Thiazinoquinones as New Promising Multistage Schistosomicidal Compounds Impacting Schistosoma mansoni and Egg Viability

Arylpiperazine Derivatives and Cancer: A New Challenge in Medicinal Chemistry

Background: In recent decades, there has been a startling rise in the number of cancer patients worldwide, which has led to an amazing upsurge in the development of novel anticancer treatment candidates. On a positive note, arylpiperazines have garnered attention in cancer research due to their potential as scaffolds for developing anticancer agents. These compounds exhibit a diverse array of biological activities, including cytotoxic effects against cancer cells. Indeed, one of the key advantages of arylpiperazines lies in their ability to interact with various molecular targets implicated in cancer pathogenesis. Aim: Here, we focus on the chemical structures of several arylpiperazine derivatives, highlighting their anti-proliferative activity in different tumor cell lines. The modular structure, diverse biological activities, and potential for combination therapies of arylpiperazine compounds make them valuable candidates for further preclinical and clinical investigations in the fight against cancer. Conclusion: This review, providing a careful analysis of different arylpiperazines and their biological applications, allows researchers to refine the chemical structures to improve potency, selectivity, and pharmacokinetic properties, thus advancing their therapeutic potential in oncology.

Identification of Antioxidant Methyl Derivatives of Ortho-Carbonyl Hydroquinones That Reduce Caco-2 Cell Energetic Metabolism and Alpha-Glucosidase Activity

α-glucosidase, a pharmacological target for type 2 diabetes mellitus (T2DM), is present in the intestinal brush border membrane and catalyzes the hydrolysis of sugar linkages during carbohydrate digestion. Since α-glucosidase inhibitors (AGIs) modulate intestinal metabolism, they may influence oxidative stress and glycolysis inhibition, potentially addressing intestinal dysfunction associated with T2DM. Herein, we report on a study of an ortho-carbonyl substituted hydroquinone series, whose members differ only in the number and position of methyl groups on a common scaffold, on radical-scavenging activities (ORAC assay) and correlate them with some parameters obtained by density functional theory (DFT) analysis. These compounds' effect on enzymatic activity, their molecular modeling on α-glucosidase, and their impact on the mitochondrial respiration and glycolysis of the intestinal Caco-2 cell line were evaluated. Three groups of compounds, according their effects on the Caco-2 cells metabolism, were characterized: group A (compounds 2, 3, 5, 8, 9, and 10) reduces the glycolysis, group B (compounds 1 and 6) reduces the basal mitochondrial oxygen consumption rate (OCR) and increases the extracellular acidification rate (ECAR), suggesting that it induces a metabolic remodeling toward glycolysis, and group C (compounds 4 and 7) increases the glycolysis lacking effect on OCR. Compounds 5 and 10 were more potent as α-glucosidase inhibitors (AGIs) than acarbose, a well-known AGI with clinical use. Moreover, compound 5 was an OCR/ECAR inhibitor, and compound 10 was a dual agent, increasing the proton leak-driven OCR and inhibiting the maximal electron transport flux. Additionally, menadione-induced ROS production was prevented by compound 5 in Caco-2 cells. These results reveal that slight structural variations in a hydroquinone scaffold led to diverse antioxidant capability, α-glucosidase inhibition, and the regulation of mitochondrial bioenergetics in Caco-2 cells, which may be useful in the design of new drugs for T2DM and metabolic syndrome.

Evidence of Insulin-Sensitizing and Mimetic Activity of the Sesquiterpene Quinone Avarone, a Protein Tyrosine Phosphatase 1B and Aldose Reductase Dual Targeting Agent from the Marine Sponge Dysidea avara

Type 2 diabetes mellitus (T2DM) is a complex disease characterized by impaired glucose homeostasis and serious long-term complications. First-line therapeutic options for T2DM treatment are monodrug therapies, often replaced by multidrug therapies to ensure that non-responding patients maintain target glycemia levels. The use of multitarget drugs instead of mono- or multidrug therapies has been emerging as a main strategy to treat multifactorial diseases, including T2DM. Therefore, modern drug discovery in its early stages aims to identify potential modulators for multiple targets; for this purpose, exploration of the chemical space of natural products represents a powerful tool. Our study demonstrates that avarone, a sesquiterpene quinone obtained from the sponge Dysidea avara, is capable of inhibiting in vitro PTP1B, the main negative regulator of the insulin receptor, while it improves insulin sensitivity, and mitochondria activity in C2C12 cells. We observe that when avarone is administered alone, it acts as an insulin-mimetic agent. In addition, we show that avarone acts as a tight binding inhibitor of aldose reductase (AKR1B1), the enzyme involved in the development of diabetic complications. Overall, avarone could be proposed as a novel natural hit to be developed as a multitarget drug for diabetes and its pathological complications.

Insights into Cytotoxic Behavior of Lepadins and Structure Elucidation of the New Alkaloid Lepadin L from the Mediterranean Ascidian Clavelina lepadiformis

The chemical investigation of the Mediterranean ascidian Clavelina lepadiformis has led to the isolation of a new lepadin, named lepadin L, and two known metabolites belonging to the same family, lepadins A and B. The planar structure and relative configuration of the decahydroquinoline ring of lepadin L were established both by means of HR-ESIMS and by a detailed as extensive analysis of 1D and 2D NMR spectra. Moreover, microscale derivatization of the new alkaloid lepadin L was performed to assess the relative configuration of the functionalized alkyl side chain. Lepadins A, B, and L were tested for their cytotoxic activity on a panel of cancer cell lines (human melanoma [A375], human breast [MDA-MB-468], human colon adenocarcinoma [HT29], human colorectal carcinoma [HCT116], and mouse myoblast [C2C12]). Interestingly, a deeper investigation into the mechanism of action of the most cytotoxic metabolite, lepadin A, on the A375 cells has highlighted its ability to induce a strongly inhibition of cell migration, G2/M phase cell cycle arrest and a dose-dependent decrease of cell clonogenity, suggesting that it is able to impair self-renewing capacity of A375 cells.

Antimalarial application of quinones: A recent update

Atovaquone belongs to a naphthoquinone class of drugs and is used in combination with proguanil (Malarone) for the treatment of acute, uncomplicated malaria caused by Plasmodium falciparum (including chloroquine-resistant P. falciparum/P. vivax). Numerous quinone-derived compounds have attracted considerable attention in the last few decades due to their potential in antimalarial drug discovery. Several semi-synthetic derivatives of natural quinones, synthetic quinones (naphtho-/benzo-quinone, anthraquinones, thiazinoquinones), and quinone-based hybrids were explored for their in vitro and in vivo antimalarial activities. A careful literature survey revealed that this topic has not been compiled as a review article so far. Therefore, we herein summarise the recent discovery (the year 2009-2020) of quinone based antimalarial compounds in chronological order. This compilation would be very useful towards the exploration of novel quinone-derived compounds against malarial parasites with promising efficacy and lesser side effects.

The Ascidian-Derived Metabolites with Antimicrobial Properties

Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods.

Chemotherapy for human schistosomiasis: how far have we come? What's new? Where do we go from here?

Globally, schistosomiasis threatens more than 700 million lives, mostly children, in poor localities of tropical and sub-tropical areas with morbidity due to acute and chronic pathological manifestations of the disease. After a century since the first antimonial-based drugs were introduced to treat the disease, anti-schistosomiasis drug development is again at a bottleneck with only one drug, praziquantel, available for treatment purposes. This review focuses on promising chemotypes as potential starting points in a drug discovery effort to meet the urgent need for new schistosomicides.

Antiplasmodial Activity of p-Substituted Benzyl Thiazinoquinone Derivatives and Their Potential against Parasitic Infections

Malaria is a life-threatening disease and, what is more, the resistance to available antimalarial drugs is a recurring problem. The resistance of Plasmodium falciparum malaria parasites to previous generations of medicines has undermined malaria control efforts and reversed gains in child survival. This paper describes a continuation of our ongoing efforts to investigate the effects against Plasmodium falciparum strains and human microvascular endothelial cells (HMEC-1) of a series of methoxy p-benzyl-substituted thiazinoquinones designed starting from a pointed antimalarial lead candidate. The data obtained from the newly tested compounds expanded the structure–activity relationships (SARs) of the thiazinoquinone scaffold, indicating that antiplasmodial activity is not affected by the inductive effect but rather by the resonance effect of the introduced group at the para position of the benzyl substituent. Indeed, the current survey was based on the evaluation of antiparasitic usefulness as well as the selectivity on mammalian cells of the tested p-benzyl-substituted thiazinoquinones, upgrading the knowledge about the active thiazinoquinone scaffold.

Investigating the Antiparasitic Potential of the Marine Sesquiterpene Avarone, Its Reduced form Avarol, and the Novel Semisynthetic Thiazinoquinone Analogue Thiazoavarone

The chemical analysis of the sponge Dysidea avara afforded the known sesquiterpene quinone avarone, along with its reduced form avarol. To further explore the role of the thiazinoquinone scaffold as an antiplasmodial, antileishmanial and antischistosomal agent, we converted the quinone avarone into the thiazinoquinone derivative thiazoavarone. The semisynthetic compound, as well as the natural metabolites avarone and avarol, were pharmacologically investigated in order to assess their antiparasitic properties against sexual and asexual stages of Plasmodium falciparum, larval and adult developmental stages of Schistosomamansoni (eggs included), and also against promastigotes and amastigotes of Leishmania infantum and Leishmania tropica. Furthermore, in depth computational studies including density functional theory (DFT) calculations were performed. A toxic semiquinone radical species which can be produced starting both from quinone- and hydroquinone-based compounds could mediate the anti-parasitic effects of the tested compounds.

In Vitro Antiproliferative Evaluation of Synthetic Meroterpenes Inspired by Marine Natural Products

Several marine natural linear prenylquinones/hydroquinones have been identified as anticancer and antimutagenic agents. Structure-activity relationship studies on natural compounds and their synthetic analogs demonstrated that these effects depend on the length of the prenyl side chain and on the type and position of the substituent groups in the quinone moiety. Aiming to broaden the knowledge of the underlying mechanism of the antiproliferative effect of these prenylated compounds, herein we report the synthesis of two quinones 4 and 5 and of their corresponding dioxothiazine fused quinones 6 and 7 inspired to the marine natural product aplidinone A (1), a geranylquinone featuring the 1,1-dioxo-1,4-thiazine ring isolated from the ascidian Aplidium conicum. The potential effects on viability and proliferation in three different human cancer cell lines, breast adenocarcinoma (MCF-7), pancreas adenocarcinoma (Bx-PC3) and bone osteosarcoma (MG-63), were investigated. The methoxylated geranylquinone 5 exerted the highest antiproliferative effect exhibiting a comparable toxicity in all three cell lines analyzed. Interestingly, a deeper investigation has highlighted a cytostatic effect of quinone 5 referable to a G0/G1 cell-cycle arrest in BxPC-3 cells after 24 h treatment.