Usnic lichens

Table 1 Experiment 2. Guided isolation and identification of potential allelochemicals from Cladonia foliacea. O, fraction O P, fraction P UA, usnic acid ca, caulonema ch, chloronema sb, side branches. Protonemal system from shoots after 21 days in culture tested against three fractions from C. foliacea thallus and in control Mohr medium. The observations represent means calculated from about 300 protonemata for each species. P. squarrosa is the species least affected, while 7. flavovirens is the most affected by lichen fractions. 

Not all neomycin salts, however, possess advantages such as a reduced toxicity. In fact, the orotic acid(1,2,3,6-tetrahydro-2,6-dioxo-4-pyrimidine carboxylic acid) salt was reported to have a greater toxicity than neomycin itself74f75. some uncertainty of this fact is apparent as other authors have reported the two compounds to be of a similar toxicity 6. The salt of neomycin with usnic acid(an antibacterial substance found in lichens) has been reported to have less antibacterial activity than the neomycin used in the preparation of the salt. 

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... 

Threats to orceins, orcinol, picrolichenic acid, usnic acid, and other metabolites not shown in Table 16.2.5.1, reflect the sensitivity of lichens to environmental pollution worldwide (Huneck 1999). 

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... 

Romagni, J.G., Meazza, G, Nanayakkara, N.P.D., Dayan, F.E. The phytotoxic lichen metabolite, usnic acid, is a potent inhibitor of plant p-hydroxyphenylpyruvate dioxygenase. FEBS Letters 2000 480 301-305. 

The objectives of this paper are broad. Our first objective is to describe the primary mechanism of action of usnic acid on plants as ascertained by our laboratory.33 A second objective is to describe the phytotoxic activity of selected lichen anthraquinone analogues. In addition to the phytotoxic activity, we describe the effects of these secondary metabolites on phloem-feeding insects. Finally, we provide a hypothesis to explain the functional roles of these metabolites in the ecosystem. 

Lichens containing usnic acid may exhibit phytotoxic activity. In nature, (-)-usnic acid may decrease interspecific competition by inhibiting growth of seedlings in the canopy. Since it is primarily an HPPD inhibitor and secondarily inhibits Protox, there may be a decreased chance for resistance in those competing species. 

We used a leaf disk bioassay adapted from Rowland et al.35 to test the insecticidal activity of lichen secondary products on B. tabaci. Two lichen secondary compounds, (-)-usnic acid and vulpinic acid, showed significant results when compared to the controls. Vulpinic acid had an average mortality of 18%, and (-)-usnic acid had an average mortality of 14%. From the dose response of (-)-usnic acid, LD50 was not reached at 1000pM, but a positive correlation was established with increasing concentration and whitefly population response (data not shown). 

Lauterwein, M., Oethinger, M., Belsner, K., Peters, T., and Marre, R., 1995. In vitro activities of the lichen secondary metabolites vulpinic acid, (+)-usnic acid and (-)-usnic acid against aerobic and anaerobic microorganisms. Antimicrob. Agents Chemo. 39, 2541-2543. 

Romagni, J. G., Meazza, G., Nanayakkara, and D., Dayan, F. E., 2000. The Phytotoxic Lichen Metabolite, Usnic Acid, is a Potent Inhibitor of Plant p-Hydroxyphenylpyruvate Dioxygenase. FEBS Letters 480 (2-3), 301-305. 

The importance of the revised structure 5 for biosynthesis was impressive. We decided to carry out a synthesis of the important lichen compound usnic acid 7. Although we,5 and... 

Usnic acid, found in lichens, has three different cis enol units within the one molecule, and one of these is very short80). In order to locate the protons the X-ray determination was done on a crystal at —110 °C. The unit cell contains two usnic acid molecules whose dimensions for the cis enol OHO bonds differ slightly - see Fig. 6. The shortest hydrogen bond shows that the proton is not centred in either molecule - in one it is nearer the acetyl carbonyl, in the other nearer the ring carbonyl. 

Among phytotoxic compounds produced by lichens, usnic acid (74) is one that is unique and relatively abundant.48 Usnic acid also effectively inhibits HPPD.37... 

Dibenzofurans (Phe furan Phe) include various fungal infection-induced plant antifungal compounds (phytoalexins) such as the Rosaceae-derived cotonefuran (from Cotoneaster lactea) and a-pyrofurans (from Pyrus communis). Usnic acid from lichens (notably Usnea species) is anti-mycobacterial, anti-mitotic, an uncoupler and a potent inhibitor of plant protoporphyrinogen synthetase and 4-hydroxphenylpyruvate dioxygenase. 

Usnic acid Usnea articulata (lichen) Uncoupler (< 1)... 

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. 

Figure 4. Effect of the synthetic diphenyl ether acifluorfen (triangles), the natural diphenyl ether fungal metabolite cyperine (squares) and the dibenzofurandione lichen metabolite usnic acid (circles) on the activity of protoporphyrinogen oxidase. The dotted line represents 50% inhibition of enzyme activity.

Mushrooms and various fungi and lichens are rich in enol metabolites and many exhibit significant bioactivities , such as usnic acid (14) which serves as a regulator for plant growth and shows antitumor and antibiotic activities " . The widely distributed quinone polyporic acid (15a, PPA) from the Purple-Dye Polypore mushroom (Hapalopilus nidu-lans) and other sources is a weak inhibitor (IC50 = 0.1 to >1.5 mM " ) of dihydroorotate... 

Plants Barley dust, lichens (o-usnic acid), hops (colophony), hetzil, sawdust, sesquiterpene lactones compositae, frullania spp.), tulips (tulipalin A), poison ivy (urushiol)... 

ICELAND MOSS, Lichen islandicus consists of the dried thallus of Cetraria islandica (L.) Acharius sensu latiore, family Parmeliaceae. Characteristic constituents include bitter-tasting lichen acids usnic acid gives the bitter-taste and has antibacterial effects. It also contains polysaccharides, which form a mucilage Lichenin, a linear cellulose-like polymer of D-glucose, is soluble in hot water, and on cooling it forms a gel. The other polysaccharide is isolichenin, a linear starch-like polymer of D-glucose, soluble in cold water. 

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. 

Usnic Acid. 2I6 Diacetyl 7t9-dihydraxy 8i9b-di-methyl-It3(2H,9bH)-dibenzofurandione usninic acid usnein Usniacin. C H,407 mol wt 344.31. C 62.79%. H 4.68%, O 32.53%. Antibacterial substance found in lichens. Isolation from varieties of Usnea barbota (L.) Wigg., Usneaceae Rochleder, Heidi> Ann. 48, If (1843) Widman Ann. 310, 230 (1900) 324, 139 (1902). Isoin from Ramalina reticulata Marshak, Public Health Reports 62, 3 (1947) Stark et of., J. Am. Chem. Soc. 72, 1819 (1950). Occurs in nature in both the d- and /-forms as well as a racemic mixture. Structure Curd, Robertson, J. Chem. Soc. 1937, 894 Schopf, Ross, Ann. 546, (1941) Barton, Brunn, /. Chem. Soc. 1953, 603. Resolution of ( )-usnic acid Dean et ai, ibid. 1250. Synthesis Barton et a/., ibid. 1956, 530. Biosynthesis in vitro Penttila, FaJes, Chem. Commun 1966, 656. Abs config of (+)-fomv S. Huneck et aL, Tetrahedron Letters 22, 351 (1981). 

Cansaran, D., S. Aras, and O. Atakol. 2008. Determination of usnic acid content in some lichen species found in Anatolia. /. Appl. Biol Sci. 2(3) 41-44. 

Cansaran, D., D. Kahya, E. Yurdakulol, and O. Atakol. 2006. Identification and quantitation of usnic acid from the lichen Usnea species of Anatolia and antimicrobial activity. Z. Naturfor. 61(11/12) 773. 

Dailey, R.N., D.L. Montgomery, J.T. Ingram, et al. 2008. Toxicity of the lichen secondary metabolite (+)-usnic acid in domestic sheep. Vet. Pathol Online 45(1)-.19. 

CigHiftO, Mr 344.32, yellow prisms, mp. 150-152 °C, [a]o +490° or-490° (dioxan). A dibenzofuran derivative from lichen the (+)-form occurs in Cladonia mitis and Sphaerophorus ramulifer, the (-)-form in Cladoniapleurota. I. is considerably less common than usnic acid. The biosynthesis involves phenol oxidation of methylphloracetophenone. 

---