Toxicity of the marine glycosidic macrolides, polycavernoside E and akunolides, from Okinawan cyanobacterium Okeania sp. in mice.

The toxicity of polycavernoside E and its structurally related macrolides, akunolides A, B, and C, was evaluated in mice. These compounds were recently isolated from the marine cyanobacterium Okeania sp. collected in Okinawa, Japan. The minimal toxicity of polycavernoside E was estimated as 0.81 mg/kg by intraperitoneal injection, whereas those of akunolides A-C were >13 mg/kg. Owing to the considerable toxicity of polycavernoside E, the occurrence of this cyanobacterium should be considered in seaweed production environments.

Amantamide C, an Antitrypanosomal Linear Lipopeptide from a Marine Okeania sp. Cyanobacterium.

Amantamides are lipopeptides that act as selective CXC chemokine receptor 7 agonists and modulate spontaneous calcium oscillations in primary cultured neocortical neurons. We isolated a new analog of amantamides, amantamide C, from marine Okeania sp. cyanobacterium collected in Japan and established its structure based on NMR and MS/MS analyses, and degradation reactions. In addition, we evaluated the biological activity of amantamide C and revealed novel biological features of amantamide-type compounds.

Pemuchiamides A and B, Proline-Rich Linear Lipopeptides, Isolated from a Marine Hormoscilla sp. Cyanobacterium.

Pemuchiamides A and B (1 and 2) were isolated from a marine Hormoscilla sp. cyanobacterium collected from Pemuchi Beach on Hateruma Island, Japan. Although 1 and 2 existed as a complex mixture of rotamers in chloroform-d, detailed analyses of their 2D NMR and tandem mass spectra revealed their planar structures, respectively. The absolute configurations of 1 and 2 were established via the degradation and derivatization reactions. Pemuchiamide A (1) exhibited potent growth-inhibitory activity against Trypanosoma brucei rhodesiense, the causative organism of African sleeping sickness, while 2 showed 10-fold weaker activity than 1. This result indicates that the presence of a hydroxy group at the C-3 position of the 4-aminobutanoic acid moiety negatively affects antitrypanosomal activity.

Wajeepeptin, a Cytotoxic and Antitrypanosomal Cyclic Depsipeptide from a Marine Moorena sp. Cyanobacterium.

Here, we report wajeepeptin (1), a new cyclic depsipeptide isolated from a marine Moorena sp. cyanobacterium. The structure was elucidated by a combination of spectroscopic analyses, X-ray diffraction analysis, and degradation reactions. Wajeepeptin (1) showed moderate cytotoxicity (IC50 = 3.7 µM against HeLa cells) and potent antitrypanosomal activity (IC50 = 0.73 ± 0.14 µM against Trypanosoma brucei rhodesiense).

Enhancing Human Health and Wellbeing through Sustainably and Equitably Unlocking a Healthy Ocean's Potential.

A healthy ocean is essential for human health, and yet the links between the ocean and human health are often overlooked. By providing new medicines, technologies, energy, foods, recreation, and inspiration, the ocean has the potential to enhance human health and wellbeing. However, climate change, pollution, biodiversity loss, and inequity threaten both ocean and human health. Sustainable realisation of the ocean's health benefits will require overcoming these challenges through equitable partnerships, enforcement of laws and treaties, robust monitoring, and use of metrics that assess both the ocean's natural capital and human wellbeing. Achieving this will require an explicit focus on human rights, equity, sustainability, and social justice. In addition to highlighting the potential unique role of the healthcare sector, we offer science-based recommendations to protect both ocean health and human health, and we highlight the unique potential of the healthcare sector tolead this effort.

Total Synthesis of Bipenicilisorin and Assignment of the Absolute Configuration.

The first total synthesis of bipenicilisorin (1) isolated from Penicillium chrysogenum SCSIO 41001 via its monomer natural product, penicilisorin (2), was achieved. Penicilisorin was synthesized in four steps from a o-bromobenzaldehyde derivative via the Pd-catalyzed one-pot fluorocarbonylation/lactonization/ß-elimination cascade reaction. Iodination of penicilisorin gave 7-iodopenicilisorin which was dimerized by Pd-catalyzed homodimerization to provide (±)-bipenicilisorin. The unknown absolute configuration of naturally occurring (+)-bipenicilisorin was examined by optical resolution of the (±)-synthetic bipenicilisorin and a comparison of experimental and theoretical electronic circular dichroism (ECD) spectra. These results support the absolute configuration of the natural product to be Sa. A cytotoxic activity test of (+)-and (-)-bipenicilisorin using A549 cells revealed that (+)-1 has a lower IC50 value than (-)-1.

Isolation and structure determination of a new analog of polycavernosides from marine Okeania sp. cyanobacterium.

Polycavernoside E (1), a new polycavernoside analog, was isolated from a marine Okeania sp. cyanobacterium. The relative configuration was elucidated primarily by analyzing the two dimensional nuclear magnetism resonance (2D NMR) data. The absolute configuration was clarified by comparing the electronic circular dichroism (ECD) data of 1 with those of known analogs. Polycavernoside E (1) exhibited moderate antitrypanosomal activity against Trypanosoma brucei rhodesiense. Furthermore, the isolation of polycavernoside E (1) from marine cyanobacteria provides additional evidence that marine cyanobacteria, and not red algae, are responsible for the biosynthesis of polycavernosides.

Kagimminols A and B, Cembrene-Type Diterpenes from an Okeania sp. Marine Cyanobacterium.

Kagimminols A (1) and B (2), new cembrene-type diterpenoids, were isolated from an Okeania sp. marine cyanobacterium. By combining DP4 analysis with an efficient NMR chemical shift calculation protocol, we clarified the relative configurations of 1 and 2 without consuming precious natural products. We determined the absolute configurations by a comparison of theoretical electronic circular dichroism (ECD) spectra with experimental spectra, and the absolute configuration of 1 was verified experimentally. Finally, we found that 1 and 2 showed selective growth-inhibitory activity against the causative agent of human African trypanosomiasis. This study exemplifies that computational chemistry is an efficient tool for clarifying the configurations of natural products possessing tautomers in equilibrium.

Isolation and Structure Determination of Akunolides, Macrolide Glycosides from a Marine Okeania sp. Cyanobacterium.

Akunolides A (1), B (2), C (3), and D (4), new macrolide glycosides, were isolated from a marine Okeania sp. cyanobacterium. Their structures were elucidated by spectroscopic analyses and derivatization reactions. Akunolides A-D (1-4) are classified as 16-membered macrolide glycosides, which are relatively rare structures for marine cyanobacterium-derived natural products. Akunolides A-D (1-4) showed moderate antitrypanosomal activities against Trypanosoma brucei rhodesiense, with IC50 values ranging from 11 to 14 µM. Furthermore, akunolides A (1) and C (3) exhibited no cytotoxicity against normal human WI-38 cells even at a concentration of 150 µM.

Total Synthesis of Ikoamide, a Highly N-Methylated Antimalarial Lipopeptide.

Ikoamide (1) is a highly N-methylated antimalarial lipopeptide that was isolated from a marine cyanobacterium, an Okeania sp. in 2018, which shows strong antimalarial activity without cytotoxicity against human cancer cell lines. To establish a synthetic method for obtaining enough ikoamide for its biological evaluations, we have established a total synthesis of ikoamide. The synthetic method presented here lays the foundation for the development of novel ikoamide analogues, which may lead to a discovery of pharmaceutically unique antimalarial drug leads.

Differentiation-Promoting Effects of Okeaniamides A and B from an Okeania sp. Marine Cyanobacterium on Preadipocytes.

The linear lipopeptides okeaniamide A (1) and okeaniamide B (2) were isolated from an Okeania sp. marine cyanobacterium collected in Okinawa. The structures of these compounds were established by spectroscopic analyses, and the absolute configurations were elucidated based on a combination of chemical degradations, Marfey's analysis, and derivatization reactions. Okeaniamide A (1) and okeaniamide B (2) dose-dependently promoted the differentiation of mouse 3T3-L1 preadipocytes in the presence of insulin.

Isolation of Hennaminal and Isolation and Total Synthesis of Hennamide, Pyrrolinone Compounds from the Marine Cyanobacterium Rivularia sp.

Two new natural products were isolated from the marine cyanobacterium Rivularia sp. collected in Japan. Hennaminal possesses a very rare functional group, ß,ß-diamino unsaturated ketone, which has only been found in bohemamine-type natural products so far. Hennamide possesses a reactive N-acyl pyrrolinone moiety, which induces self-dimerization. The isolation and structure determination supported by computational chemistry and total synthesis, as well as the antitrypanosomal activities of hennaminal and hennamide are described.

Isolation and Identification of Plant-Growth Inhibitory Constituents from Polygonum chinense Linn and Evaluation of Their Bioherbicidal Potential.

Polygonum chinense Linn. is a medicinal and invasive plant that belongs to the family Polygonaceae. The pharmacological activities and phytochemical constituents of Polygonum chinense are well reported, but the allelopathic effects and potent allelopathic substances of P. chinense remain to be investigated. Hence, this experiment was conducted to separate and characterize potentially allelopathic substances from an extract of the Polygonum chinense plant. The Polygonum chinense plant extracts highly suppressed the growth of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crusgalli (L.) P. Beauv.), and timothy grass (Phleum pratense L.) seedlings in a species- and concentration-dependent way. Two active substances were separated using a series of purification procedures and determined through spectral analysis as (-)-3-hydroxy-ß-ionone and (-)-3-hydroxy-7,8-dihydro-ß-ionone. These two compounds significantly suppressed the seedling growth of Lepidium sativum (cress) at concentrations of 0.01 and 1 mM, respectively. The extract concentrations necessary for 50% growth inhibition (I50 values) of the cress hypocotyls and roots were 0.05 and 0.07 mM for (-)-3-hydroxy-ß-ionone, respectively, and 0.42 and 1.29 mM for (-)-3-hydroxy-7,8-ß-ionone, respectively. These findings suggest that these two compounds are in charge of the inhibitory effects of the Polygonum chinense extract and may serve as weed control agents.

Unique Initiation and Termination Mechanisms Involved in the Biosynthesis of a Hybrid Polyketide-Nonribosomal Peptide Lyngbyapeptin B Produced by the Marine Cyanobacterium Moorena bouillonii.

Lyngbyapeptin B is a hybrid polyketide-nonribosomal peptide isolated from particular marine cyanobacteria. In this report, we carried out genome sequence analysis of a producer cyanobacterium Moorena bouillonii to understand the biosynthetic mechanisms that generate the unique structural features of lyngbyapeptin B, including the (E)-3-methoxy-2-butenoyl starter unit and the C-terminal thiazole moiety. We identified a putative lyngbyapeptin B biosynthetic (lynB) gene cluster comprising nine open reading frames that include two polyketide synthases (PKSs: LynB1 and LynB2), four nonribosomal peptide synthetases (NRPSs: LynB3, LynB4, LynB5, and LynB6), a putative nonheme diiron oxygenase (LynB7), a type II thioesterase (LynB8), and a hypothetical protein (LynB9). In vitro enzymatic analysis of LynB2 with methyltransferase (MT) and acyl carrier protein (ACP) domains revealed that the LynB2 MT domain (LynB2-MT) catalyzes O-methylation of the acetoacetyl-LynB2 ACP domain (LynB2-ACP) to yield (E)-3-methoxy-2-butenoyl-LynB2-ACP. In addition, in vitro enzymatic analysis of LynB7 revealed that LynB7 catalyzes the oxidative decarboxylation of (4R)-2-methyl-2-thiazoline-4-carboxylic acid to yield 2-methylthiazole in the presence of Fe2+ and molecular oxygen. This result indicates that LynB7 is responsible for the last post-NRPS modification to give the C-terminal thiazole moiety in lyngbyapeptin B biosynthesis. Overall, we identified and characterized a new marine cyanobacterial hybrid PKS-NRPS biosynthetic gene cluster for lyngbyapeptin B production, revealing two unique enzymatic logics.

Total Synthesis of Caldorazole, a Potent Mitochondrial Respiratory Chain Inhibitor without Chiral Centers.

Caldorazole (1) is a novel polyketide that was isolated from a marine cyanobacterium in 2022. It is a unique natural product that exhibits potent inhibitory activity against mitochondrial respiratory chain complex I despite having no chiral centers. To establish a method for obtaining caldorazole without relying on biological resources and for constructing a useful synthetic route for studies of its structure-activity relationship, we achieved the first total synthesis of caldorazole using a convergent synthetic route.

Allelopathic Substances of Osmanthus spp. for Developing Sustainable Agriculture.

Osmanthus fragrans Lour. has been cultivated for more than 2500 years because of the fragrance and color of the flowers. The flowers and roots have been used in tea, liquors, foods, and traditional Chinese medicine. The species contains more than 180 compounds including terpenoids, phenylpropanoids, polyphenols, flavonoids, and sterols. However, there has been limited information available on the allelopathic properties and allelopathic substances of O. fragrans. We investigated the allelopathy and allelopathic substances of O. fragrans and Osmanthus heterophyllus (G.Don) P.S. Green, as well as Osmanthus × fortunei Carrière, which is the hybrid species between O. fragrans and O. heterophyllus. The leaf extracts of O. fragrans, O. heterophyllus, and O. × fortunei suppressed the growth of cress (Lepidium sativum L.), alfalfa (Medicago sativa L.), Lolium multiflorum Lam., and Vulpia myuros (L.) C.C.Gmel with the extract concentration dependently. The extract of the hybrid species O. × fortune was the most active among the extracts. The main allelopathic substances of O. × fortunei and O. fragrans were isolated and identified as (+)-pinoresinol and 10-acetoxyligustroside, respectively. (+)-Pinoresinol was also found in the fallen leaves of O. × fortunei. Both compounds showed an allelopathic activity on the growth of cress and L. multiflorum. On the other hand, several allelopathic substances including (+)-pinoresinol may be involved in the allelopathy of O. heterophyllus. O. fragrans, O. heterophyllus, and O. × fortunei are evergreen trees. but their senescent leaves fall and cover the soil under the trees. It is possible that those allelopathic substances are liberated through the decomposition process of the leaves into their rhizosphere soil, and that they accumulate in the soil and provide a competitive advantage to the species through the inhibition of the growth of the neighboring competing plants. Therefore, the leaves of these Osmanthus species are allelopathic and potentially useful for weed management options in some agriculture settings to reduce commercial herbicide dependency for the developing sustainable agriculture systems.

Isolation of Caldorazole, a Thiazole-Containing Polyketide with Selective Cytotoxicity under Glucose-Restricted Conditions.

Caldorazole (1) was isolated from the marine cyanobacterium Caldora sp. collected on Ishigaki Island, Okinawa, Japan. Its structure was determined to be a new polyketide that contained two thiazole rings and an O-methylenolpyruvamide moiety. Caldorazole (1) showed strong cytotoxicity toward tumor cells that had been seeded at a high density. Cell death induced by 1 in HeLa and A431 cells was also observed only in the presence of the glycolysis blocker 2-deoxy-d-glucose (2DG). Co-treatment with 1 and 2DG remarkably decreased ATP levels in these cells. Furthermore, 1 selectively inhibited complex I in the mitochondrial respiratory chain. Thus, 1 was demonstrated to exert cytotoxicity toward human tumor cells by blocking mitochondrial respiration.

Isolation and Total Synthesis of Beru'amide, an Antitrypanosomal Polyketide from a Marine Cyanobacterium Okeania sp.

A 68 µg amount of an acyclic polyketide, named beru'amide, was isolated from a marine cyanobacterium Okeania sp. Beru'amide contains six unique moieties in its relatively small skeleton. By applying several cutting-edge techniques, including DFT-based chemical shift calculations, we achieved the structure determination and the total synthesis of this highly functionalized scarce natural product. Furthermore, beru'amide was shown to have strong antitrypanosomal activity.

Structural Determination, Total Synthesis, and Biological Activity of Iezoside, a Highly Potent Ca2+-ATPase Inhibitor from the Marine Cyanobacterium Leptochromothrix valpauliae.

Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is a membrane protein on the endoplasmic reticulum (ER) that transports Ca2+ from the cytosol into the ER. As its function is associated with various biological phenomena, SERCA has been recognized as a promising druggable target. Here, we report the second-strongest SERCA-inhibitory compound known to date, which we isolated from the marine cyanobacterium Leptochromothrix valpauliae and named iezoside (1). The structure of iezoside (1) is fundamentally different from that of any other SERCA inhibitor, and its potency is the strongest among marine natural products (Ki 7.1 nM). In this article, we report our comprehensive analysis of iezoside (1), which covers its isolation, structural characterization supported by density functional theory (DFT) calculations and statistical analysis, total synthesis, and clarification of the mode of action of its potent antiproliferative activity (IC50 6.7 ± 0.4 nM against HeLa cells).

Targeted Discovery of Amantamide B, an Ion Channel Modulating Nonapeptide from a South China Sea Oscillatoria Cyanobacterium.

Amantamide B (1) is a new linear nonapeptide analogue of the cyanobacterial natural product amantamide A (2), and both have methyl ester and butanamide termini. These compounds were discovered in this study from the organic extract of a tropical marine filamentous cyanobacterium, Oscillatoria sp., collected around the Paracel Islands in the South China Sea. The use of LC-MS/MS molecular networking for sample prioritization and as an analytical dereplication tool facilitated the targeted isolation of 1 and 2. These molecules were characterized by spectroscopy and spectrometry, and configurational assignments were determined using chemical degradation and chiral-phase HPLC analysis. Compounds 1 and 2 modulated spontaneous calcium oscillations without notable cytotoxicity at 10 µM in short duration in vitro testing on primary cultured neocortical neurons, a model system that evaluates neuronal excitability and/or the potential activity on Ca2+ signaling. Both molecules were also found to be moderately cytotoxic in longer duration bioassays, with in vitro IC50 values of 1-10 µM against CCRF-CEM human T lymphoblastoid cells and U937 human histiocytic lymphoma cells. These formerly undiscovered bioactivities of known compound 2 expand upon its previously reported function as a selective CXCR7 agonist among 168 GPCR targets.