Polysaccharides of the red algae 'Pterocladia' growing on the Lebanese coast: Isolation, structural features with antioxidant and anticoagulant activities.

In addition to their high nutritional value, red algae are of great interest as a source of therapeutic substances. However, despite their abundance on the Lebanese coast red algae have never been studied before. Therefore, we attempted to study among the available biomass one of the species of red algae growing on the Lebanese coast “Pterocladia”. We performed the extraction of trace elements, fatty acids, sulfated galactans and watersoluble polysaccharides of the phycocolloids family (carrageenans) whose physicochemical gelling or stabilizing effects attract many industrial sectors. The analysis of trace elements shows large amounts of potassium, calcium, silicon and iron. Moreover, Pterocladia appears to be rich in saturated fatty acids (69%) with palmitic acid as major fatty acid and 31% of monounsaturated fatty acids. The extraction yields were 2.7% for sulfated galactans and 11.5% for carrageenan. In order to elucidate their structures, H¹ NMR spectroscopy was performed as well as Infra-Red spectroscopy which allowed us to reveal their functional groups. A study of the antioxidant effect by the electrolysis method showed a greater effect for sulfated galactans. Furthermore, the study of the anticoagulant effect by APTT test, activated partial thromboplastin time, showed more pronounced anticoagulant power of sulfated galactans. The results of the present study confirmed the potential use of the red algae Pterocladia as a source of active known molecules.

Glass transition and degree of conversion of a light-cured orthodontic composite

OBJECTIVE: This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s). RESULTS: Fill Magic presented lower Tg than Concise (35-84ºC versus 135ºC), but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm² is necessary to reach adequate conversion level and obtain satisfactory adhesion.