Curcuma longa - Turmeric - Monograph

Alternative Medicine Review, Sept, 2001

Description

Curcuma longa, a perennial herb, is a member of the Zingiberaceae (ginger) family. The plant grows to a height of three to five feet, and is cultivated extensively in Asia, India, China, and other countries with a tropical climate. It has oblong, pointed leaves and bears funnel-shaped yellow flowers. (1) The rhizome is the portion of the plant used medicinally; it is usually boiled, cleaned, and dried, yielding a yellow powder. Dried Curcuma longa is the source of the spice turmeric, the ingredient that gives curry powder its characteristic yellow color. Turmeric is used extensively in foods for both its flavor and color. Turmeric has a long tradition of use in the Chinese and Ayurvedic systems of medicine, particularly as an anti-inflammatory agent, and for the treatment of flatulence, jaundice, menstrual difficulties, hematuria, hemorrhage, and colic. Turmeric can also be applied topically in poultices to relieve pain and inflammation. (2) Current research has focused on turmeric's antioxidant, hepatoprotective, anti-inflammatory, anticarcinogenic, and antimicrobial properties, in addition to its use in cardiovascular disease and gastrointestinal disorders.

Active Constituents and Pharmacokinetics

The active constituents of turmeric are the flavonoid curcumin and volatile oils including tumerone, atlantone, and zingiberone. Other constituents include sugars, proteins, and resins. The best-researched active constituent is curcumin, which comprises 0.3 to 5.4 percent of raw turmeric. (2) Pharmacokinetic studies in animals demonstrate that 40-85 percent of an oral dose of curcumin passes through the gastrointestinal tract unchanged, with most of the absorbed flavonoid being metabolized in the intestinal mucosa and liver. (3,4) Due to its low rate of absorption, curcumin is often formulated with bromelain for increased absorption and enhanced anti-inflammatory effect.

Antioxidant Effects

Water- and fat-soluble extracts of turmeric and its curcumin component exhibit strong antioxidant activity, comparable to vitamins C and E. (5) A study of ischemia in the feline heart demonstrated that curcumin pretreatment decreased ischemia-induced changes in the heart. (6) An in vitro study measuring the effect of curcumin on endothelial heme oxygenase-1, an inducible stress protein, was conducted utilizing bovine aortic endothelial cells. Incubation (18 hours) with curcumin resulted in enhanced cellular resistance to oxidative damage. (7) Another in vitro study demonstrated that low concentrations of curcumin incubated with activated macrophages resulted in a decrease in mRNA levels and nitric oxide synthase activity. This study demonstrates curcumin's antioxidant role in down-regulating nitric oxide formation, a key element in inflammation and possibly in the process of carcinogenesis. (8)

Hepatoprotective Effects

Turmeric has been found to have a hepatoprotective characteristic similar to that of silymarin. Studies have shown its hepatoprotective effects in protecting animal livers from a variety of hepatotoxic insults, including carbon tetrachloride (CCIA), (9,10) galactosamine, (11) acetaminophen (paracetamol), (12) and Aspergillus aflatoxin. (13) Its hepatoprotective effect is mainly a result of turmeric's antioxidant properties. In rats with CCL4-induced acute and subacute liver injury, curcumin administration significantly decreased certain liver enzyme values, resulting in decreased liver injury in the test animals compared to controls. (10) Turmeric extract inhibited fungal aflatoxin production by 90 percent when given to ducklings infected with Aspergillus parasiticus at concentrations of 5-10 mg/mL. Turmeric and curcumin were also found to reverse biliary hyperplasia, fatty changes, and necrosis induced by aflatoxin production. Curcumin alone had no effect on aflatoxin production. (13) Sodium curcuminate, a salt of curcumin, also exerts choleretic effects by increasing biliary excretion of bile salts, cholesterol, and bilirubin, as well as increasing bile solubility, therefore possibly preventing and treating cholelithiasis. (14)

Anti-inflammatory Effects

The volatile oils and curcumin of Curcuma longa exhibit potent anti-inflammatory effects. (15-17) Oral administration of curcumin in instances of acute inflammation was found to be as effective as cortisone or phenylbutazone, and one-half as effective in cases of chronic inflammation. (17) In rats with Freud's adjuvant-induced arthritis, oral administration of Curcuma longa significantly reduced inflammatory swelling compared to controls. (16) In monkeys, curcumin was shown to inhibit neutrophil aggregation associated with inflammation. (18) C. longa's anti-inflammatory properties may be attributed to its ability to inhibit pro-inflammatory arachidonic acid, as well as neutrophil function during inflammatory states. Curcumin may also be applied topically to animal skin to counteract inflammation and irritation associated with inflammatory skin conditions and allergies. (17)