Carrageenan from Gigartina skottsbergii: A Novel Molecular Probe to Detect SARS-CoV-2

The COVID-19 pandemic has caused an unprecedented health and economic crisis, highlighting the importance of developing new molecular tools to monitor and detect SARS-CoV-2. Hence, this study proposed to employ the carrageenan extracted from Gigartina skottsbergii algae as a probe for SARS-CoV-2 virus binding capacity and potential use in molecular methods. G. skottsbergii specimens were collected in the Chilean subantarctic ecoregion, and the carrageenan was extracted -using a modified version of Webber's method-, characterized, and quantified. After 24 h of incubation with an inactivated viral suspension, the carrageenan's capacity to bind SARS-CoV-2 was tested. The probe-bound viral RNA was quantified using the reverse transcription and reverse transcription loop-mediated isothermal amplification (RT-LAMP) methods. Our findings showed that carrageenan extraction from seaweed has a similar spectrum to commercial carrageenan, achieving an excellent proportion of binding to SARS-CoV-2, with a yield of 8.3%. Viral RNA was also detected in the RT-LAMP assay. This study shows, for the first time, the binding capacity of carrageenan extracted from G. skottsbergii, which proved to be a low-cost and highly efficient method of binding to SARS-CoV-2 viral particles.

Synthesis, molecular structure and antioxidant activity of bis [L(μ2-chloro)copper(II)] supported by phenoxy/naphthoxy-imine ligands

A new series of Cu(II) complexes [bis[{(μ₂-chloro)-2-MeO-Ph-CH₂-(N=CH)-2,4-tert-butyl-2-OC₆H₂)}Cu(II)] (Cu1); bis[{(μ₂-chloro)-2-MeS-Ph-CH₂-(N=CH)-2,4-tert-butyl-2-(OC₆H₂)}Cu(II)] (Cu2); bis[{(μ₂-chloro)-2-MeO-Ph-CH₂-(N=CH)-2-(OC₁₀H₆)} Cu(II)] (Cu3); bis[{(μ₂-chloro)-2-MeS-Ph-CH₂-(N=CH)-2-(OC₁₀H₆)}Cu(II)] complex (Cu4); bis[{2-MeS-Ph-CH₂-(N=CH)-2,4-tert-butyl-2-(OC₆H₂)}Cu(II)] (Cu5)] have been synthesized and characterized by elemental analysis, IR, UV-Visible and by X-ray crystallography for Cu1, Cu4 and Cu5. In the solid state, Cu1 features of a chloro-bridged dimer complex with κ² coordination of the monoanionic phenoxy-imine ligand onto the copper center. On the other hand, the molecular structure of Cu4 reveals the naphthoxy-imine ligand with pendant S-group coordinated to the copper atom in tridentate meridional fashion. Treatment of [Cu(OAc)₂·H₂O] with two equiv. of [2-MeS-Ph-CH₂-(N=CH)-2,4-tert-butyl-2-(HOC₆H₂)] led to a monomeric complex Cu5, with the ONS-donor Schiff base acting as a bidentate ligand. The redox behavior was explored by cyclic voltammetry. The reduction/oxidation potential of Cu(II) complexes depends on the structure and conformation of the central atom in the coordination compounds. Antioxidant activities of the complexes, Cu1 - Cu5, were determined by in vitro assays such as 1,1-diphenyl-2-picryl-hydrazyl free radicals (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS⁺). The dinuclear compounds Cu1-Cu4, from the concentration of 5 μM, presented a good activity in scavenging DPPH radical. In addition, most of the Cu(II) complexes showed ABTS^.+ radical-scavenging activity. The monomeric complex Cu5 at all concentrations tested showed antioxidant inability. The cytotoxicity of the Cu1 and Cu3 was determined in V79 cell line by reduction of 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay.