Volume 53, Issue 5

There has been a significant increase in the occurrence of chronic diseases caused by oxidative stress and hypertension in recent decades. Hypertension is a sustained increase in blood pressure and is a controllable risk factor in the development of a number of cardiovascular diseases such as stroke and coronary infarction. As a result, the number of investigations aimed at identification of dietary compounds from natural sources that can be effective in preventing such diseases has increased. Macroalgae, also known as seaweeds or sea vegetables, have been traditionally incorporated into Pacific and Asian foods for hundreds of years and have recently become a popular addition to some Western diets. Macroalgae are classified into three higher taxa according to their pigmentation: brown (Class Phaeophyceae), green (Phylum Chlorophyta) and red (Phylum Rhodophyta). Owing to the harsh environments in which many macroalgae exist, they have developed effective defence mechanisms and, as a result, are a rich source of bioactive compounds, including polysaccharides, polyphenols, fatty acids and peptides, with different structures and activities from those found in terrestrial plants. This review explores the potential use of macroalgal species as bioactive ingredients that could be incorporated into functional foods for use in the prevention and/or treatment of hypertension and oxidative stress-related diseases.

We investigated production of radical oxygen species (ROS) in sorus development of sporophyte discs and during zoospore germination of Saccharina japonica (Phaeophyceae) using the fluorescent dye 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Quantitative analysis of ROS showed high intracellular production during the stages of zoosporangium formation when paraphyses elongated. In this stage, remarkable ROS release was observed. ROS production was also observed histologically (under a fluorescence microscope) in the elongating paraphyses and the sorus zoosporangia. The sorus had significantly higher phenol content, antioxidant capacity and ROS scavenging enzyme activities (ascorbate peroxidase, catalase, glutathione reductase and superoxide dismutase) than adjacent non-sorus blade sectors. Thus, intracellular ROS scavenging mechanisms are active during ROS production in sorus formation. In contrast, iodine content was lower in the sorus than in the adjacent non-sorus tissues, suggesting the existence of an antioxidant defense mechanism based on iodine efflux. We demonstrated that ROS production is an important phenomenon in the reproduction of the S. japonica sporophyte. Furthermore, ROS were also observed in the zoospore germination processes. We discuss the physiological and ecological roles of ROS production in sorus formation and zoospore germination.

Information about past periods of climate change can provide a framework for investigating how marine communities may have adapted to changes both geographically and ecologically. The spatial distribution of variable haplotypes from the nuclear ribosomal DNA internal transcribed spacer (ITS1-5.8S-ITS2) region and a ribosomal DNA group-I intron from the obligate, rocky shore intertidal red alga Porphyra umbilicalis were used to reconstruct its biogeographical history since the last glacial maximum in the North Atlantic. Haplotype distributions from European and North American samples representing the range of P. umbilicalis are consistent with the hypothesis that North American populations were extirpated during the last glacial maximum and subsequently recolonized from European donor populations. A non-coding intergenic region between the mitochondrial cytochrome oxidase ( cox )2 and cox 3 genes was also investigated, but because there were extremely low levels of intraspecific variation, the spacer was not useful for phylogeographical analysis.

Laurencia caduciramulosa and L. minuscula (Ceramiales, Rhodophyta) are reported for the first time from the Cuban archipelago based on materials collected from the northwestern coast of Cuba (Havana and Rincón de Guanabo). The specimens of these two species, both characterized by a markedly reduced size, were collected twice, in April 2006 and June 2007, growing epiphytically on Thalassia testudinum . In the present study, the morphological characters of both species are described, and the geographical distribution of L. caduciramulosa is expanded to the Caribbean Sea and to the northwestern Atlantic Ocean.

We evaluated seed storage and effects of plant growth regulators and fertilizers on in vitro germinated seedlings with a view to optimizing restoration of Cymodocea nodosa . Storage of seeds in seawater at room temperature (22±2°C) and 18°C retarded germination potential for up to one year, though the best results were seen within the first six months. Seeds stored in water at 4°C or under dry conditions lost their germination potential immediately. Neither plant growth regulators (PGRs) nor fertilization had anatomical effects in seedlings that would have indicated increased robustness. Gibberellic acid (10 -3   m ) promoted leaf growth in seedlings, but most treatments with other auxins and cytokinins were ineffective or even inhibitory in achieving the desired hardening effect on the seedling. Seedlings appeared to be well nourished and most likely grew by utilizing their abundant nutrient reserves.

Total biomass, shoot density, leaf length and leaf width of the dominant seagrass Thalassia testudinum were compared between two coastal environments in the northeastern part of the Yucatan peninsula (Mexico). The coastal environments were (a) an exposed sublittoral zone (<1 km from the shoreline) and (b) a sheltered coastal lagoon. Plant morphology was monitored at monthly intervals from June 2001 to May 2002. There was a clear morphological variation between coastal environments throughout the period of study. In the exposed sublittoral zone, total biomass and shoot density were lower and leaves were longer and wider. In contrast, in the sheltered lagoon, total biomass and shoot density were higher and the leaves shorter and narrower. Overall, high values of total biomass, shoot density and leaf width were observed during the warm weather seasons (rainy and dry) whereas the low values were observed during the cold fronts weather season (nortes); leaf length followed a reverse trend. Results presented here stress the need to take into account the natural pattern of morphological variation in the design of sampling and monitoring programs.

Eleven brown algae, six green algae and eight red algae occurring along the coast of Tamilnadu state, southern India were screened for their fungal endophyte assemblages. The green algae had a low diversity of endophytes but were more densely colonized. The brown algae supported a higher diversity of endophytes. There were a few dominant endophyte species with a wide host range and several with low colonization frequency that were restricted to a few algal species. The endophytes produced bioactive compounds that inhibited bacteria, an alga and a fungus. They also produced antioxidants and insecticidal metabolites.

Fungi are major contributors to the process of denitrification in terrestrial environments, but their role as denitrifiers in the ocean has not been addressed thus far. We measured the nitrate reducing capacity of fungi based on respiratory electron transport system (ETS) activity and nitrite accumulation in oxygen-depleted laboratory microcosms. Specific fungal and bacterial activities in these microcosms were studied by fortifying the sediments with antibiotics and anti-fungal compounds, respectively. The higher ETS activity in the microcosm with antibiotics indicated higher fungal than bacterial activity. Activity of two fungi, # An-2 (MTCC accession number 9376) and # MT-811 (JMC accession number 11502) in pure cultures under aerobic and anaerobic conditions, and in the microcosms was also studied. ETS activity in the fungal cultures grown under anaerobic conditions was half the activity measured under aerobic growth conditions. Simulated laboratory microcosm data show that fungi participate in denitrification activity in sediments from marine hypoxic environments.