Antibiotics in lichens

Figure 2 shows an overall view of antibiotics in lichen substances it is approximate. One should note that the variable results, especially in the titers dealing with inhibition of tuberculosis strains, are due to many factors the culture medium used, the inoculation type and amount, the cultivation time, etc. According to the schematic illustration, the main effect is on the rapidly growing gram-positive bacteria, Mycobacterium tuberculosis, and some pathogenic fungi. 

The drug resistance of human and animal pathogens is one of the best documented in biological evolution and a serious problem in both developed and developing countries. The consumption of more than one ton daily antibiotics in some European countries has resulted in resistance to bacterial populations, thus causing a serious public health problem. In view of this scenario, the search for new antimicrobial substances from natural sources, including lichens, has gained importance in pharmaceutical companies. 

Neither Usno nor other lichen medicines have, however, gained a permanent position in the medical praxis the fight for a place in the sun among antibiotics is too hard. Since the last decade the medicinal research of lichens has turned to new directions the untiring Japanese group Nakazava, Komatsu, Hamada, Fujikawa, Hirai, Shibata et al. has studied the antitumor activity of lichens intensively since 1962. This activity obviously depends on the polysaccharide component in lichens, as found in Umbilicaria, Lasallia, Cetraria, Cladonia, Parmelia, and Usnea, and from psoromic acid. 

Using FmA catalysis and protected 4-hydroxybutanal, compound (97) has been stereoselectively prepared as a synthetic equivalent to the C-3-C-9 fragment of (-F)-aspicillin, a lichen macrolactone (Figure 10.35) [160]. Similarly, FruA mediated stereoselective addition of (25) to a suitably crafted aldehyde precursor (98) served as the key step in the synthesis of the noncarbohydrate , skipped polyol C-9-C-16 chain fragment (99) of the macrolide antibiotic pentamycin [161,162]. 

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... 

In the form of decoctions Iceland moss is used to treat dry coughs. Here the antibiotic and bacteriostatic lichen acids may be of significance. A further indication is lack of appetite and gastro-enteritis. 

Sparassol. 2-Hydroxy-4-methoxy-6-methylbenzoic acid methyl ester 4-methoxy-2,6-cresotic acid methyl ester everninic acid methyl ester orseJJinic acid methyl ester 4-methyl ether. CMH1204 mol wt 196.20. C 61.21%, H 6.17%, O 32.62%. Antibiotic substance produced by the fungus Sparassis ramose Falck, Ber. 56, 2555 (1923). Also obtained in methanol extracts of the lichen Evernla prunasti-Stenhouse, Ann. 68, 55 (1848) Spath, Jeschki, Ber. 57, 471 (1924). Structure Fischer. Hoesch, Ann. 391, 347 (1912) Wedekind. Fleischer, Ber. 56, 2556 (1923). Synthesis <3. Nicollier el at. Helv. Chim. Acta 61, 2899 (1978). 

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