Lithospermum canescens - "hoary puccoon" - Boraginaceae

"Lithospermum canescens"

Lithospermum canescens Lehm., Boraginaceae (Native American name: "hoary puccoon") occurs in open prairies in northern USA and southern Canada. Because it contains pigments from shikonin-type (Wiedenfeld et al., 1998) it is used as a body dye by native people (Densmore, 1928). As L. canescens belongs to the boraginaceae family the presence of pyrrolizidine alkaloids (PA) could be expected. Based on structural aspects (double-bond in position 1,2; esterification at both necic OH-functions) PA can show toxic effects. Toxicity occurs not only after oral administration but also after percutaneous absorption although to a smaller extent than by ingestion (Brauchli et al, 1982). Thus, according to the German Federal Health Bureau regulations the sale of PA containing products for external use is restricted in Germany to a daily dose of 100 µg and a maximum use of six weeks per year (Bekanntmachung, 1992). Aerial parts of the plant L. canescens were therefore investigated. Seven PA were isolated and their structures determined by GC-mass spectroscopy and homo- as well as heteronuclear 2D-NMR correlated spectroscopy. Four of them have not been described previously. The known alkaloids belong to the retronecine-type and are O9-(-)-viridifloryl-retronecine (= lycopsamine), its O7-acetylderivative (= acetyllycopsamine) and O7-acetyl-O9-(+)-trachelanthoyl-retronecine (= acetylintermedine), The new PA show the structures of O7-(3-hydroxy-3-methyl-butanoyl)-O9-(+)-trachelanthoyl-heliotridine (= O7-(3-hydroxy-3-methyl-butanoyl)-rinderine), O7-(3-hy-droxy-3-methyl-butanoyl)-O9-(-)-viridifloryl-heliotridine (= O7-(3-hydroxy-3-methyl-butano-yl)-echinatine), O13-Acetyl-O7-(3-hydroxy-3-methyl-butanoyl)-O9-(+)-trachelanthoyl-heliotri-dine, O13-Acetyl-O7-(3-hydroxy-3-methyl-butanoyl)-O9-(-)-viridifloryl-heliotridine. Based on structure-toxicity relationships (Wiedenfeld and Roeder, 1984) toxic side effects must be expected for all substances found.

Bekanntmachung über die Zulassung und Registrierung von Arzneimitteln BAnz Nr. 111 vom 17.6.1992/ Pharm. Ind. 54 (7), VII/177 (1992).
Brauchli, J., Lüthy, J., Zweifel, U., Schlatter, Ch. (1982), Pyrrolizidine alkaloids from Symphytum officinale L., and their percutaneous Absorption in rats. Experientia 38, 1085-1087.
Densmore, F. (1928), Indian Use of Wild Plants for Crafts, Food, Medicine and Charms. Smithsonian Institute, Bureau of American Ethnology, United States Government Printing Office, Washington, p.290.
Wiedenfeld, H., Roeder, E. (1984). Pyrrolizidine alkaloids : structure and toxicity. Dtsch. Apoth. Ztg. 124, 2116- 2122.
Wiedenfeld, H., Pietrosiuk, A., Furmanowa, M., Roeder, E. (1998), Pigment compounds in Lithospermum canescens Lehm. Abstracts of Plenary Lectures, Short Lectures and Posters of the 46th Annual Congress Society for Medicinal Plant Research, University of Vienna, Vienna, Austria, p. G21

 

Strukturen der Pyrrolizidinalkaloide, die in lithospermum canescens vorkommen können:

Literatur:

Pyrrolizidine Alkaloids from Lithospermum canescens Lehm., Z. Naturforsch. 58c, 173 (2003) full paper

Lithospermum-PA and insects:

Life History Parameters of the Two-spotted Spider Mite (Tetranychus urticae Koch) Feeding on Bean Leaves Treated with Pyrrolizidine Alkaloids, J. Appl. Toxicol. 23, 187 (2003)

 full paper

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Dr. Helmut Wiedenfeld