Synthesis, characterization, and biological studies of diosgenyl analogs.

A series of diosgenyl analogs were prepared from diosgenin to evaluate their anticancer activity and antithrombotic property. Analog 4, which had a spiroketal structure with a 6-aminohexanoic acid residue, exhibited the highest potency against all five tumor cell lines. It significantly blocked tumor growth, induced cell apoptosis and autophagy, and regulated cellular calcium concentration, mitochondrial membrane potential, adenosine triphosphate, and cell cycle. In addition, fluorescence-tagged compounds indicated that the analogs could rapidly accumulate in the cytoplasm, but no specific localization in the nucleus of cancer cells was observed. Furthermore, preliminary structure-activity relationship studies demonstrated that spiroketal analogs exhibit better antithrombotic activity than furostanic analogs, which exhibit the opposite effect by promoting thrombosis. Our study indicates that compound 4 may be a promising anticancer drug candidate for cancer patients with thromboembolism.

Novel polyacetylenes from Coreopsis tinctoria Nutt.

Phytochemical investigation of the 95% EtOH extract of Coreopsis tinctoria Nutt. resulted in the isolation of two novel polyacetylenes, (2S)-(3Z,11E)-decadiene-5,7,9-triyne-1,2-diol (1) and (2R)-(3E,11Z)-decadiene-5,7,9-triyne-1,2-diol (2), together with two known polyacetylenes (3 and 4). The structures of these novel compounds were determined by extensive two-dimensional nuclear magnetic resonance, high-resolution mass spectrometry, and optical rotation. Compounds 1, 2, and 4 were evaluated for their anti-proliferative activities against C26 cell growth and inhibitory effects on the lipo-poly-saccharides-induced nitric oxide production using murine macrophage RAW 264.7 cells. However, compounds 1, 2, and 4 just showed weak activities.

Novel organic gelators based on pentose derivatized diosgenyl saponins.

Much attention has been paid to diosgenin saponins because of their various bioactivities, whereas their gelation ability has never been reported. We synthesized some new saponins with pentose directly connected to diosgenin in a shorter procedure, which neither removed the acetyl group of the anomeric hydroxyl group selectively nor activated it and led to a higher yield, compared with the common synthesis of other diosgenyl saponins. We found these compounds are gelators of various organic solvents and their gel formation was studied with FTIR and SEM. This serendipitous discovery enriches the diversity of steroidal small molecular gelators. Meanwhile, single crystal X-ray analysis gave additional information about their intermolecular interactions in the solid state.

Synthesis of diosgenin-ibuprofen derivatives and their activities against insulin-dependent diabetes mellitus.

The synthesis and anti-diabetes activities of diosgenin-ibuprofen derivatives were investigated. Ibuprofen (IBU) was chemically coupled with diosgenin either directly or through amino acid esters linkers. The effects of these compounds on lipopolysaccharide (LPS)-induced nitric oxide (NO) generation were assessed. The results showed spirost-5-en-3ß-yl (2-(4-isobutyl-phenyl)-propionate) (4) was of better activity to suppress the production of NO in the supernatant of LPS-stimulated RAW264.7 cells. In vivo investigation on nonobese diabetic (NOD) mice indicated that compound 4 decreased the incidence of insulin-dependent diabetes mellitus (IDDM; type 1 diabetes) of NOD mice which suggested a potential activity of compound 4 against type 1 diabetes.

Synthesis, characterization and biological studies of diosgenyl analogues.

A series of optical amino acid diosgenyl esters and diosgenyl salicylate conjugates were designed and synthesized to develop new anticancer and anti-inflammatory agents. The analogue 9c that contains an 6-aminohexanoic acid residue at C-3 of diosgenin exhibits higher potency against all three tumor cell lines with IC(50) values ranging from 4.7 µM in C26 cells to 14.6 µM in Hep G2 cells. In addition, seven of newly synthesized compounds significantly inhibit xylene-induced ear edema and exhibit comparable or better anti-inflammatory activities than those of diosgenin and aspirin. Furthermore, preliminary structure-activity relationship studies demonstrate that diosgenyl salicylate conjugates have stronger anti-inflammatory activities than amino acid diosgenyl esters.

Mitochondria targeting and near-infrared fluorescence imaging of a novel heptamethine cyanine anticancer agent.

The future of personalized cancer treatments relies on the development of functional agents that have tumor-targeted anticancer activities and can be detected in tumors using imaging. However, application of these functional agents in the clinic has been limited due to inefficient drug delivery, low specificity for tumor imaging, development of drug resistance, low signal-to-noise ratio and safety concerns regarding potential toxicity. Currently, the most common strategy to develop these functional agents is to conjugate therapeutic agents with the appropriate fluorescent probe. The present study synthesized a novel mitochondria-targeted heptamethine cyanine (Cy) derivative Cy­triphenylphosphonium. The newly developed compound exhibited stronger near infrared (NIR) fluorescence and reacted with bovine serum albumin. In addition, it preferentially accumulated in the mitochondria of cancer cells, as observed using confocal microscopy, and efficiently reduced cancer cell viability (IC50=3.04 µM). This novel multifunctional heptamethine Cy derivative, with cancer mitochondria targeting and NIR fluorescence imaging, may be promising as an alternative anticancer agent.

Haloemodin as novel antibacterial agent inhibiting DNA gyrase and bacterial topoisomerase I.

Drug-resistant bacterial infections and lack of available antibacterial agents in clinical practice are becoming serious risks to public health. We synthesized a new class of haloemodins by modifying a traditional Chinese medicine component, emodin. The novel haloemodin exerts strong inhibitory activity on bacterial topoisomerase I and DNA gyrase, and not on the topoisomerases of human origin. In principle, it shows remarkable antibacterial activities against laboratory and clinically isolated Gram-positive bacteria, including vancomycin-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus. We further expanded its antibacterial spectrum into against Gram-negative bacteria with the assistance of polymyxin B nonapeptide, which helps haloemodin to penetrate through the bacterial outer membrane. Finally, the therapeutic effect of haloemodin in vivo was confirmed in curing S. aureus-induced keratitis on rabbit model. With distinctive structural difference from the antibiotics we used, the haloemodins are of value as promising antibacterial pharmacophore, especially for combat the infections caused by drug-resistant pathogens.

Anti-thrombosis effect of diosgenyl saponins in vitro and in vivo.

Thrombosis in coronary or cerebral arteries is the major cause of morbidity and mortality worldwide. Diosgenin and total steroidal saponins extracted from the rhizome of Dioscorea zingiberensis C.H. Wright are demonstrated to have anti-thrombotic activity. However, few studies describe the anti-thrombotic activity of the diosgenyl saponin monomer. In the present study, a simple and convenient method for the preparation of a new disaccharide saponin, diosgenyl ß-D-galactopyranosyl-(1→4)-ß-D-glucopyranoside (3), is described. We evaluated the anti-thrombotic effects of diosgenin and four diosgenyl saponins by measuring the bleeding time; the results showed that compound 3 exhibits outstanding efficiency in prolonging the bleeding time. Furthermore, we assessed whether compound 3 could alter platelet aggregation in vitro and in vivo. In addition, activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin time (PT), coagulation factors and protection rate in mice were measured to evaluate the anti-thrombotic effect of compound 3. The results show that compound 3 inhibited platelet aggregation, prolonged APTT, inhibited factor VIII activities in rats, and increased the protection rate in mice in a dose-dependent manner. Taken together, these findings suggested that diosgenyl saponins, especially compound 3, had anti-thrombotic activity. It may execute anti-thrombotic activity through inhibiting factor VIII activities and platelet aggregation.

Determination of deltonin in rat plasma by using HPLC-MS/MS and the application of this method in pharmacokinetic studies.

Deltonin is a naturally occurring spirostanol glycoside from Dioscorea zingiberensis C.H. Wright, which is used in traditional Chinese medicine. It exerts strong cytotoxic effect on C26 cells, inhibits C26 derived-tumor growth, and prolongs the survival of tumor-bearing mice after its oral administration, indicating its potential for use as an anti-tumor drug. To investigate the pharmacokinetic profiles of deltonin, a rapid, sensitive, and simplified high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay was developed and validated for the determination of deltonin in rat plasma. After acetonitrile-mediated plasma protein precipitation, chromatographic separation of deltonin was achieved using a reversed phase Hypersil Gold column (150mm×2.1mm, 5µm), with gradient elution using 0.1% formic acid and acetonitrile. Thereafter, deltonin was quantified using MS/MS with electrospray ionization (ESI) in positive multiple reaction monitoring (MRM) mode. The flow rate of the mobile phase was 200µL/min, and the retention time was 9.03min for deltonin and 6.31min for the internal standard (IS: 20(S)-ginsenoside Rb1). The linear range of the calibration curve was 2-5000ng/mL (r(2)>0.99), and the limit of detection (LOD) was 0.46ng/mL. The intra- and inter-day accuracies ranged from -2.8% to 11.1% and precisions (RSD) were within 13.1%. Deltonin was found to be stable under short-term temperature conditions, post-preparative temperature conditions, and after 3 freeze-thaw cycles conditions. The validated method was successfully applied to a pharmacokinetic study in rats after oral administration of deltonin (50 and 100mg/kg). The pharmacokinetics is characterized by high apparent clearance (CL/F) and apparent volume of distribution (Vd/F).