responsible for converting the inert glucosinolates to ITC is myrosinase, a very labile molecule. If Wasabia is air-dried, its myrosinase breaks down; therefore, the ITCs that produce the characteristic heat, flavor and biomedical activity of Wasabia are not formed. This is why traditionally only fresh rhizomes and leaves are used. Now researchers are finding that freeze-drying Wasabia will stabilize the activity of the myrosinase until exposed to water or digestive fluids.
There is a tremendous amount of ongoing research, especially in Asian countries, on Wasabia and its medicinal benefits. Current findings center on the ITCs that provide the majority of activity. Many scientists have focused on 6-MITC, of which Wasabia japonica contains a high concentration. However, all of Wasabia’s many ITCs (20 or more) likely contribute to the medicinal action. Combined with traditional knowledge, research on Wasabia japonica is providing insight into the actions of Wasabia in the body. Scientific evidence suggests many biomedical applications for the natural components found in Wasabia. The following is a research summary of Wasabia japonica and its ITCs.
Wasabia may be useful for controlling seasonal allergies and asthma. ITCs are effective agents for inflammation based on their rapid action and the low levels needed. 6-MITC can inhibit lipoxygenase, cyclooxygenase and cAMP phosphodiesterases that are involved in inflammation. Isothiocyanates of Wasabia and other crucifers are anti-inflammatory (Depree et al., 1998) and anti-asthmatic (Dorsch et al., 1984) agents. Depree et al. (1998) were so impressed with results when testing ITCs that they made the following statements: “The anti-inflammatory effects and inhibition of platelet aggregation by omega-methylthioalkyl isothiocyanates is perhaps of more interest given the rapid action of the compounds and the low levels at which they are effective.” This could potentially be used to counter inflammatory conditions such as allergies, asthma, eczema or even anaphylaxis. The ability of the Wasabia isothiocyanates to inhibit platelet aggregation could also have medical applications, particularly in the treatment of heart attacks. Further work on the pharmacology of these compounds and their possible medicinal use, as well as other medicinal properties of Wasabia, seems warranted. A growing experience from natural health practitioners suggests that Wasabia can be an effective treatment for seasonal allergies as well as asthma and eczema.
ITCs have an inhibitory effect on several strains of bacteria, yeast and mold. In fact, Wasabia japonica was first introduced into the raw fish diet of the Japanese for its anti-microbial properties. Isothiocyanate vapors inhibit the growth of several strains of bacteria, yeast and mold (Depree et al., 1998). Several scientific studies (Ono et al., 1998; Shin and Lee, 1999) have shown that 6-MITC from Wasabia extracts have potent anti-bacterial properties against Staphylococcus aureus and Escherichia coli. Isothiocyanates in Wasabia have demonstrated an inhibitory effect against Streptococcus mutans,the bacterium responsible for dental cavities (Masuda et al., 2000). These results may lead to Wasabia extracts being used in a variety of products (i.e., toothpastes and mouthwashes) for cavity prevention. More recent research has proven Wasabia extracts inhibit mutant strains of the Staphylococcus. Another biomedically important bacterium that Wasabia and ITCs inhibit is Helicobacter pylori (Masuda et al., 2001; Shin et al., 2004; Haristoy et al., 2005). This bacterium is known to be responsible for gastric ulcers and ensuing stomach cancers. Wasabia extracts kill the bacterium, even if it has entered cells lining the stomach.
The inhibition of inappropriate platelet aggregation is important for protection against heart attacks and strokes. The 6-MITC of Wasabia has been found to inhibit platelet aggregation (Kumagai et al., 1994; Morimitsu et al., 2000; Morimitsu et al., 2002), a property useful in the elderly, where preventing excessive clotting is vital. Platelet aggregation is a precipitating factor in cardiovascular diseases. 6-MITC inhibits platelet aggregation by a number of different mechanisms, including the inhibition of lipoxygenase, cyclooxygenase, cAMP phosopodiesterases and cGMP phosphodiesterase.
There is a growing base of evidence on how ITCs work against cancerous cells. Isothiocyanates act to inhibit enzymes that cause pre-carcinogenic compounds to turn into carcinogenic ones (Phase I enzymes).They also can induce detoxifying Phase II enzymes (Yu et al., 1996; Hecht, 1999; Kirlin et al., 1999), like glutathione S-transferase (Morimitsu et al., 2000), possibly through gene expression (Yu et al., 1996; Gao and Talalay, 2004), and inhibit initiation of cancerous growths (Yano et al., 2000). 6-MITC has also been shown to block the cell cycle of cancerous cells (Hashimoto et al., 2004) and to affect protein production in cancerous cells (Hou et al., 2000). Metastasis, a critical stage in spreading cancer beyond local extension, can be blocked by ITCs and in particular 6-MITC. Fuke and her co-workers (1997, 2000, 2006) and Manesh and Kuttan (2003) have shown that 6-MITC from Wasabia suppressed dissemination or metastasis of certain tumor cells. In numerous cases, the ITCs from Wasabia have been shown to cause cancerous cells to undergo apoptosis or cell death. This has been shown in leukemia cells (Nakamura et al., 2001; Fimognari et al., 2004), breast cancer cells (Nomura et al., 2005), lung cancer (Kuang and Chen, 2004), colorectal cancer (Lund et al., 2001) and cancerous cells of other types (Watanabe et al., 2003; Fimognari et al., 2005).
An important point is that ITCs are efficacious against the cancerous cells but do no harm to healthy cells. No side effects have been encountered! Musk and co-workers (1993, 1995) showed that allyl isothiocyanates (AITC), another ITC in Wasabia, was selectively toxic toward colorectal tumor cells. Nakamura et al. (2001) found in the case of leukemia that the ITCs from Wasabia inhibit the growth of leukemia cells but do not inhibit normal cells.
Other Health Effects
In addition to the above health benefits, there is now evidence showing that Wasabia and its isothiocyanates provide other medical effects: It reduces diarrhea (Nakayama et al., 1998); protects nephrons in diabetes patients (Fukuchi et al., 2004); acts as antioxidants (Gao et al., 2001; Lee et al., n.d.); provides immune modulation (Manesh and Kuttan, 2003); inhibits cancer and lessens treatment toxicities (Manesh and Kuttan, 2005); and protects cardiovascular function (Wu et al., 2004).
Wasabia japonica contains another potentially exciting compound. Suzuki and his co-authors (Suzuki et al., 1997; Suzuki and Yamaguchi, 1999) found that a compound in Wasabia japonica leaf stalk extract has a significant stimulatory effect on bone calcification in vitroand in vivo. The authors’ findings revealed that the compound was easily extracted from the plant tissue, is of small molecular weight and functions at low concentrations.
It is likely that Wasabia will become a useful adjunct for many of the chronic health conditions that plague our world. These include asthma, seasonal allergies, arthritis, IBS, Crohn’s disease, allergic reactions, food poisoning, dental carries, gingivitis, H. pylori-caused infection and ulcers, heart disease, stroke, blood clots, protection against certain cancers (breast, prostate, colon, lung, pancreas, esophagus, bladder, leukemia and more), toxicity from chemotherapy and radiation treatment, and osteoporosis. Hopefully, Wasabia and the ITCs found in the whole plant will eventually prove effective against diseases that kill millions of people yearly, like heart disease, cancer, chronic inflammatory diseases and infections. Recent advances in herbal processing have made the active glucosinolates in Wasabia stable until mixed with digestive juices, allowing the full spectrum of fresh Wasabia rhizome ITCs to be available. This is indeed an exciting time to be discovering the ancient wisdom of medicinal plants. Wasabia has a long traditional use in the East and the potential to become a useful food, supplement and/or medicine for the rest of the world.
Glen Nagel, ND has been a practicing herbalist for the last 20 years. He has worked in the herbal industry and as an herbal educator, offering classes and courses in herbal medicine. Nagel is also a licensed ND in Washington and Oregon, and has practiced naturopathic medicine since 1993. He is a former assistant professor of botanical medicine at Bastyr University. Currently, Nagel works as a clinical supervisor at NCNM and as a director of education for Eclectic Institute Inc.
Brian Oates, PhD is the founder and president of Pacific Coast Wasabi (PCW). Oates became interested in Wasabia japonica after uncovering the abundant biomedical efficacies of this plant. Prior to starting up PCW, Oates was a research scientist and lecturer for 15 years in the department of botany at the University of British Columbia. He has acted as a consultant for several companies, developing new biologically based products. Dr Oates is a graduate of the University of California, Irvine.
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