New Triterpenes of Lantana camara. A Comparative Study of the Constituents of Several Taxa

Abstract

The triterpenes of Lantana camara vary widely between taxa. In taxa toxic to livestock 22β-angeloyloxy-3-oxoolean-12-en-28-oic acid (lantadene A) and 22β-dimethylacryloyloxy-3-oxoolean-12-en-28- oic acid (lantadene B) are present, usually as major constituents, although 3-oxolup-20(29)-en-28-oic acid (betulonic acid) predominates in the taxon Helidon White. 22β-Angeloyloxy-3β-hydroxyolean- 12-en-28-oic acid, 22β -dimethylacryloyloxy-3β -hydroxyolean-12-en-28-oic acid and 22β-hydroxy-3-oxoolean-12-en-28-oic acid, not previously known to occur in L. camara, have been isolated as well as a number of other well-known triterpenes. The non-toxic Townsville Prickly Orange contains small amounts of lantadenes A and B, and is the only taxon found to contain 228-angeloyloxy-23- hydroxy-3-oxoo1ean-12-en-28-oic acid (icterogenin). Another constituent is the new triterpene 24-hydroxy-3-oxoolean-12-en-28-oic acid. Common Pink, which is non-toxic and does not contain lantadenes A and B, is characterized by triterpene acids which have a C3, C25 oxide-bridge. It contains lantanolic acid, lantic acid, and a new acid, lantabetulic acid, considered to be 3,25-epoxy- 3a-hydroxylup-20(29)-en-28-oic acid. A mixture of the 22β-angeloyloxy and 22β-dimethylacryloyloxy derivatives of lantanolic acid from Common Pink has been converted into 22P-hydroxylantanolic acid. Wolff-Kishner reduction of 22~-hydroxy-3-oxoolean-12-en-28-oic acid gives a low yield of 22β-hydroxyolean-12-en-28-oic acid, and the major product is the C22-epimer, 22a-hydroxyolean- 12-en-28-oic acid. Corresponding products are obtained from Wolff-Kishner reduction of 22β- hydroxylantanolic acid.