July 29 2007 post: I recently came across a rather curious item called glycyrrhizin, which is extracted from the root of liquorice, or Glycyhrrhiza glabra, a plant native to Turkey, Iraq, Spain, Greece and northern China. According to Wikipedia, it is 30-50 times as potent as table sugar. But it is not merely a sweetener. In ancient Greece, China and Egypt (see the MD Anderson write-up: http://tinyurl.com/2ylhja), liquorice was used to treat gastritis, coughs and colds. The MD Anderson summary gives an interesting bit of the history of liquorice; for instance, in ancient Egypt a liquorice drink was used to to honor spirits of the pharaohs, and then during World War II a Dutch physician discovered that it was effective against peptic ulcers. I should note that the liquorice FAQ page has not been updated since 2005 but is still informative (side effects, dosage and whatnot).
Glycyrrhizin is the active ingredient of liquorice root: it has anti-viral activity, ranging from the flu virus to herpes simplex and even hepatitis B and C; liver-protective (hepatoprotective) effects, and anti-HIV activity. It also clears up microbial and parasitic infections, is a thrombin inhibitor (see: http://tinyurl.com/364qr4), and is effective against allergies, chronic fatigue, asthma, arthritis and free radicals, just to give a few examples. Oh, and how about this for an interesting titbit (see: http://tinyurl.com/3yx72p)? Glycyrrhizin inhibits the replication of the SARS virus (remember that scare a few years ago?). It also apparently inhibits NF-kB and has anti-inflammatory properties. Very good. Nope, no studies on glycyrrhizin and MM cells. Too bad. However, there are other studies, so here follows a bit of a laundry list.
A June 2007 study (http://tinyurl.com/2mr62v) examines the cytotoxicity of glycyrrhetinic acid (GA) in combination with dehydrozingerone (DZ). The latter is extracted from ginger and possesses anti-inflammatory and antioxidant properties. I am going to do more research into this particular combination, but for now, I will leave it at that. When combined, these two conjugates were found to have potent cytotoxic activity ; however, when administered separately, they were inactive. An August 2007 study (http://tinyurl.com/38rhx3) examined sixteen GA derivatives and determined which had the strongest anti-proliferative and apoptotic effects against the previously-seen HL-60 leukaemia cells. This apoptotic effect on HL-60 cells had already been observed, as can be seen in this 2005 study: http://tinyurl.com/28osnh A 2006 study (http://tinyurl.com/3yd7q8) looked at the effects of a glycyrrhizin extract on human hepatoma, promyelotic leukemia and stomach cancer cells. Apoptosis was again the result.
A 2005 study (http://tinyurl.com/2sssqa) states that Glycyrrhetinic acid (GA) and its related compounds are known to have anti-inflammatory activity and also to inhibit liver carcinogenesis and tumor growth. It concludes that GA may be important in the treatment of liver cancer. Another 2005 study (http://tinyurl.com/38oszl) shows that GA protects our bodies from the damage caused by UVB radiation, but has no effect on metastatic melanoma cells. A 2001 study (http://tinyurl.com/2sc6nv) tells us that Glycyrrhizic acid is an inhibitor of lipoxygenase and cyclooxygenase, inhibits protein kinase C, and downregulates the epidermal growth factor receptor. Licorice polyphenols induce apoptosis in cancer cells.
This is all very interesting, and there seems to be a lot of apoptosis going on, but, and there is a but!, it appears that ingesting too much glycyrrhizin may not be such a good idea if you suffer from hypertension, heart disease or have water retention problems (you can read more about that in the MD Anderson FAQ page). In fact, this German Senate Commission on Food Safety report (http://tinyurl.com/2tor53) recommends that no more than 100 mg should be ingested per day on a regular basis. High doses of this compound may also reduce potassium levels. Of course, we MMers don’t want that to happen!
Final note. There is a type of liquorice without glycyrrhizin, known as Deglycyrrhizinated liquorice or DGL. So you can still enjoy the taste and some of the benefits without any unwanted side effects. And the following just occurred to me: some curcumin-takers have reported having gastric problems after ingesting curcumin well, how about trying some liquorice to settle your stomach? And here is a thought (to be discussed with your doctor, of course) for those doing chemotherapy or about to have a SCT: taken in powder form mixed with water (as a mouthwash), I read that DGL can be effective against mouth ulcers. It can also can help prevent nausea and vomiting. I don’t like the taste of liquorice, actually, but if some day a study proves that it has an anti-myeloma effect, I will be running to the nearest liquorice store!