Natural plant products have been used throughout the history of mankind for a variety of different purposes. Many of these plants have evolved alongside us and are billions of years old.
Around 61% of the drugs introduced worldwide between 1981 and 2002 can trace back their origins to natural products. This is hardly a surprising statistic considering that around 80% of individuals in developing countries rely entirely on natural products for their healthcare.
In today’s article we are going to look at one of these natural products, curcumin, an active component of the perennial herb Turmeric (also known as Curcuma longa), a member of the Zingiberaceae family.
Traditional use of Curcumin
Curcumin was first isolated in 1815 and was sourced in a crystalline form in 1870 – it is frequently used as a spice and provides curry with its distinctive yellow colour. It is also commonly used as a colouring agent in cheese and butter.
Topically, turmeric is used for analgesia, ringworm, bruising, eye infections, inflammatory skin conditions, inflammation of the oral mucosa and infected wounds.
Rheumatoid arthritis: A clinical trial compared the effects of curcumin with a well known anti-rheumatic drug, phenylbutazone. The 18 patients in the trial received a daily dose of either curcumin or phenylbutazone for 2 weeks. Curcumin was well tolerated, had no side effects, and exerted an anti-rheumatic activity comparable to that of phenylbutazone (Satoskar et al 1986).
Cardiovascular disease: An 8 week trial with 32 postmenopausal women compared the effectiveness of curcumin and exercise in improving vascular function. The researchers concluded “Curcumin is as effective in improving vascular function in postmenopausal women as a moderate aerobic exercise training programme” (Akazawa et al 2012).
Bioavailability and Absorption
Many studies have shown that curcumin is safe even at high doses. However, it is also considered to have a low systemic bioavailability andthis has made clinical trials difficult to date. This is due to its low aqueous solubility and extensive hepatic and intestinal metabolism. Curcumin undergoes extensive Phase I and Phase II hepatic metabolism.
When metabolized in the liver, the major metabolic products of curcumin are glucuronides of Tetrahydrocurcumin (THC) and Hexahydrocurcumin (HHC), which are less active than curcumin itself. Thus, to improve the oral bioavailability of curcumin, both low solubility and high metabolic clearance must be overcome.
When curcumin is co-administered with piperine, which increases intestinal absorption and reduces enterohepatic metabolism, bioavailability is increased; in one study serum levels of curcumin increased by 2000% (Shoba et al 1998).
When turmeric/curcumin is heated gently and dissolved in oil (as in traditional Indian cooking) it bypasses intestinal enzymes and can be directly absorbed into chylomicrons and then thelymphatic system, thus bypassing the liver. So other delivery platforms are also beinginvestigated and used eg liposomal or phospholipid formulations to improve absorption.
Conclusion;
Curcumin is believed to have over 90 molecular targets and many mechanisms of its action are understood thanks to in vitro and animal models. Clinical trials were initially hampered by its low bioavailability. This has now been improved by concomitantly administering curcumin with piperine or liposomal formulations. It is an exciting area of research to watch.