Biosciences

The seasonal variations in the polyphenolic contents and potential
antioxidant activities of seven seaweed species (Padina gymnospora, Gracilaria salicornia, Palisada papillosa, Galaxaura rugosa, Enteromorpha intestinalis, Codium arabicum and Dictyosphaeria cavernosa) and five seagrass species (Syringodium isoetifolium, Halodule uninervis, Thalassodendron ciliatum, Halophila ovalis and
Halophila stipulacea) were assessed. In summer, the highest total phenolic content was recorded in the seaweed P. gymnospora and the lowest in G. rugosa. The total phenolic contents in the seagrass species were significantly higher than those observed in the
seaweed species during both seasons. The highest flavonoid concentrations (FC) were observed in the seaweed species E. intestinalis in winter and in the seaweed P. gymnospora
in summer. All tested species had higher FC in winter. The highest antioxidant activity (assessed using the Ferric ion reducing antioxidant power) was in the seaweed P. gymnospora during summer (FRAP: 9.7 ± 0.3 X10¯³ Fe²+mM/g DW). However, the seaweed P. gymnosperm extract and the extracts from all 5 seagrass species had
significantly different (p<0.01) antioxidant activities (assessed using the Trolox equivalent antioxidant capacity assay) in winter compared to the summer season. The collective data are indicative of the potential of Mauritian seaweeds and seagrasses as possible sources of secondary metabolites for pharmaceuticals. Further analysis using bio efficacy models are warranted to justify the phytoceutical capacity of the seaweeds and seagrasses.

KEY WORDS: Antioxidant; Total Phenols; Total Flavonoids; FRAP; TEAC; Seagrass;
Seaweed; Seasonal variation; Mauritius

A detailed literature review of relevant Ulva biology and chemical composition is included. Marine algae are known to produce a wide range of volatile organic compounds that are primarily used in chemical communications. These compounds are released in seawater and act as either pheromones or allelochemicals. Aldehydes have been reported to be the main group of volatile compounds in green algae Ulva. Cultivation of Ulva as feed on abalone farms in South Africa has been a success but there has been little research on the chemistry of South African Ulva. This study aims to investigate the potential effects of environmental variables and grazing on the chemical profile, and specifically on the aldehyde-type natural products produced (δ H 9.00-10.50) by laboratory cultured Ulva using 1 H NMR spectroscopy and multivariate statistical analysis. Ulva armoricana was cultured at different salinities: 5, 10, 20, 25 and 35 ‰ (all ± 0.1 ‰) and nutrient treatments: 100 % Provasoli ES medium (high nutrient supply) and 0 % Provasoli ES medium (low nutrient supply) at 10 °C and 15 °C for 6 days under constant light (39.2 ± 0.43 µmol photons m-2 s-1) on a 16:8 hours light:dark photoperiod. Natural grazing (using Tricolia capensis Dunker) and artificial grazing (stimulated by scissors) was performed to determine their effects on the chemical composition of Ulva armoricana. Results obtained show that grazing and nutrient experiments mostly affected the aromatic, hydroxylic and carbonyl compounds regions, while salinity change mostly affected the alcohol, ester and phenolic regions. The aldehyde profiles included a prominent peak at δ H 9.76 in almost all treatments that was provisionally identified as hexanal. Ulva armoricana grown at 10 °C under low nutrient condition and in a medium with salinity at 25 ‰ was found to be the ideal condition to produce a higher intensity of the main aldehyde.

ABSTRACT: The seasonal variations in the polyphenolic contents and potential antioxidant activities of seven seaweed species (Padina gymnospora, Gracilaria salicornia, Palisada papillosa, Galaxaura rugosa, Enteromorpha intestinalis, Codium arabicum and Dictyosphaeria cavernosa) and five seagrass species (Syringodium isoetifolium, Halodule uninervis, Thalassodendron ciliatum, Halophila ovalis and Halophila stipulacea) were assessed. In summer, the highest total phenolic content was recorded in the seaweed P. gymnospora and the lowest in G. rugosa. The total phenolic contents in the seagrass species were significantly higher than those observed in the seaweed species during both seasons. The highest flavonoid concentrations (FC) were observed in the seaweed species E. intestinalis in winter and in the seaweed P. gymnospora in summer. All tested species had higher FC in winter. The highest antioxidant activity (assessed using the Ferric ion reducing antioxidant power) was in the seawee...

Marine sponges belonging to the genus Neopetrosia represent a quasi-inexhaustible source of novel cytotoxic compounds. Yet studies delineating their molecular mechanisms of action in cancer cells remain scarce. We investigated the cytotoxic and apoptosis inducing potential of the Mauritian marine sponge Neopetrosia exigua derived crude extract, hexane and ethyl acetate fraction. Their cytotoxic activity was screened against four cancer cell lines and two non-malignant cell lines via the Alamar Blue metabolic assay. The level of intracellular reactive oxygen species (ROS) production, endogenous antioxidant enzyme activity (catalase and superoxide dismutase) and mitochondrial membrane potential were determined. The ability of the active extract to induce apoptosis in cancer cells and modulate the expression levels of apoptotic markers (caspases and polyADP-ribose polymerase (PARP)) was further evaluated via western blot. The ethyl acetate fraction (NEEAF) displayed the highest inhibit...

Sponges are very important in the marine ecosystems and also represent organisms known for producing a diversity of chemicals. The present study was performed from September 2009 to February 2010 and aimed at making a mapping of the sponge Xestospongia exigua in the lagoon of Trou aux Biches. This research is a first in the lagoons of Mauritius and it gives indication of sponge distribution and the physico-chemical parameters affecting their abundance. Such knowledge adds to the lack of information on the biology of these marine invertebrates in Mauritius. Visual censuses were made along the 2.5 Km lagoon during fifteen snorkeling sessions (15 days) covering a snorkeling distance of approximately 500 m per session. The distribution and mapping of sponge was done following surveys and recording of GPS positions of the sponge patches present. Abundance of sponge was assessed by random throws of 1.0 m 2 quadrats (n = 30). Moreover, physical and chemical parameters such as depth, pH and salinity were also recorded. The sponge size and the immediate habitats of sponges living in Trou aux Biches were assessed by random throw of 900 cm 2 quadrats. Observations showed that the sponge species Xestospongia exigua were distributed in six different patches of different sizes with a largest patch of 48922 m 2 . From aerial maps, it was also observed that the distribution of sponges was not uniform (patches were of irregular forms) within the lagoon of Trou aux Biches. From statistical analysis (ANOVA), it has been observed that water depth, pH and salinity have an effect on the sponge abundance within the lagoon. The study shows that increasing depth is favorable to sponge abundance (8.0 specimen/m 2 at a depth of 3.0 m). Sponges were also observed to be abundant in water of higher pH (5.6 specimens/m 2 at pH 8.27). However, with increasing water salinity, a decrease in sponge abundance was observed. The study also showed that Xestospongia exigua sponges in Trou aux Biches were more abundant in habitats of dead corals.

Actinobacteria commonly known as actinomycetes are often constituents of the sponge-associated bacterial communities and are well known producers of bioactive compounds.  In the present study, 7 actinomycete species representing 3 genera were successfully isolated from the sponge Spheciospongia vagabunda (Ridley, 1884) and Neopetrosia exigua (Kirkpatrick, 1900) from Mauritius.  The sponge N. exigua hosted a higher actinomycete diversity resulting in 71% of the total number of actinomycete strains recorded.  Streptomyces sp. and Micrococcus sp. were the most common actinomycete genera, both representing 43% of the total actinomycetes isolated from both host sponges.  Actinomycete Isolation Agar was the most effective medium for the selection of actinobacteria, yielding in 57% of the total actinobacterial strains isolated.  This study is the first to report on sponge-associated actinomycete communities from Mauritius and paves the way for future sponge-associated actinobacterial resea...

The distribution and abundance of the sponge Spheciospongia vagabunda (Ridley, 1884) was investigated in a shallow lagoon (Albion) of Mauritius (Western Indian Ocean). Sponge abundance and environmental parameters were assessed. Sponges in Albion lagoon were mostly distributed in the central part of the lagoon some distance from wave action. Two distinctive sponge patches were found, the largest patch being 15350 m2 in area. Unlike most Porifera, S. vagabunda was mostly anchored in sand and not on hard substratum. A t-test revealed a significant difference in sponge size between sponge assemblages (t = 3.01; p &lt; 0.05). One-way ANOVA indicated that environmental parameters did not influence sponge abundance within the lagoon (p &lt;0.05). This study provides a baseline for future monitoring of these benthic animals in the Albion lagoon. Corresponding author: SSB Email: [email protected] INTRODUCTION The Phylum Porifera is the oldest metazoan group found in our oceans (Müller, ...

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The cellular mechanisms responsible for the regulation of nutrient exchange, immune response, and symbiont population growth in the cnidarian–dinoflagellate symbiosis are poorly resolved. Here, we employed liquid chromatography–mass spectrometry to elucidate proteomic changes associated with symbiosis in Breviolum minutum, a native symbiont of the sea anemone Exaiptasia diaphana (‘Aiptasia’). We manipulated nutrients available to the algae in culture and to the holobiont in hospite (i.e., in symbiosis) and then monitored the impacts of our treatments on host–endosymbiont interactions. Both the symbiotic and nutritional states had significant impacts on the B. minutum proteome. B. minutum in hospite showed an increased abundance of proteins involved in phosphoinositol metabolism (e.g., glycerophosphoinositol permease 1 and phosphatidylinositol phosphatase) relative to the free-living alga, potentially reflecting inter-partner signalling that promotes the stability of the symbiosis. P...

Understanding susceptibility to bleaching may indicate how corals cope with increasing seawater temperatures resulting from climate change. In Belle Mare lagoon, Mauritius, Acropora muricata colonies at reef sites but not near the coast exhibited bleaching. We compared seawater temperatures and light intensity both on a summer day and a winter day at a reef station and a near-coast station. The total phenolic contents, non-enzymatic antioxidant activities of the coral holobiont, in situ photophysiological parameters of in hospite Symbiodinium as well as their cladal diversity were assessed. Both sites had comparable maximum temperatures but fluctuations were higher in the near-coast station (2-3°C) compared to the reef station (1-1.5°C) on both days. Light intensity was higher on the summer day than the winter day at both stations. Higher total phenolic contents and ferrous reducing antioxidant potential were observed in near-coast colonies than in reef colonies on the summer day. Only Clade A-like Symbiodinium sp. variants were detected at both locations, but higher maximum relative electron transport rates and maximum non-photochemical quenching were measured in near-coast colonies. Our data show that the near-coast colonies exhibited enhanced photophysiological responses, antioxidant activities and increased total phenolic contents in response to higher thermal and light fluctuations. This acclimatization may explain the variability in bleaching along a coast-reef scale.

Coral bleaching events are increasing worldwide as a result of climate change. Coral show differential bleaching susceptibilities depending on host and/or symbiont responses to changing environmental factors. Coral responses have been shown to vary over broad geographical scales with thermally-disparate environments. Of these, physiological characteristics such as Symbiodinium density and size, chlorophyll a content and estimated productivity along a coast-reef scale (<1 km) remain to be thoroughly understood. In this study, we examined these characteristics seasonally in Acropora muricata colonies that harbor Symbiodinium clade A along a coast-reef scale in Belle Mare lagoon, Mauritius. The studied reef and coast habitats are characterized by contrasting thermal and light conditions as well as bleaching histories, with bleaching occurring only at the reef site in 2009. We observed higher symbiont density in winter for coast colonies but similar symbiont cell size compared to reef colonies. These two parameters showed seasonal variation. Chlorophyll a content was 30% lower in reef than coast colonies, irrespective of sampling season and was significantly influenced by site. Estimated productivity was influenced by both site and season, with summer samples of coast colonies displaying 56% higher values than reef colony samples. This significant difference was maintained but less pronounced (18%) in winter samples. Our data suggest that Symbiodinium clade A may show physiological acclimatization along a coast-reef scale possibly as a consequence of difference in temperature and light conditions and nutrient concentrations at these two sites.

In order to find new sources of natural antioxidants, the antioxidant potential of 70% methanolic extracts from the inflorescences and leaves of 16 species from the genus Sorbus s.s. was evaluated using two complementary in vitro test systems: the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay and the AAPH [2,2′-azobis-(2amidinopropane)dihydrochloride]-induced linoleic acid (LA) peroxidation test. The radical-scavenging capacities of the extracts towards the DPPH radical were in the range of 0.25−0.86 millimolar Trolox ® equivalents/g dry weight. They were significantly correlated (r = -0.8089, p < 0.001) with the results of the LA-peroxidation test, indicating the Sorbus extracts to be universal antioxidants. Significant linear correlations were also found between the different antioxidant potentials and total phenolic contents as estimated by the Folin-Ciocalteu method and further verified by serial determinations of proanthocyanidins, chlorogenic acid isomers and flavonoids (⎜r⎢in the range of 0.71−0.95, p < 0.001). Cluster analysis of the data matrix identified the ten samples (inflorescences of S. aucuparia, S. pohuashanensis, S. decora, S. koehneana, S. commixta, S. gracilis, and S. sitchensis, and the leaves of S. wilfordii, S. pogonopetala, and S. gracilis) exhibiting the highest

In order to find new sources of natural antioxidants, the antioxidant potential of 70% methanolic extracts from the inflorescences and leaves of 16 species from the genus Sorbus s.s. was evaluated using two complementary in vitro test systems: the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay and the AAPH [2,2′-azobis-(2amidinopropane)dihydrochloride]-induced linoleic acid (LA) peroxidation test. The radical-scavenging capacities of the extracts towards the DPPH radical were in the range of 0.25−0.86 millimolar Trolox ® equivalents/g dry weight. They were significantly correlated (r =-0.8089, p < 0.001) with the results of the LA-peroxidation test, indicating the Sorbus extracts to be universal antioxidants. Significant linear correlations were also found between the different antioxidant potentials and total phenolic contents as estimated by the Folin-Ciocalteu method and further verified by serial determinations of proanthocyanidins, chlorogenic acid isomers and flavonoids (⎜r⎢in the range of 0.71−0.95, p < 0.001). Cluster analysis of the data matrix identified the ten samples (inflorescences of S. aucuparia, S.