Effect of extracts from several sponges of Yucatan Coast on Giardia lamblia and preliminary chemical investigation of the bioactive extract of Haliclona (Reinera) tubifera

In this study, twenty-four organic extracts from six marine sponge species, collected at shallows of Yucatan, Mexico, were evaluated against Giardia lamblia trophozoites and Vero cells. The dichloromethane and hexane extracts of Haliclona tubifera exhibited the highest antigiardiasic activity (IC50 = 1.00 and 2.11 µg/mL, respectively), as well as high selectivity (SI = 41.8 and > 47.4, respectively), while ethyl acetate and methanol extracts of Cinachyrella alloclada, and methanol extract of Suberites aurantiaca showed moderate activity. Contrastingly, the extracts of Halichondria magniculosa and Oceanapia nodosa were considered non actives. Consequently, the dichloromethane extract of H. tubifera were subject to an exploratory chemical study, isolating cholesterol, two benzaldehyde derivatives, three benzoic acid derivatives, cytosine, and thymine.

Molecular orbital and topological electron density study of n → π* interactions: amides and thioamides cases

The n → π* interactions were studied in amides and thioamides systems models, through the analysis of the electron density topology along with the Natural Bonding Orbital (NBO) approach. The effect of the dispersion terms was assessed using different DFT functionals. The NBO, independent gradient model (IGM), and the analysis of the reduced density gradient outcomes show that dispersion forces play a significant role in the strength of n → π* interactions. The IGM results indicate that δg height values for n → π* interactions do not extend beyond 0.025. All the methods used in this work predict that n → π* interaction between pairs of thioamides is stronger than those between amides. However, the electron density topology-based methods were not able to replicate the trends in the relative force of this interaction found in the experimental and NBO results.

Cytotoxic and antiproliferative activity of thiazole derivatives of Ochraceolide A

A series of 15 novel 1,3-thiazole amide derivatives of the pentacyclic triterpene Ochraceolide A (1) was synthesized, characterized, and evaluated in vitro against three human cancer cell lines (MCF-7, MDA-MB-231 and SiHa) and a normal cell line (Vero). Synthetic derivatives were obtained by acylation of the 2-aminothiazole triterpene 2, previously reported. Remarkably, the 5-nitrofuramide derivative (2o) showed better cytotoxic and antiproliferative activity than compound 2 and the other derivatives against the three cancer cell lines with CC₅₀ and IC₅₀ values of 1.6-12.7 µM. Furthermore, butyramide derivative (2c) was approximately 25 times more selective than 2, as well as 3.4 times more selective than Docetaxel, against SiHa cells in the cytotoxic assay, while the phenyl amide derivatives were inactive against the three cancer cell lines.

The origin of the regiospecificity of acrolein dimerization

The NCI at the transition state are the key factor controlling the regiospecificity in the acrolein dimerization.

Cytotoxic activity against breast cancer cells of two species of marine sponges from shallows of Yucatan peninsula

This study aimed to evaluate the in vitro activity of extracts of two marine sponge species, occurring in the shallows of the Yucatan peninsula coast, on two cancer and one normal mammalian cell lines. Hexane, dichloromethane, ethyl acetate and methanol extracts of Halichondria magniconulosa and Halichondria melanadocia were screened for their cytotoxic activity against hormone-dependent breast cancer (MCF-7) and human cervix cancer (SiHa) cell lines. The ethyl acetate extract of H. magniconulosa exhibited significant cytotoxicity against MCF-7 cells to a CC₅₀ of 0.8 µg/mL, as well as high selectivity (SI = 24.5). On the other hand, SiHa cells were moderately sensitive to the dichloromethane and ethyl acetate extracts of the same species. (CC₅₀ = 34.9 and 31.5 µg/mL, respectively). None of the extracts of H. melanadocia were considered active due their CC₅₀'s were ranged from 59.0 to 94.5 µg/mL.

Identification of Insect-Deterrent Metabolites from Acremonium masseei strain CICY026, a Saprophytic Fungus from a Sinkhole in Yucatán

Micromycetes from unexplored sources represent an opportunity to discover novel natural products to control insect pests. With this aim, a strain of Acremonium masseei CICY026 isolated from a tropical sinkhole was identified, cultured on fermented rice, and its ethyl acetate extract (EAE) was evaluated against three serious phytophagous insects (Bemisia tabaci, Myzus persicae, and Rhopalosiphum padi). DNA from A. masseei CICY026 was used to confirm its identity. EAE caused settling inhibition (SI) of M. persicae and R. padi (67.5% and 75.3%, respectively). Bioassay-guided fractionation of the active EAE led to the isolation of a novel metabolite, named hexahydroacremonintriol (1), and of acremonin A glucoside (2). The structures of 1 and 2 were determined using IR, one- and two-dimensional NMR, HRMS, and confirmed by theoretical data. The aphid M. persicae was noticeably sensitive to 1 and 2 (SI: 55.6% and 67.2%, respectively), whereas R. padi was only slightly affected by 1 (SI: 59%). This new knowledge about mycobiota from these special sinkhole ecosystems will inform the development of new biorational pesticides.

Biomonitoring Organochlorine Pesticides in Didelphis virginiana from Yucatan, Mexico by GC-ECD

The aim of the present work was to apply a validated methodology for the detection of organochlorine pesticides in Didelphis virginiana (Virginia opossum) serum samples collected in Yucatan, Mexico. Recent studies performed to investigate the presence of Organochlorines (OCLs) in water, human blood and milk, and animal tissues from Yucatan have shown that the OCLs concentrations are high and can be associated with potential human health risk. Since opossum is considered an important synanthropic species in Yucatan, 40 opossum serum samples were analyzed by gas chromatography with electron capture detector. The most common OCLs found in opossum sera were lindanes, chlordanes, drines, and endosulfan. Heptachlor, heptachlor epoxide, and lindanes were found at the highest concentrations, while dichlorodiphenyl trichloroethane and its metabolites were found at the lowest concentrations in the samples. The good linearity, precision, and accuracy obtained in the evaluated parameters in the extraction and chromatographic methods support its application for the monitoring of OCLs pesticides in populations of opossums and other wild species in Yucatan.

Crystal structure and Hirshfeld surface analysis of N-(5-iodo-4-phenyl-thia-zol-2-yl)acetamide

The title compound crystallizes with two independent mol­ecules in the asymmetric unit. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, C—H⋯π, I⋯S and I⋯I inter­actions into a three-dimensional network.

Two crystallographically independent mol­ecules (A and B) are present in the asymmetric unit of the title compound, C₁₁H₉IN₂OS, which differ mainly in the dihedral angle between the phenyl and thia­zole rings [38.94 (16) and 32.12 (15)°, respectively]. In the crystal, the mol­ecules form ⋯A⋯B⋯A⋯B⋯ chains along the [001] and [010] directions through moderate N—H⋯O hydrogen bonds and C—H⋯π inter­actions, respectively. The overall three-dimensional network is formed by I⋯I and I⋯S inter­actions. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯C/C⋯H (26.2%), H⋯H (20.9%), H⋯I/I⋯H (19.4%) and H⋯O/O⋯H (6.8%) inter­actions.

Biosynthesis of Grandione: An Example of Tandem Hetero Diels-Alder/Retro-Claisen Rearrangement Reaction?

Mechanistic theoretical studies about the feasibility of the traditional proposed mechanism of formation for icetexane diterpene dimer grandione were assessed using density functional method at the M06-2X/6-31G(d,p) level of theory. Bulk water solvent effects were taken into account implicitly using the polarizable continuum model (SCI-PCM). The results were compared with the selectivity found in the biomimetic synthesis performed by experimental research groups. The relative free energy calculation shows that the one-step H-DA formation mechanism nominated in the literature is not a viable mechanism. We found that an alternative competing Tandem pathway is consistent with the experimental trends. Thus, our results suggested that the compound grandione is formed via a H-DA/retro-Claisen rearrangement and not by the traditional H-DA mechanism proposed early in the experimental studies. The H-DA initial step produce a biecyclic adduct followed by a domino retro-Claisen rearrangement that releases the energy strain of the bicyclic intermediary. Steric issues and hyperconjugation interactions are the mainly factors driving the reaction nature and the selectivity in the formation reaction. Finally, the enzymatic assistance for dimer formation was analyzed in terms of the calculated transition state energy barrier.

Crystal structure of ochraceolide A isolated from Elaeodendron trichotomum (Turcz.) Lundell

The title compound, C₃₀H₄₄O₃ [systematic name: 6aR,6 bR,8aS,9aR,12aR,14bR)-4,4,6a,6;b,8a,14b-hexa-methyl-12-methyl-eneicosa-hydro-3H-phenanthro[1',2':6,7]indeno-[2,1-b]furan-3,11(2H)-dione], is a triterpene lactone, which was isolated from di-chloro-methane extract of Elaeodendron trichotomum (Turcz.) Lundell (celastraceae) stem bark. The compound has a lupane skeleton and consists of four fused six-membered rings and two five-membered rings. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds into a three-dimensional network. The configuration of ochraceolide A was proposed based on analogue compounds which belong to the lupane type.

Diversifying Complexity by Domino Benzannulation of Polycyclic Natural Products

Herein we describe a salicylaldehyde-annulation reaction as a plug and play toolkit to diversify the complexity of naturally occurring ketones. The protocol entails the transformation of the polycyclic natural ketone into its propargyl vinyl ether derivative (two synthetic steps) and its microwave-assisted imidazole-catalyzed domino rearrangement to generate the salicylaldehyde ring. This annexed unit allows further synthetic transformations: e.g., the installation of a pharmacophore module to generate natural product-pharmacophore hybrids endowed with unknown biological (pharmaceutical) annotations.

Anti-giardia activity and acute toxicity of a methanol extract of Senna racemosa bark

ETHNOPHARMACOLOGICAL RELEVANCE

Senna racemosa (Mill.) H.S. Irwin & Barneby (syn. Cassia racemosa Mill.) is a plant used in traditional Mayamedicinal practices to treat diarrhea. A methanol extract of S. racemosa bark has been shown to have in vitro activity against Giardia intestinalis. No studies of its efficacy and toxicity in in vivo models have been done. The present study objective was to analyze the activity of this methanol extract of S. racemosa bark against Giardia intestinalis trophozoites in experimentally infected mice, and evaluate its toxicological effects in rats.

MATERIAL AND METHODS

S. racemosa was collected in Merida, Yucatan, Mexico (21°58'N, 89°36'W) in June 2005. The bark methanol extract was obtained and high performance liquid chromatography (HPLC-DAD) was used to generate a constituent profile. In vivo anti-giardia activity was assayed with an experimental model of G. intestinalis infection in neonatal CD-1 mice. Nine doses ranging from 0.25-15mg extract/kg body weight were tested to determine the dose required to kill 50% of the trophozoites (ED₅₀). An acute toxicity assay was run in which one of four single doses (200, 1000, 2000 and3000mg/kg body weight) was orally administered to adult Wistar rats. Animal weight, death rates, toxic effects and behavioral parameters were observed over a 14-d period. They were then euthanized and a necropsy performed.

RESULTS

The S. racemosa bark extract inhibited growth of G. intestinalis (ED₅₀=1.14mg/Kg) in neonatal CD-1 mice. No toxic or lethal effects were observed even at the highest dosage (3000mg/Kg), and neither were signs of toxicity observed in internal organs. The active compounds chrysophanol and physcion were present in the extract at a 1.76 ratio.

CONCLUSIONS

The results strongly support traditional use of S. racemosa bark for treatment of diarrhea caused by Giardia intestinalis infection.

ANTIPROTOZOAL ACTIVITY OF EXTRACTS OF ELAEODENDRON TRICHOTOMUM (CELASTRACEAE)

Background:

Chagas disease, amebiasis, giardiasis and trichomoniasis represent a serious health problem in Latin America. The drugs employed to treat these illnesses produce important side effects and resistant strains have appeared. The present study was aimed to evaluate the antiprotozoal activity of leaves, stem bark and root bark of Elaeodendron trichotomum, a celastraceus, that is used in Mexico as an anti-infective in febrile-type diseases.

Materials and methods:

Dichloromethane and methanol extracts of leaves, bark and roots of Elaeodendron trichotomum were tested against Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis, and Trypanosoma cruzi. A quantitative HPLC analysis of pristimerin and tingenone was performed.

Results:

The dichloromethane extract of roots was active against E. histolytica, G. lamblia, T. vaginalis, and T. cruzi, at IC50’s of 0.80, 0.44, 0.46, and 2.68 μg/mL, respectively. The HPLC analysis revealed the presence of tingenone (3.84%) and pristimerin (0.14%).

Conclusions:

The dichloromethane extract of the roots bark showed significant activity against all screened protozoa.

2-Amino-4-arylthiazole Derivatives as Anti-giardial Agents: Synthesis, Biological Evaluation and QSAR Studies

A series of seven 2-amino-4-arylthiazoles were prepared following Hantzsch’s modified method under microwave irradiation. A set of 50 derivatives was obtained and the in vitro activity against Giardia intestinalis was evaluated. The results on the biological activity revealed that, in general, the N-(5-bromo-4-aryl-thiazol-2-yl)-acetamide scaffold showed high bioactivity. In particular, compounds 6e (IC50 = 0.39 μM) and 6b (IC50 = 0.87 μM) were found to be more potent than the positive control metronidazole. Citoxicity and acute toxicity tests performed showed low toxicity and high selectivity of the most active compounds (6e SI = 139, 6b SI = 52.3). A QSAR analysis was applied to a data set of 37 obtained 2-amino-4-arylthiazoles derivatives and the best model described a strongly correlation between the anti-giardiasic activity and molecular descriptors as E2M, RDF115m, F10, MATS6v, and Hypnotic-80, with high statistical quality. This finding indicates that N-substituted aminothiazole scaffold should be investigated for the development of highly selective anti-giardial agent.

Bis(2-amino-4-phenyl-1,3-thia-zol-3-ium) tetra-chlorido-palladate(II)

The title compound, (C9H9N2S)2[PdCl4], consists of two monoprotonated 2-amino-4-phenyl-1,3-thia-zole molecules and one tetra-chlorido-palladate anion. The organic molecules exhibit a dihedral angle between the main rings planes of 31.82 (9)°. In the anion, the Pd(II) atom is located on a crystallographic centre of symmetry with a square-planar geometry. In the crystal, the anions and cations are connected through bifurcated N-H⋯Cl hydrogen bonds, and these inter-actions lead to hydrogen-bonded tapes of cations and anions along [100].

Two New 24-Isopropenyl-lanostanoids from Tillandsia brachycaulos

The leaves of Tillandsia brachycaulos afforded two novel tetracyclic triterpenoids identified as (24S)-24-isopropenyl-29-nor-5α-lanosta-7-en-3β-ol (1) and (24S)-24-isopropenyl-29-nor- 5α-lanosta-7-en-3-one (2), in addition to the known isopimaric acid (3) and chlorogenic acid (4). Their structures were elucidated on the basis of spectral analysis, including homo- and heteronuclear correlation NMR experiments (COSY, ROESY, HMQC and HMBC) and by comparison with data in the literature. The antimicrobial and antifungal activities were studied. The compounds did not show significant activity.

Antiproliferative evaluation of N-sulfonyl-2-alkyl-six membered azacycles. A QSAR study

A series of functionalized N-sulfonyl-piperidines and N-sulfonyl-tetrahydropyridines were evaluated for their antiproliferative activity against the representative panel of human solid tumor cells A2780 (ovarian), SW1573 (non-small cell lung) and WiDr (colon). The SAR study showed for WiDr cells a correlation between the biological activity and the length of the N-sulfonyl group, the nature of the substituents and the type of alkyl side chain. Further QSAR studies indicate that the size and nature of the N-sulfonyl group, the atomic polarizability (MP) and the partition coefficient are the most important descriptors for the activity. The major contribution is the size (F05C-S) of the N-sulfonyl group.

The rotational barrier in ethane: a molecular orbital study

The energy change on each Occupied Molecular Orbital as a function of rotation about the C-C bond in ethane was studied using the B3LYP, mPWB95 functional and MP2 methods with different basis sets. Also, the effect of the ZPE on rotational barrier was analyzed. We have found that σ and π energies contribution stabilize a staggered conformation. The σ(s) molecular orbital stabilizes the staggered conformation while the stabilizes the eclipsed conformation and destabilize the staggered conformation. The π(z) and molecular orbitals stabilize both the eclipsed and staggered conformations, which are destabilized by the π(v) and molecular orbitals. The results show that the method of calculation has the effect of changing the behavior of the energy change in each Occupied Molecular Orbital energy as a function of the angle of rotation about the C-C bond in ethane. Finally, we found that if the molecular orbital energy contribution is deleted from the rotational energy, an inversion in conformational preference occurs.

Rapid access to ketones related to oleanolic and ursolic acids

We describe in this article a process with which to obtain different ketones related to oleanolic and ursolic acids from a natural source, Salvia canariensis L., with minimal use of chromatography columns. Amongst the isolated compounds was 12α-bromo-3-oxo-olean-13, 28-olide (3), which was fully characterised, including a characterisation of its molecular configuration by X-ray crystallographic analysis by 1 and 2-dimensional NMR techniques.

21beta-Hydroxy-oleanane-type triterpenes from Hippocratea excelsa

Stem bark of Hippocratea excelsa afforded six pentacyclic triterpenes, five oleanane and one ursane types. They were identified as 11beta,21beta-dihydroxy-olean-12-ene-3-one (2), 3alpha,11alpha,21beta-trihydroxy-olean-12-ene (3), 3alpha,21beta-dihydroxy-11alpha-methoxy-olean-12-ene (4), 3alpha,21beta-dihydroxy-olean-9(11),12-diene (5), 3alpha,21beta-dihydroxy-olean-12-ene (6) and 3alpha,21beta-dihydroxy-11alpha-methoxy-urs-12-ene, isolated as its diacetate derivative (7), as well as 3alpha,21beta-dihydroxy-olean-12-ene (1) previously isolated from the root bark. The known alpha- and beta-amyrin, oleanoic and ursolic acids, trans-polyisoprene, and the ubiquitous beta-sitosterol were also isolated. Structures were elucidated on the basis of spectroscopic analyses, including homo- and heteronuclear correlation NMR experiments (COSY, ROESY, HSQC and HMBC) and comparison with literature data. The antigiardial activity of compounds 2-5 was not significant.

Antigiardial activity of triterpenoids from root bark of Hippocratea excelsa

Two new triterpenoids, 21 beta-hydroxyolean-12-en-3-one (1) and a seco-dinor derivative of pristimerine named dzununcanone (2), were isolated from the root bark of Hippocratea excelsa. Their structures were assigned on the basis of spectroscopic evidence, mainly 1H and 13C 1D and 2D NMR including DEPT, COSY, ROESY, HSQC, and HMBC experiments, as well as EIMS and HREIMS. The known 21alpha-hydroxy-3-oxofriedelane (3), a compound new to the species, and the known methide quinones pristimerine (4) tingenone (5), and xuxuarine Ebeta (7) were also isolated. The antiprotozoal activities were determined against Giardia intestinalis. Pristimerine and tingenone were the most active antigiardial compounds, with IC50 values of 0.11 and 0.74 microM, respectively, compared with metronidazole, the current drug of choice (IC50 1.23 microM).

Triterpenoids from Hippocratea excelsa. The Crystal Structure of 29-Hydroxytaraxerol

The root bark of Hippocratea excelsa afforded a new derivative of β -amyrin, which was identified as its ferulate, together with components new in this species. They were identified as the rare 29-hydroxytaraxerol, 29-hydroxyglutinol, 29-hydroxyfriedelin and the sterol 6β -hydroxystigmast-4- en-3-one. The known triterpene quinone methides pristimerin and tingenone characteristics of this genus, β -sitosterol, trans-polyisoprene, squalene, β -amyrin, and the alditol galacticol characteristic of the Celastraceae were also isolated. The structures were established on the basis of spectral analysis, including homo- and heteronuclear correlation NMR experiments (COSY, DEPT, HMQC and HMBC) and by comparison with data reported in the literature. The structure of 29-hydroxytaraxerol was confirmed by X-ray diffraction. The antimicrobial and antifungal activities of the compounds were studied, but no significant activity was found.

Racemochrysone, a dihydroanthracenone from Senna racemosa

From the hexane extract of the bark of the stems of Senna racemosa (syn. Cassia racemosa) a new dihydroanthracenone derivative, named racemochrysone, was isolated. Its structure was established as 8,9-dihydroxy-3-methoxy-2,2,6-trimethyl-(2H)-anthracen-1-one based on spectroscopical data, mainly 1D and 2D NMR experiments. In addition beta-sitosterol, stigmasterol, chrysophanol and physcion were obtained. From the leaves extracts the piperidine alkaloid cassine and the hexitol pinitol were obtained.

Cassine, an antimicrobial alkaloid from Senna racemosa

The leaves of Senna racemosa yielded the piperidine alkaloid cassine and an inositol methyl ether. Antimicrobial screening of the compounds revealed antibacterial activity of cassine with minimum inhibitory concentrations of 2.5 mg/ml for Staphylococcus aureus and Bacillus subtilis and 5.0 mg/ml for Candida albicans.

Antimicrobial activity of Fabaceae species used in Yucatan traditional medicine

The methanol and water extracts of six Fabaceae species, traditionally used in Mayan medicine for the treatment of diarrhoea and eye infections, were phytochemically screened and tested for in vitro antimicrobial activity. Four species showed activity against Gram positive bacteria, five exhibited some activity against Candida albicans, two exhibited activity against Aspergillus niger and only one, Mimosa pigra, inhibited growth of Pseudomonas aeruginosa. None of the extracts was active against Escherichia coli.