Abstract
Thirteen new and eighteen known natural products were isolated from a bloom material of an assembly of various Microcystis spp. collected in November, 2008, from a commercial fishpond near Kibbutz Kfar Blum, the Jordan Valley, Israel. The new natural products included the prenylated aeruginosin KB676 (1), microphycin KB921 (2), anabaenopeptins KB906 (3) and KB899 (4) and micropeptins KB928 (5), KB956 (6), KB970A (7), KB970B (8), KB984 (9), KB970C (10), KB1048 (11), KB992 (12) and KB1046 (13). Their structures were elucidated primarily by interpretation of their 1D and 2D nuclear magnetic resonance spectra and high-resolution mass spectrometry. Marfey’s and chiral-phase high performance liquid chromatography methods were used to determine the absolute configurations of their chiral centers. Aeruginosin KB676 (1) contains the rare (2S,3aS,6S,7aS)-Choi and is the first prenylated aeruginosin derivative described in the literature. Compounds 1 and 5–11 inhibited trypsin with sub-μM IC50s, while Compounds 11–13 inhibited chymotrypsin with sub-μM IC50s. The structures and biological activities of the new natural products and our procedures of dereplication are described.
Highlights
Cyanobacterial water blooms are initiated from dormant cells under appropriate environmental conditions, which develop into a stable population of different biomass intensities and toxin content, which eventually collapses, disintegrates and discharges toxins to the water environment [1]
As part of our continuous interest in the pharmacological properties and the ecological role of cyanobacterial natural products [11], we chemically investigated the extracts of a bloom material composed of an assembly of Microcystis spp. collected in November, 2008, from a commercial fishpond near Kibbutz Kfar Blum, the Jordan Valley, Israel
Dereplication and verification of the purity of the isolated natural products was achieved by running liquid chromatography mass spectrometry (LCMS) and nuclear magnetic resonance (NMR) spectra on each one of the isolated compounds
Summary
Cyanobacterial water blooms are initiated from dormant cells under appropriate environmental conditions, which develop into a stable population of different biomass intensities and toxin content, which eventually collapses, disintegrates and discharges toxins to the water environment [1]. These blooms are frequently described as a single-species phenomenon. Recent studies have suggested that microcystins are involved in quorum sensing and might be produced to manage cyanobacterial colonies in the environment [8] and not necessarily produced for their toxic effects
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