Thamnolic acid

Thamnolia vermicularis is an arctic-alpine, fruticose, soil-dwelling lichen that enjoys a very wide distribution. The species consists of two chemical strains, one predominantly found in the Northern Hemisphere and the other in the Southern Hemisphere, with most populations from intermediate regions exhibiting intermediate chemical types. Sato (1965) showed that the southern strain accumulates thamnolic acid [403], whereas the northern strain is characterized by two compounds, squamatic acid [404] and baeomycic acid [405]. Populations from Greenland, Novaya Zemlya, and Svalbard exhibited only the northern profile. Two populations from South America exhibited only the southern type, while collections from New Zealand showed nearly pure southern type. 

Thamnolic acid boat-shaped yellow plates... 

Fig. 35. A Squamatic acid [from Cladonia crispata (Ach.) Plot], GE. Bar 10)im. B Tenuiorin, GE. Bar 100)im. C Thamnolic acid, saturated aqueous solution of Ba(OH)2. Bar 100 jam. D Thamnolic acid with decarboxythamnolic acid, An. Bar 100 jim...

Deriv Diemethyl thamnolate, yellowish prisms (benzene or EtOH), mp 158 °C, from thamnolic acid with CH2N2 at 0 °C in 30 s StL Thamnolia vermicularis (Sw.) Ach. ex Schaer. 

The most frequently encountered / -depside in the -orcinol series is atranorin (57) and the most widely occurring m-depside, thamnolic acid (58). Phenarctin (59) is characterized by complete substitution of the depside skeleton. 

PD+,K+ Depsides alectorialic acid, atranorin, baeomycesic acid, barbatolic acid, chloroatranorin, decarboxythamnolic acid, haemathamno-lic acid, nephroarctin, thamnolic acid, Depsidones constictic acid, fumarprotocetraric acid, norstictic acid, physodalic acid, proto-cetraric acid, salazinic acid, stictic acid, virensic acid... 

Fig. 1. Color reactions of lichen substances. The structural part responsible for the color reaction is drawn in heavy lines, (a) C+ compounds lecanoric acid (left) and norlichexanthone (right) (b) PD+ thamnolic acid reacting with /7-phenylenediamine (c) KC+ lobaric acid hydrolyzed with KOH to yield a compound with 2 free m-hydroxyls (d)lichexanthone reacting with Dimroth s reagent to give a fluorescent compound.

A 10-25% aqueous solution ofpotassium hydroxide is used as the reagent. The solution is stable, but etches glass vessels slowly. Quinonoid lichen pigments (anthraquinones, naphthoquinones, terphenylquinones) give a positive dark red to violet K test, whereas pulvinic-agid derivatives, xanthones, and usnic acids do not respond. Some depsides (e.g., atranorin, thamnolic acid) and many /5-orcinol depsidones exhibit yellow to red colors with K. 

The use of a few different solvents in succession will often effect a certain degree of separation of the constituents. The series benzene-ethyl ether-acetone is commonly used. Most lichen substances will appear in benzene and ether extracts, but certain compounds (e.g., erythrin, thamnolic acid, /3-orcinol depsidones) will only be extracted by acetone. Polyols (erythritol, arabinitol, mannitol, etc.) are usually found in the acetone extract, but saccharides (especially polysaccharides) have to be extracted with alcoholic solvents or water after prior removal of other constituents (cf. Lindberg et al., 1953 Lewis and Smith, 1967). 

Continuous extraction procedures (Soxhlet ex tractors) are usually preferred. The extraction may be complete after a few to 24 hours, but longer extraction times are sometimes necessary. The unextractable pigment of Mycoblastus sanguinarius (Zopf, 1899) was isolated by a 2 weeks extraction procedure (Bohman, 1970). In some cases, prolonged extraction might lead to the formation of artifacts. After one week in refluxing acetone, thamnolic acid may be decarboxylated to the extent of 5-10%. 

N.A. Lobelia pulmonaria L. d-Usnic acid, thamnolic, polysaccharides, anthraquinones.154 Stimulate immune system, antitumor, cancer. 

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