Cheng-Zhu Wu

Enzymatic Glycosylation of Nonbenzoquinone Geldanamycin Analogs via Bacillus UDP-Glycosyltransferase

ABSTRACT Geldanamycin (GM) is a naturally occurring anticancer agent isolated from several strains of Streptomyces hygroscopicus. However, its potential clinical utility is compromised by its severe toxicity and poor water solubility. For this reason, considerable efforts are under way to make new derivatives that have both good clinical efficacy and high water solubility. On the other hand, glycosylation is often a step that improves the water solubility and/or biological activity in many natural products of biosynthesis. Here, we report the facile production of glucose-conjugated nonbenzoquinone GM analogs using the Bacillus UDP-glycosyltransferase BL-C. Five aglycon substrates containing nonbenzoquinone aromatic rings were chosen to validate the in vitro glycosylation reaction. Putative glucoside compounds were determined through the presence of a product peak(s) and were also verified using LC/MS analyses. Further, the chemical structures of new glucoside compounds 6 and 7 were elucidated using spectroscopy data. These glucoside compounds showed a dramatic improvement in water solubility compared with that of the original aglycon, nonbenzoquinone GM.

Scutellaria baicalensis Georgi extract protects against alcohol‑induced acute liver injury in mice and affects the mechanism of ER stress

The aims of the present study were to examine the hepatoprotective effect of Scutellaria baicalensis Georgi extract (Scutellariae Radix extract; SRE) against acute alcohol-induced liver injury in mice, and investigate the mechanism of endoplasmic reticulum (ER) stress. High performance liquid chromatography was used for the phytochemical analysis of SRE. Animals were administered orally with 50% alcohol (12 ml/kg) 4 h following administration of doses of SRE every day for 14 days, with the exception of normal control group. The protective effect was investigated by measuring the levels of aspartate transaminase (AST), alanine transferase (ALT) and triglyceride (TG) in the serum, and the levels of glutathione (GSH) and malondialdehyde (MDA) in liver tissues. The levels of glucose-related protein 78 (GRP78) were detected using immunohistochemical localization and an enzyme-linked immunosorbent assay. Hepatocyte apoptosis was assessed using terminal-deoxynucleoitidyl transferase mediated nick end labeling. The SRE contained 31.2% baicalin. Pretreatment with SRE had a marked protective effect by reversing the levels of biochemical markers and levels of GRP78 in a dose-dependent manner. The results of the present study demonstrated that pretreatment with SRE exerted a marked hepatoprotective effect by downregulating the expression of GRP78, which is a marker of ER stress.

Biosynthesis of novel glucosides geldanamycin analogs by enzymatic synthesis

Two new glucosides (1 and 2) of geldanamycin (GA) analogs were obtained from in vitro glycosylation by UDP-glycosyltransferase (YjiC). Based on spectroscopic (HR-ESI-MS, 1D, and 2D-NMR) analyses, the glucosides were elucidated as 4,5-dihydro-7-O-descarbamoyl-7- hydroxyl GA-7-O-β-D-glucoside (1) and ACDL3172-18-O-β-D-glucoside (2). Furthermore, the water solubility of compounds 1 and 2 was about 215.2 and 90.7 times higher respectively, than that of the substrates. Among compounds 1-4, only 3 showed weak antiproliferative activity against four human tumor cell lines: MDA-MB-231, SMMC7721, HepG2, and SW480 (IC50: 13.6, 15.1, 31.8, and 22.7 micrometer, respectively).

Non-benzoquinone geldanamycin analogs trigger various forms of death in human breast cancer cells.

BackgroundHsp90 proteins are important therapeutic targets for many anti-cancer drugs in clinical trials. Geldanamycin (GA) was identified as the first natural inhibitor of Hsp90, increasing evidence suggests that GA was not a good choice for clinical trials. In this study, we investigated two new non-benzoquinone geldanamycin analogs of Hsp90 inhibitors, DHQ3 and 17-demethoxy-reblastatin (17-DR), to explore the molecular mechanisms of their anti-cancer activity in vivo and vitro.MethodsMTT and colony formation assays were used to measure cell viability. Flow cytometry, DAPI staining, ATP assay, electron microscopy, western blots, siRNAs transfection and immunofluorescence were used to determine the molecular mechanism of DHQ3- or 17-DR-induced different forms of death in human breast cancer MDA-MB-231 cells. Malachite green reagent was used to measure ATPase activity of the analogs.ResultsDHQ3 and 17-DR presented efficiently inhibitory effect in MDA-MB-231 cell lines, and DHQ3 induced necroptosis by activation of the RIP1-RIP3-MLKL necroptosis cascade. And DHQ3-induced cell death was inhibited by a necroptosis inhibitor, necrostatin-1 (Nec-1), but not by a caspase inhibitor z-VAD-fmk. On the other hand, 17-DR induced apoptosis in MDA-MB-231 cells, indicating a caspase-dependent killing mechanism. We further demonstrated that down-regulation of RIP1 and RIP3 by siRNA protected against DHQ3 but not 17-DR induced cell death. These results were confirmed by electron microscopy. DHQ3 and 17-DR induced the degradation of Hsp90 client proteins, and they showed strong antitumor effects in MDA-MB-231 cell-xenografted nude mice.ConclusionsThese findings supported that DHQ3 and 17-DR induce different forms of death in some cancer cell line via activation of different pathways. All of the results provided evidence for its anti-tumorigentic action with low hepatotoxicity in vivo, making them promising anti-breast cancer agents.

Determination of isobavachalcone in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A simple and selective specific high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of isobavachalcone (IBC) in rat plasma was developed. Neobavaisoflavone was used as an internal standard (IS). After protein precipitation with acetonitrile (2:1, v/v), the analyte and IS were separated on a 2.6 μm Kinetex C18 column (100 mm×2.1 mm i.d., Phenomenex) by isocratic elution with acetonitrile:water (60:40, v/v) as the mobile phase at a flow rate of 0.2 mL/min. An electrospray ionization (ESI) source was applied and operated in the negative ion mode; multiple reactions monitoring (MRM) mode was used for quantification, and the target fragment ions m/z 323.0→118.9 for IBC and m/z 321.1→265.0 for the IS were chosen. Good linearity was observed in the concentration range of 3.79-484.5 ng/mL for IBC in rat plasma. The recovery of IBC in plasma was in the range of 81.2-89.8%. Intra-day and inter-day precision were both lower than 10%. This method was suitable for pharmacokinetic studies after oral administration of 80 mg/kg IBC in rats. We also obtained pharmacokinetic parameters and concentration-time profiles for IBC after oral administration of IBC in rats.

Synthesis and Evaluation of Bakuchiol Derivatives as Potential Anticancer Agents

A series of bakuchiol derivatives were synthesized and evaluated for their anti-proliferative and the inhibitory activities on SMMC7721 cell line migration using PX-478 as a positive control. The results showed (S,E)-4-(7-methoxy-3,7-dimethyl-3-vinyloct-1-en-1-yl)phenol (10) to have the best activity among the tested compounds, which included PX-478. In addition, compound 10 showed greater inhibitory activity than that of bakuchiol in the transwell migration and invasion assays at every dose. In western blotting tests, compound 10 showed a promising ability to downregulate the expression of HIF-1α and its associated downstream proteins MMP-2 and MMP-9. Moreover, this effect was dose-dependent and could represent a possible mechanism of action for the anticancer activity of compound 10.