New natural products from Siphoneugena densiflora Berg (Myrtaceae) and their chemotaxonomic significance

• Main Author: Gallo,Margareth B. C.
• Publication Date: 2006
• Other Authors: Silva,Fernando C. da, Vieira,Paulo C., Fernandes,João B., Silva,Maria Fátima das G. F. da
• Format: Article
• Language: eng
• Source: Journal of the Brazilian Chemical Society (Online)
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532006000200010
• topic: Siphoneugena densiflora; Myrtaceae; chemotaxonomy; hydrolysable tannin; pentacyclic triterpene

Siphoneugena Berg (Myrtaceae) is a small eugenioid genus segregated from Eugenia by Berg. The phytochemical survey of Siphoneugena densiflora was carried out in order to find secondary metabolites which may be considered as chemotaxonomic characters and help to distinguish between the two genera. Five novel hydrolysable tannins were isolated from the methanolic extract of root bark and were characterized as ellagic acid 4-O-alpha-L-2"-O- and its isomer 4-O-alpha-L-3"-O-acetylrhamnopyranoside, siphoneugenin, that supports a new aglycone with a dibenzo-1,4-dioxin structure, 3,4'-di-O-methylellagic acid 4-O-beta-D-6"-O- and 4-O-beta-D-3",6"-diacetylglucopyranoside, accompanied by ellagic acid 4-O-alpha-L-4"-O-acetylrhamnopyranoside, eschweilenol C, sitosterol, daucosterol, rhamnose, casuarinin, castalagin, ellagic, gallic and syringic acids. From methanolic extract of leaves, in addition to the well known compounds quercetin, quercitrin, guiajaverin, reynoutrin, chebuloside II, terminolic, madecassic and asiatic acids, lupeol, alpha- and beta-amyrin, a new pentacyclic triterpene was isolated and named as beta-D-glucopyranosyl-2alpha,3beta,6beta-trihydroxyolean-12-en-28-ate. Structures were established on the basis of spectroscopic and chemical evidence, along with the comparison of the data reported in the literature.