A Concise Synthesis of Pyrrole-Based Drug Candidates from α-Hydroxyketones, 3-Oxobutanenitrile, and Anilines.

A simple and concise three-component synthesis of a key pyrrole framework was developed from the reaction between α-hydroxyketones, oxoacetonitriles, and anilines. The synthesis was used to obtain several pyrrole-based drug candidates, including COX-2 selective NSAID, antituberculosis lead candidates BM212, BM521, and BM533, as well as several analogues. This route has potential to obtain diverse libraries of these pyrrole candidates in a concise manner to develop optimum lead compounds.

Selective One-Pot Multicomponent Synthesis of N-Substituted 2,3,5-Functionalized 3-Cyanopyrroles via the Reaction between α-Hydroxyketones, Oxoacetonitriles, and Primary Amines.

A one-step, three-component reaction between α-hydroxyketones, oxoacetonitriles, and primary amines gives N-substituted 2,3,5-functionalized 3-cyanopyrroles with complete selectivity in up to 90% isolated yields. The reaction worked on a wide substrate scope under mild reaction conditions (AcOH as a catalyst, EtOH, 70 °C, 3 h). The reaction proceeded with very high atom efficiency as water is the only molecule lost during the reaction. The practicality of the reaction was demonstrated on a large gram scale. The structures of the 3-cyanopyrroles were confirmed by single-crystal X-ray diffraction and NMR; this work provides a general and practical entry to pyrrole scaffolds suitably decorated for the synthesis of various bioactive pyrroles in a concise manner.

A Practical Synthesis of Densely Functionalized Pyrroles via a Three-Component Cascade Reaction between Carbohydrates, Oxoacetonitriles, and Ammonium Acetate.

A practical three-component reaction between unactivated carbohydrates, oxoacetonitriles, and ammonium acetate gave densely functionalized pyrroles in 75-96% yields. Disaccharides afforded novel pyrrolo-glycosides. This metal-free, Et3N-catalyzed cascade reaction proceeded with exclusive chemo-, regio-, and stereoselectivities and showed a wide substrate scope with high atom economy. It also proceeded successfully at a 2 g scale, demonstrating potential for large-scale synthesis. The functional groups on the pyrroles permit easy transformation to other handles for the construction of more complex structures. The reaction proceeded through a cascade mechanism involving several intermediates identified by mass spectrometric analysis. This work has great potential for the sustainable production of densely functionalized pyrroles from cheap and widely available carbohydrates and represents a key advancement in the sustainable synthesis of these ubiquitous heterocycles.

Perfluorophenylboronic acid-catalyzed direct α-stereoselective synthesis of 2-deoxygalactosides from deactivated peracetylated d-galactal.

Perfluorophenylboronic acid 1c catalyzes the direct stereoselective addition of alcohol nucleophiles to deactivated peracetylated d-galactal to give 2-deoxygalactosides in 55-88% yield with complete α-selectivity. The unprecedented results reported here also enable the synthesis of disaccharides containing the 2-deoxygalactose moiety directly from the deactivated peracetylated d-galactal. This convenient and metal-free glycosylation method works well with a wide range of alcohol nucleophiles as acceptors and tolerates a range of functional groups without the formation of the Ferrier byproduct and without the need for a large excess of nucleophiles or additives. The method is potentially useful for the synthesis of a variety of α-2-deoxygalactosides.

Glabridin resensitizes p-glycoprotein-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic agents.

Multidrug resistance (MDR) remains an obstacle to chemotherapy related with the overexpression of several efflux membrane proteins, and p-glycoprotein (P-gp) is the most studied among them. Thus, continuous investigational efforts are necessary to find valuable MDR reversal agents, and the flavonoid compound glabridin (GBD) seems to be a promising candidate. This study aimed to investigate the potential of GBD against MDR and explore the possible mechanisms. First, we found that GBD could decrease the half maximal inhibitory concentration of paclitaxel and doxorubicin (DOX) in breast cancer cells like MDA-MB-231/MDR1 cells and MCF-7/ADR cells. It was further explained that GBD enhanced the apoptosis of MDA-MB-231/MDR1 cells induced by DOX, due to the increased accumulation of DOX. Then, tests were performed to explore the possible MDR reversal mechanisms. On one hand, GBD can suppress the expression of P-gp. On the other hand, GBD can downregulate the activity of P-gp ATPase when cotreated with DOX or verapamil, revealing that GBD was a substrate of P-gp. Moreover, the obtained kinetic inhibition parameters proved that GBD was a competitive inhibitor of P-gp, and in molecular docking simulation modeling, GBD exhibited stronger binding affinity with P-gp than DOX. In conclusion, GBD can increase the accumulation of DOX in MDA-MB-231/MDR1 cells by suppressing the expression of P-gp and competitively inhibiting the P-gp efflux pump and enhance the apoptosis of MDA-MB-231/MDR1 cells induced by DOX, and thus realize reversal effects on MDR. Therefore, the combination therapy of anticancer drugs and flavonoid-like GBD is a promising strategy to overcome P-gp-mediated MDR.

Inhibition of P-Glycoprotein Mediated Efflux in Caco-2 Cells by Phytic Acid.

Phytic acid (IP6) is a natural phosphorylated inositol, which is abundantly present in most cereal grains and seeds. This study investigated the effects of IP6 regulation on P-glycoprotein (P-gp) and its potential mechanisms using in situ and in vitro models. The effective permeability of the typical P-gp substrate rhodamine 123 (R123) in colon was significantly increased from (1.69 ± 0.22) × 10-5 cm/s in the control group to (3.39 ± 0.417) × 10-5 cm/s (p < 0.01) in the 3.5 mM IP6 group. Additionally, IP6 can concentration-dependently decrease the R123 efflux ratio in both Caco-2 and MDCK II-MDR1 cell monolayers and increase intracellular R123 accumulation in Caco-2 cells. Furthermore, IP6 noncompetitively inhibited P-gp by impacting R123 efflux kinetics. The noncompetitive inhibition of P-gp by IP6 was likely due to decreases in P-gp ATPase activity and P-gp molecular conformational changes induced by IP6. In summary, IP6 is a promising P-gp inhibitor candidate.

Self-nanoemulsifying drug delivery systems of myricetin: Formulation development, characterization, and in vitro and in vivo evaluation.

Despite various pharmacological effects, myricetin (Myr) shows low oral bioavailability (<10%) due to its poor solubility, which limits its applications. To address this problem, self-nanoemulsifying drug delivery systems (SNEDDS) were developed by investigating the solubility of Myr in various excipients, constructing pseudo-ternary phase diagrams, and optimizing based on droplet size and emulsification efficacy after drug loading. The obtained Myr-SNEDDS were F04 (Capryol 90/Cremophor RH 40/PEG 400 4:3:3), F08 (Capryol 90/CremophorRH40/1,2-propanediol 4:3:3), F13 (Capryol 90/Cremophor EL/Transcutol HP 4:3:3) and F15 (Capryol 90/Cremephor RH 40/Transcutol HP 2:7:1), with droplet sizes less than 200nm. Additional evaluations showed that these Myr-SNEDDS formulations had fast release properties (over 90% in 1min), low cytotoxicity, and improved permeability and solubility compared with the free drug. Consequently, the oral bioavailabilities of Myr were 5.13, 6.33, 4.69 and 2.53-fold for F04, F08, F13 and F15, respectively, relative to Myr alone. The present study demonstrated that SNEDDS is a viable platform for the oral delivery of insoluble drugs such as Myr.

Calcium Phosphate-Reinforced Reduction-Sensitive Hyaluronic Acid Micelles for Delivering Paclitaxel in Cancer Therapy.

For addressing the dilemma of in vivo stability and antitumor effects of micellar drugs, novel organic and inorganic hybridized nanoparticle, that is, hyaluronic acid-mineralized micelles, are designed to efficiently deliver paclitaxel (PTX). The resulting micelles exhibit excellent drug loading (30.6%) and entrapment efficiency (87.8%) for PTX with a small size (134.8 nm). Notably, the dual-sensitive release of PTX-loaded mineralized micelles is obtained in the conditions of 40 mM GSH and pH 5.0, whereas release is slow in the physiological environment. With favorable cell uptake, mineralized micelles show decent tumor accumulation, which corresponds to their significant targeting capacity from the observed real-time images. Compared with Taxol, PTX-loaded mineralized micelles show a lower half-maximal inhibitory concentration value (0.025 µg/mL), higher cell apoptosis rate (23.5%) in MDA-MB-231 cells, lower systemic toxicity to nude mice, and more potent in vivo tumor inhibition (1.57-times higher than that of Taxol (p < 0.05)).

Preparation and evaluation of chitosan-based nanogels/gels for oral delivery of myricetin.

A novel nanogel/gel based on chitosan (CS) for the oral delivery of myricetin (Myr) was developed and evaluated comprehensively. The particle size of the obtained Myr-loaded CS/ß-glycerol phosphate (ß-GP) nanogels was in the range of 100-300nm. The rheological tests showed that the sol-gel transition happened when the nanogels were exposed to physiological temperatures, and 3D network structures of the gelatinized nanogels (gels) were confirmed by Scanning Electron Microscopy. Myr was released from CS/ß-GP nanogel/gel in acidic buffers via a Fickian mechanism, and this release was simultaneously accompanied by swelling and erosion. Moreover, the nanogel/gel exhibited no cytotoxicity by MTT assay, and the oral bioavailability of Myr in rats was improved with an accelerated absorption rate after Myr was loaded into CS/ß-GP nanogel/gel. In summary, all of the above showed that CS/ß-GP nanogel/gel was an excellent system for orally delivering Myr.

The effect of phytic acid on tight junctions in the human intestinal Caco-2 cell line and its mechanism.

This study investigated the effect of phytic acid (IP6), a potential absorption enhancer of flavonoid components, on tight junction (TJ) integrity in Caco-2 cell monolayers and its possible mechanisms. Transepithelial electrical resistance (TEER) across the monolayers decreased rapidly, and the flux of fluorescein sodium (a paracellular marker) increased after treating with IP6 in a concentration-dependent manner. Confocal microscopy results showed that IP6 produced a concentration-dependent attenuation in the distribution of occludin, ZO-1, and claudin-1. Immunoblot analysis revealed that IP6 could down-regulate the expression level of these TJ proteins, which resulted in the opening of TJ. Additionally, the divalent cations Ca(2+) and Mg(2+) influenced the IP6-induced distribution of occludin, ZO-1, and claudin-1 in different directions, which enhanced barrier function. In conclusion, IP6 can decrease the integrity of Caco-2 cell monolayers by modulating the TJ proteins' localization and down-regulating the expression levels of TJ proteins including claudin-1, occludin, and ZO-1; the reduction effects of divalent cations such as Ca(2+) and Mg(2+) on the regulation of TJ induced by IP6 should be addressed. The present work will offer some useful guidance for the application of IP6 in drug delivery area.

Comparison of isorhamnetin absorption properties in total flavones of Hippophae rhamnoides L. with its pure form in a Caco-2 cell model mediated by multidrug resistance-associated protein.

Total flavones of Hippophae rhamnoides L. (TFH) are extracted from the widely distributed thorny bush Sea buckthorn (Hippophae rhamnoides L.). Isorhamnetin (IS) is one of the representative ingredients in TFH. In this study, the absorption properties of IS in TFH and its pure form were compared through transepithelial transport and cellular uptake experiments in a Caco-2 cell model. Our results show that the absorption properties of IS in TFH and its pure form were remarkably different: (1) Both PappAB and PappBA of IS in TFH were dramatically increased compared with those of IS pure form; consequently, its Pratio was 2.3-fold higher than that of IS; (2) Both the accumulation and efflux of IS in TFH were significantly enhanced compared with the single compound. One likely reason for these differences is that the multiple components in TFH significantly down regulated the mRNA expression level of MRP2, which lead to a decrease in the protein level of MRP2, based on western blotting and RT-PCR assays. This study highlights the significant differences in the absorption properties of flavonoid components in different forms and the potential multi-component interactions in TFH.