Water-soluble arginyl-diosgenin (Arg-DG) conjugate was designed, synthesized, and evaluated for a biological activity. The Arg-DG conjugate was characterized using FT-IR, 1 H NMR, 13 C NMR, and HPLC-MS analyses, followed by a biological activity evaluation. Compared with DG, the Arg-DG conjugate showed a decreased cytotoxicity against L929 cells and an increased antiproliferative activity against hepatocellular cells. The safety of the Arg-DG conjugate was confirmed using the highly sensitive Alamar Blue assay, which indicated that it increased the cellular metabolic activity at suitable concentrations. The Arg-DG conjugate promoted an endothelial tube formation as well. Furthermore, the Arg-DG conjugate improved the bone morphogenetic protein 2 (BMP2)-induced osteoblastic differentiation with synergistic effects on alkaline phosphatase (ALP) activity and mineralization. These results suggest that the Arg-DG conjugate developed in this study has great potentials for biomedical applications such as bone tissue engineering.
K E Y W O R D SALP assay, arginyl-diosgenin conjugate, bone tissue engineering, cytotoxicity, tube formation assay
| INTRODUCTIONDiosgenin [(25R)-spirost-5-en-3ß-ol] (DG) is a major naturally occurring steroid saponin, which is abundantly distributed in the rootstock of yams (Dioscorea sp.) and other plants such as Smilax bockii warb and Trigonella foenum graecum. [1,2] DG has exhibited biological effects in the treatment of various diseases such as hypercholesterolemia, climacteric syndromes including diabetic neuropathy and even cancer. [3][4][5][6] It has also been claimed to have an osteogenic property. DG was reported to inhibit osteoclastogenesis and enhance osteoblastic cell differentiation and the synthesis of cellular bone matrix protein. [7,8] It has been hypothesized that DG could be a potential activator of bone formation and potential therapeutic agent for bone-related diseases including osteoporosis.[8]However, the medical application of DG is considerably limited because of its solubility problem and associated toxicity. The aqueous solubility of DG was determined to be 0.7 ng/ml (1.69 nm).[9] It was also revealed that the low solubility of DG led to poor bioavailability and gastrointestinal mucosal toxicity. [10] As poor solubility has been recognized as a frequently encountered challenge in the field of pharmaceutics, different approaches have been employed to improve the solubility and bioavailability of poorly watersoluble compounds including DG. [11] For instance, an inclusion of complexation of DG and β-cyclodextrin was formed. [12] Iron oxide nanoparticles loaded with DG were prepared. [13] Improving the solubility of DG and decreasing its intrinsic cytotoxicity or at least avoiding any additional toxicity against normal cells are the major challenges to its biomedical application. Numerous efforts have been made to chemically modify this compound to improve its applicable biological activities. Diosgenyl saponin, dioscin analogues were designed to improve its anticancer a...