Diosgenin (DG), a well-known steroidal sapogenin, is present abundantly in medicinal herbs such as Dioscorea rhizome, Dioscorea villosa, Trigonella foenum-graecum, Smilax China, and Rhizoma polgonati. DG is utilized as a major starting material for the production of steroidal drugs in the pharmaceutical industry. Due to its wide range of pharmacological activities and medicinal properties, it has been used in the treatment of cancers, hyperlipidemia, inflammation, and infections. Numerous studies have reported that DG is useful in the prevention and treatment of neurological diseases. Its therapeutic mechanisms are based on the mediation of different signaling pathways, and targeting these pathways might lead to the development of effective therapeutic agents for neurological diseases. The present review mainly summarizes recent progress using DG and its derivatives as therapeutic agents for multiple neurological disorders along with their various mechanisms in the central nervous system. In particular, those related to therapeutic efficacy for Parkinson’s disease, Alzheimer’s disease, brain injury, neuroinflammation, and ischemia are discussed. This review article also critically evaluates existing limitations associated with the solubility and bioavailability of DG and discusses imperatives for translational clinical research. It briefly recapitulates recent advances in structural modification and novel formulations to increase the therapeutic efficacy and brain levels of DG. In the present review, databases of PubMed, Web of Science, and Scopus were used for studies of DG and its derivatives in the treatment of central nervous system diseases published in English until December 10, 2019. Three independent researchers examined articles for eligibility. A total of 150 articles were screened from the above scientific literature databases. Finally, a total of 46 articles were extracted and included in this review. Keywords related to glioma, ischemia, memory, aging, cognitive impairment, Alzheimer, Parkinson, and neurodegenerative disorders were searched in the databases based on DG and its derivatives.

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The subgranular zone (SGZ) of hippocampal dentate gyrus (HDG) is a primary site of adult neurogenesis. Toll-like receptors (TLRs), are involved in neural system development of Drosophila and innate immune response of mammals. TLR2 is expressed abundantly in neurogenic niches such as adult mammalian hippocampus. It regulates adult hippocampal neurogenesis. However, the role of TLR2 in adult neurogenesis is not well studied in global or focal cerebral ischemia. Therefore, this study aimed to investigate the role of TLR2 in adult neurogenesis after photochemically induced cerebral ischemia. At 7 days after photothrombotic ischemic injury, the number of bromodeoxyuridine (BrdU)-positive cells was increased in both TLR2 knock-out (KO) mice and wild-type (WT) mice. However, the increment rate of BrdU-positive cells was lower in TLR2 KO mice compared to that in WT mice. The number of doublecortin (DCX) and neuronal nuclei (NeuN)-positive cells in HDG was decreased after photothrombotic ischemia in TLR2 KO mice compared to that in WT mice. The survival rate of cells in HDG was decreased in TLR2 KO mice compared to that in WT mice. In contrast, the number of cleaved-caspase 3 (apoptotic marker) and the number of GFAP (glia marker)/BrdU double-positive cells in TLR2 KO mice were higher than that in WT mice. These results suggest that TLR2 can promote adult neurogenesis from neural stem cell of hippocampal dentate gyrus through increasing proliferation, differentiation, and survival from neural stem cells after ischemic injury of the brain.

Malignant tumor is one of the major diseases with high morbidity and mortality. The purpose of this study is to prepare berberine hydrochloride (BH) in situ thermo-sensitive hydrogel based on glycyrrhetinic acid (GA) modified nano graphene oxide (NGO) (GA-BH-NGO-gel). NGO was taken as the photosensitizer, GA was taken as the target molecule, and BH was taken as the model drug. The physicochemical properties and anti-tumor activity in vivo and in vitro were also studied. This subject could provide a certain theoretical basis for the chemo-photothermal therapy combined treatment of malignant tumor. The release behavior of GA-BH-NGO-gel in vitro presented sustained and temperature-dependent drug release effect. The anti-tumor activity studies in vivo and in vitro had shown that GA-BH-NGO-gel had stronger anti-tumor activity, which could be targeting distributed to the tumor tissues. Moreover, the inhibitory effect of GA-BH-NGO-gel was enhanced when combined with 808 nm of laser irradiation. In this research, the chemo-photothermal combination therapy was applied into the tumor treatment, which may provide certain research ideas for the clinical treatment of malignant tumor.

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...