Indian spices are renowned for their medicinal properties and have been used to cure several ailments since time immemorial. Turmeric or haldi as it is commonly known is a common inhabitant in most Indian kitchens. It is a potent anti-inflammatory compound and has been used to cure diseases like jaundice and stomach ache. Turmeric is an age-old antiseptic and can effectively treat wounds and cuts. The medicinal properties of turmeric come from its active principle: Curcumin.
Curcumin is a known anti-oxidant that has shown promise as an anti-cancer agent. Despite this, the potential of curcumin as a therapeutic drug remains untapped. A drug’s efficiency can be gauged by its bioavailability. Bioavailability is the fraction of the drug that enters the blood unchanged. A major limitation of curcumin as a drug stems from its poor bioavailability, instability in water and degradation in light.
The various ways in which these problems can be addressed have been explored in a paper that was recently published in Accounts of Chemical Research. This has been authored by the researchers, from the Indian Institute of Science. The instability of curcumin in water can be circumvented to an extent by binding it to metal ions like zinc and vanadium. These metal-curcumin complexes have been shown to be effective anti-cancer compounds, proving that metal binding does not hamper the pre-existing medicinal properties of curcumin.
A new form of cancer therapy known as Photodynamic Therapy (PDT) is becoming increasingly famous. This form of treatment uses a drug known as a photosensitizer which interacts with a specific wavelength of light. This interaction produces a form of oxygen which is extremely toxic to cancer cells but does not affect the photo-unexposed normal cells. The photosensitizer currently being used is associated with some side-effects like liver and skin damage. Curcumin-based metal complexes can be evaluated as potential candidates for this form of cancer therapy. Preliminary studies have shown that the binding of metals to curcumin increases the light dependent toxicity of curcumin towards cancer cells. Researchers at the Indian Institute of Science have designed metal based curcumin complexes that show toxicity towards cancerous cells when irradiated with visible light thereby minimizing damage to the skin.
The applications of metal complexes of curcumin are manifold. Apart from being used as anti-cancer compounds, these complexes can also be used for imaging cancer cells thereby helping in localization studies. Curcumin complexes with copper also serve as a potent anti-oxidant. Studies have shown that some metal nitrates can also form complexes with curcumin which confer an enhanced antibacterial activity. Recent reports have emerged where curcumin complexes were used to stain protein aggregates that are hallmarks of Alzheimer’s disease. Complexes of curcumin with fluorine and gallium have shown immense potential as radiotracers for imaging lung cancer as well as Alzheimer’s disease.
A major challenge faced in cancer chemotherapy is the transport of the drug in a selective manner to the site of cancer. Metal complexes of curcumin have been able to surpass this challenge and studies have indicated efficient tumor targeting activity of these complexes. “We have made curcumin-metal complexes which may become promising for PDT as well as cellular imaging”, says Dr. Samya Banerjee, one of the researchers who was involved in this study. This method has given an insight into the unrealized potential of curcumin-based metal complexes as anti-oxidants, drugs for cancer detection and therapy.
About the authors: Akhil R Chakravarthy is a Professor in the Department of Inorganic and Physical Chemistry, Indian Institute of Science. Samya Banerjee recently obtained PhD from the same department.
Contact: 91-80-2293 2533 (Prof Akhil R Chakravarthy)