Polysulfides (H2Sx) represent a class of reactive sulfur species (RSS) which includes molecules such as H2S2, H2S3, H2S4, and H2S5, and whose presence and impact in biological systems, when compared to other sulfur compounds, has only recently attracted the wider attention of researchers. Studies in this field have revealed a facet-rich chemistry and biological activity associated with such chemically simple, still unusual inorganic molecules. Despite their chemical simplicity, these inorganic species, as reductants and oxidants, metal binders, surfactant-like “cork screws” for membranes, components of perthiol signalling and reservoirs for inorganic hydrogen sulfide (H2S), are at the centre of complicated formation and transformation pathways which affect numerous cellular processes. Starting from their chemistry, the hidden presence and various roles of polysulfides in biology may become more apparent, despite their lack of clear analytical fingerprints and often murky biochemical footprints. Indeed, the biological chemistry of H2Sx follows many unexplored paths and today, the relationship between H2S and its oxidized H2Sx species needs to be clarified as a matter of “unmistaken identity”. Simultaneously, emerging species, such as HSSeSH and SenS8−n, also need to be considered in earnest.
Selenocyanates demonstrate pronounced activity against bacteria of the ESKAPE family, yeast and nematodes with limited cytotoxicity against human cells.
Selenium is an essential trace element. Although this chalcogen forms a wide variety of compounds, there are surprisingly few small-molecule organic selenium compounds (OSeCs) in biology. Besides its more prominent relative selenocysteine (SeCys), the amino acid selenomethionine (SeMet) is one example. SeMet is synthesized in plants and some fungi and, via nutrition, finds its way into mammalian cells. In contrast to its sulfur analog methionine (Met), SeMet is extraordinarily redox active under physiological conditions and via its catalytic selenide (RSeR’)/selenoxide (RSe(O)R’) couple provides protection against reactive oxygen species (ROS) and other possibly harmful oxidants. In contrast to SeCys, which is incorporated via an eloquent ribosomal mechanism, SeMet can enter such biomolecules by simply replacing proteinogenic Met. Interestingly, eukaryotes, such as yeast and mammals, also metabolize SeMet to a small family of reactive selenium species (RSeS). Together, SeMet, proteins containing SeMet and metabolites of SeMet form a powerful triad of redox-active metabolites with a plethora of biological implications. In any case, SeMet and its family of natural RSeS provide plenty of opportunities for studies in the fields of nutrition, aging, health and redox biology.
Background: Vegetables and fruits are consumed in considerable amounts worldwide producing huge quantities of organic leftovers comprising primarily of peels. Peels of potatoes (PP) and carrots (CP), for instance, are often considered as waste, albeit they still represent a rich source of interesting phytochemicals. Traditional waste management of such materials, usually vermicomposting, therefore represents a low value approach and also a considerable burden to the environment. Objective: Aiming to turn some of this waste into raw materials for further applications, methods were explored to prepare suspensions of PP and CP. Antioxidant activities of these suspensions were compared to bulk-suspensions and the corresponding ethanolic extracts in anticipation of possible applications in Nutrition and Cosmetics. Methods: The peels of potatoes and carrots were subjected to high speed stirring (HSS) and high pressure homogenization (HPH) to produce the suspensions which were characterized for size distribution by Laser Diffraction (LD), Photon Correlation Spectroscopy (PCS) and light microscopy (LM). The ethanolic extracts of peels were also produced. All of the samples were evaluated for antioxidant activity employing 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Results: HPH produced suspensions of peels comprised of particles with diameters in the range of 268 - 335 nm for PP and 654 - 1,560 nm for CP. These suspensions exhibited a significantly stronger antioxidant activity compared to the bulk-suspensions. Moreover, the suspension of PP (1% w/w) exhibited comparable antioxidant activity to the ethanolic extract (1% w/w) whilst the CP suspension (1% w/w) exhibited lower activity compared to the ethanolic extract. Conclusion: Production of suspensions of vegetable peels may unlock some biological potential which could be optimised for applications in Nutrition, Agriculture, Medicine and Cosmetics.
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