Amoxetamide A, a new anoikis inducer, produced by combined-culture of Amycolatopsis sp. and Tsukamurella pulmonis

Cancer cells including colorectal cancer cells are resistant to anoikis, an anchorage-independent programmed death, which enables metastasis and subsequent survival in a new tumor microenvironment. In this study, we identified a new anoikis inducer, amoxetamide A (1) with a β-lactone moiety, that was produced by combined-culture of Amycolatopsis sp. 26-4 and mycolic acid-containing bacteria (MACB) Tsukamurella pulmonis TP-B0596. The structure of 1 including the stereochemistry of C8 was determined by MS and NMR spectroscopy and modified Mosher's method, and the absolute configurations of C11 and C12 were suggested as 11R and 12S, respectively, by GIAO NMR calculations. Amoxetamide A (1) exhibited anoikis-inducing activity in human colorectal cancer HT-29 cells in anchorage-independent culture conditions.

Marine natural products targeting the eukaryotic cell membrane

The cell membrane, with high fluidity and alternative curvatures, maintains the robust integrity to distinguish inner and outer space of cells or organelles. Lipids are the main components of the cell membrane, but their functions are largely unknown. Even the visualization of lipids is not straightforward since modification of lipids often hampers its correct physical properties. Many natural products target cell membranes, some of which are used as pharmaceuticals and/or research tools. They show specific recognition on lipids, and thus exhibit desired pharmacological effects and unique biological phenotypes. This review is a catalog of marine natural products that target eukaryotic cell membranes. Chemical structures, biological activities, and molecular mechanisms are summarized. I hope that this review will be helpful for readers to notice the potential of marine natural products in the exploration of the function of lipids and the druggability of eukaryotic cell membranes.

Self-Assembled 2,3-Dicyanopyrazino Phenanthrene Aggregates as a Visible-Light Photocatalyst

In this study, 2,3-dicyanopyrazino phenanthrene (DCPP), a commodity chemical that can be prepared at an industrial scale, was used as a photocatalyst in lieu of Ru or Ir complexes in C-X (X = C, N, and O) bond-forming reactions under visible-light irradiation. In these reactions, [DCPP]_n aggregates were formed in situ through physical π-π stacking of DCPP monomers in organic solvents. These aggregates exhibited excellent photo- and electrochemical properties, including a visible light response (430 nm), long excited-state lifetime (19.3 μs), high excited-state reduction potential (E_red([DCPP]_n*/[DCPP]_n^·-) = +2.10 V vs SCE), and good reduction stability. The applications of [DCPP]_n aggregates as a versatile visible-light photocatalyst were demonstrated in decarboxylative C-C cross-coupling, amidation, and esterification reactions.

Longicatenamides A-D, Two Diastereomeric Pairs of Cyclic Hexapeptides Produced by Combined-culture of Streptomyces sp. KUSC_F05 and Tsukamurella pulmonis TP-B0596

Longicatenamides A-D, two diastereomeric pairs of new cyclic hexapeptides, were isolated from the combined-culture of Streptomyces sp. KUSC_F05 and Tsukamurella pulmonis TP-B0596. Their planar structures were determined by spectroscopic analysis including extensive 2D NMR and MS analysis. The absolute configurations of their component amino acids were determined by the use of highly sensitive reagents we recently developed; the highly sensitive-advanced Marfey's method (HS-advanced Marfey's method), which led us to reduce the sample loss and prevent incorrect structural determination. Particularly, the C_β-stereochemistry of hyGlu in longicatenamides A and C was assigned without any use of C_β-Marfey's methods. Longicatenamide A exhibited weak but preferential antimicrobial activity against Bacillus subtilis.

Chemical diversity and mode of action of natural products targeting lipids in the eukaryotic cell membrane

Covering: up to 2019Nature furnishes bioactive compounds (natural products) with complex chemical structures, yet with simple, sophisticated molecular mechanisms. When natural products exhibit their activities in cells or bodies, they first have to bind or react with a target molecule in/on the cell. The cell membrane is a major target for bioactive compounds. Recently, our understanding of the molecular mechanism of interactions between natural products and membrane lipids progressed with the aid of newly-developed analytical methods. New technology reconnects old compounds with membrane lipids, while new membrane-targeting molecules are being discovered through the screening for antimicrobial potential of natural products. This review article focuses on natural products that bind to eukaryotic membrane lipids, and includes clinically important molecules and key research tools. The chemical diversity of membrane-targeting natural products and the molecular basis of lipid recognition are described. The history of how their mechanism was unveiled, and how these natural products are used in research are also mentioned.