Lichen substances

Usnic acid (7.53)—a highly biologically active dibenzofuran—is a phenol oxidation product of an acylphlorogludnol. It is produced by numerous lichens, including several Usnea species. Apart from its antibiotic and anti-leukemic activity, it has insect anti-feedant activity. Its presence may account for the observation that many lichens are resistant to serious insect attack. 

A second large group of polyketide metabolites that have been isolated from lichens are heptaketide xanthones. Their structures are mainly based on norli-chexanthone (7.54). An interesting feature of these compounds is the presence of chlorine in several of the metabolites. Lichens also produce some anthraquinone pigments, exemplified by physcion (7.6) from Xanthora species. 

A further family of aromatic compounds produced by lichens is derived from shikimic add via phenylalanine and is exemplified by vulpinic acid (7.55), which was isolated from Letharia vulpina. Vulpinic acid has been synthesized by the lead tetra-acetate oxidation of polyporic acid. Lichens also produce some alkylated citric acid derivatives such as lichesterinic acid (7.56) and some sterols. 

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Flechte, /. lichen plait, twist skin eruption, flechten, v.t. plait, twist, braid, interweave, Flechten-far toffi m. lichen coloring matter, -rot, n, orcein, -saure, /. fumaric acid (old name). -stSrkemehl, n. lichenin, moss starch, -stoffe, m.pl. lichen substances. 

Hunek S, Yoshimura I (1996) Identification of Lichen Substances. Springer, Berlin... 

Huneck, S. and Yoshimura, I., 1996. In Identification of Lichen Substances, Springer-Verlag, Berlin, 228-229. 

Lawrey, J. D., 1986. Biological role of lichen substances. Bryologist9, HI-... 

Rocks colonized by lichens weather faster than uncolonized rock surfaces, as a direct result of metal chelation by lichen substances and organic acids (Fig. 15.3). Fomina et al. and Smits (Chapters 10 and 13, this volume) provide comprehensive discussions of the effects of fungi on mineral weathering processes, and therefore only a brief summary of the effects of lichens on this phenomenon will be presented here. Essentially, lichen colonization can influence the rate of silicate weathering through... 

Takani, M., Yajima, T., Masuda, H. Yamauchi, O. (2002). Spectroscopic and structural characterization of copper(II) and palladium(II) complexes of a lichen substance usnic acid and its derivatives. Possible forms of environmental metals retained in lichens. Journal of Inorganic Biochemistry, 91, 139-50. 

Biosynthesis of lichen substances, products of a symbiotic association, K. Mosbach, Angew. Chem. Int. Ed. Engl., 1969, 8, 240. 

New Study of Antimicrobrial Activity and Identification of Lichenical Substances of Some Lichens From South Spain." P/zar/w Ft 49(5) 278285, 1991. Abstract. 

D. are condensation products of aromatic hydroxy-carboxylic acids in which the carboxy group of the acidic molecule (S) is esterified by the phenolic hydroxy group of the 2nd acidic molecule (A, alcohol). Depending on the number of hydroxycarboxylic acids in the molecule distinction is made between di- and tridep-sides and on the linkage between para- and meta-de-psides. D. occur mainly in lichens ( lichen substances) where the substituents in the above formula can be r, R =CHj, n-CjH, n-CsH, R, R =H, CHj, CHO,... 

A small group of aromatic lichen substances [ picio-lichenic acid, subpicrolichenic acid, and superpicroli-... 

C21H20O7, Mr 384.39, orange-red cryst., mp. 201 °C. An anthraquinone from the foliose lichen Solorina crocea, the undersides of the thalli are colored orange. S. is used as a reference substance for HPLC analysis of lichen substances. 

C 9H,40, Mr 386.31, needles, mp. 270-272°C (decomp.). A depsidone with a cyclic hemiacylal group in the alcohol part of the molecule occurs in numerous lichens, especially of the family Parmeliaceae. Lit. Culberson, p. 161 ff. Huneck Yoshimura, Identification of Lichen Substances, Heidelberg Springer 1996 Phytochemistry 25, 550 (1986). - [CAS 549-06-4]... 

Asahina Shibata, Chemistry of Lichen Substances, Tokyo Japan Soc. for the Promotion of Science 1954... 

Contents D. A. H. TAYLOR The Chemistry of the Limonoids from Melia-ceae. — J. A. ELIX, A. A. WHITTON, M. V. SARGENT Recent Progress in the Chemistry of Lichen Substances. — Y. SHIMIZU Paralytic Shellfish Poisons. 

Maass, W.S.G. Lichen Substances IV. Incorporation of Pulvinic- C Acids into Calycin by the Lichen Pseudocyphellaria crocata. Canad. J. Biochem. 48, 1241 (1970). 

Mosbach, K. On the Biosynthesis of Lichen Substances 2. The Pulvinic Acid Derivative Vulpinic Acid. Biochem. Biophys. Res. Commun. 17, 363 (1964). 

Fischer synthesized hcanoric acid, a depside found in lichen substances. 

Saxony, Germany, died 1917 at Feuerbach near Stuttgart), who published 18 papers on lichen substances in the period between 1861 and 1905 and wrote an article on Flechtenstoffe in the 1912 edition of Abderhalden s Biochemisches Handlexikon. 

The lichen substances first known in their structure were vulpinic acid (Spiegel 1883) and... 

Asahina and Shibata published another classic, Chemistry of Lichen Substances, in 1954. Both scientists and their coworkers not only elucidated the structure of numerous compounds, but also described their synthesis and introduced the determination of lichen substances by microcrystallization, a remarkable progress in times without thin layer chromatography and high performance liquid chromatography. Other important work on the chemistry of lichen substances was done by Roller, Pfau,... 

A milestone in the field of lichen substances was the publication of Chicita F. Culberson s Chemical and Botanical Guide to Lichen Products, which appeared in 1969. Together with two supplementary volumes (C.F. Culberson 1970 C.F. Culberson et al. 1977b), this trilogy siunma-rizes data of about 430 lichen substances and their occurrence known up to 1976. 

General Meaning of Lichen Substances and Their Use in Past and Present Time... 

The field of chemistry and biochemistry of lichen substances has been reviewed regularly since 1968 by Huneck (1968,1971,1984c, 1991), Elix et al. (1984c), Galun (1988) and Fahselt (1994). 

The pharmacological activities of lichen substances to 1906 were summarized in Zopf s monography (Zopf 1907). Subramanian (1966) reported on drugs from lichens, while Hanssen and Schadler (1985), Richardson (1988) and Schindler (1988) gave overviews on the medicinal aspects of lichens. 

According to more recent investigations, the biological activities of lichens and lichen substances can be divided into ... 

Antitumour and Antimutagenic Activity. The following lichen substances have antitumour and antimutagenic activity (-)-... 

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