There is an emergence and widespread use of herbal supplements and nutraceuticals1, substances that have nutritive value and physiological benefit. Most of them are natural products2 from plant-based sources. Their positive effect on health are anchored on historical and anecdotal accounts with some of them used as home remedies for certain ailments. These health benefits are being investigated in preclinical and clinical trials with the results becoming the basis for drug development. A prime example of such is the natural product curcumin.
Curcumin is one of the most widely studied compounds by chemists3. It comes from turmeric, a rhizome and a member of the ginger family2. Curcumin generally makes up 2 to 9 percent of turmeric, depending on the soil where it is grown. It is a biologically active compound that renders medicinal properties to turmeric.
Turmeric is converted into a powder and is used as a spice in Indian Cuisine. It is also used as a dye since the powdered form produces a yellow pigment and is applied on fabrics and cosmetic products. Furthermore, turmeric has been used in Ayurvedic or traditional Indian medicine4 as a home remedy for wounds and insect bites as well as in urologic, hepatobiliary, and gastrointestinal diseases2.
Three major compounds constitute curcumin. These are called curcuminoids. Of the three, curcumin makes up the majority, about 60 to 70 percent. Demethoxycurcumin represent 20 to 27 percent while bisdemethoxycurcumin contribute 10 to 15 percent in the overall composition2.
Pharmacological preparations of curcumin exist as purified extracts or synthetic curcuminoids. The powdered form is cast into a capsule or a pill. Curcumin is a relatively safe and well tolerated substance. Levels of 12 g/day and below are still considered to be safe. Lifelong studies among Indian population identified 100 mg daily supplementation to be safe. It is a nonmutagenic substance and is considered by the US Food and Drug Administration as a Generally Recognized As Safe (GRAS) product. The side effect attributed to curcumin is diarrhea and its occurrence is rare5.
Curcumin has a low bioavailability due to its poor absorption, extensive hepatic first pass metabolism, and rapid elimination. It undergoes glucuronidation and sulfation in the liver. It is poorly soluble in water. Derivatives have been developed to increase its bioavailability such as liposomal preparations and nanoparticle systems. Adjuncts such as piperine and quercetin are also used to enhance bioavailability5.
Curcumin exhibits a variety of biological effects. It has antioxidant, anti-inflammatory, antineoplastic, and metabolic properties. It exhibits its antioxidant activity by scavenging reactive oxygen species (ROS) such as hydroxyl, superoxide, and peroxynitrite radicals3. These free radicals are toxic and may damage the cell.
There is direct interaction between curcumin and inflammatory molecules such as cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF