Rosa E. del Río

Purely olefinic alkamnides in Heliopsis longipes and Acmella (Spilanthes) oppositifolia

Abstract Acmella (Spilanthes) oppositifolia and Heliopsis longipes are collected from the wild and used as medicinal, flavouring and insecticidal plants. These species contain purely olefinic alkamides (not containing acetylenic bonds) with affinin 1 as the main lipidic component and N -2-methylbutyldeca-2 E ,6 Z ,8 E -trienamide 2 , in lower quantities. In A. oppositifolia N -isobutyl-dodeca-2 E ,4 E ,8 Z ,10 E -tetraenamide 3 was detected with the above mentioned alkamides. For this species the same components can be found in roots and aerial parts. Heliopsis longipes alkamides are present only in roots. A comparison of the purely olefinic alkamide structures observed in the Heliantheae is discussed briefly.

Molecular dynamics analysis of PVA- AgnP composites by dielectric spectroscopy

The molecular dynamics of PVA/AgnP composites were studied by dielectric spectroscopy (DS) in the 20-300°C temperature range. Improper water elimination leads to misinterpretation of thermal relaxations in PVA composites in agreement with the previous report for pristine PVA. The evaporation of water and its plasticizing effect are more evident in pure PVA confirming the existence of strong interaction between OH groups of PVA chains and AgnP. Dry films show a single nonlinear VFT dependence (from 45°C until melting) associated to the α-relaxation and, therefore, to the glass transition phenomenon and from dielectric measurements, the Tg of composites vary from 88*deg;C for pristine PVA to 125°C for PVA/AgnP (5wt%). Below 45°C, dry films exhibit a single Arrhenius behavior showing a 3D hopping conductivity as explained based on the variable range hopping model. PVA/AgnP composites have higher conductivity compared to pristine PVA, and it increases as AgnP weight percent increases. Finally, DMA measurements support the statement that a secondary relaxation was erroneously assigned as the glass transition of PVA and composites in previous reports.

Absolute configuration of labdanes and ent-clerodanes from Chromolaena pulchella by vibrational circular dichroism

The aerial parts of Chromolaena pulchella biosynthesize two groups of diterpenes belonging to opposite enantiomeric series, specifically, the furanoid ent-clerodanes (5R,8R,9S,10R)-(-)-hardwikiic acid (1), methyl (5R,8R,9S,10R)-(-)-hardwikiate (2), (5S,8R,9S,10R)-(-)-hautriwaic acid lactone (3), methyl (5R,8R,9S,10R)-(-)-nidoresedate (4) and methyl (8R,9R)-(-)-strictate (5), as well as the labdanes (5S,8R,9R,10S)-(+)-(13E)-labd-13-ene-8,15-diol (6) and (5S,8R,9R,10S)-(+)-isoabienol (7). The absolute configuration of the two groups of diterpenes was unambiguously assigned by comparison of the vibrational circular dichroism spectra of 3 for ent-clerodanes, and of 7 for labdanes with their theoretical spectra obtained by density functional theory calculations. The results support a biogenetic proposal to diterpenes found in the studied botanical species.

Cassane diterpenes from Caesalpinia platyloba

The dichloromethane extract from the leaves of Caesalpinia platyloba provided cassane diterpenes whose structures were determined as (-)-(5S,6R,8S,9S,10R,14R)-6-acetoxyvouacapane (1), (-)-(5S,6R,8S,9S,10R,12Z,14R)-6-acetoxycassa-12,15-diene (3), and (-)-(5S,6R,8S,9S,10R,13E)-6-acetoxycassa-13,15-diene (4). Compound 1 was chemically correlated with (-)-(5S,6R,8S,9S,10R,14R)-6-hydroxyvouacapane (2), (+)-(5S,8S,9S,10R,14R)-6-oxovouacapane (5), and (+)-(5S,6S,8S,9S,10R,14R)-6-acetoxyvouacapane (6), the last one previously isolated from Dipteryx lacunifera. The absolute configurations of all six diterpenes 1-6 were established by comparison of DFT calculated vibrational circular dicroism spectra of 1, 2 and 5 with those obtained experimentally. In addition, several reported chemical shifts for 2 and 5 were reassigned based on two-dimensional NMR measurements.

Absolute configuration of (13R)- and (13S)-labdane diterpenes coexisting in Ageratina jocotepecana.

Chemical investigation of the hexanes extracts of Ageratina jocotepecana afforded (-)-(5S,9S,10S,13S)-labd-7-en-15-oic acid (1), methyl (-)-(5S,9S,10S,13S)-labd-7-en-15-oate (2), (+)-(5S,8R,9R,10S,13R)-8-hydroxylabdan-15-oic acid (3), and (-)-(5S,9S,10S,13Z)-labda-7,13-dien-15-oic acid (5). The coexistence of (13R)- and (13S)-labdanes in this member of the Asteraceae family was demonstrated by vibration circular dichroism measurements of ester 2 and methyl (+)-(5S,8R,9R,10S,13R)-8-hydroxylabdan-15-oate (4) in comparison to the DFT B3LYP/DGDZVP-calculated spectra. In addition, transformation of 1 and 3 with HClO4 in MeOH yielded epimeric methyl (+)-(5S,10S,13S)-labd-8-en-15-oate (6) and methyl (+)-(5S,10S,13R)-labd-8-en-15-oate (7), respectively, confirming the presence of C-13 epimers in this plant. Diterpene 1 showed remarkable antibacterial activity against Bacillus subtilis (MIC 0.15 mg/mL) and Staphylococcus aureus (MIC 0.78 mg/mL), while diterpene 3 exhibited moderate activities against the same organisms.

Regio- and stereoselective cleavage of steroidal 22-oxo-23-spiroketals catalyzed by BF3·Et2O

The regioselective opening of the F ring of 22-oxo-23-spiroketals using BF3·OEt2 in acetic anhydride yielded novel cholestanic frameworks with pyranone E ring 20-23. The structures of the new derivatives of botogenin, diosgenin, hecogenin and tigogenin thus obtained were established using one and two dimensional (1)H, (13)C experiments (DEPT, COSY, HETCOR, HMBC). The X-ray diffraction analysis unequivocally confirmed the R configuration at C-23 in the starting 22-oxo-23-spiroketal 18 and the Z configuration of the C23-C24 double bond in the reaction product 20.

Silver nanoparticles from AgNO3–affinin complex synthesized by an ecofriendly route: chitosan-based electrospun composite production

Abstract A novel nanofibrous chitosan-based composite containing affinin and silver nanoparticles is obtained by electrospinning. Silver nanoparticles are synthesized by sunlight photoreduction of the metal complex [Ag2–(affinin)](NO3)2 in polymeric solution, via a green one-pot methodology, wherein chitosan and affinin act as reducing, dispersing and stabilizing agent.

Regioselective cleavage of 22-oxo-23-spiroketals. Novel cholestanic frameworks with pyranone and cyclopentenone E rings on the side chain

The regioselective opening of the F ring of 22-oxo-23-spiroketals using a saturated solution of HCl in acetic anhydride yielded novel cholestanic frameworks with pyranone or cyclopentenone E rings. The structures of the new derivatives of sarsasapogenin, diosgenin and hecogenin thus obtained were established using one and two dimensional (1)H, (13)C experiments (DEPT, COSY, HETCOR, HMBC, ROESY, and NOESY). The X-ray analysis for compound 11b confirmed the 23R configuration for the new stereogenic center.

Transesterification of Caesalpinia eriostachys seed oil using heterogeneous and homogeneous basic catalysts

ABSTRACT Caesalpinea eriostachys seed oil, as a source of triglycerides with potential application for biodiesel production in Mexico is introduced. Its lipid profile obtained by Gas Chromatography-Mass Spectrometry (GC-MS) revealed saturated and unsaturated glycerol esters as the constituents. Therefore, heterogeneous and homogeneous catalyzed transesterification reactions were assayed employing ZnAl hydrotalcites and KOH, as the catalysts, respectively. The transesterification reactions yielded 59% for Zn/Al(2), 79% for Zn/Al(4), and 90% for KOH, depicting typical behavior, as in biodiesel production data from literature, where Zn-Al hydrotalcites or KOH were assayed. The caloric, density, viscosity values, and fatty acid methyl esters profile from reaction products were concordant to EN 14214, suggesting C. eriostachys as a promising feedstock for biodiesel production.

Crystal structure of N-[(E)-(1,3-benzodioxol-5-yl)­methyl­idene]-4-chloro­aniline

In the title compound, C14H10ClNO2, obtained by the condensation of 4-chloroaniline and piperonal, the five-membered ring is almost planar (r.m.s. deviation = 0.023 Å) and the dihedral angle between the aromatic rings is 43.22 (14)°. In the crystal, a short O⋯Cl contact of 3.173 (2) Å is observed. The molecules are arranged into corrugated (010) layers.