Coumarins are a group of important natural compounds, and have been found to have multi-biological activities such as anti-HIV, anti-tumor, anti-hypertension, anti-arrhythmia, anti-osteoporosis, pain relief, preventing asthma and antisepsis. Natural products like esculetin, fraxetin, daphnetin and other related coumarin derivatives are recognised as inhibitors not only of the lipoxygenase and cycloxygenase enzymic systems, but also of the neutrophil-dependent superoxide anion generation. Such derivatives also possess anti-inflammatory as well as antioxidant activities. Osthole is a coumarin found in cnidium.

Coumarin Research study
Chemical aspects of coumarin compounds for the prevention of hepatocellular carcinomas.
Curr Med Chem Anti-Canc Agents. 2005.
The normalization of plasma alanine aminotransferase (ALT) has been proved to be a strategy for preventing the development of hepatocellular carcinoma (HCC) in hepatitis C virus (HCV)-infection. Glycyrrhizin, a plant medicine, normalizes plasma ALT and prevents HCC. However, glycyrrhizin is administered intravenously and thereby chemical which is effective on oral administration is required. Coumarin compounds are active components of herbs used for the treatment of various diseases. The ability of coumarin compounds to lower plasma ALT were examined using mice concanavalin A-induced hepatitis and mice anti-Fas antibody-induced hepatitis. Furanocoumarins pd-Ia, pd-II and pd-III lower plasma ALT, but they are large molecules that are hardly absorbed on oral administration. Furocoumarin effectively lowers plasma ALT, but the safety range between the effective and toxic dosages is narrow. In contrast, osthole, a simple coumarin, causes strong reduction of plasma ALT and also inhibits caspase-3 activation. Furthermore, this chemical is quite safe upon large dose administration. In the structure of osthole, the methoxy group at position-7 and the 3-methyl-2-butenyl group at position-8 were elucidated to be essential for the beneficial effect of this chemical. We conclude that osthole will become a leading chemical for synthesizing a compound which prevents HCC on oral administration.

Emails
Q. Why does NO Shotgun contain traces of coumarin? Isn't it a banned substance by the FDA? According to the FDA, Coumarin is "prohibited from use in human food". Here's a link that advises people not to consume NO Shotgun from VPX Sports because of the prescription drug coumarin contained in NO Shotgun. Can't VPX Sports eliminate the prescription drug coumarin contained in NO Shotgun? There are also talk that the prescription drug coumarin is harmful for the liver and kidneys. Coumarin is also known to cause liver and kidney damage! I just want that the company VPX Sports to eliminate the banned substance coumarin from their NO Shotgun supplement, so it can be safer for human consume!
   A. Small amounts are found in many plants and can actually be of health benefit. I have no idea how much coumarin is found in NO Shotgun. If the amount is minimal, this substance would not cause harm. There are many substances in the NO Shotgun product and I don't know what effect, positive or negative, this product has when ingested since I have not tried it myself.

I bought a bottle of ground cinnamon at my grocery store because I had read about the health benefits of cinnamon and specifically, cassia, which is the cinnamon normally available as a spice and supplent in North America. However, upon further research, it appears that cassia may NOT be safe to consume on a regular basis especially if used in the gram levels. This is mainly because it contains a toxin called coumarin. Instead of me explaining the bad side effects of cassia, I refer you to read the following i found on the internet: Coumarin is a flavouring which is found in higher concentrations in the types of cinnamon grouped together under the name “cassia cinnamon”. Relatively small amounts of coumarin can already damage the liver of particularly sensitive individuals. However, this is not permanent damage. Isolated coumarin may not be added to foods. If coumarin is contained in partsof plants added to flavour foods, then it is limited to two milligrams per kilogram food. Checks by the official food control authorities had shown that this level has been exceeded, in somecases considerably, in cinnamon biscuits. This prompted the Federal Institute for Risk Assessmentto assess the potential health risk for consumers from coumarin in cinnamon containing foods and to establish a tolerable daily intake (TDI). Given the high levels of coumarin measured, the Institute advises consumers to only eat moderate amounts of cinnamon-containing foods, particularly in the run-up to Christmas. In response to the numerous inquiries from the media and consumers, BfR has compiled questions and answers on coumarin in cinnamon. What is coumarin and where does it occur? Coumarin is a natural flavouring and perfume that is found in many plants. It occurs in higher concentrations in the types of cinnamon grouped together under the name “cassia cinnamon”, for instance woodruff, tonka beans and melilot.
    I have not come across human studies or reports that cinnamon use in reasonable amounts has caused harm. It is often a good idea to take breaks from use of many types of supplements.