New conjugates of antitumor antibiotic doxorubicin with water-soluble galactomannan: Synthesis and biological activity

New water-soluble conjugates in the form of Schiff bases (DGM-1 and DGM-2) were prepared by the interaction of water-soluble periodate-oxidized galactomannan with doxorubicin or @@iN@-(@@iL@-lysyl)doxorubicin, respectively. The water-soluble galactomannan (DAVANAT^+, a commercial product of Pro-Pharmaceuticals company) was obtained by partial acidic hydrolysis of high-molecular-mass galactomannan from @@iCyamopsis tetragonoloba@ (guar gum) seeds. The conjugate stability was studied in aqueous solutions. The DGM-1 anti-proliferative activity was comparable with that of doxorubicin on three models: cell lines of murine melanoma B16-F1 and human breast cancer MCF-7 (HTB-22) and human colon cancer HT-29 (HTB-38). DGM-2 was poorly active in all the three tests. DGM-1 can thus be regarded as a high-molecular-mass depot form of doxorubicin.