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Four new phenalenone-type phytoalexins, named musanolones C-F, have been isolated from infected rhizomes of banana plants (Musa acuminata; AAA cultivar Grand Nain). These phytoalexins were biosynthesized de novo by the plants upon infection by Fusarium oxysporum f. sp. cubense race 4, Panama's disease causal agent. The structures of the new phytoalexins were elucidated using spectroscopic data and chemical correlations. Hydroxyanigorufone has been previously described as a constitutive natural product, from Anigozanthos rufus, but it was never described as a phytoalexin. The chemical shift for all of the hydrogen and carbon atoms in the musanolones C-F were unambiguously established by mono- and bi-dimensional, homo- and hetero-nuclear NMR experiments (1H NMR, 13C NMR, COSY, HMQC and HMBC). Preliminary in vitro assays of all the musanolones tested until now show a strong inhibitory activity on the growth of the germination tube of F. oxysporum f. sp. cubense race 4.

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.

The aerial part of Salvia palaefolia yielded (−)-glechomafuran, 1β,10α;4α,5β-diepoxy-8β-hydroxyglechoman-8α,12-olide and the new eudesmanolides: 1α-acetoxy-8α-hydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide and 1α,8α-dihydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide. The structure of the former new compound was determined from its spectral data and chemical behaviour and its absolute configuration by CD experiments. The absolute configuration of 1β,10α;4α,5β-diepoxy-8β-hydroxyglechoman-8α,12-olide was established by X-ray diffraction analysis.

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

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.

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.

The new diterpenequinone columbaridione, together with the known compounds 7-methoxyrosmanol, 7-ethoxyrosmanol, 11-acetoxy carnosic acid, 20-deoxocarnosol and miltidiol were isolated from the aerial part of Salvia columbariae. The structure of the new diterpenequinone was established from spectral data and chemical correlations.

The new diterpenes 11,12-di-O-methylrosmanol and 11,12-di-O-methylcarnosol, together with the known compounds carnosic acid, carnosol, rosmanol, epirosmanol, isorosmanol, salvicanol and rosmadial were isolated from the aerial part of Salvia columbariae. The structures of the new diterpenes were established from their spectral data and by chemical correlations. The co-occurence of all these compounds in a single species provides further support of our previously postulated biogenetic pathway to highly oxidized abietatriene compounds involving enzymatic dehydrogenation processes and the participation of singlet oxygen.

A new aromatic diterpene has been obtained from the aerial parts of Salvia munzii and its structure identified on the basis of spectral data as 16