Lichen chlorinated

Like depsides and depsidones, most chlorinated xanthones are found in lichens, and more than 50 such compounds were described in the first survey (/ ). The lichen... 

Most of the previously identified 25 chlorinated anthraquinones are found in lichen and fungi (1). The newly discovered examples have a wider range of sources. Studies of the lichen Nephroma laevigatum from the British Columbia coast have identified the new anthraquinone, 7-chloro-l-O-methyl-co-hydroxy-emodin (2157), and the two novel hypericins, 7,7 -dichlorohypericin (2158) and 2,2, 7,7 -tetrachlorohypericin (2159) (1931), as well as 5-chloroemodin (2160), 5-c h I oro -1 - (9 - m e t h v I - o >- h yd ro x ye m od i n (2161), and 5-chloro-co-hydroxyemodin (2162) (1932). In addition to containing several known chlorinated anthraquinones, the Scandinavian fungus Dermocybe sanguinea has afforded the new 5,7-dichloroendocrocin (2163) (1933). The novel tetracyclic anthraquinones... 

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). 

Cohen PA, Towers GHN (1996) Biosynthetic Studies on Chlorinated Anthraquinones in the Lichen Nephroma laevigtum. Phytochemistry 42 1325... 

Cohen PA, Towers GHN (1997) Chlorination of Anthraquinones by Lichen and Fungal Enzymes. Phytochemistry 44 271... 

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. 

The Elements.—Downs and Adams have reviewed the chemistry of chlorine, bromine, iodine, and astatine/ The role of fluorine in our environment and the use of lichens as monitors for air pollution have been discussed by Dobbs/ Particulate rather than gaseous fluorides were shown to be the pollutants in the vicinity of one aluminium refining plant/ Bronchitis, pneumonia, nervous disorders, and skin diseases were said" to occur more frequently in workers at a Russian AIF, production plant than in a control group. 

Like the fungal and lichen xanthones, anthraquinones, which are also produced both by lichens and fungi, are derived from extended polyketides by cyclization. Several chlorinated compounds were described. 

Proton induced X-rays emission (PIXE) Samples were pelletized inserted in a boric acid cap. Samples were irradiated with a 2.0 MeV proton beam for filtered spectra and with a 1.2 MeV for filterless conditions. Spectra were obtained with a 200 eV Si(Li) X-ray detector and analysed with AXIL computer code. Concentrations were then calculated with the DATTPIXE program. Quality control was made by analysing in similar conditions to lichen samples the IAEA 336 lichen material and the CTA-OTL-1 tobacco leaves. Contents for the following elements were determined silicon, phosphorous, sulphur, chlorine, potassium, calcium, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, gallium, arsenic, bromine, rubidium, strontium, zirconium, barium, and lead (the elements which are determined by both techniques are shown in bold type). 

Garty, J., Karary, Y., Harel, J., Lurie, S., 1993b. Temporal and spatial fluctuations of ethylene production and concentrations of sulfur, sodium, chlorine and iron on/in the thallus cortex in the lichen Ramalina duriaei (De Not.) Bagl. Environ. Exp. Bot. 33, 553-563. 

Pinselic acid (293) and related compounds, isolated from Penicillium amarum, have been synthesized from 3,6-dimethoxyphthalic anhydride and the lithium derivative (291) via the ketone (292). A number of the chlorinated xanthones found in lichens have been synthesized and their structures verified, using n.m.r. The roots of Hypericum androsaemum contain several xanthones, two of which [(294) and (295)] have an oxygenation pattern not previously known... 

CiftHioCUOj, Mr 424.06, needles, mp. 232 °C. A dep-sidone with 4 chlorine atoms in the molecule occurs in the crustaceous lichen Diploicia canescens. 

CigHijClOe, Mr 362.77, needles, mp. 216-217 C. A chlorine-containing depsidone from lichens, e.g., Lecanora subaurea. 

An example of the pollutant effect of the second type is the action of HCl as well as its combination with either HNO3 orH SO on lichens. In the case of such an effect, no changes due to pollutant absorption were found in the IR spectra (Fig. 6.4). There are no bands at 1461 and 720 cm v(C-CI) [12], which are responsible for the accumulation of chlorine-containing polluting agents. 

The lack of the changes in the chemical composition of lichens is combined with substantial alterations in the thallus appearance. Under the action of HCl, the thalli discolored and mellowed to the end of the experiment the slimming of the upper and lower core occurred thus reducing its barrier function relatively detrimental compounds. The effect of HCl in combination with other acids turned out to be toxic for lichens all thalli became dingy-gray or brownish. There appear multiple small cracks and tears on the surface of upper core. It seems that the use of these indicator species in the case of air pollution by low-concentrated chlorine-containing pollutants is inappropriate. 

The IR spectroscopic arralysis of hchen samples collected in vicinity of all TPSs supplying the city of Tver (TPS-1, TPS-3 and TPS-4) and along density-traffic motor-roads allowed us to detect in air the nitrogen- and sulfur-containing pollutants, such as SOj or airborne H SO and NO, or airborne HNOj. We failed to identify the chlorine-containing compoimds in air with the help of the IR spectroscopic analysis of epiphytic lichens. 

The types of interactions of pollutants with lichens were established with the help of IR spectroscopic analysis. The chlorine-containing compounds as well as their combinations with HNO3 and H SO are highly toxic for the lichens. These pollutants are not accumulated by the thallus. The exposure to these pollutants leads to fast decomposition of thallus. The effect of both HNO and H SO as well as the effect of combinations of HNO3 and H SO manifest themselves in the formation of alkyl nitrates or sulfates (or both) in thallus. 

Extraction has to be continued until all lichen substances are dissolved (6-60 h). Often heavily soluble compounds precipitate in the extract and can be removed by filtration. One way to work up the extract is separation in an acid, a phenolic and a neutral part, by shaking successively with a solution of NaHCOj (10% in H2O) and NaOH (2% in HjO). Some compounds, e.g. chlorinated phenolics, are soluble in a solution of Na2C03 (5% in H2O). Shaking should be continued for 10-15 min. Another way is chromatography of the extract over silica gel. The ratio of product to adsorbent is about 1 30 to 1 50, and an approved sequence of eluents is n-hex-ane-diethyl ether-methanol. Many extracts are heavily soluble in n-hexane to overcome this difficulty, the mixture is dissolved in a proper... 

The Beilstein test is a simple but sensitive and reliable test for lichen substances containing chlorine. The compound (Img) is brought on the tip of a freshly glowed copper wire into the flame of a Bunsen burner a deep green flame develops for a moment in the presence of chlorine (or another halogen) in the substance. 

Table 4 summarizes the chlorine-containing lichen substances which give a positive Beilstein test. 

Elix JA, Jenkins GA, Venables DA (1990b) New chlorine-containing depsidones from lichens. Aust J Chem 43 197-201... 

Fitzpatrick L, Sala T, Sargent MV (1980) Further total syntheses of chlorine-containing lichen xanthones. J Chem Soc Perkin Trans 1 85-89... 

Nishitoba Y, Nishimura H, Nishiyama T, Mizutani J (1987) Lichen acids, plant growth inhibitors from Usnea longissitna. Phytochemistry 26 3181-3185 Nolan TJ, Murphy D (1940) The chlorination of derivatives of orsellinic acid. Sci Proc R Dublin Soc 22 315-319 Norrestam R, Glehn M von, Wachtmeister CA (1974) Three-dimensional structure of usnic acid. Acta Chem ScandB 28 1149-1152... 

Santessson J (1970c) Syntheses of orsellinic acid and related compounds. Acta Chem Scand 24 3373-3378 Santesson J, Sundholm G (1968) Chemical studies on lichens. 14. Syntheses and chlorinations of norlichexanthone. Ark Kemi 30 427-431 Santesson J, Wachtmeister CA (1969) Chemical studies on lichens. 15. 2,4-Dichloro-6-methoxy-l,3-dihydroxy-8-methylxanthone (thiophaninic acid) from Pertusaria flavicans. Ark Kemi 30 445-448 Sargent MV (1980) Synthesis of grisa-2, 5 -dien-3,4 -diones by intramolecular ipsosubstitution. Chem Commim 285... 

Yosioka I, Yamauchi H, Morimoto K, Kitagawa I (1968c) Three new chlorine containing bisanthronyls from a lichen, Anaptychia obscurata Vain. Tetrahedron Lett 3749-3752... 

Xanthones are known in free-living fungi, and recent studies indicate that they are rather common in lichens too. Unlike the fungal xanthones, many lichen xanthones have one or more nuclear chlorine substituents. The fundamental structure of the known lichen xanthones could be derived directly by linear condensation of seven acetate and malonate units with one orsellinic acid-type cyclisation. The two rings are joined by a ketonic carbon and by an ether-oxygen arising from cyclodehydration. Xanthones include arthothelin, concretin,... 

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