Lichen structure

Olafsdottir, E. S. Ingolfsdottir, K. (2001). Polysaccharides from lichens structural characteristics and biological activity. Planta Medica, 67, 199-208. 

Bodo B (1975) L acide bourgeanique nouveau metabolite des lichens. Structure, synthese et biosynthese. Bull Mus Natl Hist Nat Sci Phys Chim 3 (349) 23-97... 

Bodo, B. L Acide Bourgeanique Nouveau Metabolite des Lichens. Structure, Synthese et Biosynthese. Bull. Museum National D Histoire Naturelle, 3rd series. No. 349, 23 (1975). 

Haustoria were the first lichen structures demonstrated with the electron microscope (Moore and McAlear, 1960 Durrell, 1967). These early investigations on lichen ultrastructure confirmed only the existence of haustoria and did not reveal many details of haustorial structure and the infected algal cells. Prominent intracellular haustoria were observed in Maronella laricina (Ahmadjian, 1966), Lecanora muralis (Peveling, 1968b), Lecanora rubina... 

Numerous xanthones have been isolated from lichens structurally elucidated and synthesized by Elix and co-workers and other authors since 1984 these are summarized in Table 7. Formulae 387-464 are listed separately. 

Lobaria pulmonaria (L.) Hoffm. var. meridonalis (Vain) Zahlbr. is a widespread lichen characterized by a lobed structure similar in appearance to alveolar tissue. As Gonzalez et al. (1994) pointed out in their introduction to a discussion of the chemistry of this lichen, its specific epithet reflects its use as a treatment for pulmonary tuberculosis following the Doctrine of Signatures. The varietal name was appended much later to specimens collected in the Philippines. 

Licensing event reports (LERs), for nuclear power facilities, 7 7 539 Lichens, in nitrogen fixation, 7 7 299 Licuri wax, 26 210-211 Lidesthesin, molecular formula and structure, 5 9 It Lidocaine, 5 100... 

The structure of rhodotorulic acid, 2,3-dihydroxybenzoyl and two complexing agents produced by lichens are presented in Fig. 3. 

Although not part of soil, lichens, by virtue of their solubilising action on rocks, contribute to the elemental enrichment of soil. Several studies have identified lichen acids as complexing agents for the iron and aluminium of rocks (95, 96). An examination of the various structures indicates that the basic structure responsible for the chelation is the carboxylic acid group with an orthophenolic group. Grodzinskii (97) has found lichens to be intense accumulators of elements in the uranium-radium, actinouranium and thorium orders. 

When the enol ring is adjacent to a cyclic moiety, then it is possible to achieve very short hydrogen bonds, as in the structure of usnic acid, a natural product found in lichens. A low-temperature X-ray diffraction analysis of this compound showed two enol moieties, one in which a carbon-carbon bond of the enol was part of a cyclohexenone ring, and this had... 

The structure of retigeradiol, from the lichen Lobaria retigera, has been revised to stictane-3j8,22a-diol (211). It was originally thought to be taraxerane-3/3,19/3-diol. The ketol previously isolated from Centraria nivalis is probably 22a-hydroxystictan-3-one (212). ... 

The simplest quinones are o- and p-benzoquinone [(3) and (4) respectively]. This quinonoid structural feature is widespread in naturally occurring compounds isolated from moulds, fungi, lichens, plants and insects,52 which include not only substituted benzoquinones but also substituted polycyclic quinones [i.e. the substituted analogues of, for example, 1,2-naphthoquinone (5), 9,10-anthraquinone (6), and 9,10-phenanthraquinone (7)]. 

The cellular slime mold Dictyostelium purpureum K1001 contains AB0022A (2255), a novel antibacterial dibenzofuran, the structure of which was confirmed by total synthesis (2038). The lichen Lecanora cinereocarnea has yielded several new dibenzofurans, including three chlorinated analogues (2256-2258) (2039), and Lecanora iseana contains 2259 and 2260 (2040). The first naturally occurring polybrominated dibenzofuran, corallinafuran (2261), is present in a crustose coralline red alga that also contains corallinaether (1913) cited earlier (1769). 

Birkbeck AA, Sargent MV, Elix JA (1990) The Structures of the Lichen Depsidones Fulgidin and Isofulgidin. Aust J Chem 43 419... 

Elix JA, Robertson F, Wardlaw JH, Willis AC (1994) Isolation and Structure Determination of Demethylchodatin - a New Lichen Xanthone. Aust J Chem 47 2291... 

C-Methylation also features in the biosynthesis of usnic acid (Figure 3.41), an antibacterial metabolite found in many lichens, e.g. Usnea and Clado-nia species, which are symbiotic combinations of alga and fungus. However, the principal structural modification encountered involves phenolic oxidative coupling (see page 28). Two molecules of methylphloracetophenone are incorporated, and these are known to derive from a pre-aromatization methylation reaction and not by... 

Dayan, F. E. and Romagni, J. G., 2001. Structural diversity of lichen metabolites and their potential use in pest management. In Advances in Microbial Toxin Research and Its Biotechnological Exploitation (in press). 

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