Enhancement of NO production in activated macrophages in vivo by an antimalarial crude drug, Dichroa febrifuga

Discovery of a novel benzimidazole conjugated quinazolinone derivative as a promising SARS-CoV-2 3CL protease inhibitor

This report presents the design and synthesis of quinazolinone-based derivatives as promising SARS-CoV-2 3CL protease inhibitors. Two novel series, namely, febrifugine analogues 4a-i and quinazolinone conjugated benzimidazoles 9a-c, were successfully synthesized starting from isatoic anhydride. The synthesized quinazolinone derivatives were evaluated for their cytotoxicity against cancer cell lines and SARS-CoV-2 3CL inhibitory activity. The results showed that the synthesized compounds did not have significant toxicity for the non-cancer HEK293 cell line and MCF-7, MDA-MB-231, HEPG2 and HEPG2.2.15 cancer cell lines. Notably, compound 9b exhibited anti-3CL enzymatic activity in a dose-dependent manner, with the calculated IC50 value of 10.73 ± 1.17 μM. Docking results highlighted the interaction between 9b and 3CL protease through hydrogen bonding with key amino acids, including His41, Met49, Cys145, Met165, Arg188, His164, and Glu166, at the active site of the protease. Pharmacokinetic studies and ADME analyses provide valuable insights into the potential of compound 9b as a drug candidate. These findings support the new scaffold as a candidate for 3CLpro inhibition and advanced anti-coronavirus drug research.

Dichroa febrifuga Lour.: A review of its botany, traditional use, phytochemistry, pharmacological activities, toxicology, and progress in reducing toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Dichroa febrifuga Lour., a toxic but extensively used traditional Chinese medicine with a remarkable effect, is commonly called "Changshan" in China. It has been used to treat malaria and many other parasitic diseases.

AIM OF THE REVIEW

The study aims to provide a current overview of the progress in the research on traditional use, phytochemistry, pharmacological activities, toxicology, and methods of toxicity reduction of D. febrifuga. Additionally, further research directions and development prospects for the plant were put forward.

MATERIALS AND METHODS

The article uses "Dichroa febrifuga Lour." "D. febrifuga" as the keyword and all relevant information on D. febrifuga was collected from electronic searches (Elsevier, PubMed, ACS, CNKI, Google Scholar, and Baidu Scholar), doctoral and master's dissertations and classic books about Chinese herbs.

RESULTS

30 chemical compounds, including alkaloids, terpenoids, flavonoids and other kinds, were isolated and identified from D. febrifuga. Modern pharmacological studies have shown that these components have a variety of pharmacological activities, including anti-malarial activities, anti-inflammatory activities, anti-tumor activities, anti-parasitic activities and anti-oomycete activities. Meanwhile, alkaloids, as the material basis of its efficacy, are also the source of its toxicity. It can cause multiple organ damage, including liver, kidney and heart, and cause adverse reactions such as nausea and vomiting, abdominal pain and diarrhea. In the current study, the toxicity can be reduced by modifying the structure of the compound, processing and changing the dosage forms.

CONCLUSIONS

There are few studies on the chemical constituents of D. febrifuga, so the components and their structure characterization contained in it can become the focus of future research. In view of the toxicity of D. febrifuga, there are many methods to reduce it, but the safety and rationality of these methods need further study.

N,N-Dimethylformamide as Carbon Synthons for the Synthesis of N-Heterocycles: Pyrrolo/Indolo[1,2-a]quinoxalines and Quinazolin-4-ones

N,N-dimethylformamide (DMF) as synthetic precursors contributing especially the methyl, acyl, and amino groups has played a significant role in heterocycle syntheses and functionalization. In this protocol, a wide range of pyrrolo/indolo[1,2-a]quinoxalines and quinazolin-4-ones were obtained in moderate to good yields by using elemental iodine without any metal or peroxides. We considered that N-methyl and N-acyl of DMF participate and complete the reaction separately through different mechanisms, which displayed potential still to be explored of DMF.

Design, Synthesis, and Structure-Activity Relationship of Quinazolinone Derivatives as Potential Fungicides

Plant diseases caused by phytopathogenic fungi reduce the yield and quality of crops. To develop novel antifungal agents, we designed and synthesized eight series of quinazolinone derivatives and evaluated their anti-phytopathogenic fungal activity. The bioassay results revealed that compounds KZL-15, KZL-22, 5b, 6b, 6c, 8e, and 8f exhibited remarkable antifungal activity in vitro. Especially, compound 6c displayed the highest bioactivity against Sclerotinia sclerotiorum, Pellicularia sasakii, Fusarium graminearum, and Fusarium oxysporum, displaying appreciable IC₅₀ values (50% inhibitory concentration) of 2.46, 2.94, 6.03, and 11.9 μg/mL, respectively. A further mechanism interrogation revealed abnormal mycelia, damaged organelles, and changed permeability of cell membranes in S. sclerotiorum treated with compound 6c. In addition, the in vivo bioassay indicated that compound 6c possessed comparable curative and protective effects (87.3 and 90.7%, respectively) to the positive control azoxystrobin (89.5 and 91.2%, respectively) at 100 μg/mL concentration against S. sclerotiorum. This work validated the potential of compound 6c as a new and promising fungicide candidate, contributing to the exploration of potent antifungal agents.

Copper-mediated synthesis of quinazolin-4(3H)-ones from N-(quinolin-8-yl)benzamide and amidine hydrochlorides

An efficient copper-mediated tandem C(sp²)–H amination to provide quinazolinones from N-(quinolin-8-yl)benzamide and amidine hydrochlorides has been developed.

Biologically active quinoline and quinazoline alkaloids part I

Quinoline and quinazoline alkaloids, two important classes of N-based heterocyclic compounds, have attracted tremendous attention from researchers worldwide since the 19th century. Over the past 200 years, many compounds from these two classes were isolated from natural sources, and most of them and their modified analogs possess significant bioactivities. Quinine and camptothecin are two of the most famous and important quinoline alkaloids, and their discoveries opened new areas in antimalarial and anticancer drug development, respectively. In this review, we survey the literature on bioactive alkaloids from these two classes and highlight research achievements prior to the year 2008 (Part I). Over 200 molecules with a broad range of bioactivities, including antitumor, antimalarial, antibacterial and antifungal, antiparasitic and insecticidal, antiviral, antiplatelet, anti-inflammatory, herbicidal, antioxidant and other activities, were reviewed. This survey should provide new clues or possibilities for the discovery of new and better drugs from the original naturally occurring quinoline and quinazoline alkaloids.

Chemical synthesis of febrifugine and analogues

The quinazolinone-containing 2,3-disubstituted piperidines febrifugine and isofebrifugine have been the subject of significant research efforts since their occurrence in Dichroa febrifuga and their anti-malarial actions were first described in the late 1940s. Subsequently they have also been shown to be present in other plants belonging to the hydrangea family and various analogues of febrifugine have been prepared in attempts to tune biological properties. The most notable analogue is termed halofuginone and a substantial body of work now demonstrates that this compound possesses potent human disease relevant activities. This review focuses on the literature associated with efforts dedicated towards uncovering the structures of febrifugine and isofebrifugine, the development of practical methods for their synthesis and the syntheses of structural analogues.

Cleavage of the C–C triple bond of ketoalkynes: synthesis of 4(3H)-quinazolinones

A novel strategy to 4(3H)-quinazolinones from ketoalkynes and o-aminobenzamides through C–C triple bond fragmentation and two C–N bond formations under external oxidant and metal free conditions.

Pharmacophore modeling and 3D quantitative structure-activity relationship analysis of febrifugine analogues as potent antimalarial agent

Febrifugine and its derivatives are effective against Plasmodium falciparum. Using PHASE algorithm, a five-point pharmacophore model with two hydrogen bond acceptor (A), one positively ionizable (P) and two aromatic rings (R), was developed to derive a predictive ligand-based statistically significant 3D-quantitative structure-activity relationship (QSAR) model (r² = 0.972, SD = 0.3, F = 173.4, Q² = 0.712, RMSE = 0.3, Person-R = 0.94, and r²_pred = 0.8) to explicate the structural attributes crucial for antimalarial activity. The developed pharmacophore model and 3D QSAR model can be a substantial tool for virtual screening and related antimalarial drug discovery research.

(±)-3-Benzyloxy-1-(4-methoxybenzyl)piperidine-2-thione

The title mol­ecule, C₂₀H₂₃NO₂S, adopts a twisted conformation in which the two aromatic rings connected to the central piperidine ring are orientated trans to each other. An intra­molecular C—H⋯S contact occurs. In the crystal, C—H⋯π and C—H⋯O inter­actions act to stabilize the structure in three dimensions.

3-Hy-droxy-1-(4-meth-oxy-benz-yl)piperidin-2-one

The title compound, C₁₃H₁₇NO₃, adopts a conformation in which the aromatic ring and the mean plane of the piperidine ring are almost perpendicular to each other [dihedral angle = 79.25 (6)°]. The presence of the carbonyl group alters the conformation of the piperidine ring from a chair to a twisted half-chair conformation. In the crystal, pairs of strong O—H⋯O hydrogen bonds link the mol­ecules into inversion dimers. Weak C—H⋯O inter­actions extend the hydrogen-bonding network into three dimensions.

Antimalarial activities and therapeutic properties of febrifugine analogs

Febrifugine is the active principal isolated 50 years ago from the Chinese herb chang shan (Dichroa febrifuga Lour), which has been used as an antimalarial in Chinese traditional medicine for more than 2,000 years. However, intensive study of the properties of febrifugine has been hindered for decades due to its side effects. We report new findings on the effects of febrifugine analogs compared with those of febrifugine extracted from the dry roots of D. febrifuga. The properties of the extracted febrifugine were comparable to those obtained from the standard febrifugine provided by our collaborators. A febrifugine structure-based computer search of the Walter Reed Chemical Information System identified 10 analogs that inhibited parasite growth in vitro, with 50% inhibitory concentrations ranging from 0.141 to 290 ng/ml. The host macrophages (J744 cells) were 50 to 100 times less sensitive to the febrifugine analogs than the parasites. Neuronal (NG108) cells were even more insensitive to these drugs (selectivity indices, >1,000), indicating that a feasible therapeutic index for humans could be established. The analogs, particularly halofuginone, notably reduced parasitemias to undetectable levels and displayed curative effects in Plasmodium berghei-infected mice. Recrudescence of the parasites after treatment with the febrifugine analogs was the key factor that caused the death of most of the mice in groups receiving an effective dose. Subcutaneous treatments with the analogs did not cause irritation of the gastrointestinal tract when the animals were treated with doses within the antimalarial dose range. In summary, these analogs appear to be promising lead antimalarial compounds that require intensive study for optimization for further down-selection and development.

Effect of active synthetic 2-substituted quinazolinones on anti-platelet aggregation and the inhibition of superoxide anion generation by neutrophils

Quinazolinones, 2-substituted and 3-substituted, mainly synthesized by microwave irradiation, were subjected to anti-platelet aggregation and inhibition of superoxide anion generation assays. Interestingly, 2-phenyl-4-quinazolinone (4) exhibited significant inhibitory activities toward platelet aggregation and neutrophil activation, and it might therefore serve as a prototype lead compound.

Chemical constituents from the Hydrangea chinensis

Two quinazolone alkaloids, (+)-febrifugine (1) and isofebrifugine (2), along with three coumarin derivatives, 6-hydroxy coumarin (3), skimmin (5), and umbelliferone-7-O-alpha-L-rhamnopyranosyl(1-->4)-beta-D-glucopyranoside (6), were isolated from the roots of Hydrangea chinensis. Compound 6 is a new compound. In addition, umbelliferone (4), linoleic acid (7), two steroidal glycosides (8, 9), three furfural derivatives (10-12), and butyl-beta-D-fructofuranoside (13) were isolated from the leaves of the same plant. The structures of all isolates were elucidated by spectral methods.

Suppression of NO production in activated macrophages in vitro and ex vivo by neoandrographolide isolated from Andrographis paniculata

In this study, we investigated the in vitro and ex vivo suppressive effects of Andrographis paniculata on nitric oxide (NO) production in mouse peritoneal macrophages elicited by bacillus Calmette-Guéin (BCG) and stimulated by lipopolysaccharide (LPS). Incubation of BCG-induced macrophages with the methanol extract of A. paniculata reduced LPS stimulated NO production. The diterpene lactones andrographolide and neoandrographolide were isolated as active components from the extract. These compounds suppressed NO production in a concentration-dependent manner in the concentration range from 0.1 to 100 microM and their IC50 values were 7.9 and 35.5 microM. Neoandrographolide also suppressed NO production by 35 and 40% when the macrophages were collected after oral administration of neoandrographolide at doses of 5 and 25 mg/kg/d and LPS stimulated NO production was examined. However, andrographolide did not reduce NO production on oral administration at the same doses. These results indicate that neoandrographolide, which inhibited NO production both in vitro and ex vivo may play an important role in the use of A. paniculata as an anti-inflammatory crude drug.

Re-revision of the stereo structure of piperidine lactone, an intermediate in the synthesis of febrifugine

The stereo structure of piperidine lactone (3), an intermediate of the antimalarial agent febrifugine ((+)-1) prepared by a synthetic method, was re-revised to the cis-form from the trans-form.

Hydrachine A, a novel alkaloid from the roots of Hydrangea chinensis

A novel alkaloid, hydrachine A (3), has been isolated, along with 15 known compounds, from the roots of Hydrangea chinensis. The structure and stereochemistry of the new alkaloid 3 was determined using extensive 2D NMR data.

A diastereocontrolled synthesis of (+)-febrifugine: a potent antimalarial piperidine alkaloid

A diastereocontrolled synthesis of (+)-febrifugine, a potent antimalarial piperidine alkaloid, has been achieved using a chiral block having a bicyclo[3.2.1]octane framework which exhibits inherent convex-face selectivity.

The production of nitric oxide and TNF-alpha in peritoneal macrophages is inhibited by Dichroa febrifuga Lour

Nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) have been suggested to play an important role in endotoxin-mediated shock and inflammation. In this study, we investigated the effect of aqueous extract of Dichroa febrifuga Lour. (Saxifragaceae) roots, a traditional antimalarial drug, on the production of NO and TNF-alpha. The aqueous extract of D. febrifuga roots (AEDF) inhibited the secretion of NO and TNF-alpha in lipopolysaccharide (LPS) and/or interferon-gamma (IFN-gamma)-stimulated mouse peritoneal macrophages, without affecting cell viability. The protein level of inducible nitric oxide synthase (iNOS) in peritoneal macrophages was also decreased by AEDF. In addition, the serum level of NO was reduced by i.p. administration of AEDF. These results suggest that AEDF suppresses the endotoxin-induced inflammatory responses through inhibiting the production of NO and TNF-alpha, and could be used as an anti-inflammatory drug.

Potentiation by febrifugine of host defense in mice against Plasmodium berghei NK65

The effect of febrifugine, the main alkaloidal constituent of an antimalarial crude drug, Dichroa febrifuga Lour., on protective immunity in mice infected with erythrocytic stage Plasmodium berghei NK65 was investigated. Febrifugine was administered orally, at a dose of 1 mg/kg/day, to mice before and/or after they were infected intraperitoneally with 2 x 10(6) parasitized red blood cells. Then, mortality and the levels of parasitemia and plasma NO3- [a degradation product of nitric oxide (NO)] were monitored. Febrifugine significantly reduced the mortality and the level of parasitemia. The plasma NO3- concentration began to rise within 2 days after treatment with febrifugine and declined to normal in 2 days when the mice were treated orally with febrifugine once a day for 3 consecutive days before parasite infection. This antimalarial activity of febrifugine was reduced by both N(G)-monomethyl-L-arginine and aminoguanidine. These results indicate that the increased production of NO by febrifugine plays an important role in host defense against malaria infection in mice.