Valery M. Dembitsky

Bioactive cyclobutane-containing alkaloids.

The present review describes research on novel natural cyclobutane-containing alkaloids and synthetic compounds isolated from terrestrial and marine species. More than 210 compounds have been confirmed to show antimicrobial, antibacterial, anticancer, and other activities. Structures, origins, biosynthesis, photodimerization, and biological activities of a selection of cyclobutane-containing alkaloids and selected synthethic analogs of natural alkaloids are reviewed.

Oxidation, epoxidation and sulfoxidation reactions catalysed by haloperoxidases

Biological systems have evolved haloperoxidase (HaloPO) enzymes to catalyze the oxidation of chloride, bromide and iodide by hydrogen peroxide. Recent reviews have been published that deal with various aspects and activity of these enzymes. – 11 Three classes of haloperoxidases have been identified. The first is a class of enzymes found in bacteria without a prosthetic group. The second is hemecontaining peroxidases such as chloroperoxidase (CPO) first discovered in the marine fungus Caldariomyces fumago in 1966, myeroperoxidase, eosinophil peroxidase and lactoperoxidase from mammalian systems. The third class of haloperoxidases is vanadium-containing peroxidases that require a vanadate ion (VO4 ). Vanadium peroxidase was fist discovered in the brown alga Ascophyllum nodosum in 1984 but since then it has also been found in lichen Xanthoria parietina and in fungi.

Natural halogenated fatty acids: their analogues and derivatives.

A comprehensive survey has been made of all fatty acids containing halogen atoms covalently bonded to carbon and which are deemed as naturally occurring. Generally thought to be minor components produced by many different organisms, these interesting compounds now number more than 300. Recent research, especially in the marine area, indicates this number will increase in the future. Sources of halogenated fatty acids include microorganisms, algae, marine invertebrates, and higher plants and some animals. Their possible biological significance has also been discussed

Natural and synthetic small boron-containing molecules as potential inhibitors of bacterial and fungal quorum sensing.

Chemical communication is a phenomenon exhibited by many different organisms and nowadays is one of the most prominent research areas at the chemistry-microbiology interface.1–6 For more than 20 years, science has recognized the ability of different bacteria to coordinate phenotype expression using signaling substances, which is a crucial process for successful environment colonization in plants, other animal hosts, and also for human beings7–10

Aziridine alkaloids as potential therapeutic agents

The present review describes research on natural aziridine alkaloids isolated from both terrestrial and marine species, as well as their lipophilic semi-synthetic, and/or synthetic analogs. Over 130 biologically active aziridine-containing compounds demonstrate confirmed pharmacological activity including antitumor, antimicrobial, antibacterial effects. The structures, origin, and biological activities of aziridine alkaloids are reviewed. Consequently this review emphasizes the role of aziridine alkaloids as an important source of drug prototypes and leads for drug discovery.

Glycolipids, phospholipids and fatty acids of brown algae species

Abstract The fatty acid composition of brown algae from the Black Sea was examined. It was demonstrated that their main fatty acids were 16:0, 18:1, 18:3, 18:4 and 20:5. Examination of the glycolipid composition showed that monoglycosyldiacylglycerol content varied from 26.8 to 46.5% of total glycolipids, diglycosyldiacylglycerol content from 19.6 to 44.1%, and sulphaquinovosyldiacylglycerol content from 17.5 to 51.7%. The proportion of general lipids in various species varied from 1.2 to 4.9% and that of phospholipids from 2.9 to 19.7%. Major phospholipids were phosphatidyl choline (PC), phosphatidyl glycerol (PG) and phosphatidyl ethanolamine (PE); however, some of them were found to contain PE, PG and phosphatidyl inositol as major phospholipids but no PC. Phosphorus-containing unidentified lipids were found in certain of the species examined.

Anticancer activity of natural and synthetic acetylenic lipids

This review is a comprehensive survey of acetylenic lipids and their derivatives, obtained from living organisms, that have anticancer activity. Acetylenic metabolites belong to a class of molecules containing triple bond(s). They are found in plants, fungi, microorganisms, and marine invertebrates. Although acetylenes are common as components of terrestrial plants, fungi, and bacteria, it is only within the last 30 years that biologically active polyacetylenes having unusual structural features have been reported from plants, cyanobacteria, algae, invertebrates, and other sources. Naturally occurring aquatic acetylenes are of particular interest since many of them display important biological activities and possess antitumor, antibacterial, antimicrobial, antifouling, antifungal, pesticidal, phototoxic, HIV-inhibitory, and immunosuppressive properties. There is no doubt that they are of great interest, especially for the medicinal and/or pharmaceutical industries. This review presents structures and describes cytotoxic and anticancer activities only for more than 300 acetylenic lipids and their derivatives isolated from living organisms.

Glycolipids and fatty acids of some seaweeds and marine grasses from the black sea

Abstract Fourteen species of marine red algae belonging to the Rhodophyta, 13 species of marine green algae belonging to the Chlorophyta and two species of the marine grass from the Embryophyta were examined for their glycolipid and fatty acid compositions. Characteristic of red algae was their high content of 20:4 and 20:5. The green algal species were unusual in containing 16:4 varying from 4.9 to 23.1 % of the total fatty acids; 16:0, 18:1 and 18:3 acids were also found in high amounts. Glycolipid contents of total lipid extracts of red algae ranged from 16.4 to 31.8, μmol g − 1 dry wt, while those in green algae varied from 10.5 to 31.8. The red algae contained almost equal quantities of monoglycosyldiacylglycerol (MGDG), diglycosyldiacylglycerol (DGDG) and sulphaquinovosyldiacyl-glycerol with some exceptions. MGDG and DGDG were the major glycolipids in green algae and marine grasses, respectively.

Novel Antitumor Agents: Marine Sponge Alkaloids, their Synthetic Analogs and Derivatives

Present review describes research on novel natural antitumor agents isolated from marine sponges. More than 90 novel cytotoxic antitumor compounds and their synthetic analogs have shown confirmed activity in vitro tumor cell lines bioassay and are of current interest to NCI for further in vivo evaluation. A great problem, to use directly the reservoir of marine organisms for therapy is the very low availability and the isolation of only very small amounts of the biologically active substances from the natural materials. Thus, the synthetic chemistry is required to develop high yield synthetic methods, which are able to produce sufficient marine alkaloids for a broad biological screening. This review will present some of the aspects of the medicinal chemistry developed recently to introduce such modifications. The structures, origins, synthesis and biological activity of a selection of N-heterocyclic marine sponge alkaloids are reviewed. The emphasis is on compounds poised as potential anticancer drugs: pyrroles, pyrazines, imidazole, and other structural families. With computer program PASS some additional biological activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of marine sponge alkaloids as an important source of leads for drug discovery.

Natural occurrence of boron-containing compounds in plants, algae and microorganisms

Discovery of naturally-occurring boron compounds, all ionophoric polyketide macrodiolide antibiotics with a single boron atom critical for activity, established at least one biochemical role of boron. This review focuses primarily on presence and distribution of boron-containing compounds in vascular plants, marine algal species, and microorganisms.