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The chemical study of Ageratina deltoidea afforded grandiflorenic acid (1), ent-kaurenoic acid (2), and eight benzylbenzoates (3 - 10), two of them, 3,5-dimethoxybenzyl 2,3,6-trimethoxybenzoate (5) and 4-(β-d-glucopyranosyloxy)-3-hydroxybenzyl 2,6-dimethoxybenzoate (9), described for the first time. In addition, the new sesquiterpene lactone deltoidin C (13), together with the known 11 and 12, the phenolic compounds: ayanin, 2,6-dimethoxybenzoic acid, methyl 3,4-dihydroxycinnamate, chlorogenic acid, and 3,5-dicaffeoylquinic acid were also isolated. The structures of these compounds were determined by spectroscopic methods and chemical reactions. The antibacterial and antifungal activities of compounds 1 - 12 were evaluated on Staphylococcus aureus, Escherichia coli, and Candida albicans. Deltoidin A (11) was the most active antibacterial agent (MIC 16.0 μg ml-1 ) against E. coli, and the ent-kaurenoid derivatives (1 - 2) showed activity (MIC 31.0 μg ml-1 ) against S. aureus.

While plants of the genus Dyssodia are used by man to a certain extent, few phytochemical and pharmacological studies have been performed with species of this genus. D. tagetiflora is an endemic plant of Mexico and has been used as fodder. The aim of this research was to isolate and identify the main bioactive components and evaluate the insecticidal, antioxidant, genotoxic and cytoprotective activities of D. tagetiflora. The isolated substances included an essential oil composed of six monoterpenes, and extracts containing two flavonols, three flavonol-glycosides and four thiophenes. The compounds were characterized using spectroscopic and spectrometric methods, including GC/MS, MS and NMR. The essential oil showed insecticidal activity against Drosophila melanogaster larvae. The methanolic extract of D. tagetiflora (DTME) had strong antioxidant activity against DPPH and ABTS radicals; DTME showed no evidence of genotoxic or cytotoxic effects. In contrast, DTME showed a cytoprotective effect attenuating the formation of H2 O2 -induced micronuclei in Vicia faba roots. This report is the first to describe the phytochemical and biological activity of D. tagetiflora.

Ten new diterpenes were isolated along with some known compounds. Eight of the new diterpenes are esters of capric, lauric, myristic and palmitic acids.

The structure of the new sesquiterpenes, isocapnell-9-en-8-one and 6α-hydroxyisocapnell-9-en-8-one, isolated from two Buddleia species have been elucidated mainly on spectral grounds. The existence of a new carbon skeleton is described.

Tithonia longiradiata yielded several known compounds and the new heliangolides 3-acetyl-15-hydroxy-2′,3′-dihydroleptocarpin and 15-hydroxy-2′,3′-dihydroleptocarpin. The structures were established by spectroscopic studies, chemical transformations and confirmed by a chemical correlation with dihydrohelianginol of known stereochemistry.

Senecio toluccanus var. modestus afforded four new eremophilanolides whose structures and absolute stereochemistry were determined by spectroscopic methods and chemical transformations. An X-ray analysis of toluccanolide C was performed.

Chemical examination of the roots of Parthenium argentatum afforded the new triterpene argentatin D together with the known triterpenes incalinin, argentatin A, argentatin B and isoargentatin B, while the aerial parts of the plant afforded argentatin C. The structures of argentatin C and argentatin D were established by chemical, spectroscopic and crystallographic studies.

A chemical study of Psacalium megaphyllum afforded some known compounds and the new, kaempferol-3- O -α- l -(3- O -acetyl)rhamnopyranoside-7- O -α- l -rhamnopyranoside. The structure of the flavonol was determined by spectroscopic methods.

The methanol extract from the aerial parts of Roldana barba-johannis (Asteraceae) afforded sargachromenol, sargahydroquinoic acid, and sargaquinoic acid. These natural products and their corresponding acetylated and methylated derivatives showed insecticidal and insect growth regulatory activities against the Fall Armyworm [Spodoptera frugiperda J.E. Smith, (Lepidoptera: Noctuidae)], an important insect pest of corn. The most active compounds were sargachromenol and its acetylated derivative; sargahydroquinoic acid and its acetylated derivative; and a mixture of sargachromenol, sargahydroquinoic acid, and sargaquinoic acid (6:3:1) and the acetylated form of this mixture. All these compounds and mixtures had significant inhibitory effects between 5.0 and 20.0 ppm in diets. Most compounds were insecticidal to larvae, with lethal doses between 20 and 35 ppm. In addition, these substances also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl radical in TLC autographic and spectrophotometric assays. These compounds appear to have selective effects on the pre-emergence metabolism of the insect. The results from these compounds were fully comparable in activity to those known natural insect growth inhibitors such as gedunin and methanol extracts of Cedrela salvadorensis and Yucca periculosa. These substances may be useful as natural insecticidal agents.

The methanol extract from the bark of Yucca periculosa F. Baker afforded 4,4′-dihydroxstilbene, resveratrol and 3,3′,5,5′-tetrahydroxy-4-methoxystilbene and had growth regulatory activity against the Fall Army worm ( Spodoptera frugiperda J.E. Smith, Lepidoptera:Noctuidae) an insect pest of corn. The most active compound was 3,3′,5,5′-tetrahydroxy-4-methoxystilbene which had significant effects at 3 μg/g in diets. In addition to the inhibitory activity on bleaching of crocin induced by alkoxyl radicals, these compounds also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl in TLC autographic and spectrophotometric assays. Our results indicate that these compounds could be involved in interference of sclerotization and moulting. These compounds appear to have selective effects on the pre-emergence metabolism of the insect. The results were fully comparable to known natural insect growth inhibitors such as gedunin and Cedrela extracts and have had a possible role as natural insecticidal agents.

The aerial parts of Bahia xylopoda afforded in addition to known compounds three new guaianolides: the acetonide of bahia II, 19,20-dihydro-19-methoxybahifolin and 20-deoxybahia II. Bahia pringlei gave some known compounds and the new 20-deoxybahia II. The structures of the new compounds were determined by spectroscopic methods and chemical transformations.

The binding of [3H] l -aspartate to membranes obtained from primary cultures of chick retinal Muller cells (glia) was studied. Cells seeded in low-serum-containing medium (1%) and maintained in this condition showed an increased number of binding sites, from 1 to 5 days in vitro (DIV), when compared with controls cultured in medium containing 10% serum; these changes were not reversed by the addition of 10% serum after 48 h in vitro. Increased binding at this age was due to the expression of a low affinity binding system, competitively inhibited by the glutamate uptake blocker l -aspartate-β-hydroxamate, suggesting that high serum might inhibit the expression of uptake sites at precise maturation stages. Experiments showed the effect was due to a thermolabile serum component. The increase in binding sites is parallel in time to both an increase in aspartate uptake and the initiation of synaptogenesis in the whole retina. Our results suggest that the presence of serum at defined stages in retinal development, could result in the elevation of extracellular glutamate and the concomitant excitotoxic death of neuronal cells, due to a decreased glutamate uptake by glial cells.

Bahia schaffneri var. aristata afforded the new monoterpene 9-hydroxythymol, whose structure was determined by spectroscopic methods. From this plant we also isolated the known compounds: sitosterol, stigmasterol, taraxasterol, centaureidin, three acylglucopyranoses, ligustrin, thymol and eupatriol.

The new δ-lactone hypurticin has been isolated from Hyptis urticoides as its main secondary metabolite. The flavone salvigenin and the triterpenoid ursolic acid were also isolated. The structure of hypurticin was established mainly on spectroscopic grounds.

The isolation is reported of the new natural products from Viguiera quinqueradiata, acetylleptocarpin and (2R,3S-4′-hydroxy-3′,5,7-tri-O-methyl-flavan-3-ol. The diterpenes 15α-angeloyloxy-ent-kaur-16-en-19-oic acid, 15α-tigloyloxy-ent-kaur-16-en-19-oic acid and the sesquiterpene lactones leptocarpin and budlein A were also found.

The aerial part of Tithonia rotundifolia afforded the heliangolide rotundin and the germacrolide ( Z )-18-methylsphaerocephalin.

The structure of mortonol B, a sesquiterpene constituent of Mortonia hidalgensis , was established as 2β-acetoxy-mortonol A. Mortonol B is propose

The aerial parts of Tithonia pedunculata afforded, in addition to several known compounds, three new substances: the heliangolide 15- hydroxy-3-dehydrotifruticin, the eudesmanolide 5α-hydroxytirotundifolin A and the acyclic diterpene (E,E,E)-3-hydroxymethyl-7,11-dimethyl- 2,6,10-hexadecatrien-l,14,15-triol. Their structures were elucidated by spectroscopic methods and chemical transformations.

A chemical investigation of Tithonia rotundifolia afforded seven new sesquiterpene lactones in addition to three known ones. The structures of the new compounds 3-acetyl-15-hydroxyleptocarpin, 15-hydroxyleptocarpin and tirotundifolins A, B, C, D and E were established by spectroscopic and chemical means.

The new diterpenes, ent -beyer-15-ene-12α,19-diol and ent -atis-13-en-3β,16α-diol, were isolated as minor constituents from the aerial part of Viguiera insignis . The structures were established by biomimetic transformation, spectroscopic means and comparison with closely related compounds.

Chemical study of Verbesina virgata collected in several localities afforded two eudesmane triols as 4-cinnamates. Their structures were determined by chemical and spectroscopic means. The structure and stereochemistry of one of the triols was confirmed by X-ray crystallography.

The isolation of several known diterpenoids and one new diterpene diol from aerial parts of Viguiera insignis is reported.

Eleman-8β,12-olides containing a β-hydroxyl group at C-9 exist in equilibrium with 8β-hydroxyeleman-9,12-olides. Acetylation of 9β-hydroxyelemanolides gave a mixture of 8β-and 9β-acetyl derivatives in which the former predominates. The structures of zinaflorin II acetate, zinaflorin III and other 9β-hydroxyelemanolide acetates have been revised. The absolute stereochemistry of the δ-lactone juniperin has been established by means of an X-ray crystallographic analysis.

Seven eudesmanolides were isolated and characterized from Artemisia mexicana var. angustifolia . These included arglanin, artemexifolin, ludalbin, santamarine and three new compounds named 8α-acetoxyarmexifolin, α-epoxyludalbin and armefolin. The structure of armexifolin is revised.

Six sesquiterpene lactones and two flavones were isolated and characterized from Artemisia klotzchiana. These included chrysartemin A, matricarin, desacetyl matricarin, ridentin, hanphyllin, jaceosidin, sudatichin and the new guaianolide chloroklotzchin, which is a halogenated lactone. The X-ray structure of hanphyllin is reported.

Viguiera eriophora yielded the sesquiterpene lactones erioflorin, acetylerioflorin and 17,18-dehydroviguiepinin, which was correlated with tetrahyd

The new sesquiterpene lactones 8β-[epoxyangeloyloxy]-14-hydroxytithifolin and 8-[epoxyangeloyl]-14-acetoxy-eupatolide, were isolated from Viguiera hypargyrea. The structures were established by chemical and spectroscopic means. The chemotaxonomic implications of the chemical constituents of Viguiera are briefly discussed.

The isolation is reported of the new germacrolide, 11,13-dehydroeriolin, the new melampolide schkuhrioidin and schkuhriolide from Schkuhria schkuhrioides . 11,13-Dehydroeriolin is also a constituent of S. virgata . The structure and stereochemistry of the new compounds were established on chemical and spectroscopic grounds.

The guaianolides matricarin (Ib) and desacetylmatricarin (Ia) have been found as constituents of Artemisia klotzchiana . The eudesmanolides arglanin (VIII) and douglanin (IXa) were isolated from A. mexicana . The new guaianolides chrysartemin A (II) and B (XIV) are constituents of Chrysanthemum parthenium . Chrysartemin A (II) was also found in A. mexicana and A. klotzchiana .

The isolation of eucannabinolide and three new sesquiterpene lactones from Schkuhria anthemoidea is reported. The structures and stereochemistries of the new compounds were established by chemical and spectroscopic means. The structure of santhemoidin B was confirmed by X-ray crystallography.

The structure of mexicanin G, a guaianolide isolated from Helenium mexicanum, is established by means of an X-ray crystallographic analysis. Probably mexicanin G plays an important role in the biogenesis of helenanolides.

The isolation of eucannabinolide, jaceidin and the new glycoside absinthifolide from Bahia absinthifolia var. absinthifolia is reported. The structure and stereochemistry of the new compound was established by chemical and spectroscopic means.

Aerial parts of Viguiera linearis afforded 16α-hydroxy-ent-kauranoic acid, viguiestenin, leptocarpin, acetylleptocarpin, budlein B, clovandiol and the new heliangolide 15-hydroxy-acetylerioflorin.

The structure of budlein-A, the main sesquiterpene lactone of Viguiera buddleiaeformis was established as the 8 angeloyl ester of 1 keto, 8-β, 14-dihydroxy germacra-2,4,11 (13)-trien-3, (10 β) oxido-6 α, 12-olide. Its structure and stereochemistry was determined by chemical and spectroscopic means. Budlein-B, found in the same plant as a minor constituent, is 8 α, 15-dihydroxygermacra-1 (10), 4, 11 (13)-trien-6 α, 12-olide.

The shrub Parthenium fruticosum was shown to contain the three isomeric tetracyclic triterpenes fruticin A, fruticin B and the known incanilin. Fruticins A and B are new substances with lanostane and cycloartane skeletons, respectively. Their structures were determined by chemical and spectroscopic methods. The stereochemistry of fruticin B was established by X-ray diffraction analysis.

The new germacranolide, viguilenin, was isolated from Viguiera linearis and its structure was established by chemical and spectroscopic means.

Four sesquiterpene lactones were isolated from several populations of Parthenium confertum var. lyratum (Gray) collected in Sierra de Arteaga, southern Coahuila. Three of the compounds, hysterin, tetraneurin E and hymenin were previously isolated from other Parthenium species. The fourth constituent is the new cyclopropanoid sesquiterpene dilactone confertdiolide which represents a new structural type. The photolytic conversion of hymenin into confertdiolide confirmed its structure.

A new heliangolide and the known compounds hiyodorilactone F and eucannabinolide have been isolated form Isocarpha oppositifolia var. achyranthes .

The isolation and structure determination of two new sesquiterpene lactones of the heliangolide type, leptocarpin and 17,18-dihydroleptocarpin from Leptocarpha rivularis , are described. The structure of leptocarpin was established as the 8β-angeloyl ester of 3β,8β-dihydroxy germacra-4,11(13)-dien- 1(10)-oxido-6α,12-olide. The second component was the 17,18-dihydro derivative of leptocarpin.

The isolation of a new diterpene lactone and two known diterpenoid acids from the aerial parts of Viguiera maculata is reported.