Final Progress Report
UGC sponsored minor research project entitled “Synthesis and Structural Activity of
Metal Ion Complexes of Bioactive Curcumin”
Principal Investigator: Dr. A. Ramesha Baba
The main objectives of the proposal were comprised of synthesis of the metal
complexes of curcumin, isolated from turmeric and the study of biological activities of these
complexes against bacterial and fungal strains.
The interaction between the active ingredient of medicinal plants and metal ions in the body
frequently involving complexation and most of them through the process called metal
chelation. Many metal ions are dissolved, as free ions, in all of our bodily fluids. They are
vital to life but sometimes they can be toxic to body and we must find some way to get them
out. Medicines given to the patients for this purposes usually bind with metal ions, i.e. metal
complexation, rendering them less toxic or easier to be removed from the body. On the other
hand, some agents by themselves can be used as medicine in free form, but in the form of
metal complexes they were found to be more effective than the free form.
A complex ion with a molecule called a ligand attached to it through co-ordinate covalent
bonds. A complex salt is an ionic compound but it differs in the fact that there are these
covalent bonds attaching the metal to the ligand. The β-diketone functional group of
curcumin can be a powerful natural chelating agent which is safe even administered at high
dose in human.
With the proposed set of objectives first we have studied the different extraction procedures
for the extraction of curcumin from turmeric powder. Then our interest was to develop new
metal complexes with curcumin. Therefore the metal ion salts and extracted curcumin were
dissolved separately in ethyl alcohol in the ratio 1:2, the metal ion solution was then added to
the curcumin solution slowly and with continuous stirring. pH of the mixture was maintained
at 7.5-9.5 by adding ammonia on the water bath at 37°C, followed by reflux for 2 hours and
afforded a solid product that was then isolated by overnight in vacuum at room temperature.
Metal ion complexes such as cobalt(II) curcumin, molybdenum(II) curcumin, manganese(II)
curcumin, cadmium(II) complex and copper(II) curcumin complexes were synthesized by
following the above method. And the complexes were attempted in vitro study in comparison
with curcumin. The action of these agents is examined on several bacterial strains. The
cobalt curcumin complex is more effective against all the strains under investigation in
comparison with the molybdenum complex. The complex exhibited antibacterial activity
which is remarkably high compared with curcumin on all the strains. Therefore, the cobalt
curcumin complex is found to have more antibacterial effect than curcumin itself and could
be a suitable candidate for further in vivo investigations.
The antioxidant activity of curcumin metal complexes were also studied comparatively with
that of standard methods DPPH radical scavenging activity, inhibition of superoxide radicals
by riboflavin photoreduction method and the effect on the hydroxyl radical scavenging
activity.
All the metal complexes showed the stronger scavenging effect than the curcumin which is
comparable to standard antioxidant ascorbic acid. The results indicate that metal complex
may serve as an effective radical scavenger to react with DPPH converting it into stable
products. Further, the metal complexes, curcumin and the positive control butylatedhydroxytoluene (BHT) demonstrated an ability to inhibit superoxide anion. Cadmium metal complex
exhibited higher inhibition level than curcumin at the tested concentration, but lower than
BHT. It was also observed that the metal complexes were effective in scavenging the
hydroxyl radicals. The cadmium metal complex showed the stronger scavenging effect than
the curcumin and was comparable to standard butylatedhydroxy-toluene (BHT). The result
exhibit the good hydroxyl ion scavenging activity of metal complex.
The obtained result was interesting and is presented in the following conferences. We have
placed an acknowledgment to the UGC, SWRO, Bangalore for the financial support.
1. ”Synthesis and antibacterial activity of metal complex of curcumin,” Recent Advances in
Chemical Biology – An Overview (RACB-2013), UGC sponsored National Seminar, held
at Government Science College, Hassan, 15 – 16 March, 2013.
2.
“Synthesis and Antioxidant Activity of Metal Ion Complexes of Curcumin,” International
Symposium on Chemical Biology – Drug Discovery, University of Mysore, Mysore, 9 – 10
January, 2014.