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- Jatrophane and lathyrane diterpenoids from Euphorbia hyberna LPublication . Ferreira, Ana Margarida V. D.; Carvalho, Luı́s H. M.; Carvalho, Maria João M.; Sequeira, Miguel M.; Silva, Artur M. S.A new diterpene tetraester, from the jatrophane family, and two new diterpene triesters, with a lathyrane skeleton, have been isolated from the chloroform extract of the roots of Euphorbia hyberna L. The structures of these compounds have been established by spectroscopic methods, including 2D NMR experiments.
- Structural characterization of lignin from leaf sheaths of “dwarf cavendish” banana plantPublication . Oliveira, Lúcia; Evtuguin, Dmitry V.; Cordeiro, Nereida; Silvestre, Armando J. D.; Silva, Artur M. S.; Torres, Isabel C.Dioxane lignin (DL) isolated from leaf sheaths of banana plant (Musa acuminata Colla var. cavendish) and in situ lignin were submitted to a comprehensive structural characterization employing spectroscopic (UV, FTIR, solid state 13C CP-MAS NMR, liquid state 13C and 1H NMR) and chemical degradation techniques (permanganate and nitrobenzene oxidation). Results obtained showed that banana plant leaf sheath lignin is of HGS type with a molar proportion of p-hydroxyphenyl (H)/guaiacyl (G)/syringyl (S) units of 12:25:63. Most of the H units in DL are terminal phenolic coumarates linked to other lignin substructures by benzyl and Cgamma-ester bonds in contrast to ferulates that are mainly ether linked to bulk lignin. It is proposed that banana plant leaf sheath lignin is chemically bonded to suberin-like components of cell tissues by ester linkages via essentially hydroxycinnamic acid residues. beta-O-4 structures (0.31/C6), the most abundant in DL, comprise mainly S units, whereas a significant proportion of G units is bonded by beta-5, 5-5', and 4-O-5' linkages contributing to ca. 80% of condensed structures in DL.
- Chemical constituents of Euphorbia hyberna L. (Euphorbiaceae)Publication . Ferreira, Ana Margarida V. D.; Carvalho, Maria João; Sequeira, Miguel M.; Silva, Artur M. S.; Carvalho, Luís H. M.Chemical investigation of the aerial part and the roots of Euphorbia hyberna L. subs. hyberna. resulted in the isolation and identification of four triterpenoids (3�-O-octadecanoyllupeol (1), glut-5-en-3�-ol (2), 24-methylenecicloartan-3�-ol (3) and cicloart-23-ene-3�,25-diol (6)) along with the phenolic compounds ellagic acid (4) and 3,30 -di-O-methylellagic acid (7). Although these are all known compounds, this is the first report of their isolation from this plant. Their structures were elucidated on the basis of spectral methods, including 2D NMR experiences, and confirmed by comparing with the literature data.