If your compound is completely insoluble in water, how would it be administered to patients? Perhaps it is slightly soluble, enough to be able to carry out the experiment with a sensitive method of detection like mass spectrometry. If not maybe you could find a formulation that would allow the insoluble compound to be used in an aqueous environment, like dissolving it in liposomes or detergent or a cyclodextrin.

@Adam i am already working on drug delivery part as well by taking the drug that i describe above. But i am interested to know the reduction of the Pt IV complexes using sulfur containing bio-molecules like GSH and ASA, as they play a key role in the tumor intracellular environment. 

- If the reduction of Pt(IV) to Pt(II) is performed in DMSO, Pt(II) species may form complexes with DMSO.

http://pubs.acs.org/doi/abs/10.1021/ic00257a013

- It was reported that DMSO inhibits cytotoxicity of cisplatin and other Pt(II) complexes 

http://www.ncbi.nlm.nih.gov/pubmed/24812268

- Dimethylformamide (DMF) may be an option to try 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508678/

Yes Roman is correct - DMSO will interact with the Pt(II) products, but solvent is an important part of the reduction process for Pt(IV) complexes. Is your complex soluble in a detergent-containing buffer? Sometimes people use cell lysis buffers that contain detergent (you might use them normally making making protein lysate for Westerns) so that you are working with a 98% aqueous system that still helps solubilise very lipophilic complexes. I would play around with a DMF/water mix if you are desperate, but you need water - remember - the protons from GSH reduction need to be able to go somewhere!!

And just to be clear  - I wouldn't anticipate any DMSO interaction directly with the Pt(IV) complex, based on my experience, but you could confirm it by simple NMR 

Mathew is right - DMF should be preferably used with water: DMF is a good solvent and in this quality it is comparable with DMSO, but 100% DMF would unlikely make a good environment for your reaction for several reasons, including your interest to mimic cellular (water-based) reaction environment. So I would try the lowest concentration of DMF in water, at which your Pt(IV) complex and all other reaction components are still soluble. If DMF does not work, you have other choices of highly polar solvents that are likely to dissolve your polar Pt(IV) complexes: my first choices would be MFA/water, various glycol ethers in water, or PEG400/water  (the last one is often used in pharmaceutical formulations). I am a bit skeptical  about using detergents (surfactants) as solvents for water-insoluble inorganic compounds (detergents are good to solublize hydrophobic proteins and lipids that are otherwise difficult to dissolve in water-based environment, but your compounds are different in that they are water-insoluble polar inorganics).

I would also be somewhat concerned about using GSH as a reducing reagent for Pt(IV). In the excess of GSH, Pt(II) complexes produced in the reaction can react with GSH and form very stable and anticancer inactive Pt-GSH complexes. In fact, under some circumstances GSH may displace all other ligands in Pt(II) complexes due to strong trans effect of Pt-S bond (destabilization of bonds in trans position to Pt-S bond). This does not happen readily in cells even though there is an excess of GSH, because other cellular S-nucleophiles compete with GSH in interacting with Pt(II). However, there is a risk that GSH will react with Pt(II) complexes formed in your reaction and produce these stable (even polymeric) Pt-GSH complexes, because other kinetically preferred S-nucleophiles compiting with GSH will not be available. 

Thanks Mathew & Roman for your valuable suggestions, i will go for that and let see what comes.