Search Results (2)

The short-term effects of UV radiation and low temperature on ultrastructure, photosynthetic activity (measured as the maximal photochemical quantum yield of photosystem II: F_v/F_m), chlorophyll-a (Chl-a) contents, and UV-absorbing compounds on the carpospores of Iridaea cordata from a sub-Antarctic population were investigated. Exposure to both photosynthetically active radiation (PAR) and PAR + UV for 4 h caused ultrastructural modifications in all treatments. Under PAR + UV at 2 °C, a disruption of the chloroplast’s internal organization was observed. Plastoglobuli were often found in carpospores exposed to 2 °C. ‘Electron dense particles’, resembling physodes of brown algae, were detected for the first time in cells exposed to PAR and PAR + UV at 8 °C. F_v/F_m decreased following 4 h exposure at 2 °C under PAR + UV (64%) and PAR (25%). At 8 °C, F_v/F_m declined by 21% only under PAR + UV. The photosynthesis of carpospores previously treated with UV partially recovered after a 4 h exposure under dim light. UV-absorbing compounds were degraded in all radiation and temperature treatments without recovery after a 4 h dim light period. Chl-a did not change, whereas total carotenoids increased under PAR at 8 °C The study indicates that although carpospores of I. cordata exhibit photoprotective mechanisms, UV radiation strongly damages their ultrastructure and physiology, which were exacerbated under low temperatures. Full article

Macroalgae are sources of bioactive compounds that are interesting from both a chemical and a medical point of view. Although their use in biomedicine has increased significantly in recent years, tests conducted to date have been mostly related to species from temperate latitudes, with the potential application of Antarctic biodiversity being minor. The wide variety of algae species present on Antarctic coastal areas can be a source of new antioxidants. Bearing this in mind, the brown macroalgae Desmarestia antarctica (DA) and the red Iridaea cordata (IC) were selected for the preparation of aqueous extracts with the aim of analyzing their antioxidant activity. This analysis was performed by determining reducing power, total phenolic content, and 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity. Furthermore, both extracts were employed to synthesize gold and silver nanoparticles. The nanomaterials were fully characterized by means of UV-Visible spectroscopy, transmission electron microscopy, Z potential measurements, and Fourier transform infrared spectroscopy, which confirmed the formation of stable, spherical nanoparticles with mean diameters of 13.7 ± 3.1 and 17.5 ± 3.7 nm for Ag@DA and Ag@IC and 12.6 ± 1.9 and 12.3 ± 1.6 nm for Au@DA and Au@IC. Antioxidant assays were performed after the synthesis of the nanomaterials to evaluate their possible synergistic effect with the extracts. The results suggest that polysaccharides and proteins may play a key role in the process of reduction and stabilization. Finally, for the sake of comparison, the results obtained for the Antarctic macroalgae Desmarestia menziesii and Palmaria decipiens have also been considered in the present work. Full article