Arihiro Iwasaki

An acetylene-containing lipopeptide, jahanyne, was isolated from the marine cyanobacterium Lyngbya sp. Its gross structure was established by spectroscopic analyses, and the absolute configuration was clarified based on a combination of chiral HPLC analyses, spectroscopic analyses, and derivatization reactions. Jahanyne significantly inhibited the growth of human cancer cells and induced apoptosis in HeLa cells.

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 <i>Leptochromothrix valpauliae</i> and named iezoside (<b>1</b>). The st

Kurahyne, a new acetylene-containing lipopeptide, was isolated from a marine cyanobacterial assemblage that mostly consisted of <italic>Lyngbya</italic> sp. Kurahyne inhibited the growth of human cancer cells and induced apoptosis in HeLa cells, and it seemed to localize in mitochondria.

Hoshinoamides A (1) and B (2), new acyclic lipopeptides, were isolated from the marine cyanobacterium Caldora penicillata. Their structures were elucidated by spectroscopic analyses and degradation reactions. Hoshinoamides A (1) and B (2) did not exhibit any cytotoxicity against HeLa cells at 10 μM, but inhibited the in vitro growth of the malarial parasite Plasmodium falciparum (IC₅₀ = 0.52 and 1.0 μM, respectively).

Abstract Kurahamide, a new dolastatin 13 analog, was isolated from a marine cyanobacterial assemblage, consisting mostly of Lyngbya sp. Its gross structure was elucidated by spectroscopic analysis, and the stereochemistries were assigned based on a chiral HPLC analysis of hydrolysis products. Kurahamide strongly inhibited elastase and chymotrypsin in vitro. In addition, kurahamide moderately inhibited the growth of human cancer cells, including HeLa and HL60 cells.

Kohamamides A, B, and C (1-3), new cyclic depsipeptides that belong to the kulolide superfamily, were isolated from an Okeania sp. marine cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Kohamamide B (2) exhibited moderate cytotoxicity against HL60 cells. Although many natural products in the kulolide superfamily have been isolated from cyanobacteria collected in various parts of the world, kohamamides 1-3 are the first members to be isolated

Biseokeaniamides A, B, and C (1-3), structurally novel sterol O-acyltransferase (SOAT) inhibitors, were isolated from an Okeania sp. marine cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Biseokeaniamide B (2) exhibited moderate cytotoxicity against human HeLa cancer cells, and compounds 1-3 inhibited both SOAT1 and SOAT2, not only at an enzyme level but also at a cellular level. Biseokeaniamides (1-3) are the first linear lipopeptides that h

Hoshinoamide C (<b>1</b>), an antiparasitic lipopeptide, was isolated from the marine cyanobacterium <i>Caldora penicillata</i>. Its planar structure was elucidated by spectral analyses, mainly 2D NMR, and the absolute configurations of the α-amino acid moieties were determined by degradation reactions followed by chiral-phase HPLC analyses. To clarify the absolute configuration of an unusual amino acid moiety, we synthesized two possible diastereomers of hoshinoamide C and determined its absolu

A 68 μg amount of an acyclic polyketide, named beru'amide, was isolated from a marine cyanobacterium <i>Okeania</i> 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.

Mebamamides A and B, new lipopeptides with four d-amino acid residues and a 3,8-dihydroxy-9-methyldecanoic acid residue, were isolated from the green alga Derbesia marina. Their gross structures were elucidated by spectroscopic and ESI-ITMS analyses. The absolute configurations except for the two leucines were revealed based on chiral-phase HPLC analyses of the acid hydrolysate and a modified Mosher's method. A distinction between D-Leu and L-Leu in the sequence was established by the applicatio