Asymmetric total synthesis and identification of tetrahydroprotoberberine derivatives as new antipsychotic agents possessing a dopamine D1, D2 and serotonin 5-HT1A multi-action profile

Integrating UPLC-MS/MS with in Silico and in Vitro Screening Accelerates the Discovery of Active Compounds in Stephania epigaea

Traditional Chinese medicines (TCMs) are popular in clinic because of their safety and efficacy. They contain abundant natural active compounds, which are important sources of new drug discovery. However, how to efficiently identify active compounds from complex ingredients remains a challenge. In this study, a method combining UHPLC-MS/MS characterization and in silico screening was developed to discover compounds with dopamine D2 receptor (D2R) activity in Stephania epigaea (S. epigaea). By combining the compounds identified in S. epigaea by UHPLC-MS/MS with reported compounds, a virtual library of 80 compounds was constructed for in silico screening. Potentially active compounds were chosen based on screening scores and subsequently tested for in vitro activity on a transfected cell line CHO-K1-D2 model using label-free cellular phenotypic assay. Three D2R agonists and five D2R antagonists were identified. (-)-Asimilobine, N-nornuciferine and (-)-roemerine were reported for the first time as D2R agonists, with EC50 values of 0.35 ± 0.04 μM, 1.37 ± 0.10 μM and 0.82 ± 0.22 μM, respectively. Their target specificity was validated by desensitization and antagonism assay. (-)-Isocorypalmine, (-)-tetrahydropalmatine, (-)-discretine, (+)-corydaline and (-)-roemeroline showed strong antagonistic activity on D2R with IC50 values of 92 ± 9.9 nM, 1.73 ± 0.13 μM, 0.34 ± 0.02 μM, 2.09 ± 0.22 μM and 0.85 ± 0.08 μM, respectively. Their kinetic binding profiles were characterized using co-stimulation assay and they were both D2R competitive antagonists. We docked these ligands with human D2R crystal structure and analyzed the structure-activity relationship of aporphine-type D2R agonists and protoberberine-type D2R antagonists. These results would help to elucidate the mechanism of action of S. epigaea for its analgesic and sedative efficacy and benefit for D2R drug design. This study demonstrated the potential of integrating UHPLC-MS/MS with in silico and in vitro screening for accelerating the discovery of active compounds from TCMs.

Carboxylic Acid-Enabled Vinylene Transfer Reaction by Co(III) Catalyst: Scope and Applications to the Five-Step Total Synthesis of Protoberberine Alkaloids Containing Free Hydroxyl Group without Protection

A Co(III)-catalyzed vinylene transfer reaction enabled by carboxylic acid is presented. This redox-neutral transformation tolerates various functional groups, including free hydroxyl groups, and features practicality. Five-step routes based on the vinylene transfer reaction and Heck annulation have been devised to the total synthesis of 8-oxodehydrodiscretamine and 2-demethyl-oxypalmatine without the protection of the free hydroxyl functionality.

C-H Alkylation of Cubanes via Catalytic Generation of Cubyl Radicals

A catalytic method for the C-H alkylation of cubanes is described. Some hydrogen atom transfer catalysts enable the direct abstraction of a hydrogen atom from the C-H bond of cubanes, followed by conjugate addition of the generated cubyl radicals to electron-deficient alkenes. Synthetic applications of the functionalization method developed are also described.

Fluoroalkoxylated C-3 and C-9 (S)-12-bromostepholidine analogues with D1R antagonist activity

To illuminate the tolerance of fluoroalkoxylated groups at the C-3 and C-9 positions of tetrahydroprotoberberines (THPBs) on D1R activity, C-3 and C-9 fluoroalkoxylated analogues of (S)-12-bromostepholidine were prepared and evaluated. All compounds examined were D1R antagonists as measured by a cAMP assay. Our structure-activity studies herein indicate that the C-3 position tolerates a 1,1-difluoroethoxy substituent for D1R antagonist activity. Compound 13a was the most potent cAMP-based D1R antagonist identified and was also found to antagonize β-arrestin translocation in a TANGO assay. Affinity assessments at other dopamine receptors revealed that 13a is selective for D1R and unlike other naturally-occurring THPBs such as (S)-stepholidine, lacks D2R affinity. In preliminary biopharmaceutical assays, excellent BBB permeation was observed for 13a. Further pharmacological studies are warranted on (S)-stepholidine congeners to harvest their potential as a source of novel, druggable D1R-targeted agents.

Discovery of Selective Dopamine Receptor Ligands Derived from (-)-Stepholidine via C-3 Alkoxylation and C-3/C-9 Dialkoxylation

We evaluated C-3 alkoxylated and C-3/C-9 dialkoxylated (-)-stepholidine analogues to probe the tolerance at the C-3 and C-9 positions of the tetrahydroprotoberberine (THPB) template toward affinity for dopamine receptors. A C-9 ethoxyl substituent appears optimal for D1R affinity since high D1R affinities were observed for compounds that contain an ethyl group at C-9, with larger C-9 substituents tending to decrease D1R affinity. A number of novel ligands were identified, such as compounds 12a and 12b, with nanomolar affinities for D1R and no affinity for either D2R or D3R, with compound 12a being identified as a D1R antagonist for both G-protein- and β-arrestin-based signaling. Compound 23b was identified as the most potent and selective D3R ligand containing a THPB template to date and functions as an antagonist for both G-protein- and β-arrestin-based signaling. Molecular docking and molecular dynamics studies validated the D1R and D3R affinity and selectivity of 12a, 12b, and 23b.

First Total Syntheses of Natural Phenanthrene Alkaloids, Uvariopsamine, Noruvariopsamine, 8-Hydroxystephenanthrine, 8-Methoxyuvariopsine, Thalihazine, and Secophoebine, and Their Potential as Antimalarial Agents

The first total syntheses of natural phenanthrene alkaloids, namely, uvariopsamine (1), noruvariopsamine (2), 8-hydroxystephenanthrine (3), 8-methoxyuvariopsine (4), thalihazine (5), and secophoebine (6), have been realized. In addition, their in vitro antimalarial activity against the multidrug-resistant K1 strain of Plasmodium falciparum and in vitro cytotoxic activity against the human nasopharynx carcinoma (KB), small cell lung cancer (NCI-H187), and breast cancer (MCF7) human cancer cell lines were investigated. All the phenanthrene alkaloids showed significant antiplasmodial activity (IC₅₀ 1.07-7.41 µM), and most compounds displayed low to no toxicity against the three cancer cell lines tested. Particularly, 3 exhibited the best antimalarial activity with an IC₅₀ value of 1.07 µM, no toxicity to NCI-H187 (IC₅₀ > 50 µM), and low toxicity against KB (IC₅₀ 24.53 µM) and MCF7 (IC₅₀ 42.67 µM) cell lines.

Development of a Fully Continuous-Flow Approach Towards Asymmetric Total Synthesis of Tetrahydroprotoberberine Natural Alkaloids

Continuous flow synthetic technologies had been widely applied in the total synthesis in the past few decades. Fully continuous flow synthesis is still extremely focused on multi-step synthesis of complex natural pharmaceutical molecules. Thus, the development of fully continuous flow total synthesis of natural products is in demand but challenging. Herein, we demonstrated the first fully continuous flow approach towards asymmetric total synthesis of natural tetrahydroprotoberberine alkaloids, (-)-isocanadine, (-)-tetrahydropseudocoptisine, (-)-stylopine and (-)-nandinine. This method features a concise linear sequence involving four chemical transformations and three on-line work-up processing in an integrated flow platform, without any intermediate purification. The overall yield and enantioselectivity of this four-step continuous flow chemistry were up to 50 % and 92 %ee, respectively, in a total residence time of 32.5 min, corresponding to a throughput of 145 mg/h.

Identification and evaluation of a lipid-lowering small compound in preclinical models and in a Phase I trial

Developing non-statin-based small compounds to battle the global epidemic of hyperlipidemia remains challenging. Here, we report the discovery of DC371739, an indole-containing tetrahydroisoquinoline compound with promising lipid-lowering effects, both in vitro and in vivo, and with good tolerability in a Phase I clinical trial (NCT04927221). DC371739 significantly reduced the plasma levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides simultaneously in several animal models and showed preliminary positive results in the Phase I trial. Mechanistically, DC371739 acts in a distinct manner from other known lipid-lowering reagents. We show that it physically binds HNF-1α, impeding the transcription of both PCSK9 and ANGPTL3, two genes that are known to contribute to hypercholesterolemia and dyslipidemia. Moreover, the distinct mechanism of action of DC371739 allows its combination with atorvastatin treatment to additively improve dyslipidemia, while providing a potential alternative therapeutic strategy for individuals with statin intolerance.

Isolation, synthesis and bioactivity evaluation of isoquinoline alkaloids from Corydalis hendersonii Hemsl. against gastric cancer in vitro and in vivo

Isoquinoline alkaloid displays significant anti-gastric cancer effects due to its unique structure, which is attracting more and more attention for the development of anti-gastric cancer drugs. In this study, we explore the active components against gastric cancer from the Tibetan Medicine Corydalis hendersonii Hemsl, which is rich in isoquinoline alkaloids. 14 compounds including 2 previously undescribed natural products were obtained. Interestingly, an new active compound displays potent anti-gastric cancer activity. After accomplishing the total syntheses of the active compound and its derivatives, the anti-gastric cancer activity of the active compound was further investigated. In vitro experiments revealed that the active compound significantly attenuated the proliferative capacity, caused G2/M phase arrest, inhibited the cell migration and invasion, and induced cell apoptosis. Mechanistically, the active compound could increase the Bax/Bcl-2 ratio, elevate cytochrome c in the cytosol, and activate caspase-9/3, along with inactivating the upstream PI3K/Akt/mTOR signaling pathway. In addition, the active compound could also cause gastric cancer cell death by inhibiting topoisomerase I activity. More importantly, the anti-gastric cancer activity of the active compound was confirmed in MGC-803 xenograft nude mice in vivo. This work not only promotes the exploitation of Corydalis hendersonii Hemsl., but also provides some experience for discovering new entities from natural sources.

A unified total synthesis of benzo[d][1,3]dioxole-type benzylisoquinoline alkaloids of aporphines, coptisines, and dibenzopyrrocolines

The first total synthesis of (S)-(+)-ovigerine, (S)-(+)-N-formylovigerine, and (6aS,6a'S)-(+)-ovigeridimerine of aporphine alkaloids with a benzo[d][1,3]dioxole structure feature was established. The strategy was based upon the well-known Pd-catalyzed arylation to set the aporphine framework, and Noyori asymmetric hydrogenation followed by diastereoselective resolution to achieve excellent enantioselectivity. By slightly modifying the total synthetic route and strategically combining it with a aza-Michael addition, Bischler-Napieralski reaction and N-arylation, this methodology was also applied to the total syntheses of benzo[d][1,3]dioxole-type benzylisoquinoline alkaloids of coptisines and dibenzopyrrocolines, including two impatiens, tetrahydrocoptisine, and quaternary coptisine bromide of coptisines and two dibenzopyrrocoline analogues, with the syntheses of all of these target compounds being efficient. Among the nine synthesized compounds, the total syntheses of the three aporphines and the two impatiens, all with ee values of greater than 99%, were reported for the first time. This work also represents the first unification of synthetic routes for the total synthesis of benzo[d][1,3]dioxole-type aporphines, coptisines, and dibenzopyrrocolines.

Hypothesis-Driven Palladium-Catalyzed Transformations for the Construction of New Molecular Architectures

The development of new synthetic protocols to access diverse molecular scaffolds from readily available starting compounds is of significance in both academia and industry. Towards this, the catalysis by transition metals has been employed as a powerful tool to access molecules with broad structural and functional diversity. An overview of the recent literature manifested the tremendous potential of transition metal-catalyzed processes in advancing organic synthesis in a new direction. This account compiles new conceptual advancements in the palladium-catalyzed Alder-ene type cycloisomerization reactions, C-H functionalizations, and one-pot multicatalytic processes, which have become essential tools to access new classes of molecules.

Dechloromethylation of the berberine to berberrubine — tricks to obtain pure product

Berberine (1), as a compound with interesting biological activities, can be modified at various positions to obtain more potent substances. Modifications at position 9 are based on demethylation with simultaneous dechloration resulting in berberrubine. The most frequent process is thermal dechloromethylation and this work describes this method with detailed tricks to obtain almost pure product in high yield.

Berberine: A Plant-derived Alkaloid with Therapeutic Potential to Combat Alzheimer's disease

Berberine (a protoberberine isoquinoline alkaloid) has shown promising pharmacological activities, including analgesic, anti-inflammatory, anticancer, antidiabetic, anti-hyperlipidemic, cardioprotective, memory enhancement, antidepressant, antioxidant, anti-nociceptive, antimicrobial, anti- HIV and cholesterol-lowering effects. It is used in the treatment of the neurodegenerative disorder. It has strong evidence to serve as a potent phytoconstituent in the treatment of various neurodegenerative disorders such as AD. It limits the extracellular amyloid plaques and intracellular neurofibrillary tangles. It has also lipid-glucose lowering ability, hence can be used as a protective agent in atherosclerosis and AD. However, more detailed investigations along with safety assessment of berberine are warranted to clarify its role in limiting various risk factors and AD-related pathologies. This review highlights the pharmacological basis to control oxidative stress, neuroinflammation and protective effect of berberine in AD, which will benefit to the biological scientists in understanding and exploring the new vistas of berberine in combating Alzheimer's disease.

Tetrahydroprotoberberines: A Novel Source of Pharmacotherapies for Substance Use Disorders?

Tetrahydroprotoberberines (THPBs) are a class of compounds that target both dopamine D1 and D2 families of receptors, making them attractive candidates for treating substance use disorder (SUD). The binding of some THPBs to serotonin and adrenergic receptors, in addition to dopamine receptors, gives rise to complex pharmacological profiles. Significant progress has been made over the last decade in examining these compounds for their therapeutic potential. Here, we evaluate recent discoveries relating to the neural mechanism and therapeutic effects of THPBs, focusing on compounds that have shown promise in animal models of SUD and preliminary clinical studies. Advancements in structure-activity relationship studies and in silico modeling of THPB binding to dopamine receptors have facilitated the synthesis of novel THPBs with enhanced therapeutic properties and provide insights regarding use of the THPB scaffold to serve as a template for innovative drug designs.

Design, synthesis, and biological evaluation of novel tetrahydroprotoberberine derivatives (THPBs) as proprotein convertase subtilisin/kexin type 9 (PCSK9) modulators for the treatment of hyperlipidemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) modulators may attenuate PCSK9-induced low-density lipoprotein receptor (LDLR) degradation in lysosome and promote the clearance of circulating low-density lipoprotein cholesterol (LDL-C). A novel series of tetrahydroprotoberberine derivatives (THPBs) were designed, synthesized, and evaluated as PCSK9 modulators for the treatment of hyperlipidemia. Among them, eight compounds exhibited excellent activities in downregulating hepatic PCSK9 expression better than berberine in HepG2 cells. In addition, five compounds 15, 18, 22, (R)-22, and (S)-22 showed better performance in the low-density lipoprotein, labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine perchlorate (DiI-LDL) uptake assay, compared with berberine at the same concentration. Compound 22, selected for in vivo evaluation, demonstrated significant reductions of total cholesterol (TC) and LDL-C in hyperlipidemic hamsters with a good pharmacokinetic profile. Further exploring of the lipid-lowering mechanism showed that compound 22 promoted hepatic LDLR expression in a dose-dependent manner in HepG2 cells. Additional results of human ether-à-go-go related gene (hERG) inhibition assay indicated the potential druggability for compound 22, which is a promising lead compound for the development of PCSK9 modulator for the treatment of hyperlipidemia.

Green and Facile Assembly of Diverse Fused N-Heterocycles Using Gold-Catalyzed Cascade Reactions in Water

The present study describes an AuPPh₃Cl/AgSbF₆-catalyzed cascade reaction between amine nucleophiles and alkynoic acids in water. This process proceeds in high step economy with water as the sole coproduct, and leads to the generation of two rings, together with the formation of three new bonds in a single operation. This green cascade process exhibits valuable features such as low catalyst loading, good to excellent yields, high efficiency in bond formation, excellent selectivity, great tolerance of functional groups, and extraordinarily broad substrate scope. In addition, this is the first example of the generation of an indole/thiophene/pyrrole/pyridine/naphthalene/benzene-fused N-heterocycle library through gold catalysis in water from readily available materials. Notably, the discovery of antibacterial molecules from this library demonstrates its high quality and potential for the identification of active pharmaceutical ingredients.

Selective blockade of spinal D2DR by levo-corydalmine attenuates morphine tolerance via suppressing PI3K/Akt-MAPK signaling in a MOR-dependent manner

Morphine tolerance remains a challenge in the management of chronic pain in the clinic. As shown in our previous study, the dopamine D2 receptor (D2DR) expressed in spinal cord neurons might be involved in morphine tolerance, but the underlying mechanisms remain to be elucidated. In the present study, selective spinal D2DR blockade attenuated morphine tolerance in mice by inhibiting phosphatidylinositol 3 kinase (PI3K)/serine–threonine kinase (Akt)-mitogen activated protein kinase (MAPK) signaling in a μ opioid receptor (MOR)-dependent manner. Levo-corydalmine (l-CDL), which exhibited micromolar affinity for D2DR in D2/CHO-K1 cell lines in this report and effectively alleviated bone cancer pain in our previous study, attenuated morphine tolerance in rats with chronic bone cancer pain at nonanalgesic doses. Furthermore, the intrathecal administration of l-CDL obviously attenuated morphine tolerance, and the effect was reversed by a D2DR agonist in mice. Spinal D2DR inhibition and l-CDL also inhibited tolerance induced by the MOR agonist DAMGO. l-CDL and a D2DR small interfering RNA (siRNA) decreased the increase in levels of phosphorylated Akt and MAPK in the spinal cord; these changes were abolished by a PI3K inhibitor. In addition, the activated Akt and MAPK proteins in mice exhibiting morphine tolerance were inhibited by a MOR antagonist. Intrathecal administration of a PI3K inhibitor also attenuated DAMGO-induced tolerance. Based on these results, l-CDL antagonized spinal D2DR to attenuate morphine tolerance by inhibiting PI3K/Akt-dependent MAPK phosphorylation through MOR. These findings provide insights into a more versatile treatment for morphine tolerance.

By blocking dopamine receptors located in the spinal cord, a compound found in a traditional Chinese herbal medicine may help mitigate tolerance to morphine, a common problem among cancer patients who regularly take the opioid painkiller. A team led by Ji-Hua Liu and Bo-Yang Yu from China Pharmaceutical University in Nanjing had previously showed that inhibiting dopamine D2 receptors in spinal neurons prevented mice from developing morphine tolerance, but it wasn’t clear why. They have now demonstrated that blocking D2 receptors prevents the relay of cellular signals from morphine-binding “μ-opioid” receptors to mediators of drug tolerance. Levo-corydalmine, a compound isolated from the Asian Corydalis plant, binds and inhibits D2 receptors. When administered directly into the spinal cords of mice and rats, it blocked downstream signaling, reducing morphine tolerance.

Regio- and enantioselective O-demethylation of tetrahydroprotoberberines by cytochrome P450 enzyme system from Streptomyces griseus ATCC 13273

Tetrahydroprotoberberines (THPBs), a class of naturally occurring isoquinoline alkaloids, contain substituent methoxyl or hydroxyl groups which play a significant role in the pharmacological properties of these molecules. In this study, we report a biocatalytic strategy for selective O-demethylation of THPBs. CYP105D1, a cytochrome P450 from Streptomyces griseus ATCC 13273, exhibited markedly regioselective demethylation of nonhydroxyl-THPBs and monohydroxyl-THPBs on the D-ring. A possible binding mode of THPBs with CYP105D1 was investigated by docking analysis, and the results revealed that the D-rings of THPBs were with the minimum distance to the heme iron. Tetrahydropalmatine was used as a model substrate and enantioselective demethylation was demonstrated. (S)-Tetrahydropalmatine was only demethylated at C-10, while (R)-tetrahydropalmatine was first demethylated at C-10 and then subsequently demethylated at C-9. The kcat/Km value for demethylation of (R)-tetrahydropalmatine by CYP105D1 was 3.7 times greater than that for demethylation of (S)-tetrahydropalmatine. Furthermore, selective demethylation of (S)-tetrahydropalmatine by the CYP105D1-based whole-cell system was demonstrated for the highly efficient production of (S)-corydalmine which has distinct pharmacological applications, such as providing relief from bone cancer pain and reducing morphine tolerance. Moreover, a homologous redox partner was identified to enhance the catalytic efficiency of the CYP105D1-based whole-cell system. This is the first enzymatic characterization of a cytochrome P450 that has regio- and enantioselective demethylation activity of THPBs for application purpose. The cytochrome P450 system could be a promising strategy for selective demethylation in the pharmaceutical industry.

Synthesis and Pharmacological Evaluation of Noscapine-Inspired 5-Substituted Tetrahydroisoquinolines as Cytotoxic Agents

A series of 5-substituted tetrahydroisoquinolines was synthesized via a 10-step linear synthesis to assess whether replacement of noscapine's southern isobenzofuranone with other moieties resulted in retained cytotoxic activity. One such molecule, 18g, bearing a para-methoxybenzyl functionality with N-ethylcarbamoyl substitution, produced cell-cycle arrest at the G2/M phase with an EC₅₀ of 2.7 μM in the MCF-7 breast-cancer cell line, a 7-fold increase compared with that of noscapine (5). This molecule had similar activity (EC₅₀ of 2.5 μM) against the resistant NCI/Adr^RES cell line, demonstrating its potential to overcome or avert known resistance mechanisms, unlike current cytotoxic agents. Compound 18g was found to modify the drug-efflux activity of P-gp and, in combination studies, potentiate the antiproliferative activity of vinblastine. These results provide insights into structural modifications to noscapine that will guide future development toward more potent cytotoxic agents that are active against resistant cancer cells.

Application of the Asymmetric Pictet-Spengler Reaction in the Total Synthesis of Natural Products and Relevant Biologically Active Compounds

Tetrahydroisoquinolines are the framework of numerous natural products predominantly alkaloids, an important and one of the most wide spread families of naturally occurring compounds in the plant kingdom. Tetrahydroisoquinolines are commonly constructed through an old reaction, the so-called Pictet−Spengler Reaction (PSR). In this reaction, a β-aryl ethylamine undergoes an acid mediated condensation with a suitable aldehyde or ketone, followed by ring closure. In this review, we aim to highlight the applications of the asymmetric variant of this old name reaction in the total synthesis of natural products, chiefly, alkaloids, which exhibit significant biological properties.

Berberine alleviates symptoms of anxiety by enhancing dopamine expression in rats with post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a trauma-induced psychiatric disorder characterized by impaired fear extermination, hyperarousal, anxiety, depression, and amnesic symptoms that may involve the release of monoamines in the fear circuit. The present study measured several anxiety-related behavioral responses to examine the effects of berberine (BER) on symptoms of anxiety in rats after single prolonged stress (SPS) exposure, and to determine if BER reversed the dopamine (DA) dysfunction. Rats received BER (10, 20, or 30 mg/kg, intraperitoneally, once daily) for 14 days after SPS exposure. BER administration significantly increased the time spent in the open arms and reduced grooming behavior during the elevated plus maze test, and increased the time spent in the central zone and the number of central zone crossings in the open field test. BER restored neurochemical abnormalities and the SPS-induced decrease in DA tissue levels in the hippocampus and striatum. The increased DA concentration during BER treatment may partly be attributed to mRNA expression of tyrosine hydroxylase and the DA transporter in the hippocampus, while BER exerted no significant effects on vesicular monoamine transporter mRNA expression in the hippocampus of rats with PTSD. These results suggest that BER had anxiolytic-like effects on behavioral and biochemical measures associated with anxiety. These findings support a role for reduced anxiety altered DAergic transmission and reduced anxiety in rats with PTSD. Thus, BER may be a useful agent to treat or alleviate psychiatric disorders like those observed in patients with PTSD.

The Genome of Medicinal Plant Macleaya cordata Provides New Insights into Benzylisoquinoline Alkaloids Metabolism

The overuse of antibiotics in animal agriculture and medicine has caused a series of potential threats to public health. Macleaya cordata is a medicinal plant species from the Papaveraceae family, providing a safe resource for the manufacture of antimicrobial feed additive for livestock. The active constituents from M. cordata are known to include benzylisoquinoline alkaloids (BIAs) such as sanguinarine (SAN) and chelerythrine (CHE), but their metabolic pathways have yet to be studied in this non-model plant. The active biosynthesis of SAN and CHE in M. cordata was first examined and confirmed by feeding ¹³C-labeled tyrosine. To gain further insights, we de novo sequenced the whole genome of M. cordata, the first to be sequenced from the Papaveraceae family. The M. cordata genome covering 378 Mb encodes 22,328 predicted protein-coding genes with 43.5% being transposable elements. As a member of basal eudicot, M. cordata genome lacks the paleohexaploidy event that occurred in almost all eudicots. From the genomics data, a complete set of 16 metabolic genes for SAN and CHE biosynthesis was retrieved, and 14 of their biochemical activities were validated. These genomics and metabolic data show the conserved BIA metabolic pathways in M. cordata and provide the knowledge foundation for future productions of SAN and CHE by crop improvement or microbial pathway reconstruction.

The first total syntheses of (±)-norphoebine, dehydrophoebine, oxophoebine, dehydrocrebanine, oxocrebanine and uthongine and their cytotoxicity against three human cancer cell lines

The first total syntheses of (±)-norphoebine, dehydrophoebine, oxophoebine, dehydrocrebanine, oxocrebanine and uthongine have been achieved. The crucial step involved the formation of ring C by a microwave-assisted direct biaryl coupling to produce the aporphine skeleton in high yields. The synthetic alkaloids were evaluated for their cytotoxicity against three human cancer cell lines MCF7, KB and NCI-H187. The results showed that uthongine was the best candidate of the series and it exhibited cytotoxicity against a human breast cancer MCF7 line with an IC50 = 3.05 μM.

Design, Synthesis, and Biological Evaluation of Novel Tetrahydroprotoberberine Derivatives (THPBs) as Selective α1A-Adrenoceptor Antagonists

A novel series of tetrahydroprotoberberine derivatives (THPBs) were designed, synthesized, and evaluated as selective α_1A-adrenergic receptors (AR) antagonists for the treatment of benign prostatic hyperplasia. On the basis of the pharmacophore model of the marketed drug silodosin, THPBs were modified by introducing an indole segment into their core scaffolds. In calcium assays, 7 out of 32 compounds displayed excellent antagonistic activities against α_1A-ARs, with IC₅₀ less than 250 nM. Among them, compound (S)-27 had the most potent biological activity; its IC₅₀ toward α_1A-AR was 12.8 ± 2.2 nM, which is 781 and 20 times more selective than that toward α_1B- and α_1D-AR, respectively. In the functional assay using isolated rat tissues, compound (S)-27 inhibited norepinephrine-induced urethra smooth muscle contraction potently (IC₅₀ = 0.5 ± 0.3 nM), without inhibiting the aortic contraction (IC₅₀ > 1000 nM), displaying a better tissue selectivity than the marketed drug silodosin. Additional results of preliminary safety studies (acute toxicity and hERG inhibition) and pharmacokinetics studies indicated the potential druggability for compound (S)-27 which is a promising lead for the development of selective α_1A-AR antagonists for the treatment of BPH.

Asymmetric Synthesis of Isoquinoline Alkaloids: 2004-2015

In the past decade, the asymmetric synthesis of chiral nonracemic isoquinoline alkaloids, a family of natural products showing a wide range of structural diversity and biological and pharmaceutical activity, has been based either on continuation or improvement of known traditional methods or on new, recently developed, strategies. Both diastereoselective and enantioselective catalytic methods have been applied. This review describes the stereochemically modified traditional syntheses (the Pictet-Spengler, the Bischler-Napieralski, and the Pomeranz-Fritsch-Bobbitt) along with strategies based on closing of the nitrogen-containing ring B of the isoquinoline core by the formation of bonds between C₁-N₂, N₂-C₃, C₁-N₂/N₂-C₃, and C₁-N₂/C₄-C_4a atoms. Methods involving introduction of substituents at the C1 carbon of isoquinoline core along with syntheses applying various biocatalytic techniques have also been reviewed.

Synthesis and evaluation of C9 alkoxy analogues of (-)-stepholidine as dopamine receptor ligands

Tetrahydroprotoberberine alkaloids have shown interesting polypharmacological actions at dopamine receptors and are a unique template from which to mine novel molecules with dual selective actions at D1 and D3 receptors. Such compounds will be valuable to evaluate as anti-cocaine therapeutics. Towards that eventual goal, we engaged an SAR study in which a series of C9 alkoxy analogues of the D1/D2/D3 ligand (-)-stepholidine that possessed or lacked a C12 bromo functionality, were synthesized and evaluated for affinity at dopamine D1, D2 and D3 receptors. We found that the analogues are generally selective for the D1 receptor. Small n-alkoxy substituents (up to 4 carbons in length) were generally well tolerated for high D1 affinity but such groups reduced D3 affinity. In the case of C12 brominated analogues, C9 alkoxylation also had little effect on D1 affinity for the smaller alkoxy groups, but reduced D2 and D3 affinities significantly. C12 bromination tends to increase D1 receptor selectivity. A number of compounds were identified that retain affinity for D1 and D3 receptors but lack D2 receptor affinity. Among them, compound 22a was found to be a selective D1/D3 dual antagonist (Ki = 5.3 and 106 nM at D1 and D3 receptors). Docking studies performed on the analogues at the D3 receptor revealed a number of interactions that are important for affinity including a critical N - Asp110 salt bridge motif, H-bonds to Ser192 and Cys181 and hydrophobic interactions between the aryl rings and Phe106 and Phe345. The analogues adopt an orientation in which ring A is located in the orthosteric binding site while the C9 alkoxy substituents attached to ring D project into the secondary binding pocket of the D3 receptor.

Polypharmacology of dopamine receptor ligands

Most neurological diseases have a multifactorial nature and the number of molecular mechanisms discovered as underpinning these diseases is continuously evolving. The old concept of developing selective agents for a single target does not fit with the medical need of most neurological diseases. The development of designed multiple ligands holds great promises and appears as the next step in drug development for the treatment of these multifactorial diseases. Dopamine and its five receptor subtypes are intimately involved in numerous neurological disorders. Dopamine receptor ligands display a high degree of cross interactions with many other targets including G-protein coupled receptors, transporters, enzymes and ion channels. For brain disorders like Parkinsońs disease, schizophrenia and depression the dopaminergic system, being intertwined with many other signaling systems, plays a key role in pathogenesis and therapy. The concept of designed multiple ligands and polypharmacology, which perfectly meets the therapeutic needs for these brain disorders, is herein discussed as a general ligand-based concept while focusing on dopaminergic agents and receptor subtypes in particular.

Tetrahydroprotoberberine alkaloids with dopamine and σ receptor affinity

Two series of analogues of the tetrahydroprotoberberine (THPB) alkaloid (±)-stepholidine that (a) contain various alkoxy substituents at the C10 position and, (b) were de-rigidified with respect to (±)-stepholidine, were synthesized and evaluated for affinity at dopamine and σ receptors in order to evaluate effects on D3 and σ2 receptor affinity and selectivity. Small n-alkoxy groups are best tolerated by D3 and σ2 receptors. Among all compounds tested, C10 methoxy and ethoxy analogues (10 and 11 respectively) displayed the highest affinity for σ2 receptors as well as σ2 versus σ1 selectivity and also showed the highest D3 receptor affinity. De-rigidification of stepholidine resulted in decreased affinity at all receptors evaluated; thus the tetracyclic THPB framework is advantageous for affinity at dopamine and σ receptors. Docking of the C10 analogues at the D3 receptor, suggest that an ionic interaction between the protonated nitrogen atom and Asp110, a H-bond interaction between the C2 phenol and Ser192, a H-bond interaction between the C10 phenol and Cys181 as well as hydrophobic interactions of the aryl rings to Phe106 and Phe345, are critical for high affinity of the compounds.

Dopaminergic receptor-ligand binding assays based on molecularly imprinted polymers on quartz crystal microbalance sensors

Molecularly imprinted polymers (MIPs) have been successfully applied as selective materials for assessing the binding activity of agonist and antagonist of dopamine D1 receptor (D1R) by using quartz crystal microbalance (QCM). In this study, D1R derived from rat hypothalamus was used as a template and thus self-organized on stamps. Those were pressed into an oligomer film consisting of acrylic acid: N-vinylpyrrolidone: N,N'-(1,2-dihydroxyethylene) bis-acrylamide in a ratio of 2:3:12 spin coated onto a dual electrode QCM. Such we obtained one D1R-MIP-QCM electrode, whereas the other electrode carried the non-imprinted control polymer (NIP) that had remained untreated. Successful imprinting of D1R was confirmed by AFM. The polymer can re-incorporate D1R leading to frequency responses of 100-1200Hz in a concentration range of 5.9-47.2µM. In a further step such frequency changes proved inherently useful for examining the binding properties of test ligands to D1R. The resulting mass-sensitive measurements revealed Kd of dopamine∙HCl, haloperidol, and (+)-SCH23390 at 0.874, 25.6, and 0.004nM, respectively. These results correlate well with the values determined in radio ligand binding assays. Our experiments revealed that D1R-MIP sensors are useful for estimating the strength of ligand binding to the active single site. Therefore, we have developed a biomimetic surface imprinting strategy for QCM studies of D1R-ligand binding and presented a new method to ligand binding assay for D1R.

Total Synthesis of 4,5-Didehydroguadiscine: A Potent Melanogenesis Inhibitor from the Brazilian Medicinal Herb, Hornschuchia obliqua

The first total synthesis of the 7,7-dimethylaporphinoid, 4,5-didehydroguadiscine (6), originally isolated from the stems and roots of Hornschuchia oblique (Annonaceae), was achieved by the condensation of homopiperonylamine (7) with an α,α-dimethylphenylacetic acid derivative (8) and subsequent Pschorr reaction of the resulting benzylisoquinoline intermediate (22). The reported (13)C NMR data were partially revised on the basis of the analysis of HMBC spectra measured under different conditions. The melanogenesis inhibitory activity (IC50 = 4.7 μM) of 6 was 40 times stronger than that of arbutin (174 μM), which was used as reference standard. Furthermore, 6 was the most potent natural melanogenesis inhibitor within this class of compounds.

Discovery of novel potent and selective ligands for 5-HT2A receptor with quinazoline scaffold

A series of compounds with quinazoline scaffold were designed, synthesized and evaluated as novel potent 5-HT2A receptor ligands. N-(4-Chlorophenyl)-2-(piperazin-1-yl)quinazolin-4-amine (5o) has a Ki value of 14.04 ± 0.21 nM, with a selectivity more than 10,000 fold over 5-HT1A receptors (D1 and D2-like receptors). The functional assay showed that this compound is an antagonist to 5-HT2A receptor with an IC50 value of 1.66 μM.

Concise Total Synthesis of 1,3-Diphenylpropane Derivatives Griffithanes A, B and F

Concise and efficient total syntheses of diarylpropanes griffithane A, B and F, isolated from Combretum griffithii, have been accomplished from methoxybenzaldehyde. The Claisen–Schmidt condensation between aldehyde and acetophenone was applied to form chalcone as a key step. The structures of chalcones are confirmed by crystal X-ray crystallography.