The Absolute Configuration of Ecklonialactones A, B, and E, Novel Oxylipins from Brown Algae of the Genera Ecklonia and Egregia

Abstract

Ecklonialactones A, B, and E, previously isolated from the brown alga Ecklonia stolonifera, have been isolated from the Oregon phaeophyte Egregia menziesii. The structure and relative stereochemistry of ecklonialactone E were independently determined by various nmr techniques. The absolute stereochemistry of ecklonialactone A was deduced by cd analysis of a dibenzoate derivative, which indicated it possessed a 11S, 12R, 13S, 15R, 16S stereochemistry. Similar 1H- and 13C-nmr data and optical rotations for all of the ecklonialactones indicate that B and E have the same stereochemistry as A at comparable stereocenters.

Epoxy allylic carbocations as conceptual intermediates in the biogenesis of diverse marine oxylipins

“…Interestingly, three of the same tricyclic metabolites previously reported from E. stolonifera were recently isolated by our group from the related Oregon "feather boa" kelp Egregia menziesii (both algae are classified in the order Laminariales) (65). The absolute stereochemistry of the series was established by selective opening of the epoxide at Cl3 in this latter isolate of ecklonialactone A (42), formation of the corresponding bis(p-bromobenzoate), and measurement of a negative exciton chirality in its CD spectrum.…”

“…The Oregon brown kelp E. menziesii was a source of two series of carbocyclic oxylipins which conceivably derive via an intermediate EAC, the ecklonialactones (42-44, see above) (65) and the egregiachlorides (46-48) (32). The structures of the egregiachlorides were assembled from detailed NMR study in concert with the full data sets, and relative stereochemistry was indicated by hOe results and comparison of 13C NMR spectral data with that of the ecklonialactones.…”

Secondary Metabolites from Marine Cyanobacteria and Algae Inhibit LFA-1/ICAM-1 Mediated Cell Adhesion

“…Selected compounds may function as an inhibitor of LFA-1/ICAM-1 binding, expression of ICAM-1, or activation of LFA-1 [4]. On further secondary assay, six compounds, Cymathere aldehyde methyl ester (1), microcolins B (8) and C (9), avrainvilleol (12), cymopol (13) and hormothamnione diacetate (16) inhibited the direct adhesion of HL-60 cells to CHO-ICAM-1 cells through LFA-1/ICAM-1 interaction ( Table 2). Several unusual fatty acid and lipopeptide metabolites (1, 3 ± 6) inhibited cell aggregation without potent cytotoxicity.…”

“…The green algal bromophenol avrainvilleol (12), sesquiterpene cymopol (13) and cryptophyte styrylchromone hormothamnione diacetate (16) contain polyhydroxylated phenolic moieties with lipophilic bromine or methoxylated substituents and all significantly inhibit cell-cell adhesion with similar potency (1.5 ± 2.7 mM). Interestingly, a decrease in the expression of ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) produced by chalcones and other compounds structurally related to 13 ± 16 has been reported [9].…”

“…Reactive oxygen species (ROS) including hydroperoxide and lipid peroxides are thought not only to injure cells but also to induce the expression of ICAM-1 [11]. Recently, we demonstrated the antioxidant effects of avrainvilleol (12), cymopols (13,14), and hormothamnione derivatives (15,16) [12]. Compounds 14 and 15 showed potent antioxidant activity in a solution-based 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) assay.…”