Fuscasins A-D, Cycloheptapeptides from the Marine Sponge Phakellia fusca

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.

Phakellisins A-E, cyclopeptides from a marine sponge Phakellia sp. guided by LC-MS

A chemical investigation of the marine sponge Phakellia sp. from the South China Sea yielded five new cyclopeptides, phakellisins A-E (1-5). Structures of these compounds were determined by comprehensive analysis of 1D/2D NMR, HRESIMS/MS spectroscopic data and the advanced Marfey's method. All compounds were evaluated for their cytotoxic activity. Compound 1 showed a strong inhibitory activity against WSU-DLCL-2 cells with an IC50 value of 5.25 ± 0.2 μM by induction of G0/G1 cell cycle arrest and apoptosis.

Cyclic Peptides from the Opportunistic Pathogen Basidiobolus meristosporus

Three new cyclic peptides, meristosporins A, B, and C (1-3), one of which features an unusual amino acid, were isolated from the opportunistic pathogen Basidiobolus meristosporus and identified by 1D, 2D NMR, MS/MS, and Marfey's analysis. The biosynthetic pathway of the hexapeptide meristosporin A (1) was deduced based on nonribosomal peptide synthetase gene clusters analysis. Compounds 1 and 2 showed cytotoxicity to RAW264.7 and 293T cells, respectively. These compounds may be involved in the fungal injury caused to human cells.

Cyclic pentapeptides with anti-inflammatory, cytotoxic or α-glucosidase inhibitory activities from Basidiobolus meristosporus

Basidiobolus meristosporus is an opportunistic pathogen of mammals with unique habitats, but its metabolites have not been extensively studied. Through semi-preparative HPLC, nine undescribed cyclic pentapeptides were isolated from mycelia of B. meristosporus RCEF4516. The structure of the compounds 1-9 were identified with MS/MS and NMR data and designated as basidiosin D-L respectively. The absolute configurations were determined according to the advanced Marfey's method after compound hydrolysis. Bioactivity testing showed that compounds 1, 2, 3, 4 and 8 decreased NO production in LPS-activated RAW264.7 cells in a concentration-dependent manner. The nine compounds showed cytotoxicity against RAW264.7, 293 T and HepG2 cells. All the compounds except compound 7 showed stronger inhibitory effects on α-glucosidase than acarbose.

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.

Axinellasins A-D, Immunosuppressive Cycloheptapeptide Diastereomers, Discovered via a Precursor Ion Scanning-Supercritical Fluid Chromatography Strategy from the Marine Sponge Axinella species

The precursor ion scanning-supercritical fluid chromatography (PI-SFC) method was applied to explore new methionine sulfoxide-containing cycloheptapeptides, axinellasins A-D (1-4), from the marine sponge Axinella sp. Their structures, including absolute configurations, were elucidated by detailed spectroscopic analyses and X-ray crystallography. The total synthesis of 4 was completed via an Fmoc solid/solution-phase synthesis. Compounds 1-4 exhibited immunosuppressive effects via inhibition of T and B cell proliferation, and 1 and 4 showed better inhibitory activities than their corresponding diastereomers.

Novel Marine Secondary Metabolites Worthy of Development as Anticancer Agents: A Review

Secondary metabolites from marine sources have a wide range of biological activity. Marine natural products are promising candidates for lead pharmacological compounds to treat diseases that plague humans, including cancer. Cancer is a life-threatening disorder that has been difficult to overcome. It is a long-term illness that affects both young and old people. In recent years, significant attempts have been made to identify new anticancer drugs, as the existing drugs have been useless due to resistance of the malignant cells. Natural products derived from marine sources have been tested for their anticancer activity using a variety of cancer cell lines derived from humans and other sources, some of which have already been approved for clinical use, while some others are still being tested. These compounds can assault cancer cells via a variety of mechanisms, but certain cancer cells are resistant to them. As a result, the goal of this review was to look into the anticancer potential of marine natural products or their derivatives that were isolated from January 2019 to March 2020, in cancer cell lines, with a focus on the class and type of isolated compounds, source and location of isolation, cancer cell line type, and potency (IC₅₀ values) of the isolated compounds that could be a guide for drug development.

New bisabolane-type phenolic sesquiterpenoids from the marine sponge Plakortis simplex

Six new bisabolane-type phenolic sesquiterpenoids, including plakordiols A-D (1-4), (7R, 10R)-hydroxycurcudiol (5) and (7R, 10S)-hydroxycurcudiol (6) were isolated from the marine sponge Plakortis simplex collected from the South China Sea. Their structures were determined based on extensive analysis of spectroscopic data. Their configurations were assigned by coupling constant analysis, NOESY correlations, and the modified Mosher's method. Furthermore, their cytotoxic and antibacterial activities were evaluated.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) 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 (1490 in 440 papers for 2019), 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. Methods used to study marine fungi and their chemical diversity have also been discussed.

Survey of natural products reported by Asian research groups in 2019

The new natural products reported in 2019 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2019 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Pancreatic Lipase Inhibitory Cyclohexapeptides from the Marine Sponge-Derived Fungus Aspergillus sp. 151304

Three new cyclohexapeptides, petrosamides A-C (1-3), were isolated from the sponge-derived fungus Aspergillus sp. 151304. Their structures were elucidated by detailed 1D and 2D spectroscopic analyses, and the absolute configurations of the amino acid residues were determined by the advanced Marfey's method. These peptides displayed significant and dose-dependent pancreatic lipase (PL) inhibitory activities, with IC₅₀ values of 7.6 ± 1.5, 1.8 ± 0.3, and 0.5 ± 0.1 μM, respectively. Further inhibition kinetics analyses showed that compound 3 inhibited PL in a noncompetitive manner, while molecular dynamics simulation revealed that it could bind to PL at the entrance of the catalytic pocket.