Algicidal diterpenes from the brown alga Dictyota dichotoma

Bioassay-guided fractionation of an ethanol extract of the brown alga, Dictyota dichotoma, led to the isolation of a novel chlorine-containing perhydroazulene diterpene together with two known diterpenes, dictyolactone and sanadaol. The structure of the novel compound, named dictyol J, was elucidated on the basis of spectroscopic information. Dictyolactone showed the highest algicidal activity against red-tide phytoplanktons among the three isolated compounds.     

Cytotoxic hydroazulene diterpenes from the brown alga Cystoseira myrica

Cytotoxicity-guided fractionation of the alcohol extract of the brown alga, Cystoseira myrica, afforded four new cytotoxic hydroazulene diterpenes, dictyone acetate (2), dictyol F monoacetate (4), isodictytriol monoacetate (6), and cystoseirol monoacetate (8), together with two known cytotoxic hydroazulene diterpenes, pachydictyol A (1) and dictyone (3). The constitution of each isolated compound has been determined on the basis of spectroscopic and chemical evidence.     

Diterpenes from the Far-eastern brown alga Dictyota dichotoma

Two diterpenes, ent-erogorgiaene and (+)-1,5-cyclo-5,8,9,10-tetrahydroerogorgiaene, were isolated from the Russian Far-eastern population of the brown alga Dictyota dichotoma along with three previously known from this alga terpenoids. In addition, pentadecane was the first time isolated as natural product from this species. The structures of all compounds and their stereochemistry were determined using 1D and 2D NMR ((1)H-(1)H COSY, DEPT, HSQC, HMBC and NOESY), mass spectrometry, and optical rotation data.     

The plastome of a brown alga,Dictyota dichotoma

Summary Plastids of the brown algaDictyota dichotoma contain a single homogeneous DNA species which bands at a buoyant density of 1.693 g/cm³ in neutral CsCl equilibrium density gradients. The corresponding nuclear DNA has a density of 1.715 g/cm³. The molecular size of the plastid DNA is 123 kbp as calculated by both electron microscopy of spread intact circular molecules and gel electrophoresis following single and double digestions with various restriction enzymes. A restriction map has been constructed using the endonucleases Sal I, Bam HI, and Bgl II which cleave theDictyota plastome into 6, 12, and 17 fragments, respectively. No large repeated regions, as found in chlorophycean andEuglena plastid DNAs, were detected.Dictyota dichotoma is the first member from the chlorophyll c-line of the algal pedigree for which a physical map of plastid DNA has been established. Dedicated to Professor Dr. W. Stubbe on the occasion of his 65th birthday.     

Diterpenes from the brown algae Dictyota dichotoma and Dictyota linearis

Nineteen secondary metabolites of the brown alga Dictyota dichotoma (Huds.) Lam. and fifteen metabolites of the brown alga D. linearis (Ag.) Grev. were isolated and their chemical structures were elucidated on the basis of their NMR and mass spectral data. The diterpenes isopachydictyolal (1) from D. dichotoma and 4alpha-acetyldictyodial (2) from D. linearis are new natural products. The antiviral activity of metabolites isolated in adequate amounts was evaluated in laboratory assays against Herpes simplex virus I (HSV I) and Poliomyelitis Virus I, using Vero cells as hosts.     

Diterpenes from the brown alga Dictyota mertensii

Here we report the variation of diterpenes from three populations of the brown alga Dictyota mertensii. The populations were analyzed by ¹H NMR and GC-MS techniques. Both chemical GC-MS and ¹H NMR profiles of D. mertensii presented diterpenes as major constituents. In all populations, we detected the prenylated guaiane diterpenes, dictyoxide, pachydictyol A, isopachydictyol A, dictyol B and its acetate, and dictyol C. Although dictyol H has been described as a taxonomic marker, this diterpene was found in only two of the three studied populations. This result reinforces the need for studies of temporal and geographic variation for the establishment of the taxonomic limits of the species chemical patterns. It was also possible to observe mass spectra fragmentation and proton chemical shift in the NMR spectra characteristic from xeniane diterpenes, for the first time in this species, which led to the detection of dictyodial, suggesting that D. mertensii belongs to the chemotaxonomic group of species D. ciliolata, D. jamaicensis, and D. menstrualis, all of which are producers of diterpene from chemical groups I and III.     

Ultrastructural study of plasmodesmata in the brown alga Dictyota dichotoma (Dictyotales, Phaeophyceae)

Plasmodesmata are intercellular bridges that directly connect the cytoplasm of neighboring cells and play a crucial role in cell-to-cell communication and cell development in multicellular plants. Although brown algae (Phaeophyceae, Heterokontophyta) are phylogenetically distant to land plants, they nevertheless possess a complex multicellular organization that includes plasmodesmata. In this study, the ultrastructure and formation of plasmodesmata in the brown alga Dictyota dichotoma were studied using transmission electron microscopy and electron tomography with rapid freezing and freeze substitution. D. dichotoma possesses plasma membrane-lined, simple plasmodesmata without internal endoplasmic reticulum (desmotubule). This structure differs from those in land plants. Plasmodesmata were clustered in regions with thin cell walls and formed pit fields. Fine proteinaceous "internal bridges" were observed in the cavity. Ultrastructural observations of cytokinesis in D. dichotoma showed that plasmodesmata formation began at an early stage of cell division with the formation of tubular pre-plasmodesmata within membranous sacs of the cytokinetic diaphragm. Clusters of pre-plasmodesmata formed the future pit field. As cytokinesis proceeded, electron-dense material extended from the outer surface of the mid region of the pre-plasmodesmata and finally formed the nascent cell wall. From these results, we suggest that pre-plasmodesmata are associated with cell wall development during cytokinesis in D. dichotoma.     

Trihydroxylated linear diterpenes from the brown alga Bifurcaria bifurcata

Two novel polar diterpenes were isolated from the brown alga Bifurcaria bifurcata collected off the Atlantic coast of Morocco, and their structures established by spectral methods. Both compounds are trihydroxylated acyclic diterpenes derived from 12-hydroxygeranylgeraniol. They were tested in vitro for their cytotoxicity and proved to be active against the NSCLC-N6 cell line. Their absolute configuration at the C-12 position has been determined with a modified Mosher's method [J. Am. Chem. Soc. 113 (1991) 4092] and that of the 12-hydroxygeranylgeraniol (bifurcadiol) has been revised.     

Novel acyclic diterpenes from the brown alga Cystoseira crinita

Three acyclic diterpenes have been isolated from the brown alga Cystoseira crinita and characterized as (2E,10E)-1,6-dihydroxy-7-methylene-13-keto-3,11,15-trimethylhexadeca-2,10,14-triene, (2E,5E,10E)-1,7-dihydroxy-13-keto-3,7,11,15-tetramethylhexadeca-2,6,10,14-tetracne and (2E, 1OE)-1-hydroxy-6,13-diketo-7-methylene-3,11,15-trimethylhexadeca-2,10,14-triene.     

Linear diterpenes from the marine brown alga Bifurcaria bifurcata: a chemical perspective

This article will give a complete overview of linear diterpenes isolated from the brown alga Bifurcaria bifurcata. For this purpose all published acyclic diterpenoids are listed and gathered in three main biosynthetic families with respect to their structural similarities. These are the C-12 oxidized (e.g. eleganediol), the C-13 oxidized (e.g. eleganolone), and the direct geranylgeraniol derivatives. The origin and plausible biosynthesis of all compounds are discussed. Additionally, the issues concerning the configurational assignment such as the configuration of trisubstituted double bonds and the configuration of oxidized stereogenic centers are pointed out. Special emphasis is also given on synthesis, biological activities (cytotoxic, antimicrobial, and antifouling activities), chemotaxonomy, and ecology of the compounds.     

(S)-12-hydroxygeranylgeraniol-derived diterpenes from the brown alga Bifurcaria bifurcata

Four novel diterpenes were isolated from the brown alga Bifurcaria bifurcata collected off the Atlantic coast from Morocco, and their structures established by spectral and chemical methods. These compounds are acyclic diterpenes derived from (S)-12-hydroxygeranylgeraniol. One of them is its dehydration product at C-12, while the others are its oxidation derivatives: the methyl ester of the acid at C-1 and two stereoisomers (Z and E) of the aldehyde at C-1. These results are discussed from a chemotaxonomic point of view.     

Rhizoid production in excised Dictyota dichotoma

Excised segments of fronds of Dictyota dichotoma (Huds.) Lamour. show a marked basipetal increase in rhizoid production when grown in culture. Rhizoid production is inhibited by bright light and apparently enhanced by red light (λ 600–690 mμ).     

Two minor diterpenes related to dictyodial A from the brown alga Dictyota crenulata

4β-Hydroxydictyodial A and 18,O-dihydro-4β-hydroxydictyodial A 18-acetate are two minor aldehydic diterpenes in the brown alga Dictyota crenulata. ¹H NMR and lanthanide-induced chemical shift studies indicate that the relative stereochemistry of both compounds is 2R*, 3R*, 4S*, 10S*.     

The aqueous extract and powder of the brown alga Dictyota dichotoma (Hudson) differentially alleviate the impact of abiotic stress on rice (Oryza sativa L.)

Physiology and Molecular Biology of Plants - Algal supplements can improve crop productivity and afford protection against abiotic stress by virtue of their rich content of plant nutrients and...