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Red seaweed carrageenans are frequently used in industry for its texturizing properties and have demonstrated antiviral activities that can be used in human medicine. However, their high viscosity, high molecular weight, and low skin penetration limit their use. Low-weight carrageenans have a reduced viscosity and molecular weight, enhancing their biological properties. In this study, ι-carrageenan from Solieria chordalis, extracted using hot water and dialyzed, was depolymerized using hydrogen peroxide and ultrasound. Ultrasonic depolymerization yielded fractions of average molecular weight (50 kDa) that were rich in sulfate groups (16% and 33%) compared to those from the hydrogen peroxide treatment (7 kDa, 6% and 9%). The potential bioactivity of the polysaccharides and low-molecular-weight (LMW) fractions were assessed using WST-1 and LDH assays for human fibroblast viability, proliferation, and cytotoxicity. The depolymerized fractions did not affect cell proliferation and were not cytotoxic. This research highlights the diversity in the biochemical composition and lack of cytotoxicity of Solieria chordalis polysaccharides and LMW fractions produced by a green (ultrasound) depolymerization method.

Macroalgae are a potentially novel source of nutrition and biologically active molecules. Proliferative species such as Eucheuma denticulatum, Solieria chordalis (red algae) and Sargassum muticum (brown alga) constitute a huge biomass that can be exploited. In this study, we focus on the extraction of polysaccharides from these three macroalgae species and the characterization of cell wall polysaccharides such as carrageenans, fucoidans and alginates by Fourier Transform Infrared spectroscopy with Attenuated Reflectance Module (FTIR-ATR). The comparison of purified extracts with commercial solutions of fucoidans, alginates or carrageenans shows a strong similarity between the spectra. It demonstrates that the methods of extraction that have been used are also suitable purifying technics. Moreover, it validates infrared spectroscopy as a quick, simple and non-destructive method for the accurate analysis of polysaccharides. The FTIR technique applied to samples collected at different periods of the year allowed us to highlight differences in the composition of fucoidans, alginates and carrageenans. Different classes corresponding to the season can be distinguished by statistical multidimensionnal analysis (Principal Component Analysis) showing that the structure of algal polysaccharides, related to bioactivity, depends on the period of harvest. FTIR results showed that S. chordalis and E. denticulatum possess a dominant type of carrageenan called iota-carrageenan. This type of carrageenan is in the majority when the alga is at maturity in its development cycle. During its growth phase, iota-carrageenan precursors can be detected by FTIR spectra, enabling a better control of the extraction and an application of these compounds in various economic sectors. When the alga E. denticulatum is in its juvenile stage, we found traces of kappa-carrageenan and nu-carrageenan polysaccharides in some extracts.

Objective: To investigate phenolics, fatty acids composition and biological activities of various extracts and fractions of Malaysian Aaptos aaptos. Methods: Fatty acid methyl ester was analyzed by gas chromatography-flame ionization detector. Antioxidant activity was determined using 2,2-diphenyl-picrylhydrazyl radical scavenging assay and total phenolics content by Folin-Ciocalteu procedure. Vero cells viability was evaluated using methyl thiazole tetrazolium and the inactivation of herpes simplex virus type 1 by neutral red uptake assay. p-Hydroxybenzamide isolated by column chromatography was characterized by utilizing nuclear magnetic resonance spectroscopy and electron impact mass spectrometry. Results: The chloroform, ethyl acetate and methanol extracts of Aaptos aaptos produced higher portions of straight-chain saturated fatty acid, while hexane extract mainly consisted of unsaturated fatty acid. The five majors of fatty acid methyl ester were identified as behenic acid, cis-10-heptadecenoic acid and cis-10-pentadecenoic acids, palmitic acid and tricosanoic acid. In addition, among all organic extracts, chloroform extract inactivated herpes simplex virus type 1 while exhibited weak cytotoxic activity against normal Vero cells and also exhibited strong cytotoxic activity on HL-60, MCF-7, K562, CEM-SS and WEHI-3B cells. A phenolic compound, p-hydroxybenzamide was also isolated from the sponge. Conclusions: Aaptos aaptos could be a source to derive the potential antiviral and anticancer agents. However, further studies are needed to determine the mechanism involved in the process.