New topoisomerases inhibitors: synthesis of rutaecarpine derivatives and their inhibitory activity against topoisomerases

Computational Docking as a Tool in Guiding the Drug Design of Rutaecarpine Derivatives as Potential SARS-CoV-2 Inhibitors

COVID-19 continues to spread around the world. This is mainly because new variants of the SARS-CoV-2 virus emerge due to genomic mutations, evade the immune system and result in the effectiveness of current therapeutics being reduced. We previously established a series of detection platforms, comprising computational docking analysis, S-protein-based ELISA, pseudovirus entry, and 3CL protease activity assays, which allow us to screen a large library of phytochemicals from natural products and to determine their potential in blocking the entry of SARS-CoV-2. In this new screen, rutaecarpine (an alkaloid from Evodia rutaecarpa) was identified as exhibiting anti-SARS-CoV-2 activity. Therefore, we conducted multiple rounds of structure-activity-relationship (SAR) studies around this phytochemical and generated several rutaecarpine analogs that were subjected to in vitro evaluations. Among these derivatives, RU-75 and RU-184 displayed remarkable inhibitory activity when tested in the 3CL protease assay, S-protein-based ELISA, and pseudovirus entry assay (for both wild-type and omicron variants), and they attenuated the inflammatory response induced by SARS-CoV-2. Interestingly, RU-75 and RU-184 both appeared to be more potent than rutaecarpine itself, and this suggests that they might be considered as lead candidates for future pharmacological elaboration.

Potassium tert-Butoxide-Mediated Cascade Synthesis of Rutaecarpine Alkaloid Analogues: Access to Molecular Complexity on Multigram Scales

In this study, we present a novel and cost-effective approach for synthesizing biologically significant analogues of rutaecarpine alkaloid through a one-step cascade reaction. The pentacyclic core of rutaecarpine alkaloid analogues is efficiently constructed using 2-aminobenzonitriles and substituted indole-2-carbaldehydes in the presence of the affordable base KOtBu. The salient feature of this approach is the promotion of a sequential cascade process within a single reaction vessel including the formation of a dihydroquinazolinone ring, oxidation, and cyclization. This method can be successfully applied on a larger scale, making it economically viable.

Promising derivatives of rutaecarpine with diverse pharmacological activities

Rutaecarpine (RUT) is a natural pentacyclic indolopyridoquinazolinone alkaloid first isolated from one of the most famous traditional Chinese herbs, Evodia rutaecarpa, which is used for treating a variety of ailments, including headaches, gastrointestinal disorders, postpartum hemorrhage, amenorrhea, difficult menstruation, and other diseases. Accumulating pharmacological studies showed that RUT possesses a wide range of pharmacological effects through different mechanisms. However, its poor physicochemical properties and moderate biological activities have hampered its clinical application. In this regard, the modification of RUT aimed at seeking its derivatives with better physicochemical properties and more potency has been extensively studied. These derivatives exhibit diverse pharmacological activities, including anti-inflammatory, anti-atherogenic, anti-Alzheimer's disease, antitumor, and antifungal activities via a variety of mechanisms, such as inhibiting cyclooxygenase-2 (COX-2), acetylcholine (AChE), phosphodiesterase 4B (PDE4B), phosphodiesterase 5 (PDE5), or topoisomerases (Topos). From this perspective, this paper provides a comprehensive description of RUT derivatives by focusing on their diverse biological activities. This review aims to give an insight into the biological activities of RUT derivatives and encourage further exploration of RUT.

Evodiamine and Rutaecarpine as Potential Anticancer Compounds: A Combined Computational Study

Evodiamine (EVO) and rutaecarpine (RUT) are the main active compounds of the traditional Chinese medicinal herb Evodia rutaecarpa. Here, we fully optimized the molecular geometries of EVO and RUT at the B3LYP/6-311++G (d, p) level of density functional theory. The natural population analysis (NPA) charges, frontier molecular orbitals, molecular electrostatic potentials, and the chemical reactivity descriptors for EVO and RUT were also investigated. Furthermore, molecular docking, molecular dynamics simulations, and the analysis of the binding free energies of EVO and RUT were carried out against the anticancer target topoisomerase 1 (TOP1) to clarify their anticancer mechanisms. The docking results indicated that they could inhibit TOP1 by intercalating into the cleaved DNA-binding site to form a TOP1−DNA−ligand ternary complex, suggesting that they may be potential TOP1 inhibitors. Molecular dynamics (MD) simulations evaluated the binding stability of the TOP1−DNA−ligand ternary complex. The calculation of binding free energy showed that the binding ability of EVO with TOP1 was stronger than that of RUT. These results elucidated the structure−activity relationship and the antitumor mechanism of EVO and RUT at the molecular level. It is suggested that EVO and RUT may be potential compounds for the development of new anticancer drugs.

Comparison of the effects of rutaecarpine on molecular subtypes of breast cancer

Objective

Natural compounds have gained considerable attention in recent years due to disadvantages and properties of current chemotherapy drugs in cancer therapy. In addition, the impact of these compounds is specific for each type and/or subtypes of cancer due to different treatment response. Rutaecarpine, an alkaloid obtained from Evodia Rutaecarpa Chinese herb, has anticancer activity by inhibiting topoisomerase and/or cyclo-oxygenase-2 levels. However, the effectiveness of rutaecarpine has not been well known in breast cancer in terms of subtype. Therefore, we investigated the potential therapeutic effects of rutaecarpine on two different subtypes of breast cancer cells.

Materials and Methods

The cytotoxic and apoptotic effects of rutaecarpine on MCF-7 and MDA-MB-231 cells were analyzed by WST-1, Annexin V, cell cycle, and acridine orange staining.

Results

WST-1 results indicated that rutaecarpine significantly inhibited the growth of both cancer cells for 48 h (P < 0.05). In addition, rutaecarpine treatment caused apoptotic cell death through chromatin condensation and nuclear blebbing and G0/G1 arrest in both breast cancer cells. However, the efficacy of rutaecarpine was more profound in MCF-7 cells than MDA-MB-231 cells.

Conclusions

Consequently, rutaecarpine has a potential therapeutic effect on breast cancer. However, the effectiveness of rutaecarpine is dependent on the subtype of breast cancer.

Copper-catalyzed, N-auxiliary group-controlled switchable transannulation/nitration initiated by nitro radicals: selective synthesis of pyridoquinazolones and 3-nitroindoles

Within the scope of nitration reactions, the efficiency of sensitive heteroaromatics such as indoles is often eroded by various competitive oxidative decomposition pathways.

Redox Condensations of o-Nitrobenzaldehydes with Amines under Mild Conditions: Total Synthesis of the Vasicinone Family

A total synthesis of the vasicinone family of natural products from bulk chemicals was developed. Reductive condensation of o-nitrobenzaldehydes with amines utilizing iron pentacarbonyl as a reducing agent followed by subsequent oxidation leads to a great variety of polycyclic nitrogen-containing heterocycles under mild conditions. Enantiomerically pure vasicinone, rutaecarpine, isaindigotone, and luotonin were synthesized from readily available starting materials like hydroxyproline, nitrobenzaldehyde, pyrrolidine, and piperidine in two to four operational steps without chromatography. The antifungal activity of all products was tested.

Synthesis and topoisomerases inhibitory activity of heteroaromatic chalcones

The critical role of nuclear topoisomerase enzymes during cell proliferation process guided topoisomerases to be one of the major targets for anticancer drug development. We have designed and synthesized 22 heteroaromatic ring incorporated chalcone derivatives substituted with epoxide or thioepoxide. Topoisomerase enzyme inhibitory activity and cytotoxic tests were also conducted to evaluate compounds' pharmacological efficacy. In the topoisomerase I inhibitory test, compound 1 was most active one, 24% of inhibition at 20μM, among all the compounds but it was lower than camptothecin. Compounds 9, 11, and 13 inhibited the function of topoisomerase II more strongly than etoposide with almost same magnitude (around 90% and 30% inhibition at 100 and 20μM, respectively) which were higher than those of etoposide (72% and 18% inhibition). In the cytotoxicity test, compound 9 inhibited T47D cancer cell growth with the IC₅₀ value of 6.61±0.21μM. On the other hand, compound 13 (IC₅₀: 4.32±0.18μM) effectively suppressed MDA-MB468 cancer cell growth.

Progress in Studies on Rutaecarpine. II.--Synthesis and Structure-Biological Activity Relationships

Rutaecarpine is a pentacyclic indolopyridoquinazolinone alkaloid found in Evodia rutaecarpa and other related herbs. It has a variety of intriguing biological properties, which continue to attract the academic and industrial interest. Studies on rutaecarpine have included isolation from new natural sources, development of new synthetic methods for its total synthesis, the discovery of new biological activities, metabolism, toxicology, and establishment of analytical methods for determining rutaecarpine content. The present review focuses on the synthesis, biological activities, and structure-activity relationships of rutaecarpine derivatives, with respect to their antiplatelet, vasodilatory, cytotoxic, and anticholinesterase activities.

A short and highly convergent approach for the synthesis of rutaecarpine derivatives

Synthesis of rutaecarpine analogues is accomplished from anthranilamide and chloroaldehyde through the halocyclization strategy.

Low-cytotoxic synthetic bromorutaecarpine exhibits anti-inflammation and activation of transient receptor potential vanilloid type 1 activities

Rutaecarpine (RUT), the major bioactive ingredient isolated from the Chinese herb Evodia rutaecarpa, possesses a wide spectrum of biological activities, including anti-inflammation and preventing cardiovascular diseases. However, its high cytotoxicity hampers pharmaceutical development. We designed and synthesized a derivative of RUT, bromo-dimethoxyrutaecarpine (Br-RUT), which showed no cytotoxicity at 20 μM. Br-RUT suppressed nitric oxide (NO) production and tumor necrosis factor-α release in concentration-dependent (0~20 μM) manners in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages; protein levels of inducible NO synthase (iNOS) and cyclooxygenase-2 induced by LPS were downregulated. Br-RUT inhibited cell migration and invasion of ovarian carcinoma A2780 cells with 0~48 h of treatment. Furthermore, Br-RUT enhanced the expression of transient receptor potential vanilloid type 1 and activated endothelial NOS in human aortic endothelial cells. These results suggest that the synthetic Br-RUT possesses very low cytotoxicity but retains its activities against inflammation and vasodilation that could be beneficial for cardiovascular disease therapeutics.

3-(3-Butylamino-2-hydroxy-propoxy)-1-hydroxy-xanthen-9-one acts as a topoisomerase IIα catalytic inhibitor with low DNA damage

As a continuous study we prepared several alkylamine (n = 3-6) and evaluated for the pharmacological activity and mode of action. In the topoisomerase IIα (topo IIα) inhibition test, compound 4 showed strongest inhibitory activity among the compounds at 10 μM. Inhibitory activities of the compounds are in the order of 4 (n = 4) > 1 (n = 3) >> 5 (n = 5) ≈ 6 (n = 6); 8 (n = 4) >> 7 (n = 3) ≈ 9 (n = 5) ≈ 10 (n = 6) where n is the number of carbon in the aliphatic side chain in ring C and compounds 7-10 have additional methoxy group in ring A compared to compounds 1, 4-6. Compound 4 showed efficient cytotoxicities against T47D (IC₅₀: 0.93 ± 0.04 μM) and HCT15 (IC50: 0.78 ± 0.01 μM) cells, which are higher than etoposide. Compound 4 was also an ATP-competitive human topo IIα catalytic inhibitor with partially blocking human topo IIα-catalyzed ATP hydrolysis and intercalating into DNA. Compound 4 induced much less DNA damage than etoposide in HCT15 human colorectal carcinoma cells. Overall, compound 4 can be a potential anticancer agent acting as topo IIα catalytic inhibitor with low DNA damage.