Isolation and Structural Elucidation of Acylated Pentacyclic Triterpenoids from the Leaves of Eucalyptus camaldulensis var. obtusa

Abstract

Ten pentacyclic triterpenoids including two new constituents, eucalyptic acid and eucalyptolic acid, and eight known compounds (ursolic acid lactone, betulinic acid, oleanolic acid, ursolic acid, 3β-O-cis-p-coumaroylalphitolic acid, alphitolic acid, 3β-O-trans-p-coumaroylalphitolic acid, and 3β-O-trans-p-coumaroylmaslinic acid) have been isolated from the fresh and uncrushed leaves of Eucalyptus camaldulensis var. obtusa. Their structures were elucidated through detailed 1D and 2D NMR studies. The new natural products were characterized as 2α-hydroxy-3β-E-feruloyloxy-lup-20(29)-en-28-oic acid and 2α-hydroxy-3β-E-feruloyloxy-olean-12-en-28-oic acid, respectively. Except for oleanolic acid, all the known compounds are hitherto unreported from this plant. This is the first report of the isolation of 2-oxygenated 3-O-acylated triterpenoids from Eucalyptus genus.

Key words

Eucalyptus camaldulensis var. obtusa - Myrtaceae - leaves - triterpenes - eucalyptic acid (2α-hydroxy-3β-E-feruloyloxy-lup-20(29)-en-28-oic acid) - eucalyptolic acid (2α-hydroxy-3β-E-feruloyloxy-olean-12-en-28-oic acid.)