Zahira E. Aguiar

Diterpenes from Salvia mellifera and their biogenetic significance

Abstract The new diterpenes, 11,12-dihydroxy-20-nor-abieta-5(10),8,11,13-tetraen-1-one and isogaldosol, together with the known compounds carnosic acid, carnosol, rosmanol, rosmadial, galdosol and isorosmanol were isolated from the aerial part of Salvia mellifera . The structures of the new diterpenes were established from their spectral data and by chemical correlations. The co-occurrence of all these compounds in one species taken together with their chemical behaviour led to the postulation of a biogenetic pathway to highly oxidized abietatriene diterpenes in which enzymatic dehydrogenation processes and the participation of singlet-state oxygen appear to play an important role.

Chromenes from Ageratum conyzoides

Abstract-Analysis of the aerial part of Ayeratum conyzoides afforded 11 chromenes, sitosterol, (+)-sesamin and caryophyllene oxide. One chromene is new and eight of the others were obtained for the first time from this species. The ‘C NMR spectral data for four of the chromenes have not been published before. INTRODUCIION Over the last two or three decades, great attention has been focused on the biological activity of natural com- pounds of plant origin for their potential as natural pesticides against phytophagous insects. In Colombia, plants have been used for centuries for their insecticidal. repellent or antifeedant properties in the protection of crops from insect attack [I]. Ageratum conyzoides, a widespread weed in Colombia and elsewhere, known to contain precocene I and precocene II [2,3], has been used both in folk medicine and as an insecticide. A study of the insecticidal activity of various fractions of an n-hexane extract of

Diterpenes and diterpene quinones from the roots of Salvia apiana

Abstract The new natural diterpenes, 6,7-didehydroferruginol, 6,7-didehydrosempervirol, 16-hydroxy-6,7-didehydroferruginol, 11,12,16-trihydroxy-20(10 → 5)abeo-abieta-1(10),6,8,11,13-pentaene, the diterpene quinones, 16-hydroxyroyleanone and 6-deoxo-5,6-didehydrolanugon Q plus the known compounds ferruginol, miltiodiol, cryptotanshinone, lanugon Q and salvicanol were isolated from the roots of Salvia apiana . Their structures were established by spectrometry. The co-occurrence of so many abietane diterpenes with different degrees of oxidation and modified skeletons is in accordance with the biosynthetic route previously proposed for these compounds.

Methoxyflavones from Ageratum conyzoides

Abstract Nine methoxyflavones were obtained from aerial parts of Ageratum conyzoides , two of which are new: 5,6,8,3′,4′,5′-hexamethoxyflavone and 8-hydroxy-5,6,7,3′,4′,5′-hexamethoxyflavone.

Flavonoids from Salvia texana

Abstract From a methanolic root extract of Salvia texana, 5-hydroxy-7,4′-dimethoxyflavone and (+)-2(S)-5-hydroxy-7-methoxyflavanone were isolated and characterized by spectroscopy. The absolute configuration of the latter compound was established by CD readings.

Quinone methide diterpenoids from the roots of Salvia texana

Abstract Four new diterpene methylenequinones, 6-deoxo-2α-hydroxytaxodione, 2α-hydroxytaxodione, 2α-hydroxytaxodone and 2α, 7-dihydroxytaxodone, were is

Minor sesquiterpene lactones from Salvia palaefolia

Abstract Five minor eudesmane constituents of Salvia palaefolia were isolated from the same extract which had earlier yielded the two fully characterized eudesmanolides. The five new natural compounds were identified by spectral studies and comparison with known substances.

A C-methyl chalcone from Dalea caerullea

Abstract A petrol extract of Dalea caerullea yielded the new 4′,6′-dihydroxy-3′,5′-dimethyl-2′-methoxychalcone which was characterized by spectroscopy. Mono- and sesquiterpenes were also obtained from extracts of this plant.