Design, Synthesis, and Biological Evaluation of Water-Soluble Prodrugs of C5-Curcuminoid GO-Y030 Based on Reversible Thia-Michael Reaction.

Although curcumin and its analogs exhibit anticancer activity, they are still not used as anticancer drugs because of their water insolubility and extremely poor bioavailability. This study describes the development of water-soluble prodrugs of GO-Y030, a potent antitumor C5-curcuminoid, in an attempt to enhance its bioavailability. These prodrugs release the parent compound via a retro-thia-Michael reaction. To endow sufficient hydrophilicity onto GO-Y030 via a single thia-Michael reaction of an aqueous entity, we used a modified glycoconjugate with a thiol group. The water-solubilizing motif was installed on GO-Y030 by the thia-Michael reaction of propargyl-polyethylene glycol (PEG)-thiol and subsequent click chemistry (CuAAC) reaction with 1-glycosyl azide. Turbidity measurements revealed a significantly improved water solubility of the prodrugs, demonstrating that disaccharide conjugates were completely dissolved in water at 100 µM. Their cytotoxicity was comparable to that of the parent compound GO-Y030, indicating the gradual in situ release of GO-Y030. The release of GO-Y030 from GO-Y199 via the retro-thia-Michael reaction was demonstrated through a degradation study in water. Our retro-thia-Michael reaction-based prodrug system can be used for targeting cancer cells.

Ratiometric analysis of reversible thia-Michael reactions using nitrile-tagged molecules by Raman microscopy.

Ratiometric Raman analysis of reversible thia-Michael reactions was achieved using α-cyanoacrylic acid (αCNA) derivatives. Among αCNAs, the smallest derivative, ThioRas (molecular weight: 167 g mol-1), and its glutathione adduct were simultaneously detected in various subcellular locations using Raman microscopy.

Controllable conformation and reactivity of bicyclic α-methylene cyclopentanones and their NF-κB pathway inhibitory activity.

Tuning the electrophilicities of Michael acceptors is important for the development of targeted covalent drugs. To this end, the electronic effects of electrophilic structures have been well investigated, but not the steric effects. In this work, we synthesized ten α-methylene cyclopentanones (MCPs), screened them for NF-κB inhibitory activity, and analyzed their conformations. We found that MCP-4b, MCP-5b, and MCP-6b are novel NF-κB inhibitors, whereas the corresponding diastereomers MCP-4a, MCP-5a, and MCP-6a are inactive. Conformational analysis suggested that the stereochemistry of the side chain (R) on MCPs dictates the stable conformation of the core bicyclic 5/6 ring system. The conformational preference seemed to influence their reactivity toward nucleophiles. Consequently, a thiol reactivity assay showed that MCP-5b has higher reactivity than MCP-5a. The results indicate that the conformational switching of MCPs may control reactivity and bioactivity in the presence of steric effects.

Structure-activity relationship and mechanistic study on guggulsterone derivatives; Discovery of new anti-pancreatic cancer candidate.

Pancreatic cancer is one of the deadliest types of malignancies. A new intervention aiming to combat pancreatic cancer is targeting its extra-ordinary ability to tolerate nutrition starvation, a phenomenon known as "Austerity". As a part of a research program aiming to develop a new-generation of anticancer agents, known as "anti-austerity agents", guggulsterone derivatives (GSDs) were identified as unique anti-austerity agents in terms of potency and selectivity. These agents are able to exert preferential cytotoxic activity only under nutrient-deprived conditions with little or no toxicity under normal conditions. In the present study, a library of 14 GSDs was synthesized and screened against PANC-1 human pancreatic cells. Among tested compounds, GSD-11 showed the most potent activity with PC50 a value of 0.72 µM. It also inhibited pancreatic cancer cell migration and colony formation in a concentration-dependent manner. A mechanistic study revealed that this compound can inhibit the activation of the Akt/mTOR signaling pathway. Therefore, GSD-11 could be a promising lead compound for the anticancer drug discovery against pancreatic cancer.

Synthetic E-guggulsterone derivative GSD-1 inhibits NF-κB signaling and suppresses the metastatic potential of breast cancer cells.

Guggulsterone (GS) [4,17(20)-pregnadiene-3,16-dione], is the main active phytosterol constituent in guggul, the gum resin of Commiphora wightii (Arnott.) Bhand./Commiphora mukul Engl. tree, and is known for its medicinal effects. In this study, we report that GSD-1, a structurally-related synthetic GS derivative, strongly inhibits NF-κB activation induced by TNF-α. GSD-1 prevented the nuclear translocation of p65 through the blockade of IκBα degradation and p65 phosphorylation, and further inhibited the activation of upstream kinases, including transforming growth factor-ß activated kinase 1 (TAK1), IκB kinase (IKK) α, and IKKß. Furthermore, GSD-1 inhibited the cell-intrinsic activation of NF-κB, and exerted its direct anti-cancer and anti-metastatic effects in both murine and human breast cancer cell lines. This study demonstrated GSD-1 to be an attractive compound to target NF-κB activation that has potential for treating breast cancer growth and metastasis.

Divinylcarbinol Desymmetrization Strategy: A Concise and Reliable Approach to Chiral Hydroxylated Fatty Acid Derivatives.

By the aid of the catalytic desymmetrization of divinylcarbinol as one-pot asymmetric induction and protection of olefin, asymmetric total syntheses of two chiral hydroxylated fatty acid derivatives were successfully achieved. The desired stereoisomers could be concisely prepared in mild conditions in a highly convergent manner. Thus, this novel strategy can help stereochemical elucidations of natural products, which have difficulties in spectroscopic stereochemical analyses due to their local symmetries in the vicinities of the stereogenic secondary hydroxyl units.

Synthesis of guggulsterone derivatives as potential anti-austerity agents against PANC-1 human pancreatic cancer cells.

E- and Z-guggulsterones and nine guggulsterone derivatives (GSDs) were synthesized and evaluated for their preferential cytotoxicity against human PANC-1 cell in nutrient deprived medium utilizing antiausterity strategy. Among the synthesized compounds, GSD-1 and GSD-7 showed potent cytotoxicity against PANC-1 cells under nutrient-deprived conditions in a concentration dependent manner, with a PC50 value of 1.6 µM and 3.2 µM, respectively. The effect of GSD-1 and GSD-7 was further evaluated in a real time using live cell imaging. Both of these compounds altered PANC-1 cell morphology, leading to cell death at sub micromolar concentration range. GSD-1 and GSD-7 also inhibited PANC-1 cell colony formation in a concentration-dependent manner. GSD-1 and GSD-7 are lead structure for the anti-austerity drug development.

Facile o-quinodimethane formation from benzocyclobutenes triggered by the Staudinger reaction at ambient temperature.

Electron-donating iminophosphoranes were found to significantly enhance 4π-ring opening of benzocyclobutenes to generate o-quinodimethanes at 20-25 °C. These iminophosphorane benzocyclobutenes can be conveniently generated from azide benzocyclobutenes and phosphines via the Staudinger reaction. Thus, Staudinger reaction-triggered sequential molecular transformations of the azide benzocyclobutenes have been established via o-quinodimethanes at ambient temperature, which is expected to exhibit potential for a wide range of applications.

Reversibility of the thia-Michael reaction of cytotoxic C5-curcuminoid and structure-activity relationship of bis-thiol-adducts thereof.

C5-curcuminoids [a.k.a. bis(arylmethylidene)acetones] are curcumin analogues bearing a reactive cross-conjugated dienone structure essential for eliciting cytotoxicity. To gain insight into the mode of action of C5-curcuminoids, we investigated the reversibility of the thia-Michael reaction of 1,5-bis(3,5-bis(methoxymethoxy)phenyl)-1,4-pentadiene-3-one, named GO-Y030 which is the most potent cytotoxic C5-curcuminoid, using spectroscopic methods. A panel of GO-Y030-bis-thiol-adducts were synthesized and the structure-reactivity relationship regarding the retro thia-Michael reaction as well as the cell growth inhibitory activity against human colon cancer HCT116 were evaluated. Some C5-curcuminoid thiol-adducts exhibited comparable cytotoxicity with GO-Y030, demonstrating their potential use as prodrugs. These results imply that C5-curcuminoids elicit cytotoxicity by covalently interacting with various biothiols via a reversible thia-Michael reaction.

Identification of anti-cancer chemical compounds using Xenopus embryos.

Cancer tissues have biological characteristics similar to those observed in embryos during development. Many types of cancer cells acquire pro-invasive ability through epithelial-mesenchymal transition (EMT). Similar processes (gastrulation and migration of cranial neural crest cells [CNCC]) are observed in the early stages of embryonic development in Xenopus during which cells that originate from epithelial sheets through EMT migrate to their final destinations. The present study examined Xenopus embryonic tissues to identify anti-cancer compounds that prevent cancer invasion. From the initial test of known anti-cancer drugs, AMD3100 (an inhibitor of CXCR4) and paclitaxel (a cytoskeletal drug targeting microtubules) effectively prevented migration during gastrulation or CNCC development. Blind-screening of 100 synthesized chemical compounds was performed, and nine candidates that inhibited migration of these embryonic tissues without embryonic lethality were selected. Of these, C-157 (an analog of podophyllotoxin) and D-572 (which is an indole alkaroid) prevented cancer cell invasion through disruption of interphase microtubules. In addition, these compounds affected progression of mitotic phase and induced apoptosis of SAS oral cancer cells. SAS tumors were reduced in size after intratumoral injection of C-157, and peritoneal dissemination of melanoma cells and intracranial invasion of glioma cells were inhibited by C-157 and D-572. When the other analogues of these chemicals were compared, those with subtle effect on embryos were not tumor suppressive. These results suggest that a novel chemical-screening approach based on Xenopus embryos is an effective method for isolating anti-cancer drugs and, in particular, targeting cancer cell invasion and proliferation.

A Curcumin Analog, GO-Y078, Effectively Inhibits Angiogenesis through Actin Disorganization.

BACKGROUND: The inhibition of angiogenesis is a theoretically ideal chemotherapy for cancer, but there remains room for improvement. Most inhibitors of angiogenesis approved to date target vascular endothelial growth factors (VEGFs); however, VEGFs are only one of the many classes of participant in tumor angiogenesis. Because tumor angiogenesis is orchestrated by many components, including growth factors, signal transducers, and effectors, its regulation exhibits redundancy. Curcumin can associate with many proteins, and it reportedly inhibits tumor angiogenesis. OBJECTIVE: We investigated the ability of a new curcumin analog, GO-Y078, to inhibit tumor angiogenesis. RESULTS: GO-Y078 inhibited human umbilical vascular endothelial cell sprouting. GO-Y078 also induced complete anoikis in vascular endothelial cells. Moreover, GO-Y078 suppressed the migration and invasion of vascular endothelial cells into extracellular matrix proteins. However, expression analysis revealed that GO-Y078 did not suppress molecules involved in VEGF signaling. Rather, GOY078 induced actin disorganization, dissociation of vinculin from actin, and destruction of focal adhesion, resulting in the inhibition of vascular endothelial cell mobility. GO-Y078 also suppressed in-vivo vasculogenesis in Xenopus laevis tadpoles. CONCLUSION: Actin organization is a common effecter related to vascular endothelial cell mobility in angiogenesis. We demonstrated that GO-Y078 inhibits angiogenesis through actin disorganization.

Structure-Activity Relationships of the Antitumor C5-Curcuminoid GO-Y030.

1,5-Bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadiene-3-one (2) was isolated from Curcuma domestica as a curcumin (1)-related compound, which we named C5-curcumin. Intrigued by the potent antitumor activity of C5-curcumin (2)-related 1,5-bisaryl-1,4-pentadiene-3-ones [bis(arylmethylidene)acetones, termed C5-curcuminoids], we previously conducted a structure-activity relationship study of C5-curcuminoids and showed that highly active GO-Y030 [1,5-bis(3,5-bis(methoxymethoxy)phenyl)-1,4-pentadiene-3-one (4)] is the most promising antitumor compound. In this study, a panel of C5-curcuminoids based on GO-Y030, consisting of 30 new and 10 known compounds, was synthesized to elucidate in detail which moiety of GO-Y030 is significant for antitumor activity. The results confirmed that both the cross-conjugated dienone moiety and the 3,5-bis(methoxymethoxy) substituent are important for the antitumor activity.