Syntheses of Minutuminolate and Related Coumarin Natural Products and Evaluation of Their TNF-α Inhibitory Activities.

The concise syntheses of the coumarin natural product, minutuminolate (1), and its related natural products, 7-methoxy-8-(2-acetoxy-3-methyl-1-oxobut-2-enyl) coumarin (2) and muralatin I (3), were accomplished for the first time in 4-5 steps from the commercially available umbelliferone. The key step involves a palladium-catalyzed oxidative rearrangement reaction to assemble the α-acyloxyenone moiety in 1 and 2. The incorporation of this functionality enables the successful synthesis of coumarin 3 through an acidic hydrolysis reaction. The anti-inflammatory activities of the compounds were also evaluated against tumor necrosis factor-alpha production in lipopolysaccharides-stimulated RAW264.7 cells. Our developed synthetic route will facilitate the development of analogues and derivatives of 1-3 with potent anti-inflammatory activities.

Degradation of MK2 with natural compound andrographolide: A new modality for anti-inflammatory therapy.

The p38MAPK-MK2 signaling axis functions as an initiator of inflammation. Targeting the p38MAPK-MK2 signaling axis represents a direct therapeutic intervention of inflammatory diseases. We described here a novel role of andrographolide (AG), a small-molecule ent-labdane natural compound, as an inhibitor of p38MAPK-MK2 axis via MK2 degradation. AG was found to bind to the activation loop of MK2, located at the interface of the p38MAPK-MK2 biomolecular complex. This interaction disrupted the complex formation and predisposed MK2 to proteasome-mediated degradation. We showed that AG induced MK2 degradation in a concentration- and time-dependent manner and exerted its anti-inflammatory effects by enhancing the mRNA-destabilizing activity of tristetraprolin, thereby inhibiting pro-inflammatory mediator production (e.g., TNF-α, MCP-1). Administration of AG via intratracheal (i.t.) route to mice induced MK2 downregulation in lung alveolar macrophages, but not lung tissues, and prevented macrophage activation. Our study also demonstrated that the anti-inflammatory effects achieved by AG via MK2 degradation were more durable and sustained than that achieved by the conventional MK2 kinase inhibitors (e.g., PF-3644022). Taken together, our findings illustrated a novel mode of action of AG by modulating the p38MAPK-MK2 signaling axis and would pave the way for the development of a novel class of anti-inflammatory agents targeting MK2 for degradation by harnessing the privileged scaffold of AG.

Impact of Preoperative Echocardiograms on In-Hospital Outcomes of Patients Undergoing Surgical Hip Fracture Repair and Their Clinical Appropriateness.

OBJECTIVES: Preoperative transthoracic echocardiograms (TTE) before hip fracture repairs are controversial. This study aimed to quantify the frequency of ordering TTE, the appropriateness of testing based on current guidelines, and the impact of TTE on in-hospital morbidity and mortality outcomes. METHODS: This retrospective chart review of adult patients admitted with hip fracture compared the length of stay (LOS), time to surgery, in-hospital mortality, and postoperative complications between TTE and non-TTE groups. TTE patients were risk stratified using the Revised Cardiac Risk Index (RCRI) to compare TTE indication according to current guidelines. RESULTS: Of the 490 patients included in this study, 15% received preoperative TTE. The median LOS of the TTE and non-TTE groups was 7.0 and 5.0 d, respectively, whereas the median time to surgery was 34 and 14 h, respectively. The odds of in-hospital mortality remained significantly higher in the TTE group after adjusting for RCRI but not when adjusted for the Charlson Comorbidity Index. Significantly more patients in the TTE groups had postoperative heart failure and up triage in the intensive care unit. Furthermore, 48% of patients with an RCRI score of 0 received preoperative TTE, with cardiac history as the most typical indication. TTE changed perioperative management in 9% of patients. CONCLUSIONS: Patients subjected to TTE before hip fracture surgery had a longer LOS and time to surgery, with higher mortality and intensive care unit up triage rates. TTE evaluations were typically conducted for inappropriate indications, which rarely made meaningful changes to patient management.

Calcaratarin D, a labdane diterpenoid, attenuates mouse asthma via modulating alveolar macrophage function.

BACKGROUND AND PURPOSE: Alveolar macrophages (AMs) contribute to airway inflammation and remodelling in allergic asthma. Calcaratarin D (CalD), a labdane diterpenoid from rhizomes of the medicinal plant Alpinia calcarata, has recently been shown to possess anti-inflammatory properties. The present study evaluated protective effects of CalD in a house dust mite (HDM)-induced asthma mouse model. EXPERIMENTAL APPROACH: The effects of CalD on AMs in contributing to anti-inflammatory effects in asthma were investigated through in vivo, ex vivo, and in vitro experiments. KEY RESULTS: CalD reduced total bronchoalveolar lavage fluid and differential cell count, serum IgE levels, mucus hypersecretion, and airway hyperresponsiveness in HDM-challenged mice. Additionally, CalD affected a wide array of pro-inflammatory cytokines and chemokines and oxidative damage markers in isolated lung tissues. CalD suppressed the HDM-induced increase in Arg1 (M2 macrophage marker) in AMs from lung tissue and reduced lung polyamine levels. CalD weakened antigen presentation capability of AMs by reducing CD80 expression, reduced AM-derived CCL17 and CCL22 levels, and lessened Th2 cytokines from CD4+ T-cells from asthma lung digest. CalD blocked the HDM-induced FoxO1/IRF4 pathway and restored impaired the Nrf2/HO-1 antioxidant pathway in lung tissues. CalD inhibited IL-4/IL-13-stimulated JAK1/STAT6 pathway, FoxO1 protein expression, and chemokine production in primary AMs. Structure-activity relationship study revealed the α,ß-unsaturated γ-butyrolactone in CalD is capable of forming covalent bonds with cellular protein targets essential for its action. CONCLUSION AND IMPLICATIONS: Our results demonstrate for the first time that CalD is a novel anti-inflammatory natural compound for allergic asthma that modulates AM function.

Small-molecule enhancers of CRISPR-induced homology-directed repair in gene therapy: A medicinal chemist's perspective.

CRISPR technologies are increasingly being investigated and utilized for the treatment of human genetic diseases via genome editing. CRISPR-Cas9 first generates a targeted DNA double-stranded break, and a functional gene can then be introduced to replace the defective copy in a precise manner by templated repair via the homology-directed repair (HDR) pathway. However, this is challenging owing to the relatively low efficiency of the HDR pathway compared with a rival random repair pathway known as non-homologous end joining (NHEJ). Small molecules can be employed to increase the efficiency of HDR and decrease that of NHEJ to improve the efficiency of precise knock-in genome editing. This review discusses the potential usage of such small molecules in the context of gene therapy and their drug-likeness, from a medicinal chemist's perspective.

COVID-19 and the promise of small molecule therapeutics: Are there lessons to be learnt?

The coronavirus disease 2019 (COVID-19) pandemic had grounded the world to a standstill. As the disease continues to rage two years on, it is apparent that effective therapeutics are critical for a successful endemic living with COVID-19. A dearth in suitable antivirals has prompted researchers and healthcare professionals to investigate existing and developmental drugs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although some of these drugs initially appeared to be promising for the treatment of COVID-19, they were ultimately found to be ineffective. In this review, we provide a retrospective analysis on the merits and limitations of some of these drugs that were tested against SARS-CoV-2 as well as those used for adjuvant therapy. While many of these drugs are no longer part of our arsenal for the treatment of COVID-19, important lessons can be learnt. The recent inclusion of molnupiravir and Paxlovid™ as treatment options for COVID-19 represent our best hope to date for endemic living with COVID-19. Our viewpoints on these two drugs and their prospects as current and future antiviral agents will also be provided.

Promoting GAINs (Give Attention to Limitations in Assays) over PAINs Alerts: no PAINS, more GAINs.

Many concepts and guidelines in medicinal chemistry have been introduced to aid in successful drug discovery and development. An example is the concept of Pan-Assay Interference Compounds (PAINS) and the elimination of such nuisance compounds from high-throughput screening (HTS) libraries. PAINs, along with other guidelines in medicinal chemistry, are like double-edged swords. If used appropriately, they may be beneficial for drug discovery and development. However, rigid and blind use of such concepts can hinder productivity. In this perspective, we introduce GAINS (give attention to limitations in assays) and highlight its relevance for successful drug discovery.

Discovery and development of labdane-oxindole hybrids as small-molecule inhibitors against chikungunya virus infection.

Chikungunya virus (CHIKV) infection, a febrile illness caused by a mosquito-transmitted alphavirus, has afflicted millions of people worldwide. There is currently no approved effective antiviral treatment for CHIKV infection. In this study, we report a new class of small-molecule CHIKV inhibitors, the oxindole-labdanes, that potently block the replication of CHIKV with good selectivity. Andrographolide, a previously reported inhibitor of CHIKV infection, was used as the lead compound for our initial structure-activity relationship (SAR) study. From a focused library of 72 andrographolide analogues, we identified the lead compound (E)-2 with improved antiviral activities. Further optimization of (E)-2 led to the discovery of the normal-labdane 7-chloro-oxindole (E)-42 as potent inhibitor against two low-passage CHIKV isolates from human patients with an EC50 of 1.55 µM against CHIKV-122508 and 0.14 µM against CHIKV-6708. Compound (E)-42 displayed minimal cytotoxic liability (CC50 > 100 µM), thus furnishing good selectivity relative to the host cells. Mechanistically, (E)-42 does not inactivate the viral particles but rather acts on the host cells to interfere with the viral replication, demonstrating both prophylactic and therapeutic effects. Our findings open a new avenue for the development of oxindole-labdane compounds as promising antiviral drugs against CHIKV infection.

Candida-Induced Emphysematous Gastritis in a Multiple Myeloma Patient: Conservative Management With Favorable Outcome.

Emphysematous gastritis is a rare, and often fatal, infection with unclear recommendations on management. We report the first documented case of emphysematous gastritis caused by Candida species in a patient on chemotherapy for multiple myeloma. Our patient, who presented with gastrointestinal symptoms was found to have gas in the stomach wall, peri-gastric, and portal veins on CT scan. Nasogastric tube cultures grew Candida albicans and Candida glabrata and the patient was treated with antibiotics and antifungals. Prompt recognition and conservative management led to a favorable outcome.

Evaluation of 2-Bromoisobutyryl Catechol Derivatives for Atom Transfer Radical Polymerization-Functionalized Polydopamine Coatings.

The use of α-bromoisobutyryl-functionalized polydopamine (PDA), derived from an in situ mixture with dopamine (DA) and α-bromoisobutyryl bromide, enables surface-initiated atom transfer radical polymerization (SI-ATRP) of a broad range of methacrylate monomers for surface functionalization. Although the putative intermediate 2-bromo-N-(3,4-dihydroxyphenethyl)-2-methylpropanamide 1 has been proposed to account for the SI-ATRP activity of α-bromoisobutyryl-functionalized PDA, there has not been a systematic investigation on the efficacy of other catechol-derived 2-bromoisobutyryl derivatives for SI-ATRP. In this work, a number of catechol-derived ATRP initiators containing the 2-bromoisobutyryl moiety were designed and synthesized, in an effort to investigate the effect of changes in structure on initiator immobilization, and subsequent ATRP performance. The change in the length of the linker unit bearing the 2-bromoisobutyryl moiety, the introduction of a free amine group, or the replacement of the amide with an ester were found to have profound effects on the ability of the molecule to deposit ATRP-initiator-modified PDA coatings, as well as the subsequent SI-ATRP performance. Among the ATRP initiators synthesized, 5-(2-aminoethyl)-2,3-dihydroxyphenethyl 2-bromo-2-methylpropanoate hydrobromide 4·HBr was most efficiently incorporated into ATRP-initiator-modified PDA coatings and also the best at effecting SI-ATRP with 2-hydroxyethyl methacrylate; the high performance of this initiator is likely due to the presence of a free amine and an appropriately long methylene linker unit to the 2-bromoisobutyryl moiety. This methodology was found to be suitable for the functionalization of a range of organic and inorganic surfaces, for the fabrication of high-value surface-grafted polymer brush coatings for various applications.

Polypharmacology of andrographolide: beyond one molecule one target.

Covering: 1951 to 2020Andrographolide is one of the most widely studied plant secondary metabolites, known to display diverse pharmacological actions. Current literature has documented a sizeable list of pharmacological targets for andrographolide, suggesting its multi-targeting nature. Many of these targets are central to the pathophysiology of highly prevalent diseases such as cardiovascular diseases, neurodegenerative disorders, autoimmunity, and even cancer. Despite its well-documented therapeutic efficacy in various disease models, for years, the discrepancies between in vivo bioavailability and bioactivity of andrographolide and the debate surrounding its multi-targeting properties (polypharmacology or promiscuity?) have hindered the development of this versatile molecule into a potential therapeutic agent. Is andrographolide a valuable lead for therapeutic development or a potential invalid metabolic panacea (IMP)? This perspective article aims to discuss this by considering various contributing factors to the polypharmacology of andrographolide.

Gold(I)-Catalyzed Intramolecular Hydroarylation of Phenol-Derived Propiolates and Certain Related Ethers as a Route to Selectively Functionalized Coumarins and 2H-Chromenes.

Methods are reported for the efficient assembly of a series of phenol-derived propiolates, including the parent system 56, and their Au(I)-catalyzed cyclization (intramolecular hydroarylation) to give the corresponding coumarins (e.g., 1). Simple syntheses of natural products such as ayapin (144) and scoparone (145) have been realized by such means, and the first of these subject to single-crystal X-ray analysis. A related process is described for the conversion of propargyl ethers such as 156 into the isomeric 2H-chromene precocene I (159), a naturally occurring inhibitor of juvenile hormone biosynthesis.

From irreversible to reversible covalent inhibitors: Harnessing the andrographolide scaffold for anti-inflammatory action.

Covalent drugs with prolonged actions often show superior potency, yet integrated strategies for optimizing their structural and electronic features are lacking. Herein, we present our effort directed towards understanding the contribution of chemical reactivity to biological potency to rationally design new covalent inhibitors based on the ent-ladane andrographolide scaffold for anti-inflammatory action. Specifically, a series of andrographolide derivatives comprising various Michael acceptors was developed and their thiol reactivity was assayed under various chemical and biological conditions. The cell-based SAR studies permitted the assessment of the inhibitor efficacy in more complex systems, which were often limited in traditional covalent drug development using isolated proteins or peptides. Our in vitro study identified enone 17 as the most promising candidate which demonstrated potent anti-inflammatory activity and superior safety profiles as compared to the lead compound andrographolide. Its reversibility following a Michael addition reaction with biological thiols resulted in more predictable pharmacological responses. In addition, 17 exhibited good in vivo efficacy at doses as low as 0.3 mg/kg when tested in LPS-induced acute lung injury model. Given a good balance of chemical reactivity and biological potency, enone 17 potentially offers a new therapeutic option based on natural product chemistry for the management of inflammatory conditions.

Slow-, Tight-Binding Inhibition of CYP17A1 by Abiraterone Redefines Its Kinetic Selectivity and Dosing Regimen.

Substantial evidence underscores the clinical efficacy of inhibiting CYP17A1-mediated androgen biosynthesis by abiraterone for treatment of prostate oncology. Previous structural analysis and in vitro assays revealed inconsistencies surrounding the nature and potency of CYP17A1 inhibition by abiraterone. Here, we establish that abiraterone is a slow-, tight-binding inhibitor of CYP17A1, with initial weak binding preceding the subsequent slow isomerization to a high-affinity CYP17A1-abiraterone complex. The in vitro inhibition constant of the final high-affinity CYP17A1-abiraterone complex ( ( K i * = 0.39 nM )yielded a binding free energy of -12.8 kcal/mol that was quantitatively consistent with the in silico prediction of -14.5 kcal/mol. Prolonged suppression of dehydroepiandrosterone (DHEA) concentrations observed in VCaP cells after abiraterone washout corroborated its protracted CYP17A1 engagement. Molecular dynamics simulations illuminated potential structural determinants underlying the rapid reversible binding characterizing the two-step induced-fit model. Given the extended residence time (42 hours) of abiraterone within the CYP17A1 active site, in silico simulations demonstrated sustained target engagement even when most abiraterone has been eliminated systemically. Subsequent pharmacokinetic-pharmacodynamic (PK-PD) modeling linking time-dependent CYP17A1 occupancy to in vitro steroidogenic dynamics predicted comparable suppression of downstream DHEA-sulfate at both 1000- and 500-mg doses of abiraterone acetate. This enabled mechanistic rationalization of a clinically reported PK-PD disconnect, in which equipotent reduction of downstream plasma DHEA-sulfate levels was achieved despite a lower systemic exposure of abiraterone. Our novel findings provide the impetus for re-evaluating the current dosing paradigm of abiraterone with the aim of preserving PD efficacy while mitigating its dose-dependent adverse effects and financial burden. SIGNIFICANCE STATEMENT: With the advent of novel molecularly targeted anticancer modalities, it is becoming increasingly evident that optimal dose selection must necessarily be predicated on mechanistic characterization of the relationships between target exposure, drug-target interactions, and pharmacodynamic endpoints. Nevertheless, efficacy has always been perceived as being exclusively synonymous with affinity-based measurements of drug-target binding. This work demonstrates how elucidating the slow-, tight-binding inhibition of CYP17A1 by abiraterone via in vitro and in silico analyses was pivotal in establishing the role of kinetic selectivity in mediating time-dependent CYP17A1 engagement and eventually downstream efficacy outcomes.

The identification of naturally occurring labdane diterpenoid calcaratarin D as a potential anti-inflammatory agent.

In this study we report, for the first time, the synthesis of the natural product calcaratarin D via a stereo- and regio-selective aldol condensation with (S)-ß-hydroxy-γ-butyrolactone as key steps. A concise synthetic route (under 10 steps) to a series of structurally related normal-labdane diterpenes was also developed and their anti-inflammatory activities were evaluated in an in vitro model of inflammation. The structure-activity relationships (SARs) pertaining to the labdane scaffold were elucidated and results suggest that an α-alkylidene-ß-hydroxy-γ-butyrolactone system is necessary for potent activity in the labdanes. Our studies identified the natural product calcaratarin D (1) as a promising anti-inflammatory agent, which effectively modulates the production of pro-inflammatory mediators (e.g., TNF-α, IL-6, NO) at both transcriptional and translational levels. These inhibitory effects are likely to occur via the suppression of nuclear factor kappa B (NF-κB) activation by reducing the p65 nuclear translocation but not its phosphorylation or protein expression. Calcaratarin D exhibited significantly greater inhibition of NF-κB activation than andrographolide, a well-known NF-κB inhibitor from the labdane family, suggesting that a normal-configuration labdane ring or the absence of hydroxyl groups at C-3 and C-19 positions is favorable for potent NF-κB inhibition. We further investigated the effects of calcaratarin D on the upstream signalling pathways and found that the compound selectively suppressed the LPS-induced activation of PI3K/Akt pathway without affecting much of the MAPK (i.e., ERK, JNK, and p38) activation. These findings demonstrate that calcaratarin D exerts its anti-inflammatory effects via a selective Akt-NF-κB-mediated mechanism and potentially offers a new therapeutic strategy for the management of inflammatory diseases.

A fluorescence-displacement assay using molecularly imprinted polymers for the visual, rapid, and sensitive detection of the algal metabolites, geosmin and 2-methylisoborneol.

A visual, rapid, and sensitive method for the detection of two algal metabolites, geosmin (GSM) and 2-methylisoborneol (2-MIB) using a competitive displacement technique based on molecular imprinted polymers (MIPs) and fluorescent tags was developed. In this method, fluorescent tags that bind to synthetic receptor sites of MIPs were designed and synthesised. In the presence of target analytes (geosmin and 2-methylisoborneol respectively), the tags are displaced leading to fluorescence signals. The MIPs were derived from the polymerisation of functional monomers and crosslinkers in the presence of suitable templates. Good to high binding capacities and selectivities were obtained with the MIPs. The displacement of fluorescent-tagged substrates from the respective MIPs by the target analytes enabled the quantitative detection of geosmin at concentrations as low as 0.38 µM (69 µg L-1), while the LOD for 2-methylisoborneol is 0.29 µM (48 µg L-1) without any cross-reactivity, non-specific (false-positive) binding, and matrix complications. Qualitative detection of geosmin and 2-methylisoborneol is also possible via visualisation of fluorescence using a hand held UV lamp, with LOD for geosmin and 2-methylisoborneol at 0.44 µM (80 µg L-1) and 0.35 µM (60 µg L-1), respectively. The sensitivity of the system can be improved with a pre-concentration step using the respective MIPs as a sorbent.

A synthetic approach to chrysophaentin F.

The chrysophaentins are a newly discovered natural product family displaying promising anti-infective activity. Herein we describe an approach to chrysophaentin F that uses an array of metal catalysed coupling reactions (Cu, Ni, Pd, W, Mo) to form key bonds.

Direct Evidence for the Critical Role of 5,6-Dihydroxyindole in Polydopamine Deposition and Aggregation.

The definitive role of the intermediate 5,6-dihydroxyindole (DHI) in the formation of polydopamine (PDA) coatings from aqueous dopamine (DA) has not been clearly elucidated and remains highly controversial. Our foray into this debate as reported in this study agrees with some reported assertions that DHI-based coatings are not synonymous with PDA coatings. Our conclusion arises from a systematic comparison of the components and properties of DHI-based coatings and PDA coatings. In addition, through careful copolymerization studies of DA and DHI, our studies reported herein unequivocally suggest that both DA and DHI are partial building blocks for PDA formation. Our results also provide additional evidence of the critical role of DHI in controlling the thickness of PDA coatings, through competitive events between PDA aggregation in solutions and deposition onto substrates. These findings highlight the complex interplay between both DHI and uncyclized DA moieties in the formation of adhesive catechol/amine materials.

The Chemistry of Bioinspired Catechol(amine)-Based Coatings.

Surface coatings are widely used for the protection of underlying materials from erosion or contamination by the external environment, with biomimetic organic coatings based on catecholamine chemistry gaining prominence in recent years. Such coatings have found use in the biomedical field, e.g., in diagnostics, implant manufacturing, and biosensing, with coatings based on polydopamine (PDA) being the most popular. This Review aims to summarize the chemistry of catechol(amine) coatings, in particular the adhesion and cohesion properties of catecholamine-based coatings. This will allow for the design and synthesis of new polymers and coating materials in a more rational manner, enabling the selection of parameters and conditions to precisely control the structure of the materials formed. Particular attention is paid to the formation mechanism, structure, and variables affecting the properties of PDA, which is the most widely reported catechol(amine) coating. The use of other catechol(amine) precursors to synthesize biomimetic coatings is also discussed. A summary of the different methods reported in the literature to effect specific chemical properties on catechol(amine) coatings will allow the reader to best choose the technique to tailor coating properties for specific applications.