Abstract
Microalgae are well known as primary producers in the hydrosphere. As sources of natural products, microalgae are attracting major attention due to the potential of their practical applications as valuable food constituents, raw material for biofuels, drug candidates, and components of drug delivery systems. This paper presents a short review of a low-molecular-weight steroid and sphingolipid glycoconjugates, with an analysis of the literature on their structures, functions, and bioactivities. The discussed data on sterols and the corresponding glycoconjugates not only demonstrate their structural diversity and properties, but also allow for a better understanding of steroid biogenesis in some echinoderms, mollusks, and other invertebrates which receive these substances from food and possibly from their microalgal symbionts. In another part of this review, the structures and biological functions of sphingolipid glycoconjugates are discussed. Their role in limiting microalgal blooms as a result of viral infections is emphasized.
Highlights
The search for new marine-derived molecules in previously insufficiently studied groups of marine organisms is one of the most important stages of drug discovery
Cholesterol was found as the only common fraction of free and all conjugated forms in these microalgae, it is a minor constituent of free sterols in some of these species [33]. These results showed that the glycosylation may occur in the studied microalgae, and that glycosylation leads to the formation of a variety of known and previously-unknown compounds
The biosynthesis of steryl glycosides in plants, including some microalgae, occurs with the participation of sterol glycosyltransferases and uridine diphosphate glucose (UDP) as a sugar donor; this was shown using the example of the parasitic chlorophyte Protothecha zopfii [55]
Summary
The search for new marine-derived molecules in previously insufficiently studied groups of marine organisms is one of the most important stages of drug discovery. Diatoms (kingdom Chromista, phylum Ochrophyta) are an abundant and widely-distributed component of the marine phytoplankton, including over 8000 species [2]. Cryptophytes (phylum Cryptophyta, kingdom Chromista) is a small group of marine and freshwater microalgae (about 200 species) which is abundant in brackish-water habitats and oligotrophic lakes. 2000 species) belong to the kingdom Protozoa [1,2], consisting mostly of unicellular motile microalgae This algal group is abundant in freshwater habitats: puddles, ditches, ponds, streams, lakes, and rivers, in waters exposed to pollutants or decaying organic matter [3]. Most microalgae are capable of performing photosynthesis, and globally produce about a half of all organic substances and oxygen each year, some groups are shown to be heterotrophs All these lower plants lie at the base of food webs in the hydrosphere, providing the major part of matter and energy for higher trophic levels.
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