The object of this study was to synthesize highly biocompatible and stable gold, silver and copper nanoparticles, without use of toxic reducing and stabilizing agents in aqueous media. In order to achieve this objective, natural polysaccharides (hemicelluloses) were isolated from Plantago ovata (PO), Mimosa pudica (MP) and Lallemantia royleana (LR) and used as reducing and stabilizing agents. The isolated polysaccharides were characterized by elemental, moisture, optical rotation, FTIR and MALDI-ToF analyses. They were found to be highly branched hemicelluloses. It was discovered that the hemicelluloses can effectively reduce noble metal ions due to presence of aldehyde groups in their structures. These hemicelluloses can absorb water several times their mass and swell like hydrogels. In swollen form they can encapsulate and disperse nanoparticles in their matrix, as evidenced by electron microscopy. The dispersion was effective in keeping the particles from each other over longer periods of time. Metal nanoparticles were readily obtained after mixing the metal salts with suspensions of these hemicelluloses in water. The reaction rate followed the order: PO ≥ LR > MP. The reduction process was witnessed by colour change (from yellow to blue/purple/ruby red depending upon the pH and reaction temperature) and monitored by recording the surface plasmon resonance spectra in the 350-800 nm range. The synthesized nanoparticles exhibited spherical shapes. Size of particles was found to depend on amount of hemicellulose used, pH and temperature of reaction mixture. Effect of these parameters was optimized by response surface methodology to get smallest possible size of the particles. The lowest surface plasmon resonance peaks representing smallest size obtained by reduction of gold with MP, PO and LR were 530, 520 and 517 nm, respectively. The SPR spectra of AgNPs started building up at pH > 6 and exhibit maxima at 412, 396 and 387 nm with PO, MP and LR, respectively. The smallest particle sizes obtained under optimum conditions were ~ 10 nm (with LR), ~10 nm (with LR) and 70 nm (with LR), respectively of gold, silver and copper. The synthesized gold nanoparticles were found to be non-toxic as shown by cytotoxic tests. The size of the gold nanoparticles ( > 30) obtained by use of MP falls in the range that is suitable for cellular uptake in various cancer cell lines, as the gold nanoparticles having size > 30 nm can rarely enter nucleus of the cell, so are suitable for safe drug delivery. On the other hand nanoparticles of silver and copper, exhibited dose-dependent antimicrobial activities against E. coli, A.tumefaciens, P. aeruginosa, B. subtilis and S. aureusand, they were found to be cytotoxic against brine shrimps and Hela cell lines and the tumours caused by A. tumefaciens. These results suggest that gold nanoparticles can be used for safe drug delivery without any therapeutic effect of their own, whereas nanoparticles of silver and copper can be used as anti-infective and anti-cancer agents. Gold nanoparticles being non-toxic were subjected to bio-distribution studies in rabbit and tumour bearing mice by use of radio labelled gold (198Au) nanoparticles. The uptakes differed with the use of hemicelluloses. Highest uptake of gold nanoparticles (radiolabelled) dispersed in PO mucilage, after 3h, was found in spleen followed by liver, heart, muscle, kidneys and lungs in rabbit. In case of gold nanoparticles synthesized by use of MP the highest uptake was in spleen followed by liver, kidneys, blood and bladder after 3h. They depleted with time in spleen and were significantly higher in liver after 24h. The particles also accumulated in epithelium carcinoma tumour. After oral administration of radiolabeled gold nanoparticles to rabbit, it was found that the particles were released to colon due to solubility of hemicelluloses in basic media suggesting that they can be used for targeted delivery at colons. In serum proteins the gold nanoparticles bound preferentially to globulins with the order; α1-globulin (6.5%) followed by α2-globulin (~2%), β-globulin (~1%), γ-globulin (0.707%) and albumin (0.66%).