Triproamide and Pemukainalides, Cyclic Depsipeptides from the Marine Cyanobacterium Symploca hydnoides

Drymariamides A-J, Antiadipogenic Cyclopeptides Incorporating Noncanonical Amino Acids from Drymaria cordata

Herein, we report an extensive phytochemical study on the whole plant of Drymaria cordata, which led to the isolation of ten new orbitides, named drymariamides A-J (1-10). Compounds 2, 3, and 5 incorporate rare residues of noncanonical amino acids of kynurenine (Kyn) or 3a-hydroxypyrroloindoline (HPI). Their structures with absolute configurations were elucidated by a combination of spectroscopic analysis, advanced Marfey's method, X-ray diffraction, and electronic circular dichroism analysis. Compounds 1-10 exhibited antiadipogenic effects in 3T3-L1 adipocytes, and the most potent compound 7 showed an EC50 value of 1.17 ± 0.19 μM.

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), 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 NP structure class diversity in relation to biota source and biome is discussed.

Aspertides A-E: Antimicrobial Pentadepsipeptides with a Unique p-Methoxycinnamoyl Amide Group from the Marine Isolates Aspergillus tamarii MA-21 and Aspergillus insuetus SD-512

Marine fungus-derived natural products are an important source of antimicrobial compounds against marine aquatic pathogens. Here, we describe the isolation and characterization of five new pentadepsipeptides, aspertides A-E (1-5), containing a unique p-methoxycinnamoyl amide group, from the marine fungi Aspergillus tamarii MA-21 and Aspergillus insuetus SD-512. Among them, aspertides B-E (2-5) also possessed uncommon amino acid residues, such as 3-hydroxyproline, 2,3-dihydroxyproline, or pipecolinic acid. The structures of these compounds were elucidated on the basis of NMR and mass spectroscopic analyses. The absolute configurations of them were established by chiral HPLC analyses of the acidic hydrolysates and NMR calculations with DP4+ probability analysis. In bio-activity assays, compounds 4 and 5 exhibited antibacterial activities against aquatic-pathogenic bacteria, including Edwardsiella tarda, Vibrio alginolyticus, Vibrio anguillarum, Vibrio vulnificus, and Staphylococcus aureus, with MIC values of 8-32 μg/mL.

Marine Organisms as a Prolific Source of Bioactive Depsipeptides

Depsipeptides, an important group of polypeptides containing residues of hydroxy acids and amino acids linked together by amide and ester bonds, have potential applications in agriculture and medicine. A growing body of evidence demonstrates that marine organisms are prolific sources of depsipeptides, such as marine cyanobacteria, sponges, mollusks, microorganisms and algae. However, these substances have not yet been comprehensively summarized. In order to enrich our knowledge about marine depsipeptides, their biological sources and structural features, as well as bioactivities, are highlighted in this review after an extensive literature search and data analysis.

Absolute Stereochemistry Determination of Bioactive Marine-Derived Cyclopeptides by Liquid Chromatography Methods: An Update Review (2018-2022)

Cyclopeptides are considered as one of the most important classes of compounds derived from marine sources, due to their structural diversity and a myriad of their biological and pharmacological activities. Since marine-derived cyclopeptides consist of different amino acids, many of which are non-proteinogenic, they possess various stereogenic centers. In this respect, the structure elucidation of new molecular scaffolds obtained from natural sources, including marine-derived cyclopeptides, can become a very challenging task. The determination of the absolute configurations of the amino acid residues is accomplished, in most cases, by performing acidic hydrolysis, followed by analyses by liquid chromatography (LC). In a continuation with the authors' previous publication, and to analyze the current trends, the present review covers recently published works (from January 2018 to November 2022) regarding new cyclopeptides from marine organisms, with a special focus on their biological/pharmacological activities and the absolute stereochemical assignment of the amino acid residues. Ninety-one unreported marine-derived cyclopeptides were identified during this period, most of which displayed anticancer or antimicrobial activities. Marfey's method, which involves LC, was found to be the most frequently used for this purpose.

Phaeosphamides A and B, Cytotoxic Cyclodecadepsipeptides from the Mangrove-Derived Fungus Phaeosphaeriopsis sp. S296

Chemical examination of the fermented broth of the mangrove-derived fungus Phaeosphaeriopsis sp. S296 resulted in the isolation of two new cyclodecadepsipeptides, namely phaeosphamides A (1) and B (2), as well as one known congener Sch 217048 (3). The structures of new metabolites, including absolute configurations, were established on the basis of extensive spectroscopic data analyses, chemical conversion, and Marfey’s method. The 2-hydroxy-3-methylpentanoic acid (Hmp) moiety and pipecolic acid (Pip) unit in structures were rarely discovered in nature. Interestingly, compounds 1–3 are examples of peptides discovered from the fungal genus Phaeosphaeriopsis for the first time. All identified compounds were evaluated for their cytotoxicity against five tumor cell lines of AGS, BEL-7402, HepG2, B16, and BIU87. Among them, compound 1 showed inhibitory activities against these tumor cell lines with IC₅₀ values ranging from 5.14 to 66.38 μM. A further mechanistic investigation found that 1 arrested AGS cells in the G2 phase and induced their apoptosis in a dose-dependent manner.