Click chemistry approach for imaging intracellular and intratissue distribution of curcumin and its nanoscale carrier

Unveiling a family of spiro-β-lactams with anti-HIV and antiplasmodial activity via phosphine-catalyzed [3+2] annulation of 6-alkylidene-penicillanates and allenoates

The molecular architecture of spirocyclic compounds has been widely explored within the medicinal chemistry field to obtain new compounds with singular three-dimensional pharmacophoric features and improved bioactivity. Herein, the synthesis of 68 new spirocyclopentene-β-lactams is described, resulting from a rational drug design and structural modulation of a highly promising lead compound BSS-730A, previously identified as having dual antimicrobial activity associated with a novel mechanism of action. Among this diverse library of new compounds, 22 were identified as active against HIV-1, with eight displaying an IC₅₀ lower than 50 nM. These eight compounds also showed nanomolar activity against HIV-2, and six of them displayed micromolar antiplasmodial activity against both the hepatic and the blood stages of infection by malaria parasites, in agreement with the lead molecule’s bioactivity profile. The spirocyclopentene-β-lactams screened also showed low cytotoxicity against TZM-bl and Huh7 human cell lines. Overall, a family of new spirocyclopentene penicillanates with potent activity against HIV and/or Plasmodium was identified. The present structure–activity relationship open avenues for further development of spirocyclopentene-β-lactams as multivalent, highly active broad spectrum antimicrobial agents.

Mechanistic Differences in the Inhibition of NF-κB by Turmeric and Its Curcuminoid Constituents

Turmeric extract, a mixture of curcumin and its demethoxy (DMC) and bisdemethoxy (BDMC) isomers, is used as an anti-inflammatory preparation in traditional Asian medicine. Curcumin is considered to be the major bioactive compound in turmeric but less is known about the relative anti-inflammatory potency and mechanism of the other components, their mixture, or the reduced in vivo metabolites. We quantified inhibition of the NF-κB pathway in cells, adduction to a peptide mimicking IκB kinase β, and the role of cellular glutathione as a scavenger of electrophilic curcuminoid oxidation products, suggested to be the active metabolites. Turmeric extracts (IC₅₀ 14.5 ± 2.9 μM), DMC (IC₅₀ 12.1 ± 7.2 μM), and BDMC (IC₅₀ 8.3 ± 1.6 μM), but not reduced curcumin, inhibited NF-κB similar to curcumin (IC₅₀ 18.2 ± 3.9 μM). Peptide adduction was formed with turmeric and DMC but not with BDMC, and this correlated with their oxidative degradation. Inhibition of glutathione biosynthesis enhanced the activity of DMC but not BDMC in the cellular assay. These findings suggest that NF-κB inhibition by curcumin and DMC involves their oxidation to reactive electrophiles, whereas BDMC does not require oxidation. Because it has not been established whether curcumin undergoes oxidative transformation in vivo, oxidation-independent BDMC may be a promising alternative to test in clinical trials.

Keto-Enol Tautomerism of Temperature and pH Sensitive Hydrated Curcumin Nanoparticles: Their Role as Nanoreactors and Compatibility with Blood Cells

In order to provide a solution for the poor aqueous solubility and poor bioavailability of curcumin, we present the synthesis and characteristic features of water-soluble curcumin hydrated nanoparticles (CNPs). They are stable and nearly monodisperse in the aqueous phase where the keto form of curcumin self-assembles into spherical CNPs, which are highly sensitive to temperature and pH variations. The CNPs are quite stable up to 40 °C and at neutral pH. A higher temperature range reduces their hydration and makes them unstable, thereby disintegrating them into smaller aggregates. Similarly, a higher pH converts the keto form of CNPs into the enol form by promoting their interparticle fusions driven by hydrogen bonding with a remarkable color change from yellow to bright orange-red which demonstrates their excellent photophysical behavior. The stable keto form CNPs are highly efficient nonreactors for the in situ synthesis of Au, Ag, and Pd NPs which are simultaneously entrapped in curcumin aggregates, thus promoting the metal NP carrying ability of curcumin aggregates. The CNPs also demonstrate their excellent dose-dependent biocompatibility with blood cells. A concentration range up to 5 mM of CNPs is quite safe for their applications in biological systems.

The anti-inflammatory activity of curcumin is mediated by its oxidative metabolites

The spice turmeric, with its active polyphenol curcumin, has been used as anti-inflammatory remedy in traditional Asian medicine for centuries. Many cellular targets of curcumin have been identified, but how such a wide range of targets can be affected by a single compound is unclear. Here, we identified curcumin as a pro-drug that requires oxidative activation into reactive metabolites to exert anti-inflammatory activities. Synthetic curcumin analogs that undergo oxidative transformation potently inhibited the pro-inflammatory transcription factor nuclear factor κB (NF-κB), whereas stable, non-oxidizable analogs were less active, with a correlation coefficient (R²) of IC₅₀versus log of autoxidation rate of 0.75. Inhibition of glutathione biosynthesis, which protects cells from reactive metabolites, increased the potency of curcumin and decreased the amount of curcumin-glutathione adducts in cells. Oxidative metabolites of curcumin adducted to and inhibited the inhibitor of NF-κB kinase subunit β (IKKβ), an activating kinase upstream of NF-κB. An unstable, alkynyl-tagged curcumin analog yielded abundant adducts with cellular protein that were decreased by pretreatment with curcumin or an unstable analog but not by a stable analog. Bioactivation of curcumin occurred readily in vitro, which may explain the wide range of cellular targets, but if bioactivation is insufficient in vivo, it may also help explain the inconclusive results in human studies with curcumin so far. We conclude that the paradigm of metabolic bioactivation uncovered here should be considered for the evaluation and design of clinical trials of curcumin and other polyphenols of medicinal interest.

Synthesis and Functional Assessment of a Novel Fatty Acid Probe, ω-Ethynyl Eicosapentaenoic Acid Analog, to Analyze the in Vivo Behavior of Eicosapentaenoic Acid

Eicosapentaenoic acid (EPA) is an ω-3 polyunsaturated fatty acid that plays various beneficial roles in organisms from bacteria to humans. Although its beneficial physiological functions are well-recognized, a molecular probe that enables the monitoring of its in vivo behavior without abolishing its native functions has not yet been developed. Here, we designed and synthesized an ω-ethynyl EPA analog (eEPA) as a tool for analyzing the in vivo behavior and function of EPA. eEPA has an ω-ethynyl group tag in place of the ω-methyl group of EPA. An ethynyl group has a characteristic Raman signal and can be visualized by Raman scattering microscopy. Moreover, this group can specifically react in situ with azide compounds, such as those with fluorescent group, via click chemistry. In this study, we first synthesized eEPA efficiently based on the following well-known strategies. To introduce four C-C double bonds, a coupling reaction between terminal acetylene and propargylic halide or tosylate was employed, and then, by simultaneous and stereoselective partial hydrogenation with P-2 nickel, the triple bonds were converted to cis double bonds. One double bond and an ω-terminal C-C triple bond were introduced by Wittig reaction with a phosphonium salt harboring an ethynyl group. Then, we evaluated the in vivo function of the resulting probe by using an EPA-producing bacterium, Shewanella livingstonensis Ac10. This cold-adapted bacterium inducibly produces EPA at low temperatures, and the EPA-deficient mutant (ΔEPA) shows growth retardation and abnormal morphology at low temperatures. When eEPA was exogenously supplemented to ΔEPA, eEPA was incorporated into the membrane phospholipids as an acyl chain, and the amount of eEPA was about 5% of the total fatty acids in the membrane, which is comparable to the amount of EPA in the membrane of the parent strain. Notably, by supplementation with eEPA, the growth retardation and abnormal morphology of ΔEPA were almost completely suppressed. These results indicated that eEPA mimics EPA well and is useful for analyzing the in vivo behavior of EPA.

One-Step Synthesis of Nanoscale Zeolitic Imidazolate Frameworks with High Curcumin Loading for Treatment of Cervical Cancer

A straightforward nanoprecipitating method was developed to prepare water dispersible curcumin (CCM)-loaded nanoscale zeolitic imidazolate framework-8 (CCM@NZIF-8) nanoparticles (NPs). The as-synthesized CCM@NZIF-8 NPs possess high drug encapsulation efficiency (88.2%), good chemical stability and fast drug release in tumor acidic microenvironments. Confocal laser scanning microscopy and cytotoxicity experiments reveal that NZIF-8 based nanocarriers promote the cellular uptake of CCM and result in higher cytotoxicity of CCM@NZIF-8 than that of free CCM toward HeLa cells. The in vivo anticancer experiments indicate that CCM@NZIF-8 NPs exhibit much higher antitumor efficacy than free CCM. This work highlights the potential of using nanoscale metal organic framworks (NMOFs) as a simple and stable platform for developing a highly efficient drug delivery system in cancer treatment.