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From an extract of the red alga Symphyocladia latiuscula, a bromophenol (1) was isolated and characterized as (2R)-2-(2,3, 6-tribromo-4,5-dihydroxybenzyl)-cyclohexanone based on the spectroscopic evidence. The bromophenol was found to be a scavenger of 1,1-diphenyl-2-picrylhydrazyl radical.
The organic extract of the red alga Sphaerococcus coronopifolius, collected along the Atlantic coast of Morocco, was tested for biological activities and exhibited antibiotic and antimalarial activities. Two new bromoditerpenes have been isolated from S. coronopifolius, sphaerolabdadiene-3,14-diol (1) and bromosphaerone (2), along with the known compounds 12S-hydroxybromosphaerodiol (3) and sphaerococcenol A (4). Bromosphaerone and 12S-hydroxybromosphaerodiol showed antibacterial activity against the Gram-positive bacterium species Staphylococcus aureus with a minimum inhibitory concentration of 0.104 and 0.146 microM, respectively. Sphaerococcenol A (4) was responsible for the antimalarial activity of the extract, against the chloroquine resistant Plasmodium falsciparum FCB1 strains with an IC(50) of 1 microM. Their structures have been assigned using 1 and 2 D NMR and HRMS.
New bisnorditerpenes, hedaols A (1), B (2), and C (3), were isolated from the Japanese brown alga Sargassum sp. Their structures were determined by spectroscopic analysis. The absolute stereocenter of 1 was determined by the modified Mosher's method. Hedaols showed low cytotoxicity against P388 cells.
Eleven sesquiterpenes (1-11) and one long chain aldehyde (12) have been isolated from the dichloromethane extract of the red alga Laurencia scoparia. Four of them are new natural products. Scopariol (1) is a new natural product with an unusual rearranged chamigrane-type structure. The other three are beta-chamigrenes: isorigidol (2), (+)-3-(Z)-bromomethylidene-10 beta-bromo-beta-chamigrene (3), and (-)-3-(E)-bromomethylidene-10 beta-bromo-beta-chamigrene (4). The in vitro activity of compounds 1-12 against the parasitant stage of Nippostrongylus brasiliensis (L4) has been studied.
Seven carotenoid metabolites including five loliolide derivatives have been isolated from the brown alga Undaria pinnatifida, including three new compounds. Structures of these compounds were confirmed by spectroscopic analyses and literature data.
The Indonesian red alga Vidalia sp. was identified as a candidate for fractionation because its crude lipid extract showed activity in a mechanism-based anticancer assay (Fyn SH2-inhibitory activity). A chemically novel phenolic metabolite, vidalenolone, as well as two previously described and structurally simple phenols, were isolated as SH2-inactive substances. Their structures were determined by an interplay of spectroscopic methods, principally 2D NMR, and reference to literature data.
Six new prenylated bromohydroquinones, 3'-methoxy-7-hydroxycymopol (1), 3-hydroxycymopolone (2), 3,7-dihydroxycymopolone (3), 7-hydroxycymopochromanone (4), 7-hydroxycymopochromenol (5), and a related 6-hydroxy derivative of cymopochromenol (6), have been isolated from the green marine alga Cymopolia barbata. The structures of these cymopol-related metabolites were determined by spectral methods.
The red alga Laurencia brongniartii and brittle star Ophiocoma erinaceus metabolites 2,3,6-tribromo-1-methylindole (1) and 2,3,5,6-tetrabromo-1-methylindole (2) are easily synthesized selectively from 2,3-dibromo-1-methylindole (5), which in turn is prepared from indole (3) in one continuous sequence in 92% yield. Moreover, 2 can be made from both 1 and 5 in 67% and 65% yields, respectively.
Three new terpenoids, 1a-3a, and the known metabolites atomaric acid, stypoquinonic acid, and 5'a-desmethyl-5'-acetylatomaric acid have been isolated from the tropical brown alga Stypopodium zonale. The structures and relative stereochemistry of the methyl ester of 1a-3a were determined by spectral methods. The methyl ester of 3a exhibits in vitro cytotoxic activity against human lung and colon carcinoma.
Sixteen secondary metabolites of the green alga Caulerpa prolifera have been isolated, and their chemical structures elucidated by analysis of their spectroscopic data. Two groups of metabolites have been established, with either a 1,2-dihydro- (2a-2i) or a 1,2,3,3'-tetrahydro-2,3-didehydro (3a-3f) caulerpenyne carbon backbone. The terminal vinyl acetoxy group of caulerpenyne was substituted by various fatty acid residues. The antifouling activity of the algal extract was tested in laboratory assays against two of the major groups of fouling organisms (bacteria, microalgae).
From the lipophilic extract of the red alga Laurencia perforata three new sesquiterpenes, (1S,2S,4S,5S, 6S,8R)-4-hydroxy-2,5,6-trimethyl-11-methylenetricyclo[6.2.1.0(1,6)]undecan-3-one (1, 4-hydroxy-1,8-epi-isotenerone), (3R,4R,4aR,9R)-3,9-dihydroxy-1,4,4a,7-tetramethyl-3,4,4a,5,8,9-hexahydro-2H-benzo[a]cyclohepten-2-one (9-hydroxy-3-epi-perforenone A, 2), and 3-epi-perforenone A (3), were isolated. The structures of all isolates were determined from their spectroscopic data (NMR, MS, IR, UV). Unusual for a species of this algal genus was the apparent absence of halogenated compounds.
Six new bromophenols, 3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)pyrocatechol (1), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-hydroxymethyldiphenylmethane (2), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-ethyloxymethyldiphenylmethane (3), (+/-)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde (4), (+/-)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde dimethyl acetal (5), and 3-bromo-4,5-dihydroxybenzoic acid methyl ester (6), together with eight known bromophenols, 3-bromo-4,5-dihydroxybenzaldehyde (7), 2,3-dibromo-4,5-dihydroxybenzyl alcohol (lanosol, 8), 2,3-dibromo-4,5-dihydroxybenzyl methyl ether (9), 2,3-dibromo-4,5-dihydroxybenzyl ethyl ether (10), 2,3-dibromo-4,5-dihydroxybenzylaldehyde (11), bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (12), 3-bromo-4-(2,3-dibromo-4,5-dihydroxybenzyl)-5-methoxymethylpyrocatechol (13), and 2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenyl methane (14), were isolated from the red alga Rhodomela confervoides. Their structures were elucidated by chemical and spectroscopic methods including IR, HRFABMS, and 1D and 2D NMR techniques.
Field collections of the red macroalgae Ochtodes secundiramea and Portieria hornemannii exhibit site-to-site variations in halogenated monoterpene (HMT) content. In contrast, microplantlets of O. secundiramea and P. hornemannii established through cell and tissue culture techniques had remarkably similar HMT profiles when cultivated in a photobioreactor under identical, controlled conditions. Both algae shared Apakaochtodene B (6) as the only cyclic HMT, 10E-bromomyrcene (3) and 10E-bromo-3-chloro-alpha-myrcene (4) as the dominant acyclic HMTs, and myrcene (1) as their common precursor. Furthermore, HMT yields were comparable between organisms (0.9-1.3 micromol/g dry mass of 6; 3.4-4.4 micromol/g of 3). P. hornemannii microplantlets also contained 7-chloromyrcene (9) as the dominant compound (37-73 micromol/g), suggesting additional chlorination capacity. Proposed pathways for HMT biosynthesis shared by P. hornemannii and O. secundiramea microplantlets possessed two common manifolds: (a) bromonium ion (Br(+))-catalyzed cyclization of 1, followed by chlorination to yield 6; (b) Markovnikov addition of Br(+) at Delta(6,10) of 1 to yield 3 with a marked selectivity (>50:1) for the E isomer, followed by chlorination of 3 to 4. This study demonstrated that bioreactor tissue culture is a new venue for bioprospecting and production of natural compounds from marine macroalgae under a controlled environment.
Nine novel oxylipin metabolites together with several known ones were isolated from the brown alga Eisenia bicyclis. Five (1-5) of them are ecklonialactone derivatives containing a chlorine or an iodine atom, and two (6 and 7) are cymathere type oxylipins with a lactone ring or a chlorine atom. The structures of these oxylipin metabolites were confirmed by NMR and mass spectroscopy and compared with spectral data in the literature. The postulated biosynthetic pathway of these metabolites is discussed.
Six new tetraprenyltoluquinol derivatives (1-6), two new triprenyltoluquinol derivatives (7 and 8), and two new tetraprenyltoluquinone derivatives (9 and 10) were isolated from the brown alga Cystoseira crinita Duby together with four known tetraprenyltoluquinol derivatives (11-14). All structures were elucidated by employing spectroscopic techniques (NMR, MS, UV, and IR). Each compound was evaluated for its antioxidative properties in the TBARS and DPPH assay, and compounds 1, 2, 6, and 10-14 were additionally assessed in the TEAC and PCL assay. Hydroquinones were found to have powerful antioxidant activity.
Five new meroditerpenes have been isolated from a brown alga of the genus Cystoseira collected around the Canary Islands. One, cystoseirone diacetate (3), possesses a new rearranged structure with an unusual ether linkage in the diterpene side chain. Its biogenetic origin was explained as derived from the oxidation of amentol chromane diacetate (2) and subsequent cyclization. Structures were determined through the interpretation of the spectral data and by means of chemical transformations. The relative stereochemistry was proposed on the basis of ROESY correlations.
Two labdane type brominated diterpenes (1 and 2) containing unprecedented eight- and seven-membered ether rings have been isolated from the organic extract of the red alga Laurencia obtusa, collected from Mitikas Bay in the Ionean Sea, Greece. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analysis, including 2D NMR experiments.
Three compounds containing moieties rarely encountered in nature, viz., 3-nonyloxirane-2 carboxylic acid methyl ester (1), 2-chlorododec-2-en-1-ol (2), and 2-chlorododec-2,11-dien-1-ol (3), were isolated from the red alga Gracilaria verrucosa, and their structures were determined by spectroscopic methods.