In vitro cytotoxic and antiproliferative activities of marine macroalgae from Yucatán, Mexico

Extracts from 27 marine algal species (14 Rhodophyta, 5 Phaeophyta, and 8 Chlorophyta) from the Yucatán Peninsula (Mexico) were evaluated for cytotoxic and antiproliferative activity by 3(4,5-dimethylthiazole-2-yl)-2,5 diphenyltetrazolium bromide (MTT) and sulforhodamine B (SRB) assays, respectively. To determine the specificity of cytotoxic activity against tumor cells, the selective index (SI) was also calculated. The following cancer cell lines were employed: normal canine kidney (MDCK) cells, human laryngeal carcinoma (Hep-2) cells, human cervical adenocarcinoma (HeLa) cells, and human nasopharyngeal carcinoma (KB) cells. The results indicated that 44% and 51% of the algal species tested showed cytotoxic and antiproliferative activity, respectively. Most of the cytotoxic extracts were from species of Chlorophyta, with Udotea flabellum and U. conglutinate showing the highest cytotoxic activity against all the cancer cell lines. For Rhodophyta, the Bryothamnion triquetrum extract showed outstanding selective cytotoxicity against Hep-2 cells (CC50 8.29 µg mL–1, SI = 12.04). Two of the five species of Phaeophyta tested (Lobophora variegata and Dictyota caribaea) showed high cytotoxicity activity against the KB cell line. The data show that these species are a potential source of compounds for the treatment of certain cancer diseases.

Effect of dark and salinity treatment in the yield and quality of agar from Gracilaria cornea (Rhodophyceae)

The alkali treatment used previous to agar extractions from the Gracilaria genus reduces, among other reactions, the sulphate content and improves the gel strength; however, at an industrial level it requires expensive effluent processing to reduce its polluting charge. The red alga Gracilaria cornea was cultivated under dark and salinity treatments to replace this alkali treatment. The different treatments tested were: (a) darkness and 33‰ salinity for 8 days, [dark treatment]; (b) darkness and 50‰ salinity for 4 days, followed by darkness and 25‰ salinity for 4 days, [4+4]; and (c) darkness and 50‰ salinity for 8 days, followed by darkness and 25‰ salinity for 4 days, [8+4]. The treatment [4+4] increased the agar yield in 26% (from 36.6 to 46.1%). All treatments reduced the sulphate content of the agar in approximately 24% when compared with agar obtained without any treatment. For G. cornea the [4+4] treatment might become in the future an additional treatment to a mild alkali treatment using less alkaline reagents for agar extraction

Photothermal characterization of the gelation process in Gelidium robustum Agar

Agar is a hydrophilic colloid formed by polysaccharides, whose ability to form reversible gels simply by cooling hot aqueous solutions is the most important property and can be regarded as the prototype and model for all gelling systems. In this paper the evolution of the gelation process of agar obtained from algae of the species Gelidium robustum, using the photopyroelectric technique is reported. It is shown that thermal effusivity increase when the agar is cooled, reaching a maximum value around 37°C. The increase in thermal effusivity can be related to the increasing of the bondings in the gel as temperature decreases, reaching the maximum at the gelation point. The decrease of the thermal effusivity at lower temperature could be due to the syneresis process involving a gradual release of water after gelation

Production and properties of agar from the invasive marine alga, Gracilia Vermiculophylla (Gracilariales, Rhodophyta)

The utilization potential, in terms of agar production, of the invasive alga, Gracilaria vermiculophylla, collected at Ria de Aveiro, northwestern Portugal was investigated. The agar yield ranged from 15% to 33%, with pre-extraction treatment with alkali generally increasing the yield. The gel quality (gel strength and apparent Young’s modulus) was best (>600 g cm−2 and >1,000 kPa, respectively) when alkali treatment with 6% NaOH for 3.5 h was performed. At these pretreatment conditions, the effect of extraction time was also investigated and highest yield and best gel quality were obtained with a 2 h extraction time. By employing these extraction conditions, G. vermiculophylla can be a source of industrial food-grade agar. The structure of agar from G. vermiculophylla was determined through chemical techniques and FTIR and NMR spectrometry. It is mainly composed of alternating 3-linked D-galactose and 4-linked 3,6-anhydro-L-galactose, with methyl substitution occurring at 16–19 mol% of C-6 in 3-linked units and 2–3 mol% of C-2 in 4-linked units. A minor sulfation on C-4 of 3-linked units was also detected; while precursor units (6-sulfated 4-linked galactosyl moieties) were found in the native extract.We thank R. Pereira for algal material collection, L. Martins for FTIR analysis, and two anonymous reviewers for valuable comments on the manuscript. RDV was supported by the Portuguese Foundation for Science and Technology, through a post-doctoral grant (SFRH/BPD/34670/2007)

Discolored Red Seaweed Pyropia yezoensis with Low Commercial Value Is a Novel Resource for Production of Agar Polysaccharides

The red seaweed Pyropia yezoensis has been demonstrated to be a novel resource for the production of high-quality agar. P. yezoensis is grown for the food industry in large-scale Japanese mariculture operations. However, discolored P. yezoensis is mostly discarded as an industrial waste, although it has some kind of utility values. Here, we evaluated the utility of discolored P. yezoensis as a resource for agar production. The quality of agar from the discolored seaweed was comparable to that from normal seaweed. In addition, as a distinguishing characteristic, agar yield was higher from discolored seaweeds than from normal types. Moreover, we successfully used agar from discolored P. yezoensis for bacterial plate media and DNA electrophoresis gels without agarose purification. Thus, our results demonstrate that discolored P. yezoensis is suitable for agar production and use in life science research. Diverting discolored P. yezoensis from disposal to agar production provides a solution to the current industrial waste problem in mariculture, as well as a secure source of agar for research purposes