Biomedical subjects

Carlos M Cerda-García-Rojas

Publications and source records attributed to Carlos M Cerda-García-Rojas.

12 recordsLinked to original sources

PubMed2005

Absolute configuration of the alpha-methylbutyryl residue in longipinene derivatives from Stevia pilosa.

The absolute configuration of the alpha-methylbutyryl residue in (4R,5S,7S,8S,9S,10R,11R,2''S)-7-angeloyloxy-9-hydroxy-8-(alpha-methylbutyryloxy)-longipin-2-en-L-one and (4R,5S,7S,8R,10R,11R,2''S)-7-angeloyloxy-8-(alpha-methylbutyryloxy)- longipin-2-en-L-one was determined by chemical correlation with (S)-(+)-benzyl alpha-methylbutyrate prepared from authentic (S)-(+)-alpha-methylbutyric acid. Both compounds were isolated from the hexane extracts of roots of Stevia pilosa Lag. together with four other longipinene derivatives. The developed correlation method is useful to ascertain the chirality of natural alpha-methylbutyryl esters found in nature and to reinforce the hypotheses on the biogenetic origin of these residues.

Molecular Conformation↗

PubMed2005

Smooth muscle relaxant action of benzyl benzoates and salicylic acid derivatives from Brickellia veronicaefolia on isolated guinea-pig ileum.

A dichloromethane-MeOH extract prepared from the aerial parts of Brickellia veronicaefolia inhibited the spontaneous contractions (IC50 = 39.22 microg/mL) of the guinea-pig ileum. Bioassay-guided fractionation of the extract led to the isolation of three new benzoic acid derivatives, 1,2-bis-O-(2-methoxybenzoyl)-beta-d-glucopyranoside (1), 3-(beta-glucopyranosyloxy)benzyl 2,6-dimethoxybenzoate (2) and 3-hydroxybenzyl 2,6-dimethoxybenzoate (3), together with the known compounds taraxasteryl acetate (4), 4-allyl-2-methyloxyphenyl-beta-glucopyranoside (5), 2-hydroxy-6-methoxybenzoic acid (6), 2-methoxybenzoic acid (7), chamazulene (8), 2-methoxybenzyl 2-hydroxybenzoate (9), benzyl 2,6-dimethoxybenzoate (10), 3-methoxybenzyl 2-hydroxy-6-methoxybenzoate (11), benzyl 2-hydroxy-6-methoxybenzoate (12), benzyl 2,3,6-trimethoxybenzoate (13), benzyl 2-hydroxy-3,6-dimethoxybenzoate (14) and 3-methoxybenzyl 2,6-dimethoxybenzoate (15). The isolates were characterized by spectral means. Compounds 2 - 6, 8 - 11, 14 and 15 induced a concentration-dependent inhibition of the spontaneous contractions of the guinea-pig ileum with IC50 values ranging from 1.49 to 4.96 microM. Their activity was comparable to that of papaverine (IC50 = 4.23 microM).

Animals↗

PubMed2004

First seco-C oleananes from nature.

[structure: see text] The triterpenes 8,14-seco-oleana-8(26),13-dien-3beta-ol (1) and its acetyl derivative 2 were isolated from Stevia viscida and Stevia eupatoria, respectively. Their structures were elucidated by 2D NMR, including carbon-carbon connectivity experiments, and confirmed by X-ray diffraction analysis of ketone 3. The absolute configuration was determined by NMR analysis of the Mosher esters of 1. The biogenetic implications of the new substances are discussed.

Crystallography, X-Ray↗

PubMed2004

DFT and NMR parameterized conformation of valeranone.

A Monte Carlo random search using molecular mechanics, followed by geometry optimization of each minimum energy structure employing density functional theory (DFT) calculations at the B3LYP/6-31G* level and a Boltzmann analysis of the total energies, generated accurate molecular models which describe the conformational behavior of the antispasmodic bicyclic sesquiterpene valeranone (1). The theoretical H-C-C-H dihedral angles gave the corresponding 1H, 1H vicinal coupling constants using a generalized Karplus-type equation. In turn, the 3J(H,H) values were used as initial input data for the spectral simulation of 1, which after iteration provided an excellent correlation with the experimental 1H NMR spectrum. The calculated 3J(H,H) values closely predicted the experimental values, excepting the coupling constant between the axial hydrogen alpha to the carbonyl group and the equatorial hydrogen beta to the carbonyl group (J(2beta, 3beta)). The difference is explained in terms of the electron density distribution found in the highest occupied molecular orbital (HOMO) of 1. The simulated spectrum, together with 2D NMR experiments, allowed the total assignment of the 1H and 13C NMR spectra of 1.

Magnetic Resonance Spectroscopy↗

PubMed2004

Preparation of moreliane-derived volatile sesquiterpenes.

A series of six volatile sesquiterpenes (9-13 and 15) was prepared by thioketalization of (4R,5S,9S,10S,11S)-morel-2-en-1,7-dione (2) and of (4R,5S,7R,9R,11R)-moreli-2,10-dien-7-ol-1-one (3), followed by Raney-nickel desulfurization. The structures of the new substances were determined by 1D and 2D NMR including COSY, NOESY, HSQC, and HMBC experiments. The geometry of (3S,4R,5R,9S,10R,11S)-morelian-7-one (11), which exhibited an intense woody odor, was calculated by density functional theory at the B3LYP/6-31G level.

Hydrolysis↗

PubMed2003

Conformational analysis of sulfur-containing 6-deoxy-l-hexose derivatives by molecular modeling and NMR spectroscopy. A theoretical study and experimental evidence of intramolecular nonbonded interactions between sulfur and oxygen.

6-Deoxy-l-mannose diphenyldithioacetal (1) unexpectedly gave the rearranged products phenyl 3,4-di-O-acetyl-2-S-phenyl-1,2-dithio-6-deoxy-beta-l-glucopyranoside (9) and 3,4-di-O-acetyl-2,5-anhydro-6-deoxy-l-glucose diphenyldithioacetal (10) upon treatment with acetyl chloride, while 6-deoxy-l-mannose ethylenedithioacetal (3) yielded (4aR,6S,7S,8R,8aS)-7,8-diacetyloxy-6-methylhexahydro-4aH-[1,4]dithiino[2,3b]pyran (11), whose structure was further confirmed by X-ray diffraction, and 3,4-di-O-acetyl-2,5-anhydro-l-rhamnose ethylenedithioacetal (12). The geometry of the four rearranged products as well as that of 1-thio-6-deoxy-l-mannopyranosides 5 and 7 and their acetyl derivatives 6 and 8 was studied by density functional theory (B3LYP/6-31G) molecular models, in combination with a Karplus-type analysis of the NMR vicinal coupling constants, revealing that the six-membered ring of pyranosides 5-9 and 11 exists in a slightly distorted chair conformation (6-13% distortion) and that the conformational behavior of the 2,5-anhydro-6-deoxy-l-glucose dithioacetals 10 and 12 is strongly influenced by the presence of stabilizing intramolecular nonbonded sulfur-oxygen 1,4- and 1,5-interactions. Compounds 9-12 were formed by a molecular rearrangement via sulfonium ion intermediates followed by stereoselective intramolecular cyclizations as formulated by the quantum chemical calculations performed in the present study.

Cyclization↗

PubMed2003

Stereoselective synthesis and determination of the cytotoxic properties of spicigerolide and three of its stereoisomers.

Stereoselective syntheses of the naturally occurring, cytotoxic lactone spicigerolide and three nonnatural stereoisomers thereof are described. The commercially available sugar l-rhamnose was in all cases the chiral starting material. Key steps in each of these syntheses were asymmetric Brown allylations and ring-closing metatheses. The cytotoxic activities of the four lactones against a range of tumoral lines were then determined.

Antineoplastic Agents↗

PubMed2003

Spermicidal activity of the crude ethanol extract of Sedum praealtum in mice.

Ethanol extract of Sedum praealtum in intravaginal doses of 10, 20, 40, 50, 100 and 150 mg/kg body weight showed a toxic effect in spermatozoa viability after 24h of administration. Spermatozoa viability was 94, 83, 58 and 24%, respectively, for extract doses of 10, 20, 40 and 50mg/kg body weight, while only dead spermatozoa were found in the vagina of the treated female mice with doses of 100 and 150 mg/kg body weight.

Administration, Intravaginal↗

PubMed2003

A new phytotoxic nonenolide from Phoma herbarum.

Reinvestigation of the fermentation broth and mycelium of the fungus Phoma herbarum led to the isolation of a new phytotoxic nonenolide, namely, (7R,9R)-7-hydroxy-9-propyl-5-nonen-9-olide, which was designated with the trivial name herbarumin III (3). The known compounds herbarumins I (1) and II (2) were also obtained. The structure of 3 was elucidated by spectroscopic methods and molecular modeling. Compounds 1-3 interacted with bovine-brain calmodulin and inhibited the activation of the calmodulin-dependent enzyme cAMP phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2002

Jiquilpane hydrocarbon skeleton generated by two successive Wagner-Meerwein rearrangements of longipinane derivatives.

The molecular rearrangement of (1R,3S,4S,5S,7S,8R,9S,10R,11R)-7,8,9-triacetyloxylongipinan-1-ol (4) under acidic conditions afforded (1S,4R,5R,7S,8R,9S,10S)-7,8,9-triacetyloxyuruap-3(12)-ene (5), while 6, the C(3)-stereoisomer of 4, after two consecutive Wagner-Meerwein rearrangements followed by two 1,2-hydride migrations, afforded (4R,5R,7S,8S,9S,10S,11S)-7,8,9-triacetyloxyjiquilp-3(12)-ene (7), which possesses a new hydrocarbon skeleton. The structures of the new substances were elucidated by 1D and 2D NMR data in combination with X-ray diffraction analyses of the uruapane, longipinane, and jiquilpane derivatives 5, 6, and 14, respectively. Molecular modeling at the ab initio level was used to study the reaction mechanisms, while deuterium labeling was employed to confirm the C-C bond migrations and the hydride shifts.

Models, Molecular↗

PubMed2002

Quirogane, prenopsane, and patzcuarane skeletons obtained by photochemically induced molecular rearrangements of longipinene derivatives.

Ultraviolet irradiation of (1R,3S,4S,5S,10R,11R)-1-acetyloxy-7-oxolongipin-8-ene (6), prepared from longipinene diesters isolated from Stevia salicifolia, afforded the new quirogane (7) and prenopsane (8) derivatives, as the major products, together with the minor secondary photoproduct (1R,3R,5R,8S,11S)-1-acetyloxy-7-oxopatzcuar-9-ene (9), which possesses a novel tricyclic sesquiterpene skeleton. The stereostructures of the new compounds 7-9 were mainly determined by NMR techniques including COSY, HSQC, HMBC, and NOESY in combination with molecular modeling obtained by density functional theory calculations. A reaction mechanism accounting for the observed transformations is proposed.

Magnetic Resonance Spectroscopy↗

PubMedDate not supplied

Stereochemical assignment of naturally occurring 2,3-epoxy-2-methylbutanoate esters.

A method to determine the absolute configuration of 2,3-epoxy-2-methylbutanoate ester residues in natural products is presented, based on (i) the reduction of the ester function to yield a 2-methyl-1,2-butanediol, (ii) esterification of the obtained primary alcohol with either (R)-(+)- or (S)-(-)-Mosher's acid to afford the corresponding Mosher's ester, and (iii) 1H-NMR spectral comparison of the final product with that of the Mosher's esters prepared from 2-methyl-1,2-butanediols of known stereochemistry.

Biological Factors↗