Abstract Crude galactans isolated from five different seaweed species collected from the Lebanese coast were chemically characterized and then evaluated for their antioxidant and antiproliferative properties in vitro. The yield of extracted sulfated galactans varied in the range 4.03%-14.32% dry weight in Tricleocarpa fragilis and Osmande dechybrida, respectively. The chemical composition of all extracted galactans exhibited high levels of carbohydrate, uronic acid and sulfate contents with trace amounts of protein. FTIR analysis showed that all the extracted galactans were agar except for Galaxaulra rugosa galactan (GRG) and O. dechybrida galactan (ODG). The antioxidant activity of all extracted galactans using multifunctional antioxidant ability was assayed by total antioxidant capacity, DPPH radical-scavenging activity, hydrogen peroxide scavenging assay and reducing power. Galactans from G. rugosa exhibited higher antioxidant activity compared with the standard antioxidant (α-tocopherol). Whereas T. fragilis galactan (TFG) showed the lowest antioxidant activity. The maximum antiproliferative potency was detected in GRG and Ligora viscida galactan (LVG) at 1.5%. The tested biological activity of the isolated galactans increased with increasing concentrations, indicating the dose-dependency of their chemical properties. The antiproliferative activity showed a significant positive correlation with antioxidant activities. Moreover, these activities were correlated with the combined effects of uronic acid and sulfate content. Identification of these sulfated polysaccharides in algal species is chemotaxonomic significance in view of their potential economical applications as a natural product. The most activated galactans have been selected for further fractionation and characterization and the necessary in vivo experiments are already in progress.

ABSTRACT Red seaweed possess various sulfated polysaccharides (SPs) that could potentially be exploited as bioactive agents for medical and industrial applications. Crude polysaccharides from the red algae Corallina officinalis (SP1) and Pterocladia capillacea (SP2) were extracted and characterized according to their chemical content and their antioxidant, anti-inflammatory, anticoagulant, antibacterial, antifungal, and antifouling activities. The isolated polysaccharides contained low levels of protein and high levels of carbohydrate and sulfate. The extracted SPs were characterized by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectral data and revealed that SP1 is composed of carrageenan, while SP2 is composed of polysaccharides containing sulfated galactans plus κ- and ι-carrageenan. Both isolated SPs exhibited all the tested biological activities but those of SP2 were superior. These results reflect the beneficial effects that red algal polysaccharides have as a natural renewable bio-product and that there is a significant relationship between polysaccharide structure, sulfate content and their biological properties. Further studies should be undertaken on the fractionation and characterization of polysaccharides extracted from species of red seaweed in addition to experiments to verify the efficiency of the extracted SPs for food and medical uses in vivo.

Seasonal changes of pigment composition [Chlorophyll a (Chl-a), total carotenoid (Car.), phycobiliproteins (phycoerythrin (PE), phycocyanin (PC), allophycocyanin (APC))], in the 5 species of Rhodophyta were investigated. Chl-a, carotenoids and phycobiliproteins levels showed high contents during winter, whereas decreased in summer showing discoloration tissue from deep red to green or yellow. The results show that the pigment contents were varied seasonally with respect to the algal species and physical and chemical parameters changes, while pH, dissolved oxygen, NO3-, NO2-, NH4+, total nitrogen (TN) and total phosphorus (TP) had direct impact on photosynthetic pigments content, and temperature had significant negative correlation on photosynthetic pigments.

Se investigaron los cambios estacionales en la composición de pigmentos [Clorofila a (Cl-a), carotenoides totales (Car.), ficobiliproteínas (ficoeritrina (PE), ficocianina (PC), aloficocianina (APC))], en 5 especies de Rhodophyta. Los niveles de clorofila a, carotenoides y ficobiliproteínas presentaron altos contenidos durante invierno, y disminuyeron en verano, mostrando decoloración de tejidos de rojo a verde o amarillo. Los resultados muestran que los contenidos de pigmentos variaron estacionalmente con respecto a las especies de algas, y a los cambios de los parámetros físico-químicos, mientras que el pH, oxígeno disuelto, NO3-, NO2-, NH4+, nitrógeno total (TN) y fósfato total (TP) tuvieron un impacto directo sobre el contenido de pigmentos fotosintéticos, y la temperatura tuvo una correlación negativa significativa sobre los pigmentos fotosintéticos.

Dois compostos-azo, 2-metil-4-(5-amino-2-hidróxi-fenilazo)-quinolina e 2-metil-4-(5-amino-2-hidróxi-nitrofenilazo)-quinolina, derivados da 4-amino-2-metilquinolina foram sintetizados. Suas estruturas químicas foram caracterizadas e confirmadas através de análise elementar, espectroscopia no infravermelho (IR), ressonância magnética nuclear (RMN) de ¹H e espectrometria de massas (MS). O comportamento eletroquímico do composto de partida (4-amino-2-metilquinolina) e dos dois azo-derivativos sintetizados foi estudado com um eletrodo de mercúrio em solução tampão universal B-R em diferentes valores de pH (2-11,5) contendo etanol 40% (v/v) usando polarografia dc, voltametria cíclica e coulometria com potencial controlado. Os caminhos de reação dos compostos no eletrodo foram elucidados e são discutidos. As constantes de dissociação (pKa) dos compostos examinados, constantes de estabilidade e estequiometria dos complexos formados em soluções dos compostos com alguns íons de metais de transição (Co(II), Ni(II), Cu(II), La(III) and UO2(2+)) foram determinadas.

Two azo-compounds, 2-methyl-4-(5-amino-2-hydroxy-phenylazo)-quinoline (2) and 2-methyl-4-(2-hydroxy-5-nitrophenylazo)-quinoline, derived from 4-amino-2-methylquinoline were synthesized. Their chemical structures were characterized and confirmed by means of elemental chemical analysis, infrared (IR) spectroscopy, ¹H nuclear magnetic resonance (NMR) and mass spectrometry (MS). The electrochemical behavior of the starting compound (4-amino-2-methylquinoline) and of the two synthesized azo-derivatives was studied at the mercury electrode in the B-R universal buffer at various pH values (2-11.5) containing 40% (v/v) ethanol using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Their electrode reaction pathways were elucidated and discussed. The dissociation constants (pKa) of the examined compounds, stability constants and stoichiometry of their complexes in solution with some transition metal ions (Co(II), Ni(II), Cu(II), La(III) and UO2(2+)) were determined.