Total Synthesis and Antimalarial Activity of 2-(p-Hydroxybenzyl)-prodigiosins, Isoheptylprodigiosin, and Geometric Isomers of Tambjamine MYP1 Isolated from Marine Bacteria

Discovery and Optimization of Tambjamines as a Novel Class of Antileishmanial Agents

Leishmaniasis is a neglected tropical disease that is estimated to afflict over 12 million people. Current drugs for leishmaniasis suffer from serious deficiencies, including toxicity, high cost, modest efficacy, primarily parenteral delivery, and emergence of widespread resistance. We have discovered and developed a natural product-inspired tambjamine chemotype, known to be effective against Plasmodium spp, as a novel class of antileishmanial agents. Herein, we report in vitro and in vivo antileishmanial activities, detailed structure-activity relationships, and metabolic/pharmacokinetic profiles of a large library of tambjamines. A number of tambjamines exhibited excellent potency against both Leishmania mexicana and Leishmania donovani parasites with good safety and metabolic profiles. Notably, tambjamine 110 offered excellent potency and provided partial protection to leishmania-infected mice at 40 and/or 60 mg/kg/10 days of oral treatment. This study presents the first account of antileishmanial activity in the tambjamine family and paves the way for the generation of new oral antileishmanial drugs.

Anti-Malassezia Drug Candidates Based on Virulence Factors of Malassezia-Associated Diseases

Malassezia is a lipophilic unicellular fungus that is able, under specific conditions, to cause severe cutaneous and systemic diseases in predisposed subjects. This review is divided into two complementary parts. The first one discusses how virulence factors contribute to Malassezia pathogenesis that triggers skin diseases. These virulence factors include Malassezia cell wall resistance, lipases, phospholipases, acid sphingomyelinases, melanin, reactive oxygen species (ROS), indoles, hyphae formation, hydrophobicity, and biofilm formation. The second section describes active compounds directed specifically against identified virulence factors. Among the strategies for controlling Malassezia spread, this review discusses the development of aryl hydrocarbon receptor (AhR) antagonists, inhibition of secreted lipase, and fighting biofilms. Overall, this review offers an updated compilation of Malassezia species, including their virulence factors, potential therapeutic targets, and strategies for controlling their spread. It also provides an update on the most active compounds used to control Malassezia species.

Prodigiosin as an antibiofilm agent against multidrug-resistant Staphylococcus aureus

Staphylococcus aureus is known for forming bacterial biofilms that confer increased antimicrobial resistance. Combining antibiotics with antibiofilm agents is an alternative approach, but the antibiofilm ability of prodigiosin (PG), a potential antibiotic synergist, against antimicrobial-resistant (AMR) S. aureus remains to be understood. The antibiofilm activity of PG against 29 clinical AMR S. aureus strains was evaluated using crystal violet staining, and its synergistic effects with vancomycin (VAN) was confirmed using the checkerboard test. The viability and metabolic activity of biofilms and planktonic cells were also assessed. The results revealed that PG exhibited promising inhibitory activity against biofilm formation and synergistic activity with VAN. It effectively reduced the metabolic activity of biofilms and suppressed the production of exopolysaccharides, which might be attributed to the downregulation of biofilm-related genes such as sarA, agrA, and icaA. These findings suggest that PG could be used as a preventive coating or adjuvant against biofilms in clinical settings.

Clauson-Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

Pyrrole is an important aromatic heterocyclic scaffold found in many natural products and predominantly used in pharmaceuticals. Continuous efforts are being made to design and synthesize various pyrrole derivatives using different synthetic procedures. Among them, the Clauson-Kaas reaction is a very old and well-known method for synthesizing a large number of N-substituted pyrroles. In recent years, due to global warming and environmental concern, research laboratories and pharmaceutical industries around the world are searching for more environmentally friendly reaction conditions for synthesizing compounds. As a result, this review describes the use of various eco-friendly greener protocols to synthesize N-substituted pyrroles. This synthesis involves the reaction of various aliphatic/aromatic primary amines, and sulfonyl primary amines with 2,5-dimethoxytetrahydrofuran in the presence of numerous acid catalysts and transition metal catalysts. The goal of this review is to summarize the synthesis of various N-substituted pyrrole derivatives using a modified Clauson-Kaas reaction under diverse conventional and greener reaction conditions.

Prodigiosin from Serratia rubidaea MJ 24 impedes Helicoverpa armigera development by the dysregulation of Juvenile hormone-dopamine system

Prodigiosin pigment is a secondary metabolite produced by many bacterial species and is known for its medicinal properties. A few of these prodigiosin-producing bacteria are also reported to be entomopathogenic. It is intriguing to unravel the role of prodigiosin in insecticidal activities and its mode of action. In this study, we have shown the production and characterization of prodigiosin from the Serratia rubidaea MJ 24 isolated from the soil of the Western Ghats, India. Further, we assessed the effect of this pigment on the lepidopteran agricultural pest, Helicoverpa armigera. Prodigiosin-fed H. armigera indicated defective development of insect growth upon treatment. Due to defective early development, about 50% mortality and 40% reduction in body weight were observed in insects fed on a 500 ppm prodigiosin-containing diet. The transcriptomic analysis of these insects indicated significant dysregulation of Juvenile hormone synthesis and response related genes. In addition, dopamine related processes and their resultant melanization and sclerotization processes were also found to be affected. The changes in the expression levels of the key transcripts were further validated using real-time quantitative PCR. The metabolome data confirmed the developmental dysregulation of precursors and products of differentially regulated genes due to prodigiosin. Therefore, the corroborated data suggests that prodigiosin majorly affects H. armigera development through dysregulation of the Juvenile hormone-dopamine system and can be considered as a bioactive scaffold to design insect-pest management compounds. This study provides the first report of in-depth analysis of insecticidal system dynamics in H. armigera insects upon prodigiosin feeding via gene expression and metabolic change via omics approach.

Marine Invertebrates: A Promissory Still Unexplored Source of Inhibitors of Biomedically Relevant Metallo Aminopeptidases Belonging to the M1 and M17 Families

Proteolytic enzymes, also known as peptidases, are critical in all living organisms. Peptidases control the cleavage, activation, turnover, and synthesis of proteins and regulate many biochemical and physiological processes. They are also involved in several pathophysiological processes. Among peptidases, aminopeptidases catalyze the cleavage of the N-terminal amino acids of proteins or peptide substrates. They are distributed in many phyla and play critical roles in physiology and pathophysiology. Many of them are metallopeptidases belonging to the M1 and M17 families, among others. Some, such as M1 aminopeptidases N and A, thyrotropin-releasing hormone-degrading ectoenzyme, and M17 leucyl aminopeptidase, are targets for the development of therapeutic agents for human diseases, including cancer, hypertension, central nervous system disorders, inflammation, immune system disorders, skin pathologies, and infectious diseases, such as malaria. The relevance of aminopeptidases has driven the search and identification of potent and selective inhibitors as major tools to control proteolysis with an impact in biochemistry, biotechnology, and biomedicine. The present contribution focuses on marine invertebrate biodiversity as an important and promising source of inhibitors of metalloaminopeptidases from M1 and M17 families, with foreseen biomedical applications in human diseases. The results reviewed in the present contribution support and encourage further studies with inhibitors isolated from marine invertebrates in different biomedical models associated with the activity of these families of exopeptidases.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

Mechanisms underlying the inhibitory effects of Cd2+ on prodigiosin synthesis in Serratia marcescens KMR-3

Prodigiosin (2-methyl-3-pentyl-6-methoxyprodiginine), a red-colored microbial pigment, is produced in large quantities by Serratia marcescens KMR-3. This bacterium can grow in a medium with a Cd²⁺ concentration of 500 mg/L, but it does not produce prodigiosin when the Cd²⁺ concentration in the medium is higher than 140 mg/L. Therefore, we investigated the mechanisms by which Cd²⁺ inhibits prodigiosin synthesis. Upon addition of Cd²⁺ to the medium, the expression of the prodigiosin (pig) gene cluster was significantly downregulated. Simultaneously, genes encoding proteins related to the synthesis of arginine and proline(prodigiosin precursors) were significantly downregulated, while the degradation-related genes were upregulated. Furthermore, PigF, which encodes a key enzyme involved in the synthesis of 4-methoxy-2,2'-bipyrrole-5-carboxaldehyde and PigC, which encodes a key enzyme involved in the last step of prodigiosin synthesis, were downregulated by 80% and 55%, respectively, following Cd²⁺ treatment. As PigC and PigF are located on the cell membrane and are involved in the final steps of prodigiosin synthesis, the cell membrane might be presumed to be the site of prodigiosin synthesis. The bacterial membrane exhibited different degrees of elongation, folding, fragmentation, and sagging after the addition of Cd²⁺, while likely destroying the site of prodigiosin synthesis.

Antimalarial Natural Products

Natural products have made a crucial and unique contribution to human health, and this is especially true in the case of malaria, where the natural products quinine and artemisinin and their derivatives and analogues, have saved millions of lives. The need for new drugs to treat malaria is still urgent, since the most dangerous malaria parasite, Plasmodium falciparum, has become resistant to quinine and most of its derivatives and is becoming resistant to artemisinin and its derivatives. This volume begins with a short history of malaria and follows this with a summary of its biology. It then traces the fascinating history of the discovery of quinine for malaria treatment and then describes quinine's biosynthesis, its mechanism of action, and its clinical use, concluding with a discussion of synthetic antimalarial agents based on quinine's structure. The volume then covers the discovery of artemisinin and its development as the source of the most effective current antimalarial drug, including summaries of its synthesis and biosynthesis, its mechanism of action, and its clinical use and resistance. A short discussion of other clinically used antimalarial natural products leads to a detailed treatment of other natural products with significant antiplasmodial activity, classified by compound type. Although the search for new antimalarial natural products from Nature's combinatorial library is challenging, it is very likely to yield new antimalarial drugs. The chapter thus ends by identifying over ten natural products with development potential as clinical antimalarial agents.

Investigating Alkylated Prodigiosenes and Their Cu(II)-Dependent Biological Activity: Interactions with DNA, Antimicrobial and Photoinduced Anticancer Activity

Prodigiosenes are a family of red pigments with versatile biological activity. Their tripyrrolic core structure has been modified many times in order to manipulate the spectrum of activity. We have been looking systematically at prodigiosenes substituted at the C ring with alkyl chains of different lengths, in order to assess the relevance of this substituent in a context that has not been investigated before for these derivatives: Cu(II) complexation, DNA binding, self‐activated DNA cleavage, photoinduced cytotoxicity and antimicrobial activity. Our results indicate that the hydrophobic substituent has a clear influence on the different aspects of their biological activity. The cytotoxicity study of the Cu(II) complexes of these prodigiosenes shows that they exhibit a strong cytotoxic effect towards the tested tumor cell lines. The Cu(II) complex of a prodigiosene lacking any alkyl chain excelled in its photoinduced anticancer activity, thus demonstrating the potential of prodigiosenes and their metal complexes for an application in photodynamic therapy (PDT). Two derivatives along with their Cu(II) complexes showed also antimicrobial activity against Staphylococcus aureus strains.