Veneta Ivanova

Microbiaeratin, a new natural indole alkaloid from a Microbispora aerata strain, isolated from Livingston Island, Antarctica.

Abstract A new sulphur‐containing natural alkaloid named microbiaeratin (1a) was isolated, together with the known microbiaeratinin (2, bacillamide) from the culture filtrate of Microbispora aerata strain IMBAS‐11A. The organism was isolated from penguin excrements collected on the Antarctic Livingston Island. The structure was elucidated by one‐ and two‐dimensional NMR experiments and mass spectrometric investigations.

Comparison of the Phytotoxic Effects of Usnic Acid on Cultures of Free-Living Alga Scenedesmus quadricauda and Aposymbiotically Grown Lichen Photobiont Trebouxia erici

The phytotoxic effects of the lichen secondary metabolite—usnic acid on cultures of free living alga—Scenedesmus quadricauda (UTEX 76) and aposymbiotically grown lichen photobiont Trebouxia erici (UTEX 911) were assessed. We found a relatively strong inhibition effect of usnic acid on the growth of alga Scenedesmus, accompanied by an increase of cell size, an alteration of assimilation pigment composition, followed by strong degradation of chlorophyll a, a decrease of chlorophyll a fluorescence, and an increase of reactive oxygen species in the cells. The content of soluble proteins remained a stable parameter. Phytotoxicity of usnic acid on cultures of Trebouxia photobiont was significantly lower. Usnic acid in lichens may act as an allochemical that controls the division of photobiont cells, thereby regulating the balance between the photobiont and mycobiont forming thallus. Higher tolerance to usnic acid in Trebouxia cultures may be an adaptation resulting from the long term co-evolution of these algae with fungi that produce secondary metabolites.

MOLECULAR STRUCTURAL STUDIES OF LICHEN SUBSTANCES WITH ANTIMICROBIAL, ANTIPROLIFERATIVE, AND CYTOTOXIC EFFECTS FROM Parmelia subrudecta

Lecanoric acid (1), orsellinic acid methyl ester (2), orcinol (3), and usnic acid (4) were isolated from the lichen Parmelia subrudecta, collected on Palma of the Canary Islands, Spain. Compounds 1, 2, 3, and 4 were purified by solvent extraction, silica gel column chromatography, and preparative high-performance liquid chromatography (HPLC) consecutively. The structures of the four compounds were elucidated by one- and two-dimensional nuclear magnetic resonance (NMR) experiments and mass spectrometric investigations. These compounds showed activity against important gram-positive and gram-negative pathogens like mycobacteria and multiresistant staphylococci. This activity is combined with antiproliferative activity and cytotoxicity.

Diphenylether and Macrotriolides Occurring in a Fungal Isolate from the Antarctic Lichen Neuropogon

Abstract The fungus, Tritirachium sp. HKI 0317, was isolated from the Antarctic lichen Neuropogon sp. Fermentation of this strain, extraction of the culture broth, and preparative separation of produced compounds furnished 4‐carboxy‐5,5′‐dihydroxy‐3,3′‐dimethyldiphenylether (1), macrosphelide A (2), and macrosphelide J (3). The structures were elucidated on the basis of MS and NMR measurements, and the previously published data for this compounds.

Structure elucidation of a new natural diketopiperazine from a Microbispora aerata strain isolated from Livingston Island, Antarctica

A new natural diketopiperazine (1) was obtained from the culture broth of Microbispora aerata strain imbas-11A, isolated from penguin excrements collected on the Antarctic Livingston Island. Compound 1 was purified consecutively by solvent extraction, silica gel column chromatography and preparative HPLC. The structure of the compound was elucidated by 1D and 2D NMR experiments and mass spectrometric investigations. The absolute configuration of compound 1 was determined by amino acid analysis and NOESY correlations. A low antiproliferative and cytotoxic effect of trans-cyclo-(D-tryptophanyl-L-tyrosyl) (1) was determined with L-929 mouse fibroblast cells, K-562 human leukemia cells and HeLa human cervix carcinoma. Trans-cyclo-(D-tryptophanyl-L-tyrosyl) (1) did not show antimicrobial activity at a concentration of 50 µg per disc against Bacillus subtilis, Staphylococcus aureus, Streptomyces viridochromogenes, Escherichia coli, Candida albicans and Mucor miehei.

Secondary metabolites from a Streptomyces strain isolated from Livingston Island, Antarctica.

Abstract The producing strain Streptomyces sp. 1010 was isolated from a shallow sea sediment from the region of Livingston Island, Antarctica. From the culture broth of this strain naturally active secondary metabolites were isolated identical to phthalic acid diethylester (C12H1404, MW.222); 1, 3-bis (3-phenoxyphenoxy)benzene (C30H22O4 , MW.446); hexaned ioic acidd ioctylester (C22H42O4 , MW.370) and the new substance 2-amino-9, 13 -dimethylheptad ecanoic acid (C19H39NO2 , MW.313). These compounds represent diverse classes of chemical structures and provideevidence for the untapped biosynthetic potential of marine bacteria from Antarctica.

Sanionins: Anti‐Inflammatory and Antibacterial Agents with Weak Cytotoxicity from the Antarctic Moss Sanionia georgico‐uncinata

Abstract Sanionins A (1) and B (2) were isolated from the moss Sanionia georgico‐uncinata, collected on the Antarctic Livingston Island. The compounds 1 and 2 were purified by solvent extraction, silica gel column chromatography, and preparative HPLC, consecutively. The structures of the both compounds were elucidated by 1D and 2D NMR experiments and mass spectrometric investigations. These compounds showed activity against important Gram‐positive pathogens, such as mycobacteria, multiresistant staphylococci, and vancomycin resistant enterococci. This activity is combined with antiinflammatoric activity and low cytotoxicity.

BIOACTIVE METABOLITES PRODUCED BY MICROORGANISMS COLLECTED IN ANTARCTICA AND THE ARCTIC

ABSTRACT Survival of microorganisms in the Antarctic and Arctic conditions of life requires of the relevant genera and species special adaptability and resistance against stressors such as lack of substrate, UV-radiation, low temperatures for a long time and short-term intense heat during the Antarctic and Arctic summer. Therefore genetic adaptation of Antarctic and Arctic organisms to stress factors would be expected. All this suggests in a global aspect synthesis of new metabolites with unique structures and specific biological activity. Antarctic and Arctic polar regions are considered as a huge reservoir of microorganisms with versatile antimicrobial potential. Our studies are motivated by an interest in the functional role played by natural products in the ecological interactions of the polar strains with the other members of the microbial community. This overview presents some of the most important secondary metabolites (antibiotics, alkaloids, high carbon amino acids, nitro compounds, diketopiperazines etc.) produced by Antarctic and Arctic microorganisms. The secondary metabolites biosynthesis probably plays an important role in the adaptation and survival of microorganisms in the ice deserts of Antarctica and the Arctic.

Antiinfluenza Virus Effect of Extracts from Marine Algae and Invertebrates

Abstract Sixty products, derived from marine organisms, typical of the Bulgarian Black Sea coast, were examined for inhibitory activity on the reproduction of influenza viruses in tissue cultures. The antiviral effect was investigated by the reduction of virus infectivity. Using representative strains of influenza virus it was shown that apparently the inhibitory effect was strain-specific. The most effective products were further studied in fertile hen’s eggs and in experimental influenza infection in white mice.

New Macrolactone of the Desertomycin Family from Sttreptomyces Spectabilis

The non-polyenic macrocyclic antibiotic complex 1012 was isolated from the culture broth of a strain Streptomyces spectabilis 1. The complex was found to belong to the desertomycin complex. Three main compounds of complex 1012 were separated and purified by preparative chromatographic methods. The identification was performed by UV, IR, NMR and mass-spectrometric studies. It was proved that two of the compounds with MW. 1191, C61H109NO21 and MW. 1190, C61H106O22 were identical to desertomycin A and D. The other com-pound with MW.1028, C55H96O17 is new macrolactone, named deser-tomycin E. The structures were established by detailed spectroscopic analysis.