Abstract B170: Identification of compounds as cytotoxic agents and inhibitors of protein kinase C, a key enzyme responsible for the control, growth, division, and differentiation of cells.
Authors: Sinha Sadhna , Ghosal Sabari 
Published: June 2012

Cancer is the second leading cause of death worldwide in humans. Present treatment options available are surgery, radiation and chemotherapy. However, all treatment procedures suffer from serious side effects and toxicity. Hence there is an urgent need to develop alternative medicines and/or drug candidates which act specifically on the cancer cells.

Protein kinases regulate a multitude of physiological processes by the transfer of phosphate residues and there by playing a central role in control of growth, division and differentiation of cells. There is sufficient evidence that over expression or elevated activity or loss of activity control of different protein kinases is involved in initiation and progression of tumors.

Protein kinase C (PKCs) with multiple functions is an interesting target for cancer therapy. PKCs are also known to modulate multidrug resistance, and thus the use of PKC modulators in combination with classical cytotoxic drugs could be beneficial.

Experimental procedure: In a joint effort with the local Amchis and scientists of IIIM, Jammu, seven medicinal plants were procured namely Christolia crassifolia, Tanacetum gracile, Echinecea purpurea (root and aerial part), Perovskia abrotanoides Rhodiola imbricata, Saussurea bracteata and Actinocarya tibetica. The plant materials were extracted by using a mixture of organic solvents (MeOH: water, 9:1). The extract was then concentrated below 50°C under reduced pressure. The concentrated methanol extract was again fractionated with n-hexane, dichloromethane, ethylacetate and aqueous fractions respectively. Solvent was evaporated under reduced pressure from each fraction. Each fraction and extracts after complete removal of solvent were evaluated for cytotoxic activity by MTT based colorimetric assay.

Separation of fractions from the concentrated extract of the plant (Tanacetum gracile) was done by column chromatography using n-hexane as mobile phase and then elution was carried out in n-hexane and ethyl acetate with solvent gradient. The fractions were collected and pooled on the basis of TLC pattern. Six compounds have been isolated and their structural analysis by various spectroscopic techniques like NMR, UV, IR and Mass spectroscopy is in process. All these compounds will be tested for protein kinase enzyme inhibition activity. This could provide a lead in further optimization of activity for use in drug development.

Results: Four plants; hexane and DCM fraction of Tanacetum gracile, hexane and DCM fraction of Echinecea purpurea (root and aerial part), hexane and DCM fraction of Perovskia abrotanoides and hexane, DCM and EtOAc fractions of Saussurea bracteata showed substantial cytotoxic activity. On an average the IC50 values of these components were between 6 to 60μg/mL.

Cytotoxicity of these six purified compounds was evaluated on PC-3 and HeLa cells by MTT Assay.

Conclusions: The results in the present study clearly demonstrates that T.gracile, P.abrotanoides, S.bracteata and E.purpurea extracts could exhibit an antiproliferative effect on human prostate cancer and tumor cells. These results reveal the initial potential of these medicinal plants as cytotoxic agents for therapy against human prostate cancer and tumor. It is therefore worthwhile to isolate the active compounds and identity their structures.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B170.