Design, synthesis and bio-evaluation of C-1 alkylated tetrahydro-β-carboline derivatives as novel antifungal lead compounds

Recent developments on the anti-Candida effect of amphotericin B combined with a second drug - a mini-review

Invasive Candida infections threaten human health due to the increasing incidence of resistance to the currently available antifungal agents. Amphotericin B (AMB) is the gold standard therapy to treat these infections. Nevertheless, the use of such substance in the clinic is aggravated by its toxicity. Since AMB binds to membrane sterols, it forms pores on human plasma membranes, mainly in kidney cells, leading to nephrotoxicity. The combination of this drug to a second substance could allow for the use of smaller concentrations of AMB, consequently lowering the probability of adverse effects. This mini-review summarizes information regarding an array of substances that enhance AMB antifungal activity. It may be noticed that several of these compounds target plasma membrane. Interestingly, substances approved for human use also presented combinatory anti-Candida activity with AMB. These data reinforce the potential of associating AMB to another drug as a promising therapeutical alternative to treat Candida infections. Further studies, regarding mechanism of action, pharmacokinetics and toxicity parameters must be conducted to confirm the role of these substances as adjuvant agents in candidiasis therapy.

Iron Trichloride-Mediated Cascade Reaction of Aminosugar Derivatives for the Synthesis of Fused Tetrahydroisoquinoline-Tetrahydrofuran Systems

A method to obtain tetrahydroisoquinolines (THIQs) fused to tetrahydrofuran rings from aminosugar derivatives has been developed. The procedure relies on a key deprotection of benzyl ethers followed by a double-cyclization sequence, using FeCl₃ as the sole reagent. This tandem reaction affords the construction of novel fused polycyclic heterocycles with total stereochemical control.

Pharmacodynamics assessment of β-carboline from the roots of Psammosilene tunicoides as analgesic compound

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Psammosilene tunicoides (W. C. Wu et C. Y. Wu) is a well-known medicinal herb for the treatment of pain, hemostasia and rheumatoid arthritis among Chinese people.

AIM OF THE STUDY

The present study aimed to investigate the antinociceptive activity and mechanism of β-carboline alkaloids 1-4 which were extracted from the roots of P. tunicoides.

MATERIALS AND METHODS

The analgesic effects were evaluated using peripheral and central pain mouse models of nociception, including the formalin test and the tail flick test. The levels of glutamic acid (Glu) and nitric oxide (NO) in cerebellar cortexes and spinal cords (L4-6) were determined. The anti-inflammatory of all compounds were then assessed on RAW264.7 cells.

RESULTS

Our results showed that compounds 1-4 had significant analgesic effects on both phases of formalin test of mice. Furthermore, all compounds showed suppressive effects on Glu in the brain and NO levels in the brain cortex and the spinal cord. Except for compound 1, the others could extend the pain threshold of hot water tail-flick in mice. In addition, compounds 2 and 3 (60 μmol/kg) could decrease GABAAα1 protein levels in spinal cord. All compounds exhibited anti-inflammatory effects by inhibiting lipopolysaccharide (LPS)-induced NO production in RAW264.7 cells with half-maximal inhibitory concentration (IC₅₀) 1.1-34.9 μM.

CONCLUSION

β-carboline alkaloids from the roots of P. tunicoides had significant analgesic activity by both central and peripheral mechanisms. Our findings suggested that regulating the release of NO or Glu or GABAα1 are some of the mechanisms of analgesic activity of β-carboline alkaloids.

Synthesis and fungicidal activity of novel pyrroloindole scaffolds and their derivatives

The key scaffold of a pyrroloindole ring is a very important structure, which is isolated from plants and fungi with a variety of medical and fungicidal activities.

Natural and synthetic β-carboline as a privileged antifungal scaffolds

The discovery of antifungal agents with novel structure, broad-spectrum, low toxicity, and high efficiency has been the focus of medicinal chemists. Over the past decades, β-carboline scaffold has attracted extensive attention in the scientific community due to its potent and diverse biological activities with nine successfully marketed β-carboline-based drugs. In this review, we summarized the current states and advances in the antifungal activity of natural and synthetic β-carbolines. Additionally, the structure-activity relationships and their antifungal mechanisms targeting biofilm, cell wall, cell membrane, and fungal intracellular targets were also systematically discussed. In summary, β-carbolines have the great potential to develop new efficient scaffolds to combat fungal infections.

A review of synthetic bioactive tetrahydro-β-carbolines: A medicinal chemistry perspective

1, 2, 3, 4-Tetrahydro-β-carboline (THβC) scaffold is widespread in many natural products (NPs) and synthetic compounds which show a variety of pharmacological activities. In this article, we reviewed the design, structures and biological characteristics of reported synthetic THβC compounds, and structure and activity relationship (SAR) of them were also discussed. This work might provide a reference for subsequent drug development based on THβC.

Anti-microbial and anti-cancer activities of Mn0.5Zn0.5DyxFe2-xO4 (x ≤ 0.1) nanoparticles

Combining two or more nanoparticles is a promising approach. Previously we have reported synthesis of nanoparticles Dysprosium (Dy) substituted with manganese (Mn) zinc (Zn) by using ultrasonication method. The five different nanoparticles (NPs) Mn_0.5Zn_0.5Dy_xFe_2-xO₄ (x ≤ 0.1) have been structurally and morphologically characterized but there is no report on the biological application of these NPs. In the present study, we have examined the anti-cancer, anti-bacterial, and anti-fungal activities of Mn_0.5Zn_0.5Dy_xFe_2-xO₄ (x ≤ 0.1) NPs. Human colorectal carcinoma cells (HCT-116) were tested with different concentrations of NPs by using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. In addition, the impact of NPs was also examined on normal cells such as human embryonic kidney cells, HEK-293. After 48 h of treatment, Mn_0.5Zn_0.5Dy_xFe_2-xO₄ NPs (x = 0.02, 0.04 and 0.06) showed no inhibitory action on cancer cell's growth and proliferation, whereas Mn_0.5Zn_0.5Dy_xFe_2-xO₄ NPs (x = 0.08 and 0.1) showed profound inhibitory action on cancer cell's growth and proliferation. However, the treatment of Mn_0.5Zn_0.5Dy_xFe_2-xO₄ NPs on the normal cells (HEK-293) did not show cytotoxic or inhibitory action on HEK-293 cells. The treatment of Mn_0.5Zn_0.5Dy_xFe_2-xO₄ NPs (x ≤ 0.1) also inhibited both the bacteria (Escherichia coli ATCC35218 and Staphylococcus aureus) with lowest MIC and MBC values of 4 and 8 mg/mL and fungus (Candida albicans) with MIC and MFC values of 4 and 8 mg/mL on treatment with x = 0.08 and 0. 1.

Structure activity relationship in β-carboline derived anti-malarial agents

Malaria, even though an avoidable and treatable disease, can be fatal if ignored. Artemisinin Combination Therapy (ACT) and RTS, S/AS01 vaccine (Mosquirix™) are the only modest means available with humans to overcome malaria, a lethal affliction wreaking havoc across the globe. Employment of ACT is associated with problems such as 'Artemisinin Resistance' and the 'Hypnozoite conundrum' that hinder the complete eradication of malaria. In this view, the natural products specifically comprising β-carboline scaffold have shown good antiplasmodial responses against different strains of malaria. Taking these observations forward, researchers have performed structure-activity relationship (SAR) studies around three different β-carboline skeletons (tetrahydro β-carbolines, dihydro β-carbolines, β-carbolines) to design new β-carboline derived heterocyclic structures or modified naturally occurring derivatives. In addition, different approaches such as dimerization and linkage to other moieties have also been adopted to enhance the antimalarial activity. The present review describes a comprehensive SAR study encapsulating various natural and synthetic β-carbolines to elaborate upon the utility of these skeletons in designing drugs to subdue this deadly disease.

Synthesis and Investigation of Tetrahydro-β-carboline Derivatives as Inhibitors of Plant Pathogenic Fungi

A series of tetrahydro-ß-carbolines substituted with an alkyl or acyl side chain was synthesized and screened for its antifungal activity against plant pathogenic fungi (Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, and Fusarium fujikuroi). The structure activity relationship revealed that the substituent at the piperidine nitrogen plays an important role for increasing antifungal activities. In this series, 2-octyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (3g) displayed potent antifungal activities with a minimum inhibitory concentration of 0.1 μg/mL, including good inhibitory activity to the radial growth of fungus at a concentration of 100 μg/mL compared to amphotericin B.

Probing the B- & C-rings of the antimalarial tetrahydro-β-carboline MMV008138 for steric and conformational constraints

The antimalarial candidate MMV008138 (1a) is of particular interest because its target enzyme (IspD) is absent in human. To achieve higher potency, and to probe for steric demand, a series of analogs of 1a were prepared that featured methyl-substitution of the B- and C-rings, as well as ring-chain transformations. X-ray crystallography, NMR spectroscopy and calculation were used to study the effects of these modifications on the conformation of the C-ring and orientation of the D-ring. Unfortunately, all the B- and C-ring analogs explored lost in vitro antimalarial activity. The possible role of steric effects and conformational changes on target engagement are discussed.

New insight of red seaweed derived Callophycin A as an alternative strategy to treat drug resistance vaginal candidiasis

Marine natural products are recognised as one among the major contributors of several important biological functions. The arguments has made to utilization of natural products against different kinds of infectious diseases. In the present study, Callophycin A was successfully prepared and its anti-candidal activity was evaluated through in-vitro and in-vivo methods. The in-vitro results revealed that, Callophycin A significantly inhibits the azole resistant and sensitive C. albicans. Further, in-vivo animal experiments have shown the effective reduction in CFU of C. albicans from its beginning day of the treatment as compared to the disease control group. At the end of Callophycin A administration, there was a decrease in inflammatory response and immune molecules such as IL-6, IL-12, IL-17, IL-22, TNF-α, macrophages, CD4 and CD8 cells were observed. Whereas the animals in the disease control group expressed all the parameters with the elevated level as compared to the control group. There are no hematological abnormalities such as neutropenia, lymphocytosis and eosinophilia was observed in any animal groups except the disease control group. Finally, the evidence based prediction of anti-candidal efficacious of Callophycin A was demonstrated.

Recent evolution on synthesis strategies and anti-leishmanial activity of β-carboline derivatives - An update

Leishmaniasis is the most widespread pathogenic disease in several countries. Currently, no effective vaccines are available, and the control of Leishmaniasis primarily relies on decade-old chemotherapy. The treatment for the Leishmaniasis is not up to the mark. Current therapy for Leishmaniasis is ancient and requires hospitalization for the administration. These medications are also highly toxic and resistant. β-carboline, a natural indole containing alkaloid, holds a vital position in the field of medicinal chemistry with a diversified pharmacological action. The current review focuses mainly on the anti-leishmanial effects of β-carboline analogs and their synthetic strategies, structural activity relationship studies (SAR). The past ten years alterations unveiled by β-carboline analogs present in phytoconstituents and various derivatives of synthesized analogs with the mechanism of action were briefly shortlisted and illustrated.