Picrorrhiza kurroa, commonly referred to as Picrorrhiza, is a small, perennial herb. Its classification exists within the Scrophulariaceae family of plants.  Picrorrhiza is native to the alpine Himalayas, growing at elevations from 3000 - 5000 feet. The root and rhizome of the plant has been used for centuries by those living in regions of Southwest Asia. It also has documented use in ancient Ayurvedic medicine - the traditional system of medicine in India. Unfortunately, over-harvesting has led to the threatened, and near extinct, status of this important plant species. 
The main constituents in Picrorrhiza are; iridoid glycosides (picrosides and kutkoside), cucurbitacin glycosides, apocynin, and drosin.  The principal component for which preparations are often standardized to contain is kutkin, which is made up of the iridoid and cucurbitacin glycosides.  Picrorrhiza is considered as a trophorestorative herb for the liver, as well as a potent immune stimulant.
Pharmacologic activity of Picrorrhiza includes anti-oxidant, anti-inflammatory, and immunomodulatory effects. In study, Picrorrhiza has demonstrated the ability to inhibit platelet aggregation as well. Animal studies suggest that an ethanol extraction of Picrorrhiza can protect against hepatic oxidation, demonstrating its potent anti-oxidant effect. The purported anti-inflammatory effects appear to be due to increased sensitivity of B-adrenergic receptors and functional impairment of pro-inflammatory cells such as neutrophils, macrophages and mast cells. 
Picrorrhiza can also positively affect immune system function by influencing neutrophil activity through reduction of oxidative burst; without affecting chemotaxis, phagocytosis, and intracellular bacteriocidal activity.  It may also enhance T-cell, B-cell, and phagocytic function.  These particular actions are thought to be caused by the constituent, apocynin. Apocynin is also responsible for anti-platelet activity as it can inhibit thromboxane synthetase and platelet-activating factor, thus inhibiting arachidonic acid-induced platelet aggregation. 
Current medicinal actions ascribed to Picrorrhiza include;
Traditionally, Picrorrhiza was used as a laxative, choleretic, galactagogue, bitter tonic, febrifuge, and for the treatment of asthma and poisonous bites and stings.
Most of the research conducted on Picrorrhiza has been either in vitro or in animal studies. Human trial data is lacking. However, the research that has been carried out, combined with centuries of traditional use, suggests Picrorrhiza may be a valuable tool in treating an array of human disorders.
The main application of Picrorrhiza that has been investigated is its hepatoprotective effect. A study in mice intoxicated with aflatoxin B2, a potent hepatotoxin and hepatocarcinogen, showed that Picrorrhiza reversed the increased lipid peroxide levels, while decreasing enzymic antioxidant levels induced by aflatoxin B.  This effect was comparable to that of another more commonly known herbal hepatoprotective agent, Silymarin. Another study confirmed this hepatoproctective affect, again comparing it to Silymarin.  Picrorrhiza has also demonstrated effectiveness against complement-mediated liver damage of secondary viral hepatitis leading to faster recovery. [8, 9]
A randomized double-blind, placebo-controlled trial of patients with acute viral hepatitis was conducted to determine the effects of a preparation containing Picrorrhiza.  Thirty-three subjects were given either 375 milligrams (mg) of powdered Picrorrhiza three times per day or placebo for two weeks. The results showed that the Picrorrhiza treatment significantly reduced bilirubin, SGOT, and SGPT (hepatic enzymes indicative of liver function) compared to placebo, and speeded the time for bilirubin to drop.
Picrorrhiza has also demonstrated anti-diabetic activity in animal studies. Rats were given an alcoholic extract of Picrorrhiza kurroa at a dose level of 75mg extract/kg of body weight.  After 2 hours the maximum level of reduction in plasma glucose was observed. As well, in alloxan-induced diabetic rats the same dose reduced plasma glucose by 43%, while doubling the dose (150 mg/kg body weight), reduced it by some 60%. The extract also showed efficacy over a 10 day administration period.
Furthermore, P. kurroa reduced increased blood urea nitrogen and serum lipid peroxides in alloxan-induced diabetic animals. It also inhibited body weight reduction and leukopenia induced by alloxan administration. The authors of the study conclude that the extract can actually address biochemical changes induced by alloxan. This experiment is promising for future uses of the extract in diabetic patients, but clinical trials are first required.
Picrorrhiza may also be of benefit in the treatment of patients with cancer. Animal studies suggest that a specific extract of P. kurroa, Picroliv, containing iridoid glycosides, possesses anti-cancer activity. Mice given a chemical to induce tumors were also given 100 and 200 mg/kg body weight of Picroliv.  In comparison to controls, the mice given the extract experienced a survival rate of 60 and 66% for the 100 and 200mg/kg Picroliv, respectively.
In another tumor model, topical applications of 1 and 5mg of Picroliv resulted in a 50 and 60% reduction in the number of animals that developed papillomas, and 48 and 64% reduction in the number of papillomas per mouse; as well as a substantial delay in the onset of first skin tumor. Oral administration of the extract also had significant effects in this model, suggesting this study should be further investigated to warrant Picroliv’s administration in human subjects.
Picrorrhiza may also be useful in treating multi-resistant strains of Salmonella typhi, demonstrating moderate anti-bacterial activity against this type of bacteria in vitro.  In addition, Picrorrhiza may be beneficial for patients with allergies, myocardial stress , arthritis, asthma, hepatic cirrhosis, recovery from viral infections, infectious diarrhea, endometrial cysts, biliary pain, rhinitis, and sinusitis. [4, 14-17]
Dosages are dependent on the type of preparation used, and the intended condition to be treated. Generally, if using a 1:2 strength tincture, a range of 1 - 4 milliliters per day is often a sufficient dose. The iridoid glycosides in Picrorrhiza are best extracted in ethanol. However, the root is so bitter that compliance may be low.  Encapsulated powdered root (usually standardized to contain 4% kutkin) is more easily taken at a dose of 400 - 1500 mg/day, up to 3.5 grams for the treatment of fevers. 
Picrorrhiza should be used with caution in cases with excessive immune function because it is a promoter of all aspects of immune function. 
There have been no published reports of toxicity in humans and there is a long history of traditional use in Ayurvedic medicine, suggesting Picrorrhiza is a relatively safe herb when used at recommended dosages. The LD50, or median lethal dose, of kutkin in rats is greater than 2600 mg/kg.  The term ‘LD50’ is the amount of a toxic agent required to kill 50 percent of the studied animal populous.
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