Lichen glycosides

Hypericin frangula (Rhamnaceae), lichen glycosides in Rheum, Polygonum (Polygonaceae), Rhamnus Rhamnaceae) spp. Hypericum perforatum, H. spp. PI3K (0.2) (CDPK, EGF-RTK,... 

The occurrence and function of low and high molecular weight carbohydrates have been reviewed 332) as were lichen glycosides 587). 

Rhamnosides are mainly found in plant heteroglycans. For instance L-rhamnose is found in saponins227 from the bark of the Quillaja tree. Glycosides isolated from lichens may contain L-rhamnose.228... 

T. Flezanka and I. A. Gushina, Glycosidic compounds of murohc, protoconstipatic and allo-murolic acids from lichens of Central Asia, Phytochemistry, 54 (2000) 635-645. 

C16H12O5, Mr 284.27, orange needles, mp. 209-210 °C, uv ,a, 431 nm (C2H5OH). An octaketide that occurs in senna leaves (Cassia senna, Fabaceae), rhubarb roots, in chrysarobinum (see chrysarobin), lichens (Parmelia species), and fungi (Aspergillus and Penicillium species), as well as in glycosidically bound form in Cassia species. It has a weak spasmolytic activity. 

Isol. from the lichens Umbilicaria pustu-lata and Umbilicaria spodochroa, sometimes in a partially acetylated form (1 Ac group for every 10-11 glycoside units). 

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. 

Benzo-l,4-quinoid structures occur in nature as the final oxidation products ofvarious mono- and polycyclic compounds. Most simple benzo-1,4-quin ones occur in microorganisms (moulds), higher fungi and lichens, and less frequently in higher plants and some insects. Common substances are glycosides occurring in colourless reduced forms (such as derivatives of hydroquinone known by the systematic name of benzene-l,4-diol). Coloured quinones are formed from these precursors by hydrolysis catalysed by saccharases and by enzymatic oxidation or autoxidation of aglycones. 

Anthraquinones are the most widespread group of natural quinones. They occur in higher plants, fungi, lichens and some inseds. Anthraquinones are accompanied by derivatives of anthranol, anthrahydroquinone (9-155) and their oxo forms anthrone and oxanthrone (9-156), which are, as glycosides, precursors of anthraquinone pigments. 

A unique disaccharide, 3-D-arabitol-D-galactopyranoside, was isi ted from a lichen (170). Chromatography was used to study (126) the disaccharide present in apiin, a flavone glycoside present in parsley seed. 

Lindberg, B., B.-G. Silvander, and C. A. Wachtmeister Studies of the Chemistry of Lichens. 19. Mannitol Glycosides in Peltigera Species. Acta Chem. Scand. 18,213 (1964). Maass, W. S. G. Lichen Substances. IV. Incorporation of Pulvinic- C Acids into Calycin by the Lichen Pseudocyphellaria crocata. Can. J. Biochem. 48, 1241 (1970). 

Roccellin (33a), mollin, and galapagin are the first phenolic glycosides known from lichens they have been isolated fromRoccellaria mollis (Hampe) Zahlbr., Schismatomma accedens (Nyl.) Zahlbr., 2iad Roccella galapagoensis Follm. 

Three lichen polyol glycosides have been described 3-0-/S-D-gluco-pyranosyl-D-mannitol, peltigeroside, and umbilicin (Lindberg and Wick-berg, 1962). 

Pueyo G (1982) Carbohydrate Constituents in Lichens. V. Glycosides. Bibliographic Review. Ann Fals Exp Chim Toxicol 809 75... 

Unusual macrolactone glycosides (52-53) and acetylinic lipids (19-28), obtained from Cetraria islandica (L.) Ach., are suspected to maintain the membrane integrity and liquid water balance in lichens occurring in regions with low temperatures [3,48,49]. Polysaccharides and polyols account for up... 

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