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In order to minimize re-discovery of already known anti-infective compounds, we focused our screening approach on understudied, almost untapped marine environments including marine invertebrates and their associated bacteria. Therefore, two sea cucumber species, Holothuria leucospilota and Stichopus vastus, were collected from Lampung (Indonesia), and 127 bacterial strains were identified by partial 16S rRNA-gene sequencing analysis and compared with the NCBI database. In addition, the overall bacterial diversity from tissue samples of the sea cucumbers H. leucospilota and S. vastus was analyzed using the cultivation-independent Illumina MiSEQ analysis. Selected bacterial isolates were grown to high densities and the extracted biomass was tested against a selection of bacteria and fungi as well as the hepatitis C virus (HCV). Identification of putative bioactive bacterial-derived compounds were performed by analyzing the accurate mass of the precursor/parent ions (MS1) as well as product/daughter ions (MS2) using high resolution mass spectrometry (HRMS) analysis of all active fractions. With this attempt we were able to identify 23 putatively known and two previously unidentified precursor ions. Moreover, through 16S rRNA-gene sequencing we were able to identify putatively novel bacterial species from the phyla Actinobacteria, Proteobacteria and also Firmicutes. Our findings suggest that sea cucumbers like H. leucospilota and S. vastus are promising sources for the isolation of novel bacterial species that produce compounds with potentially high biotechnological potential.

Erismadelphus exsul Mildbr bark is widely used in Gabonese folk medicine. However, little is known about the active compounds associated with its biological activities. In the present study, phytochemical profiling of the ethanolic extract of Erismadelphus exsul was performed using a de-replication strategy by coupling HPLC-ESI-Q/TOF with a molecular network approach. Eight families of natural compounds were putatively identified, including cyclopeptide alkaloids, esterified amino acids, isoflavonoid- and flavonoid-type polyphenols, glycerophospholipids, steroids and their derivatives, and quinoline alkaloids. All these compounds were identified for the first time in this plant. The use of molecular networking obtained a detailed phytochemical overview of this species. Furthermore, antioxidant (2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) and ferric reducing capacity (FRAP)) and in vitro antimicrobial activities were assessed. The crude extract, as well as fractions obtained from Erismadelphus exsul, showed a better reactivity to FRAP than DPPH. The fractions were two to four times more antioxidant than ascorbic acid while reacting to FRAP, and there was two to nine times less antioxidant than this reference while reacting to DPPH. In addition, several fractions and the crude extract exhibited a significant anti-oomycete activity towards the Solanaceae phytopathogen Phytophthora infestans in vitro, and, at a lower extent, the antifungal activity against the wheat pathogen Zymoseptoria tritici had growth inhibition rates ranging from 0 to 100%, depending on the tested concentration. This study provides new insights into the phytochemical characterization and the bioactivities of ethanolic extract from Erismadelphus exsul bark.

Eucalypts are a large group of woody trees with about 900 taxa in 3 genera: Eucalyptus , Corymbia and Angophora . The secondary metabolites of eucalypts have shown a plethora of biological activities. The chemistry behind the activities of eucalypts is being unearthed with advancements in modern medicine and pharmacy. This has demanded the phytochemical profiling of eucalypts with respect to their bioactive constituents. A large number of secondary metabolites (flavonoids, glycosides, triterpenoids, phloroglucinols) from several species of eucalypts have been earlier isolated by our group. In order to develop quick identification of secondary metabolites from eucalypts for de-replication purposes, we thought it worthwhile to develop qualitative HPTLC methods for these compounds in 15 eucalypts (13 Eucalyptus and 2 Corymbia ) collected from Australia and India. High-performance thin-layer chromatography (HPTLC) fingerprints using 87 compounds of the above chemical classes of natural products were developed for the quality assessment of eucalypts.

Recent advancements in NMR spectroscopy have been pivotal to the discovery of molecules that hold promise as human drugs. A sizeable portion of these newly discovered bioactive compounds are natural products, organic molecules produced by living things such as plants and microorganisms. Natural products provide an ideal vantage point for examining recent NMR advancements, because these molecules pose myriad structure elucidation challenges resulting from their diverse structures and low abundances within complex mixtures. This chapter discusses recent developments in NMR technologies and methods, as applied toward discovery of novel natural products that may hold potential as pharmaceuticals. Discussion of NMR advancements focuses on several areas that have recently emerged or matured, highlighting (1) higher magnetic fields and improved probes (e.g., microprobes and cryoprobes) that have dramatically enhanced the sensitivity of NMR during the past decade and opened doors for structure determination of minute quantities of highly bioactive natural products, (2) hyphenated NMR methods (e.g., LC-NMR, GC-NMR, CE-NMR) for structure elucidation of low abundance or unstable metabolites and de-replication of known natural products, and (3) approaches for the direct identification of molecules within mixtures, including metabolomics-based strategies for metabolite discovery. Each of these highlighted advancements in NMR-based drug discovery is presented in the context of one or more natural product exemplars.

Positive-strand RNA viruses constitute the largest group of plant viruses and have an important impact on world agriculture. These viruses have small genomes that encode a limited number of proteins and depend on their hosts to complete the various steps of their replication cycle. In this review, the contact points between positive-strand RNA plant viruses and their hosts, which are necessary for the translation and replication of the viral genomes, are discussed. Special emphasis is placed on the description of viral replication complexes that are associated with specific membranous compartments derived from plant intracellular membranes and contain viral RNAs and proteins as well as a variety of host proteins. These complexes are assembled via an intricate network of protein-protein, protein-membrane, and protein-RNA interactions. The role of host factors in regulating the assembly, stability, and activity of viral replication complexes are also discussed.