Mariana Barbosa

Valuable compounds in macroalgae extracts.

Bioactive compounds present in ethanolic extracts from 18 macroalgae of the Portuguese coast were analysed by gas chromatography-mass spectrometry (GC-MS), leading to the characterization of 14 compounds: proline, phloroglucinol, mannitol, 8 fatty acids and 3 sterols. A dose-dependent response against enzymes with biological significance (α-glucosidase, acetylcholinesterase and butyrylcholinesterase) and free radicals (DPPH, nitric oxide, superoxide and hydroxyl) was found, Phaeophyta being the most promising group. A PCA analysis was performed and allowed the establishment of a correlation between the algae chemical composition and the biological activity. Cystoseira tamariscifolia (Hudson) Papenfuss, Cystoseira nodicaulis (Withering) M. Roberts, Cystoseira usneoides (Linnaeus) M. Roberts and Fucus spiralis Linnaeus are among the most active species, which is in accordance with their higher contents in phloroglucinol, mannitol, oleic, arachidonic and eicosapentaenoic acids, and fucosterol. The results point to the potential interest of the use of Phaeophyta species as food additives, due to their potent antiradical activities, and especially highlights the importance of F. spiralis in the food chain of Mediterranean countries. Moreover, the incorporation of the extracts of these species in food products, nutraceutical and pharmaceutical preparations for human health should also be instigated, since they can suppress hyperglycemia and inhibit cholinesterases.

Bioactive Compounds from Macroalgae in the New Millennium: Implications for Neurodegenerative Diseases

Marine environment has proven to be a rich source of structurally diverse and complex compounds exhibiting numerous interesting biological effects. Macroalgae are currently being explored as novel and sustainable sources of bioactive compounds for both pharmaceutical and nutraceutical applications. Given the increasing prevalence of different forms of dementia, researchers have been focusing their attention on the discovery and development of new compounds from macroalgae for potential application in neuroprotection. Neuroprotection involves multiple and complex mechanisms, which are deeply related. Therefore, compounds exerting neuroprotective effects through different pathways could present viable approaches in the management of neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. In fact, several studies had already provided promising insights into the neuroprotective effects of a series of compounds isolated from different macroalgae species. This review will focus on compounds from macroalgae that exhibit neuroprotective effects and their potential application to treat and/or prevent neurodegenerative diseases.

Hydrogel depots for local co-delivery of osteoinductive peptides and mesenchymal stem cells

The outcome of cell-based therapies can benefit from carefully designed cell carriers. A multifunctional injectable vehicle for the co-delivery of human mesenchymal stem cells (hMSCs) and osteoinductive peptides is proposed, to specifically direct hMSCs osteogenic differentiation. The osteogenic growth peptide (OGP) inspired the design of two peptides, where the bioactive portion of OGP was flanked by a protease-sensitive linker, or its scrambled sequence, to provide faster and slower release rates, respectively. Peptides were fully characterized and chemically grafted to alginate. Both OGP analogs released bioactive fragments in vitro, at different kinetics, which stimulated hMSCs proliferation and osteogenesis. hMSCs-laden OGP-alginate hydrogels were tested at an ectopic site in a xenograft mouse model. After 4weeks, OGP-alginate hydrogels were more degraded and colonized by vascularized connective tissue than the control (without OGP). hMSCs were able to proliferate, migrate outward the hydrogels, produce endogenous extracellular matrix and mineralize it. Moreover, OGP-groups stimulated hMSCs osteogenesis, as compared with the control. Overall, the ability of the proposed platform to direct the fate of transplanted hMSCs in loco was demonstrated, and OGP-releasing hydrogels emerged as a potentially useful system to promote bone regeneration.

Biologically Active Oxylipins from Enzymatic and Nonenzymatic Routes in Macroalgae

Marine algae are rich and heterogeneous sources of great chemical diversity, among which oxylipins are a well-recognized class of natural products. Algal oxylipins comprise an assortment of oxygenated, halogenated, and unsaturated functional groups and also several carbocycles, varying in ring size and position in lipid chain. Besides the discovery of structurally diverse oxylipins in macroalgae, research has recently deciphered the role of some of these metabolites in the defense and innate immunity of photosynthetic marine organisms. This review is an attempt to comprehensively cover the available literature on the chemistry, biosynthesis, ecology, and potential bioactivity of oxylipins from marine macroalgae. For a better understanding, enzymatic and nonenzymatic routes were separated; however, both processes often occur concomitantly and may influence each other, even producing structurally related molecules.

Nonenzymatic α-Linolenic Acid Derivatives from the Sea: Macroalgae as Novel Sources of Phytoprostanes.

Phytoprostanes, autoxidation products of α-linolenic acid, have been studied in several plant species, but information regarding the natural occurrence of this large family of biologically active oxidized lipids in macroalgae is still scarce. In this work, the free phytoprostane composition of 24 macroalgae species belonging to Chlorophyta, Phaeophyta, and Rhodophyta was determined through a recently validated UHPLC-QqQ-MS/MS method. The phytoprostane profiles varied greatly among all samples, F1t-phytoprostanes and L1-phytoprostanes being the predominant and minor classes, respectively. No correlation between the amounts of α-linolenic acid in alga material and phytoprostane content was found. Therefore, it was hypothesized that the observed variability could be species-specific or result from interspecific interactions. This study provides new insight about the occurrence of phytoprostanes in macroalgae and opens doors for future exploitation of these marine photosynthetic organisms as sources of potentially bioactive oxylipins, encouraging their incorporation in food products and nutraceutical and pharmaceutical preparations for human health.

The pigments of kelps (Ochrophyta) as part of the flexible response to highly variable marine environments

Macroalgae drive the biodiversity and functioning of many shallow benthic ecosystems. Besides their key role in coastal ecosystems, they are rich sources of a wide variety of unique molecules with high impact in food science, pharmaceutical industry and public health. Carotenoids and chlorophylls present in three kelp species—Laminaria ochroleuca, Saccharina latissima and Saccorhiza polyschides—were determined by high-performance liquid chromatography coupled to a diode array detector. The effect of different harvesting times, depths and growth conditions (wild vs. aquaculture) on pigment qualitative and quantitative profiles was assessed. Stipes, blades and whole macroalgae were studied. In spite of the considerable variability observed amongst all samples, fucoxanthin was evidently the main carotenoid. Overall, the relative contents of carotenoids were significantly higher than those of chlorophylls. In addition, the cultivation of macroalgae in an integrated multi-trophic aquaculture system appears to increase pigment levels. Altogether, the results demonstrate the complexity of the influence of species-specific and environmental factors on pigment composition and reinforce that macroalgae cultivation systems may provide an interesting approach to optimize the production of some valuable metabolites.

Grafting Techniques towards Production of Peptide-Tethered Hydrogels, a Novel Class of Materials with Biomedical Interest

In recent years, new highly functional polymeric biomaterials are being developed to increase the therapeutic efficacy in tissue regeneration approaches. Peptides regulate most physiological processes and display several other biological activities. Therefore, their importance in the field of biomedical research and drug development is rapidly increasing. However, the use of peptides as therapeutic agents is restricted by some of their physicochemical properties. The development of improved routes of delivery of peptide-based therapeutics is crucial and is crucial and its biomedical value is expected to increase in the near future. The unique properties of hydrogels triggered their spreading as localized drug depots. Several strategies, such as the carbodiimide chemistry, have been used to successfully immobilize bioactive peptide sequences into the hydrogels backbone. Peptide tethering through the so-called “click” chemistry reactions is also a highly promising, yet underexplored, approach to the synthesis of hydrogels with varying dimensions and patterns. The present review focus on the approaches that are being used for the establishment of chemical bonds between peptides and non-peptidic hydrogels throughout the last decade.

Chemical profiling of edible seaweed (Ochrophyta) extracts and assessment of their in vitro effects on cell-free enzyme systems and on the viability of glutamate-injured SH-SY5Y cells

Neurodegenerative processes involve numerous and closely related events that ultimately culminate in neuronal cell injury. The aim of this study was (i) to assess, for the first time, the neuroprotective potential of acetone extracts of six edible species of Ochrophyta, by evaluating their cholinesterase and lipoxygenase inhibitory activity in cell-free assays, as well as their capacity to attenuate glutamate-induced toxicity in neuronal (SH-SY5Y) cells, and (ii) to try to relate the chemical composition of the extracts with their biological activity, evaluating also the effect of the main compounds thereof. In spite of a modest cholinesterase inhibition, a dose-dependent response towards lipoxygenase was found for all macroalgae extracts. At non-cytotoxic concentrations, the extracts from Fucus serratus Linnaeus and Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl & G.W. Saunders were able to improve the viability of glutamate-insulted SH-SY5Y cells. These results encourage further studies for a more detailed understanding of the mechanisms beyond the documented biological activities, and point to the potential interest of the selected seaweed species and their extracts as promising candidates for in vivo studies.

Edible seaweeds’ phlorotannins in allergy: A natural multi-target approach

The anti-allergenicity of phlorotannin-targeted extracts from four edible seaweed species of Fucus genus was evaluated herein for the first time. Extracts were able to act upon cellular events triggered by immunological reaction (IgE/antigen), and on cellular events downstream the Ca2+ influx caused by a chemical stimulus (calcium ionophore A23187), preventing degranulation of RBL-2H3 cells. Furthermore, a dose-dependent behaviour towards allergy-related enzymatic systems was observed for all the phlorotannin extracts. Linear correlations were found between reduction of the allergic mediators released and the total phlorotannin content, as well as between the enzyme inhibition and the amount of phlorotannins in the extracts. These results point to a multi-target anti-allergic capacity of phlorotannin-targeted extracts, which displayed effects on different critical steps of the allergic response, contributing to the valorisation of Fucus spp. both as food and for nutraceutical applications.