Elsa M. Rodríguez Pérez

Chromenes and benzofurans from Ageratina glechonophylla

Abstract A re-examination of the aerial part of Ageratina glechonophylla yielded spathulenol (1,6-dihydroxy-4(14)-eudesmene) as a natural product, six known chromenes, a mixture of three dimeric chromenes, four thymol derivatives and 3-(hydroxymethyl)-3-(acetoxymethyl)-and 3-(isobutyryloxymethyl)-6-methylbenzofuran were also identified in this plant.

Diterpenes and other constituents of Eupatorium salvia

Abstract An ethanol extract of the aerial parts of Eupatorium salvia was re-examined and five labdane-type diterpenes, one sesquiterpene and two flavonoids were obtained. Structures were elucidated by spectroscopic methods and chemical transformations.

Depsidones from Lobaria pulmonaria and their chemotaxonomic importance

Seven β-orcinol depsidones were isolated from Lobaria pulmonaria (L.) Hoffm. var. meridionalis (Vain) Zahlbr. gathered on Pinus canariensis, three, methylstictic acid, hypostictic acid and cryptostictic acid, for the first time from this species. Stictic acid and constictic acid acetone condensation derivatives were formed during the extraction process. The possible chemotaxonomic implications are discussed.

Chemical constituents of the lichen Cladina macaronesica

Column chromatography of the acetone extract of the lichen Cladina macaronesica (Sephadex LH-20, silica gel and silver nitrate-im pregnated silica gel) afforded eight triterpenes identified by chemical and spectral m eans. α-Amyrenone, lupenone, taraxerol, taraxerone and /so-arborinol acetate were isolated for the first time from lichens and (-)-usnic acid and five mononuclear phenolic compounds were also obtained, four for the first time as natural products. The possible transformation of perlatolic acid into these phenolic compounds is briefly outlined.

Chemical constituents of the lichen Stereocaulon azoreum

Column chromatography of the acetone extract of the lichen Stereocaulon azoreum afforded several substances identified by chemical and spectral means; α-amyrin, lupeol, taraxerol, ursolic acid, ergosterol peroxide, brassicasterol, cerevisterol, stictic acid and an acetone-condensation derivative, lobaric acid. Furthermore atranorin, methyl β-orsellinate, atranol and, for the first time from the genus Stereocaulon, cryptostictic acid and the dibenzofuran, strepsilin were isolated.

Synthesis of hierridin, a phenol from the lichen, Ramalina hierrensis

Abstract A five-step reaction sequence was used to synthesize hierridin (2,4-dimethoxy-6-heneicosanylphenol), a new compound isolated from the lichen Ramalina hierrensis.

Actividad antioxidante de los polifenoles de HYPOGYMNIA TAVARESII D. HAWKSW. & P. JAMES

Lichen substances have more than one phenolic hydroxyl group attached to one or more benzene rings, thus qualifying them as polyphenols. The secondary metabolites isolated from the lichen H. tavaresii have been studied in a bid to find compounds protective against oxidative stress and free radical-induced damage. The compounds were identified based on their MS and 1H-NMR spectra as well as retention factors of TLC analysis. In addition to the previously described metabolites (atranorin, chloroatranorin, physodic and physodalic acids) of H. tavaresii, a further three were identified in its thalli: 2´-O-methylphysodone, isophysodic and ursolic acids. The newly identified compounds of H. tavaresii thalli may be useful in the chemotaxonomic classification of this species. Antioxidant effectiveness of the acetone extracts fractions was measured. The compounds of the active fractions were purified and exhibited 180-800 fold less radical scavenging activity than the reference substance α-(+)-tocopherol in a DPPH• model expressed by IC50 values.

ANTIOXIDANT ACTIVITY OF POLYPHENOLS FROMHYPOGYMNIA TAVARESIID. HAWKSW. & P. JAMES

Lichen substances have more than one phenolic hydroxyl group attached to one or more benzene rings, thus qualifying them as polyphenols. The secondary metabolites isolated from the lichen H. tavaresii have been studied in a bid to find compounds protective against oxidative stress and free radical-induced damage. The compounds were identified based on their MS and 1H-NMR spectra as well as retention factors of TLC analysis. In addition to the previously described metabolites (atranorin, chloroatranorin, physodic and physodalic acids) of H. tavaresii, a further three were identified in its thalli: 2´-O-methylphysodone, isophysodic and ursolic acids. The newly identified compounds of H. tavaresii thalli may be useful in the chemotaxonomic classification of this species. Antioxidant effectiveness of the acetone extracts fractions was measured. The compounds of the active fractions were purified and exhibited 180-800 fold less radical scavenging activity than the reference substance α-(+)-tocopherol in a DPPH• model expressed by IC50 values.