Chemical constituents and biological activities of turmeric (Curcuma longa L.) - A review

Turmeric (Curcuma longa) is used as spice, preservative, colouring matter and has wide range of medicinal and pharmacological applications. It exhibits anti-inflammatory, anti-HIV, anti-bacterial, antioxidant, nematocidal, antiparasitic, antispasmodic and anticarcinogenic activities. It is a potent scavenger of a variety of reactive oxygen species (ROS) including superoxide anion, hydroxyl radical, singlet oxygen, peroxynitrite and nitric oxide. It is a inhibitor of ROS generating enzymes, cyclooxygenase and lipoxygenase and plays active role in the inhibition of COX-I and COX-II enzymes that are involved in the inflammatory reaction. The turmeric extract protects lipids, haemoglobin, and red blood cells from lipid peroxidation induced by hydrogen peroxide. It prevents oxidative damage and inhibits binding to toxic metabolites to DNA. Safety evaluation studies indicate that turmeric is well tolerated at very high dose (0.5 to 1.5 g/day/person) without any toxic effects. Turmeric contains 3-6% polyphenolic compounds, collectively known as curcuminoids, which is a mixture of curcumin, demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids are major components responsible for various biological actions. Pure curcumin has more potent superoxide anion scavenging activity than demethoxycurcumin or bisdemethoxycurcumin. Curcumin acts as a pro-oxidant in the presence of transition metal ions (Cu and Fe) and is a potent bioprotectant with a potentially wide range of therapeutic applications.