Lichen compounds, extractable

Bucar F, Schneider I, Ogmundsdottir H et al (2004) Antiproliferative lichen compounds with inhibitory activity on 12(S)-HETE production inhuman platelets. Phytomedicine 11 602-606 Bufukoglu TZ, Albayrak S, Halici MG et al (2013) Antimicrobial and antioxidant activities of extracts and lichen acids obtained from some Umbilicaria species from Central Anatolia, Turkey. J Food Process Preserv 37 1103-1110... 

Such as the abovementioned, there are many studies on the antimicrobial activity of crude lichen extracts. However, studies on antimicrobial activity of lichen compounds are scarce and scattered. Lichens have been found to contain a variety of secondary lichen substances with strong antimicrobial activity (Table 3.1). 

Section 7.2 deals with issues related to secondary metabolites (phytochemicals) from lichen. Lichen compounds and extractives because they possess some biological effects will form also the focus of this section. How they influence biological host and agents would be described briefly in the latter part of this section with proper X-ray of various reported agents of lichen otigm that display antiviral activities. The exact sources of these compounds and extractives would be fully elucidated. Here, we will lightly also mention yet-to-be-validated lichen-derived compounds with speculated or rumored antiviral property. This perhaps may inspire further comprehensive screening of such to fully validate their claims. 

Evernia prunastri has proved to be a particularly rich source of lichen compounds and extraction and g.c. — m.s. studies have revealed the presence of orcinol (99) 268, 269), 3-methoxy-5-methylphenol (100) 144), 3,5-dimethoxytoluene (101) 144), 2-chloro-3,5-dimethoxytoluene (102) 144), phenol 144), thymol 144), 2-chloro-3-methoxy-5-methylphenol (103) 144), methyl salicylate 144), methyl 4-O-methylorsellinate (90) 268, 269), and methyl (3-orcinolcarboxylate (104) (255). Rhizonic acid (105) has been isolated from Parmelia subnuda 215). 

Rapid formation of soluble colored complexes when lichen compounds or ground lichen thalli were shaken with water suspensions of minerals and rocks was reported by Schatz (1963) and Syers (1969) no information was obtained, however, for the amounts of cations complexed. Of the six lichen compounds investigated by Iskandar and Syers (1972), four formed soluble, colored complexes with biotite. The extract obtained from the interactions of lecanoric acid, a depside of the orcinol type, and biotite was reddish-yellow in color. The formation of a reddish-yellow complex when lecanoric acid is allowed to react with calcium salts is used as a specific color test for this acid (Culberson, 1969). Because a complex may be colorless or adsorbed by the silicate phase, the fact that a lichen compound does not form a colored complex does not necessarily indicate that complex formation has not occurred. Iskandar and Syers (1972) showed that significant amounts of Ca, Mg, Fe, and Al were complexed by lichen compounds. In general, greater amounts of divalent than trivalent cations were complexed. For a particular cation, a similar amount was released from the silicates by solutions of the lichen compounds and by solid lichen compounds. These findings suggest that lichen compounds are sufficiently soluble in water to form soluble metal complexes. 

In PC of lichen compounds polar solvent systems are used for the most part. Typical examples are -butanol concentrated ammonia (4 1, parts by volume), w-butanol acetone water (5 1 2), and w-butanol ethanol water (4 1 5). Better values and less trailing can sometimes be obtained if the chromatographic papers are buffered with phosphate (NaaP04 or Na2HP04) (Wachtmeister, 1956). Depsides and depsidones should be chromatographed both before and after microhydrolysis of the extracts (see below). 

Litmus is procured by fermentation of ammoniacal extracts of various lichens, especially of the species Rocella and Lecanore. The commercial product is a mixture of various substances, many of which are totally devoid of indicator properties. From such a preparation have been isolated azolitmin, erythrolitmin, erythro-lein, and spaniolitmin. Only the first of these compounds has any practical value. P. Scheitz claims that even azolitmin is a mixture. 

Lichens and mosses are extracted to isolate their aromatic components that are widely used in the fragrance industry. Oakmoss, the lichen Evemia pnmastri (L.) grows on oak trees. Its extract has a penetrating sweet, smoky, earthy odor due to a complex mixture of many compounds, including the characterizing methyl 2,4-dihydroxy-3,6-dimethyl benzoate (evemyl), and 3-methoxy-2,5-dimethyl phenol (orcinol). 

These extraction stages are in the sequence petrol ether, chloroform, ether, acetone, methanol they are carried out in either a percolation tube or a Soxhlet apparatus. After removing fat with petrol ether, the chloroform extract contains chiefly compounds of group A, e. g., daphnoretin [218], lichen components, fully methylated flavones, many furocoumarins etc. Ether then extracts all the agly-cones and some glycosides (rhamnosides). Most of the glycosides are then to be found in the acetone and methanol extracts. 

Only two lichen species are used in large quantities as raw material for the perfume industry Evemia prunastri (L.) Ach. and Pseudevemia furfuracea (L.) Zopf. Up to 9000 tons of these two species have been processed annually (1986) at Grasse, the centre of the perfume industry in France (Moxham 1981). The ethanol extract of both lichens has a typical mossy flavour and is used not only as a component in certain perfumes ( Chypre ), but also as a fixative which keeps the flavour for a long time. The essential compounds originate from the depsides present in the lichens by hydrolysis, decarboxylation of the corresponding hydro-xyacids and alcoholysis. Orcinol and methyl everninate (sparassol) are compounds with the typical mossy odour. 

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... 

Turk AO, Yilmaz M, Kivanc M et al (2003) The antimicrobial activity of extracts of the lichen Cetraria aculeata and its protolichesterinic acid constituent. Z Naturforsch 58 850-854 Turk H, Yilmaz M, Tay T et al (2006) Antimicrobial activity of extracts of chemical races of the lichen Pseudevernia furfuracea and their physodic acid, chloroatranorin, atranorin, and olivetoric acid constituents. Z Naturforsch C 61 499-507 Verma N, Behera BC, Parizadeh H et al (2011) Bactericidal activity of some lichen secondary compounds of Cladonia ochrochlora, Parmotrema nilgherrensis aadParmotrema sancti-angelii. Int J Drug Dev Res 3 222-232... 

Yamamoto Y, Kinoshita Y, Matsubara H et al (1998) Screening of biological activities and isolation of biological-active compounds from lichens. Recent Res Dev Phytochem 2 23-34 Yilmaz M, Tiirk AO, Tay T et al (2004) The antimicrobial activity of extracts of the lichen Cladonia foliacea and its (—)-usnic acid, atranorin, and fumarprotocetraric acid constituents. Z Naturforsch C 59 249-254... 

The screening of lichen extracts has been of great interest to scientists for the discovery of new compound effective in the treatment of microbial infection. There are various reports on the antimicrobial activity of crude lichen extracts. 

Jayaprakasha and Rao (2000) extracted with benzene and acetone the lichen Parmotrema stuppeum in order to investigate its antioxidant effect. Both the extracts were fractionated on 1 % oxalic acid impregnated silica gel column to obtain methyl orsenillate, orsellinic acid, atranorin and lecanoric acid, respectively. Antioxidant activities of benzene extract, acetone extract and isolated compounds were evaluated in a carotene-linoleate model system. The obtained results showed that the pure compounds and extracts have moderate antioxidant activity. 

Huda-Faujan N, Noriham A, Norrakiah AS et al (2009) Antioxidant activity of plants methanolic extracts containing phenolic compounds. Afr J Biotechnol 8 484-489 Jayaprakasha GK, Rao LJ (2000) Phenolic constituents from the lichen Parmotrema stuppeum (Nyl.) Hale and their antioxidant activity. Z Naturforsch 55 1018-1022 Kekuda PTR, Vinayaka KS, Kumar PSV et al (2009) Antioxidant and antibacterial activity of lichen extracts, honey and their combination. J Pharm Res 2 1875-1878... 

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