Luis Villarroel

Bioactive saturated pyrrolizidine alkaloids from Heliotropium floridum

Abstract Here we describe the isolation and structural determination of the new saturated pyrrolizidine monoester alkaloids, 3′-acetyltrachelanthamine, floridine, floridinine and floridimine, along with the known one, heliovicine, from Heliotropium floridum . Their structures were established by high resolution NMR (including 2D NMR experiments), mass spectrometry, chemical reactions and by correlation with published data of known compounds. Bioassays of the alkaloidal extract and its major components against several insect pests and plant pathogens showed that 3′-acetyltrachelanthamine is a strong anti-feedant, with low toxicity against Leptinotarsa decemlineata and a moderate anti-fungal agent against Fusarium monoliforme ; floridinine only showed the anti-fungal effect.

Filifolinol, a rearranged geranyl aromatic derivative from the resinous exudate of Heliotropium filifolium

Abstract The resinous exudate of Heliotropium filifolium has yielded a new rearranged geranyl aromatic derivative. This result is in agreement with the botanical affinity of some members of the Cochranea section of Heliotropium .

Pronuciferine N-Oxide, a Proaporphine N-Oxide Alkaloid from Berberis coletioides

Pronuciferine N-oxide (1), a proaporphine N-methyl-N-oxide alkaloid, along with the parent alkaloid pronuciferine (2) were isolated from Berberis coletioides. The structure of the new compound was determined by spectroscopic evidence. Compound 1 is the first naturally occurring proaporphinoid alkaloid with an N-oxide functionality.

Bioactive Eremophilanolides from Senecio Poepigii

A new bioactive eremophilanolide, 1α-tigloyloxy-8βH,10βH-eremophil-7(11)-en-8α,12-olide (1), was isolated from Senecio poepigii and its structure was elucidated by spectral analysis. 1α-Angeloyloxy-8β-methoxy-10βH-eremophil-7(11)-en-8α,12-olide (2) was also isolated. Antifungal and insect antifeedant properties were evaluated.

EXTERNAL FLAVONOIDS FROM HELIOTROPIUM MEGALANTHUM AND H. HUASCOENSE (BORAGINACEAE). CHEMOTAXONOMIC CONSIDERATIONS

Del extracto de compuestos superficiales obtenido con CH2Cl2de material fresco de especies de Heliotropium, se han aislado flavonoidesy derivados aromaticos geranilados. Entre los flavonoides, los tiposestructurales mas comunes corresponden a flavanonas y flavonolesy se han reportado solamente pocas flavonas. En este trabajo se informael aislamiento de varios flavonoides de los exudados de H. megalanthumyH. huascoense. Dos de los componentes aislados de H. huascoenseson flavonoides nuevos, que pertenecen a los grupos poco comunes de flavanonaspenta-O-substituidas y flavonoles hexa-O-substituidos. Estos resultadosmuestran una composicion de flavonoides externos en H. huascoense,diferente de las otras especies de Heliotropium estudiadas. Losresultados estan reafirmados por consideraciones morfologicas,en especial, la presencia o ausencia de tricomas glandulares en especiesde Heliotropium

Defensive Sesquiterpenes from Senecio candidans and S. magellanicus, and Their StructureActivity Relationships

Eleven eremophilanolides, 1–3 and 6–13, and two eremophilanes, 24 and 25, were isolated from Senecio candidans and S. magellanicus from the Magallanes Region (Chile). Compounds 2, 3, 9, and 10 have not been previously reported as natural products. Their structures were established by NMR spectroscopic analysis and chemical transformations. The X‐ray analysis of compounds 11, 13, and 17 were also performed. Different semisynthetic analogs from eremophilanolide 11 were generated to carry out a structureactivity relationship study. Their possible plant defensive role was tested against herbivorous insects (Spodoptera littoralis, Rhopalosiphum padi, and Myzus persicae) and plants (Lactuca sativa). Additionally, their effects on insect (Sf9) and mammalian (CHO) cell lines were tested.

Bioactive Furanoeremophilanes from Senecio otites Kunze ex DC.

Abstract The furanoeremophilanes 6β-angeloyloxy-1, 10-dehydrofuranoeremophilan-9-one (1), 6β- hydroxy-1, 10-dehydrofuranoeremophilan-9-one (2) and 6β-propionyloxy-1, 10-dehydrofuranoeremophilan- 9-one (3) were isolated from Senecio otites, their structures elucidated by spectral analyses, and their insecticidal and phytotoxic properties evaluated. Compounds 1-3 proved to be effective aphid antifeedants against Myzus persicae and Rhopalosiphum padi and had postingestive negative effects on Spodoptera littoralis larvae. These compounds did not have any phytotoxic effects on Lactuca sativa.

Megalanthine, a bioactive sesquiterpenoid from Heliotropium megalanthum, its degradation products and their bioactivities.

The new bioactive sesquiterpenoid (3R,6E)-2,6,10-trimethyl-3-(3-p-hydroxyphenylpropanoyloxy)-dodeca-6,11-diene-2,10-diol, named megalanthine, was isolated from the resinous exudates of Heliotropium megalanthum. The degradation products of this compound were identified. Several plant-defensive properties (insecticidal, antifungal, and phytotoxic) were evaluated after obtaining positive results in a preliminary etiolated wheat coleoptile bioassay. This bioassay showed the need to have both the phenolic and sesquiterpene moieties of the natural product present to achieve a biological effect. This result was confirmed in phytotoxicity bioassays. Megalanthine was ruled out as a significant plant–plant defense agent because of its lack of stability. The positive results recorded in the antifungal and antifeedant tests suggest, however, that this chemical is relevant in several ecological interactions involving H. megalanthum.

Insect Antifeedant and Ixodicidal Compounds from Senecio adenotrichius

Nine eremophilane sesquiterpenes 1 – 9, two flavonoids 11 and 12, and two known pirrolizidine alkaloids 13 and 14, were isolated from Senecio adenotrichius DC. Their structures were elucidated on the basis of spectroscopic data and by comparison with previously reported spectroscopic data of similar compounds. Compounds 5, 7, and 9 have not been previously reported as natural products. The antifeedant activity of these compounds was tested against Spodoptera litoralis and Myzus persicae. Eremophilanes 1, 3, and 8 were strong antifeedants to M. persicae, and 1 and 8 to Spodoptera littoralis. Their ixodicidal activity was tested against the tick Hyalomma lusitanicum, with eremophilanes 1, 3, and 8, being strong ixodicidal agents.