Beatriz G. Fleury

Polyphenols, Terpenes and Sterols in Brazilian Dictyotales and Fucales (Phaeophyta)

In this work concentrations of polyphenols (phlorotannins), terpenes and sterols of brown algae were estimated in species of Fucales and Dictyotales and were tested as chemical defence against the amphipod Parhyale hawaiensis. While Fucales show high quantities of sterols, the Dictyotales are rich in terpenes. Both orders were found to be very poor in polyphenols, in contrast with general results reported from temperate regions. A dolastane diterpene from Dictyota cervicornis, Dictyol H from Dictyota mertensii and the steroidal fraction from Sargassum furcatum were not active against the amphipod. In fact these metabolites seemed to some extent to stimulate grazing by the herbivore.

New Hemiketal Steroid from the Introduced Soft Coral Chromonephthea braziliensis is a Chemical Defense against Predatory Fishes

Recent studies show that chemical defenses in the exotic soft coral Chromonephthea braziliensis Ofwegen (Nephtheidae, Alcyonacea) can be one of the reasons for the success of this introduced species. We report for the first time the detailed composition of the monohydroxylated sterol fraction and a new hemiketal steroid, 23-keto-cladiellin-A, isolated from the unpalatable hexane extract from C. braziliensis. Bioassay-guided fractionation of this extract revealed that this hemiketal steroid exhibits potent feeding deterrent properties against a natural assemblage of fishes at the natural concentration. The major sterol fraction, containing the monohydroxylated sterols, was inactive in the bioassay. The results suggest that this active molecule may be driving the observed success of the invasion of this soft coral along the Brazilian Atlantic coast.

CHEMICAL COMPOSITION AND RELEASE IN SITU DUE TO INJURY OF THE INVASIVE CORAL Tubastraea (CNIDARIA, SCLERACTINIA)*

Defensive chemistry may be used against consumers and competitors by invasive species as a strategy for colonization and perpetuation in a new area. There are relatively few studies of negative chemical interactions between scleratinian corals. This study characterizes the secondary metabolites in the invasive corals Tubastraea tagusensis and T. coccinea and relates these to an in situ experiment using a submersible apparatus with Sep-Paks® cartridges to trap substances released by T. tagusensis directly from the sea-water. Colonies of Tubastraea spp were collected in Ilha Grande Bay, RJ, extracted with methanol (MeOH), and the extracts washed with hexane, dichloromethane (DCM) and methanol, and analyzed by GC/MS. Methyl stearate and methyl palmitate were the major components of the hexane and hexane:MeOH fractions, while cholesterol was the most abundant in the DCM and DCM:MeOH fractions from Tubastraea spp. The organic material retained in Sep-Paks® cartridges was tentatively identified as hydrocarbons. There was a significant difference between treatments and controls for 1-hexadecene, n-hexadecane and n-eicosane contents. The production of defensive substances by the invasive corals may be a threat to the benthic communities of the region, which include endemic species.

Sterols from brazilian marine brown algae

Abstract The sterol compositions of eight samples from marine brown algae of the Dictyotales and Fucales have been analysed qualitatively and quantitatively, mainly by GC-MS. Cholesterol or fucosterol were invariably the major components. Fucosterol, the typical brown algae sterol, was absent in some species. The amount of sterols in the Fucales was, in the mean, ten-fold that of the Dictyotales. 5α-Cholestan-3β-ol, ergosta-5,24-dien-3gb-ol and a C30-sterol were detected for the first time in brown algae.

Raman spectroscopic study of antioxidant pigments from cup corals Tubastraea spp.

Chemical investigation of nonindigenous Tubastraea coccinea and T. tagusensis by Raman spectroscopy resulted in the identification of carotenoids and indolic alkaloids. Comparison of Raman data obtained for the in situ and crude extracts has shown the potential of the technique for characterizing samples which are metabolic fingerprints, by means of band analysis. Raman bands at ca. 1520, 1160, and 1005 cm(-1) assigned to ν1(C═C), ν2(C-C), and ρ3(C-CH3) modes were attributed to astaxanthin, and the band at 1665 cm(-1) could be assigned to the ν(C-N), ν(C-O), and ν(C-C) coupled mode of the iminoimidazolinone from aplysinopsin. The antioxidant activity of the crude extracts has also been demonstrated, suggesting a possible role of these classes of compounds in the studied corals.

Photosynthetic properties of three Brazilian seaweeds

Photosynthetic performance of distinct marine macroalgae, Ulva fasciata Delile (green alga), Lobophora variegata (J. V. Lamouroux) Womersley ex E. C. Oliveira (brown alga), and Plocamium brasiliensis (Greville) M. A. Howe & W. R. Taylor (red alga), were compared using a pulse amplitude-modulated fluorometer. The maximum quantum yield (Fv/Fm) ranged from 0.80 to 0.51, and the lowest value was found in P. brasiliensis. Under 400 µmol photons m-2 s-1 irradiance, the highest value of photochemical quenching (qP = 0.92 ± 0.13) was observed for U. fasciata. The red alga P. brasiliensis dissipated high amounts of excitation energy (qN = 0.56 ± 0.09), resulting in relatively low values for the effective quantum yield of PS-II (0.23 ± 0.04), as well as for the relative electron transport rate (3.3 ± 0.7). The high photosynthetic potential found for U. fasciata partially explains the species ability for rapid growth and high productivity.

Chapter 10 - New Strategies for Identifying Natural Products of Ecological Significance from Corals: Nondestructive Raman Spectroscopy Analysis

Abstract Coral tissues commonly contain high concentrations of secondary or special metabolites. These chemicals are identified by spectroscopic analysis after extraction and purification procedures. A new alternative to the conventional techniques is the use of Raman spectroscopy, which is a nondestructive method of analysis suitable to in situ studies of biomaterials as well as chemical compounds. This approach has been successfully demonstrated with corals from the Brazilian coast. Diverse ecological roles have been investigated in crude extracts and pure compounds from the indigenous species Phyllogorgia dilatata , Leptogorgia punicea , L. violacea , and Carijoa riisei and the nonindigenous species Chromonephthea braziliensis , Tubastrea coccinea , and T. tagusensis . Compounds with possible roles in these bioactivities have been quickly characterized by Raman macro- and microspectroscopy: a feeding deterrent sterol from C. braziliensis ; carotenoids from L. violacea , C. riisei , P. dilatata , and Tubastrea spp.; and polyenals from Leptogorgia spp. and C. braziliensis and from purple spots in P. dilatata affected by purpling . Most of the chemical constituents could be identified in tissues and sclerites without the need for any previous treatment. Several Raman vibrational modes are used to correlate chemical species to a chemical substance. The polyenal biochromes could be identified by two “fingerprint” vibrational bands. A complementary analysis can be performed by Raman microimaging, which is a sensitive and selective method of investigating the distribution of compounds in both in situ and in vivo samples. The results obtained by the Raman microimaging studies of chemical compounds present in the surface of healthy and necrotic tissues of P. dilatata may be helpful in evaluating different stages and the extent of infection that causes purpling. Competition for space, antifouling defense, and chemical deterrence are the three main roles traditionally attributed to the chemically mediated bioactivity in corals. Raman spectroscopy may become a valuable nondestructive technique for monitoring the accumulation or production of metabolites during a biological interaction. It also allows information about the distribution and concentration as well as molecular information to be obtained in a very short period of time compared to the usual time and solvent-consuming separation procedures.

A Review of the Ecological Role of Chemical Defenses in Facilitating Biological Invasion by Marine Benthic Organisms

Abstract The marine biological invasion of nonindigenous species (NIS) into new areas is a growing conservation concern for marine ecologists around the world. NIS may bring loss of diversity and extinctions of endemic organisms as well as trigger changes in the function and structure of marine ecosystems, often with profound economic consequences. This review considers the role of the chemical ecology of NIS in the process of marine biological invasion. NIS oftentimes use their arsenal of chemical substances, acquired in their previous evolutionary context, to surmount obstacles presented by novel predators and competitors to success in the new invaded habitat. Alternatively, the escape from energetically costly chemical production at origin may allow more efficient establishment and expansion of NIS into new areas. We present a number of examples where chemical compounds might be the key of invasion success but, we are still hindered in drawing clear conclusions regarding the relative importance of these chemical traits by a lack of knowledge of the chemical ecology of most marine organisms.