Three diterpene-benzoate natural products, with novel carbon skeletons and an unusual proposed biosynthesis, were isolated from extracts of the Fijian red alga Callophycus serratus and identified by a combination of X-ray crystallographic, NMR, and mass spectral analyses. Bromophycolide A (1) displayed cytotoxicity against several human tumor cell lines via specific apoptotic cell death. This represents the first discovery of natural products incorporating a diterpene and benzoate skeleton into a macrolide system.The discovery of novel carbon skeletons in natural products research is uncommon, providing new targets for synthetic chemists and pharmacologists, and leading to testable hypotheses regarding biosynthetic mechanisms and ecological function. Red macroalgae are well-known for the production of brominated metabolites, including terpenoids and phenols, yet some taxa within the Rhodophyta remain relatively unstudied. Only six secondary metabolites, one oxylipin and five bromophenols, have been previously characterized from the red algal family Solieriaceae. 1,2 Herein, we report the discovery of a unique structural class of macrolides from Callophycus serratus, an understudied member of the Solieriaceae.We used bioassay-guided fractionation followed by spectroscopic and X-ray crystallographic analyses to identify three novel natural products (1-3) of unusual biosynthetic origin and possessing promising antineoplastic and antimicrobial activities. Supporting Information Available: Additional acknowledgments, experimental details, 2D NMR data (COSY, HSQC, HMBC, NOESY, ROESY), 1 H NMR spectra for 1-3, and X-ray crystallographic data (tables and CIF files) for 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org. The most abundant natural product from C. serratus, bromophycolide A (1), displayed an [M -H] − molecular ion with m/z 661.0194 and characteristic tribrominated isotopic pattern, suitable for a molecular formula of C 27 H 37 O 4 Br 3 . X-ray diffraction analysis of 1 revealed a 15-membered macrolide within a diterpene-benzoate framework (Figures 1 and 2). The bromine atom within the isopropyl appendage was disordered with respect to the isopropyl methyls over two primary positions, with 70% and 30% occupancies. The Flack parameter was refined to be −0.002(16), indicating that the geometry shown is the absolute configuration. NIH Public AccessThe NMR spectral data of 1 supported the structure derived from X-ray diffraction analysis (Table 1; Supporting Information). HMBC correlations from the methyl groups anchored the carbon skeleton, enabling assignments of all quaternary carbons. COSY and additional HMBC correlations provided the connectivity within spin systems (Supporting Information).From high-resolution mass spectral data, bromophycolide B (2) appeared to be an isomer of 1, with a parent ion with m/z 661.0191. X-ray diffraction analysis of 2 indicated a 16-membered macrolide with absolute stereochemistry predicted as in Figures 1 and 2. Chemical shift...

Chromophoric (or colored) dissolved organic matter (CDOM) has been identified as a major determinant of the optical properties of oligotrophic oceans. The factors controlling distribution of CDOM far from the direct influence of land are not well known, as CDOM abundance and distribution does not directly correlate with phytoplankton productivity or biomass, or with dissolved organic matter (DOM) concentration. As part of a larger study of the dynamics of CDOM in the open ocean, we investigated direct release from plankton as a factor contributing to distribution patterns of CDOM. We measured the production of CDOM by zooplankton (copepods, euphausiids, amphipods, salps, polychaetes), protozoans (colonial radiolaria), and by the colonial cyanobacterium Trichodesmium spp. in the North Atlantic subtropical gyre. Groups of individual species of plankton were incubated and absorption spectra were obtained for their release products. CDOM was produced by all organisms examined, and absorption spectra varied by taxa, with major taxa exhibiting characteristic absorption peaks. Plankton-produced DOM is a source of labile carbon and thus facilitates microbial activity, and CDOM may also serve as photoprotection for near-surface-living organisms. Zooplankton likely play an important role in the CDOM cycle in the Sargasso Sea, directly through release/excretion of CDOM and indirectly by providing a labile substrate (excretia) for microbial-mediated production of CDOM.KEY WORDS: Zooplankton · Trichodesmium · Chromophoric dissolved organic matter · CDOM · Excretion · Sargasso Sea · North AtlanticResale or republication not permitted without written consent of the publisher

Bromophycolides C-I (1−7) were isolated from extracts of the Fijian red alga Callophycus serratus, and identified by NMR and mass spectral techniques. These novel natural products share a carbon skeleton and biosynthetic origin with previously identified bromophycolides A (8) and B (9), which form a rare group of diterpene-benzoate macrolides. Bromophycolides C-I (1−7) displayed modest antineoplastic activity against a range of human tumor cell lines.Marine red algae have been the source of numerous isoprenoid and phenolic metabolites, 1 although natural products of combined isoprenoid and shikimate biosynthetic origin are less common. As part of a continuing investigation of bioactive substances from Fijian coral reef organisms, we recently reported the identification of three structurally unusual diterpenebenzoate macrolides from the red alga Callophycus serratus. 2 Herein, we provide data in support of the identification of seven related compounds, bromophycolides C-F (1−7), whose structures were elucidated by NMR and mass spectral analyses and by comparison with previously isolated bromophycolides A-B (8−9) and debromophycolide A (10). Results and discussionGuided by a toxicity assay using ingestion rates of the invertebrate Brachionus calyciflorus (Rotifera), 3 extracts of Callophycus serratus were separated by liquid-liquid partitioning, reversed-phase HPLC, and normal-phase HPLC, yielding bromophycolides C-I (1−7), which each represented 0.027−0.092% of algal dry mass (see Experimental section for details).Bromophycolide C (1), with an ESI molecular ion of m/z 599.1010 suitable for molecular formula C 27 H 38 O 5 Br 2 , appeared to differ from previously identified bromophycolide A (8) 2 only by the substitution of a bromine for a hydroxyl group. Comparison of NMR spectral data for 1 (Table 1 ; Supporting information) and for 8 2 suggested that the sole difference lay near the diterpene head. Specifically, the resonance for C-15 of 8 occurred at δ 67.3, compared with δ 72.0 in 1. Position 14, curiously, was not greatly affected ( 13 C δ 81.7 vs. 80.4; 1 H δ 4.75 vs. 4.65, for 1 and 8, respectively), but 13 C chemical shifts for positions 13, 26, and 27 in 1 were *To whom correspondence should be addressed: telephone: 404−894−8424; fax: 404−385−4440; email: julia.kubanek@biology.gatech.edu. Supporting Information Available: COSY, HMBC, and NOE data, and 1 H NMR spectra for 1−7, available free of charge via the Internet at http://pubs.acs.org. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript 2−7 ppm downfield relative to these positions in 8. All other 13 C and 1 H chemical shifts for 1 and 8 were within ca. 1 ppm. 1 H-1 H scalar couplings were also very similar for 1 and 8, suggesting that their relative configurations did not differ. In particular, H-14 appeared as a doublet of doublets (J=2 and 11 Hz) for both 1 and 8, establishing a common dihedral relationship to the two H-13 protons, consistent with the 14S configuration previously confirmed by the X...

Callophycoic acids A-H (1-8) and callophycols A and B (9 and 10) were isolated from extracts of the Fijian red alga Callophycus serratus, and identified by NMR, X-ray, and mass spectral analyses. These natural products represent four novel carbon skeletons, providing the first examples of diterpene-benzoic acids and diterpene-phenols in macroalgae. Compounds 1-10 exhibited antibacterial, antimalarial, and anticancer activity, although they are less bioactive than diterpene-benzoate macrolides previously isolated from this red alga.

Although macrophyte herbivore interactions in freshwater systems were generally disregarded for many years, recent data suggest that herbivory can be intense and important in structuring freshwater communities. This has led to the hypothesis that chemical defenses should be common among freshwater plants, but few studies have reported such chemical defenses, and no previous studies have assessed the frequency of chemical defenses among a substantial number of freshwater plant species. In a study of 21 macrophyte species co-occurring with the omnivorous crayfish Procambarus acutus in a southeastern USA wetland environment, we found that extracts of 11 species (52%) deterred feeding by P. acutus when tested in artificial foods at natural concentrations. Of these 11 chemically defended species, one species, Eupatorium capillifolium, consistently had a more unpalatable extract following mechanical damage to plant tissue, indicative of an activated chemical defense. Because herbivores are commonly nitrogen-limited and select food based on several plant traits, including plant nutritional value, it might be expected that chemical defenses would be especially important for protein-rich plants. However, we found no relationship between soluble protein concentration and deterrence of plant extracts.

Terpenes U 0200Antineoplastic Diterpene-Benzoate Macrolides from the Fijian Red Alga Callophycus serratus. -Preliminary tests of bromophycolides A (I), B (II) and debromophycolide A (III) reveal moderate to low cytotoxicity. Furthermore, antibacterial effects are observed for (I) and (II) and anti-HIV activity for (I). -(KUBANEK*, J.; PRUSAK, A. C.; SNELL, T. W.; GIESE, R. A.; HARDCASTLE, K. I.; FAIRCHILD, C. R.; AALBERSBERG, W.; RAVENTOS-SUAREZ, C.; HAY, M. E.; Org. Lett. 7 (2005) 23, 5261-5264; Ga. Inst. Technol., Sch. Biol., Atlanta, GA 30322, USA; Eng.) -R. Steudel 13-188

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