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1.
Front Chem ; 9: 800145, 2021.
Article in English | MEDLINE | ID: mdl-35127648

ABSTRACT

The past decade has observed a significant surge in efforts to discover biological systems for the fabrication of metal nanoparticles. Among these methods, plant-mediated synthesis has garnered sizeable attention due to its rapid, cost-effective, environmentally benign single-step procedure. This study explores a step-wise, room-temperature protocol for the synthesis of gold nanoparticles (AuNPs) using Carallia brachiata, a mangrove species from the west coast of Peninsular Malaysia. The effects of various reaction parameters, such as incubation time, metal ion concentration, amount of extract and pH, on the formation of stable colloids were monitored using UV-visible (UV-Vis) absorption spectrophotometry. Our findings revealed that the physicochemical properties of the AuNPs were significantly dependent on the pH. Changing the pH of the plant extract from acidic to basic appears to have resulted in a blue-shift in the main characteristic feature of the surface plasmon resonance (SPR) band, from 535 to 511 nm. The high-resolution-transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FESEM) images revealed the morphologies of the AuNPs synthesized at the inherent pH, varying from isodiametric spheres to exotic polygons and prisms, with sizes ranging from 10 to 120 nm. Contrarily, an optimum pH of 10 generated primarily spherical-shaped AuNPs with narrower size distribution (8-13 nm). The X-ray diffraction (XRD) analysis verified the formation of AuNPs as the diffraction patterns matched well with the standard value of a face-centered cubic (FCC) Au lattice structure. The Fourier-transform infrared (FTIR) spectra suggested that different functional groups are involved in the biosynthetic process, while the phytochemical test revealed a clear role of the phenolic compounds. The reduction of 4-nitrophenol (4-NP) was selected as the model reaction for evaluating the catalytic performance of the green-synthesized AuNPs. The catalytic activity of the small, isotropic AuNPs prepared using basic aqueous extract was more effective than the nanoanisotrops, with more than 90% of 4-NP conversion achieved in under an hour with just 3 mg of the nanocatalyst.

2.
Front Chem ; 8: 597980, 2020.
Article in English | MEDLINE | ID: mdl-33344417

ABSTRACT

Nanotechnology is one of the most interesting areas of research due to its flexibility to improve or form new products from nanoparticles (NPs), and as a fast, greener, more eco-friendly and sustainable solution to technological and environmental challenges. Among metal oxides of photocatalytic performance, the use of titania (TiO2) as photocatalyst is most popular due to its unique optical and electronic properties. Despite the wide utilization, the synthesis of TiO2 NPs bears many disadvantages: it utilizes various less environmental-friendly chemicals, high cost, requires high pressure and energy, and potentially hazardous physical and chemical methods. Hence, the development of green synthesis approach with eco-friendly natural products can be used to overcome these adverse effects. In this work, TiO2 NPs have been prepared by using Deinbollia pinnata leaves extracts, obtained by different solvents (n-hexane, ethyl acetate, and ethanol) with different polarities. The extracts acted as the reducing agent, while titanium isopropoxide as the precursor and water as the solvent. X-ray diffraction (XRD) pattern confirmed the synthesized TiO2 consist of anatase phase in high purity, with average crystallite size in the range of 19-21 nm. Characterization by using field emission scanning electron microscopy (FESEM) showed the TiO2 NPs possess a uniform semi-spherical shape in the size range of 33-48 nm. The energy dispersive X-ray (EDX) spectra of green TiO2 NPs showed two peaks for the main elements of Ti (61 Wt.%) and O (35 Wt.%). The band-gap energy of 3.2 eV was determined using UV-Vis spectroscopy. From the nitrogen sorption analysis, type V isotherm of the material was obtained, with BET surface area of 31.77 m2/g. The photocatalytic activity of synthesized TiO2 was evaluated for photodegradation of methyl orange (MO) under UV light irradiation. Based on the results, it is shown that TiO2 NPs synthesized with D. pinnata leaves extracted using ethyl acetate showed the most effective photodegradation performance, achieving 98.7% of MO conversion within 150 min. It can be concluded that the use of plant extracts in synthesis with TiO2 managed to produce highly crystalline anatase TiO2 with superior photocatalytic activity in the photodegradation of organic dye.

3.
Nat Prod Res ; 34(19): 2746-2753, 2020 Oct.
Article in English | MEDLINE | ID: mdl-30931627

ABSTRACT

Phytochemical study was conducted on the leaves of Globimetula braunii which is a hemi parasitic plant belonging to the family Loranthaceae. Extraction was carried out using cold extraction method with increasing polarity of solvents i.e n-hexane, CH2Cl2 and MeOH. The components were separated by chromatographic technique and the structures of the compounds were elucidated by extensive spectroscopic analyses including MS, FTIR, 1D and 2D NMR, HRMS and chemical methods. Six new pentacyclic triterpenoid esters named as globrauneine A (1), globrauneine B (2), globrauneine C (3), globrauneine D (4), globrauneine E (5), and globrauneine F (6), together with six known compounds (7 - 12) were successfully isolated from the leaves of G. braunii growing on Piliostigma thonningii. These results depict a substantial support to the chemotaxonomy of the genus Globimetula.


Subject(s)
Loranthaceae/chemistry , Plant Leaves/chemistry , Triterpenes/chemistry , Esters/chemistry , Fabaceae/parasitology , Hexanes/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Plant Extracts/chemistry , Solvents/chemistry , Spectroscopy, Fourier Transform Infrared
4.
Molecules ; 24(3)2019 Feb 07.
Article in English | MEDLINE | ID: mdl-30736403

ABSTRACT

An efficient microwave-assisted one-step synthetic route toward Mannich bases is developed from 4-hydroxyacetophenone and different secondary amines in quantitative yields, via a regioselective substitution reaction. The reaction takes a short time and is non-catalyzed and reproducible on a gram scale. The environmentally benign methodology provides a novel alternative, to the conventional methodologies, for the synthesis of mono- and disubstituted Mannich bases of 4-hydroxyacetophenone. All compounds were well-characterized by FT-IR, ¹H NMR, 13C NMR, and mass spectrometry. The structures of 1-{4-hydroxy-3-[(morpholin-4-yl)methyl]phenyl}ethan-1-one (2a) and 1-{4-hydroxy-3-[(pyrrolidin-1-yl)methyl]phenyl}ethan-1-one (3a) were determined by single crystal X-ray crystallography. Compound 2a and 3a crystallize in monoclinic, P21/n, and orthorhombic, Pbca, respectively. The most characteristic features of the molecular structure of 2a is that the morpholine fragment adopts a chair conformation with strong intramolecular hydrogen bonding. Compound 3a exhibits intermolecular hydrogen bonding, too. Furthermore, the computed Hirshfeld surface analysis confirms H-bonds and π⁻π stack interactions obtained by XRD packing analyses.


Subject(s)
Acetophenones/chemistry , Acetophenones/chemical synthesis , Chemistry Techniques, Synthetic , Microwaves , Crystallography, X-Ray , Hydrogen Bonding , Models, Molecular , Molecular Structure , Spectrum Analysis , Structure-Activity Relationship
5.
Phytochem Anal ; 30(1): 101-109, 2019 Jan.
Article in English | MEDLINE | ID: mdl-30288828

ABSTRACT

INTRODUCTION: Cassia singueana Del. (Fabaceae) is a rare medicinal plant used in the traditional medicine preparations to treat various ailments. The root of C. singueana is a rich source of anthraquinones that possess anticancer, antibacterial and antifungal properties. OBJECTIVE: The objective of this study was to develop an ultrasound-assisted extraction (UAE) method for achieving a high extraction yield of anthraquinones using the response surface methodology (RSM), Box-Behnken design (BBD), and a recycling preparative high-performance liquid chromatography (HPLC) protocol for isolation of anthraquinones from C. singueana. METHODOLOGY: Optimisation of UAE was performed using the Box-Behnken experimental design. Recycling preparative HPLC was employed to isolate anthraquinones from the root extract of C. singueana. RESULTS: The BBD was well-described by a quadratic polynomial model (R2  = 0.9751). The predicted optimal UAE conditions for a high extraction yield were obtained at: extraction time 25.00 min, temperature 50°C and solvent-sample ratio of 10 mL/g. Under the predicted conditions, the experimental value (1.65 ± 0.07%) closely agreed to the predicted yield (1.64%). The obtained crude extract of C. singueana root was subsequently purified to afford eight anthraquinones. CONCLUSION: The extraction protocol described here is suitable for large-scale extraction of anthraquinones from plant extracts.


Subject(s)
Anthraquinones/isolation & purification , Cassia/chemistry , Chromatography, High Pressure Liquid/methods , Plant Roots/chemistry , Research Design , Ultrasonics/methods , Chemical Fractionation/methods , Models, Statistical , Plant Extracts/chemistry , Proton Magnetic Resonance Spectroscopy , Reproducibility of Results
7.
Phytochem Anal ; 28(4): 324-331, 2017 Jul.
Article in English | MEDLINE | ID: mdl-28168765

ABSTRACT

INTRODUCTION: Prenylated and pyrano-flavonoids of the genus Artocarpus J. R. Forster & G. Forster are well known for their acetylcholinesterase (AChE) inhibitory, anti-cholinergic, anti-inflammatory, anti-microbial, anti-oxidant, anti-proliferative and tyrosinase inhibitory activities. Some of these compounds have also been shown to be effective against Alzheimer's disease. OBJECTIVE: The aim of the in silico study was to establish protocols to predict the most effective flavonoid from prenylated and pyrano-flavonoid classes for AChE inhibition linking to the potential treatment of Alzheimer's disease. METHODOLOGY: Three flavonoids isolated from Artocarpus anisophyllus Miq. were selected for the study. With these compounds, Lipinski filter, ADME/Tox screening, molecular docking and quantitative structure-activity relationship (QSAR) were performed in silico. In vitro activity was evaluated by bioactivity staining based on the Ellman's method. RESULTS: In the Lipinski filter and ADME/Tox screening, all test compounds produced positive results, but in the target fishing, only one flavonoid could successfully target AChE. Molecular docking was performed on this flavonoid, and this compound gained the score as -13.5762. From the QSAR analysis the IC50 was found to be 1659.59 nM. Again, 100 derivatives were generated from the parent compound and docking was performed. The derivative compound 20 was the best scorer, i.e. -31.6392 and IC50 was predicted as 6.025 nM. CONCLUSION: Results indicated that flavonoids could be efficient inhibitors of AChE and thus, could be useful in the management of Alzheimer's disease. Copyright © 2017 John Wiley & Sons, Ltd.


Subject(s)
Alzheimer Disease/drug therapy , Cholinesterase Inhibitors/pharmacology , Flavonoids/pharmacology , Acetylcholinesterase , Humans , Molecular Docking Simulation , Quantitative Structure-Activity Relationship
8.
Nat Prod Res ; 31(10): 1113-1120, 2017 May.
Article in English | MEDLINE | ID: mdl-27564208

ABSTRACT

A new dihydrochalcone, 2',4'-dihydroxy-3,4-(2″,2″-dimethylchromeno)-3'-prenyldihydrochalcone (1) together with 4-hydroxyonchocarpin (2), isobavachalcone (3), 4',5-dihydroxy-6,7-(2,2-dimethylpyrano)-2'-methoxy-8-γ,γ-dimethylallyflavone (4), artocarpin (5) and cycloheterophyllin (6) were successfully isolated from the leaves and heartwoods of Artocarpus lowii King (Moraceae). The structures of these compounds were fully characterised using spectroscopic methods and by direct comparison with published data. These compounds were tested for their antioxidant and tyrosinase inhibitory activities. Compound (1) displayed moderate antioxidant activity towards DPPH and tyrosinase inhibitory activities with SC50 value of 223.8 µM and IC50 value of 722.5 µM, respectively. Among the isolated compounds, cycloheterophyllin (6) showed the most potential antioxidant activity with SC50 value of 320.0 and 102.8 µM for ABTS and DPPH radicals scavenging activities, respectively, and also exhibited highest FRAP equivalent value of 4.7 ± 0.09 mM. Compound (6) showed tyrosinase inhibitory activity with the IC50 value of 104.6 µM.


Subject(s)
Artocarpus/chemistry , Flavonoids/chemistry , Flavonoids/pharmacology , Plant Leaves/chemistry , Wood/chemistry , Antioxidants/pharmacology , Benzothiazoles/chemistry , Biphenyl Compounds , Chalcones , Chromatography, Thin Layer , Enzyme Inhibitors/pharmacology , Free Radical Scavengers/pharmacology , Magnetic Resonance Spectroscopy , Mannose-Binding Lectins , Monophenol Monooxygenase/antagonists & inhibitors , Picrates , Plant Extracts/chemistry , Plant Extracts/pharmacology , Plant Lectins , Spectrophotometry, Ultraviolet , Sulfonic Acids/chemistry
9.
Phytochem Anal ; 27(5): 233-8, 2016 Sep.
Article in English | MEDLINE | ID: mdl-27527356

ABSTRACT

INTRODUCTION: Nuclear factor (erythroid-derived 2)-like factor 2 (Nrf2) is a transcription factor that regulates expression of many detoxification enzymes. Nrf2-antioxidant responsive element (Nrf2-ARE) signalling pathway can be a target for cancer chemoprevention. Glycyrrhiza glabra, common name, 'liquorice', is used as a sweetening and flavouring agent, and traditionally, to treat various ailments, and implicated to chemoprevention. However, its chemopreventive property has not yet been scientifically substantiated. OBJECTIVE: To assess the ability of liquorice root samples to induce Nrf2 activation correlating to their potential chemopreventive property. METHODS: The ability of nine methanolic extracts of liquorice root samples, collected from various geographical origins, to induce Nrf2 activation was determined by the luciferase reporter assay using the ARE-reporter cell line, AREc32. The antioxidant properties were determined by the 2,2-diphenyl-1-picryhydrazyl (DPPH) and the ferric-reducing antioxidant power (FRAP) assays. RESULTS: All extracts exhibited free-radical-scavenging property (RC50 = 136.39-635.66 µg/mL). The reducing capacity of ferrous ion was 214.46-465.59 µM Fe(II)/g. Nrf2 activation indicated that all extracts induced expression of ARE-driven luciferase activity with a maximum induction of 2.3 fold relative to control. These activities varied for samples from one geographical location to another. CONCLUSIONS: The present findings add to the existing knowledge of cancer chemoprevention by plant-derived extracts or purified phytochemicals, particularly the potential use of liquorice for this purpose. Copyright © 2016 John Wiley & Sons, Ltd.


Subject(s)
Chemoprevention , Glycyrrhiza , NF-E2-Related Factor 2/metabolism , Cell Line , Humans
10.
Medicines (Basel) ; 3(2)2016 Jun 03.
Article in English | MEDLINE | ID: mdl-28930124

ABSTRACT

This review article appraises the extraction methods, compositions, and bioactivities of the essential oils from the Citrus species (family: Rutaceae) endemic to Malaysia including C. aurantifolia, C. grandis, C. hystrix, and C. microcarpa. Generally, the fresh peels and leaves of the Citrus species were extracted using different methods such as steam and water distillation, Likens-Nikerson extraction, solvent extraction, and headspace solid-phase micro-extraction (HS-SPME). Most of the Citrus oils were found to be rich in monoterpene hydrocarbons with limonene (1) as the major component identified in the peels of C. aurantifolia (39.3%), C. grandis (81.6%-96.9%), and C. microcarpa (94.0%), while sabinene (19) was the major component in the peels of C. hystrix (36.4%-48.5%). In addition, citronellal (20) (61.7%-72.5%), linalool (18) (56.5%), and hedycaryol (23) (19.0%) were identified as the major components in the oil of C. hystrix leaves, C. grandis blossom and C. microcarpa leaves, respectively. The C. hystrix essential oil has been experimentally shown to have antimicrobial and antifeedant activities, while no bioactivity study has been reported on the essential oils of other Malaysian Citrus species.

11.
Phytother Res ; 29(6): 944-8, 2015 Jun.
Article in English | MEDLINE | ID: mdl-25779384

ABSTRACT

Glycyrrhiza glabra L. (Fabaceae), commonly known as 'liquorice', is a well-known medicinal plant. Roots of this plant have long been used as a sweetening and flavouring agent in food and pharmaceutical products, and also as a traditional remedy for cough, upper and lower respiratory ailments, kidney stones, hepatitis C, skin disorder, cardiovascular diseases, diabetes, gastrointestinal ulcers and stomach ache. Previous pharmacological and clinical studies have revealed its antitussive, antiinflammatory, antiviral, antimicrobial, antioxidant, immunomodulatory, hepatoprotective and cardioprotective properties. While glycyrrhizin, a sweet-tasting triterpene saponin, is the principal bioactive compound, several bioactive flavonoids and isoflavonoids are also present in the roots of this plant. In the present study, the cytotoxicity of the methanol extracts of nine samples of the roots of G. glabra, collected from various geographical origins, was assessed against immortal human keratinocyte (HaCaT), lung adenocarcinoma (A549) and liver carcinoma (HepG2) cell lines using the in vitro 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide cell toxicity/viability assay. Considerable variations in levels of cytotoxicity were observed among various samples of G. glabra.


Subject(s)
Flavonoids/pharmacology , Glycyrrhiza/chemistry , Keratinocytes/drug effects , Plant Extracts/pharmacology , Saponins/pharmacology , Triterpenes/pharmacology , Adenocarcinoma/pathology , Adenocarcinoma of Lung , Carcinoma, Hepatocellular/pathology , Cell Line, Tumor/drug effects , Flavonoids/chemistry , Geography , Humans , Inhibitory Concentration 50 , Liver Neoplasms/pathology , Lung Neoplasms/pathology , Molecular Structure , Plant Extracts/chemistry , Plant Roots/chemistry , Saponins/chemistry , Triterpenes/chemistry
12.
Article in English | MEDLINE | ID: mdl-25371571

ABSTRACT

BACKGROUND: The ethyl acetate and chloroform extracts of stems, leaves and fruits of Phaleria macrocarpa were screened for their antioxidant capacity and tyrosinase inhibition properties. MATERIAL AND METHOD: The total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and ferric-ion reducing power (FRAP) were used to evaluate their antioxidant capacity. Tyrosinase inhibition effect was measured using mushroom tyrosinase inhibition assay. RESULT: Ethyl acetate extract of P. macrocarpa's stem exhibited highest total phenolic content, DPPH free radical scavenging and ferric reducing power. Meanwhile, chloroform extracts of leaves and fruits demonstrated potent anti-tyrosinase activities as compared to a well-known tyrosinase inhibitor, kojic acid. CONCLUSION: Since chloroform extracts of leaves and fruits have low antioxidant capacities, the tyrosinase inhibition effect observed are antioxidant independent. This study suggests direct tyrosinase inhibition by chloroform extracts of Phaleria macrocarpa.


Subject(s)
Antioxidants/analysis , Enzyme Inhibitors/analysis , Fungal Proteins/antagonists & inhibitors , Monophenol Monooxygenase/antagonists & inhibitors , Plant Extracts/analysis , Thymelaeaceae/chemistry , Agaricales/enzymology , Fruit/chemistry , Fungal Proteins/analysis , Monophenol Monooxygenase/analysis , Phenols/analysis , Plant Leaves/chemistry
13.
J Org Chem ; 79(16): 7477-90, 2014 Aug 15.
Article in English | MEDLINE | ID: mdl-25019530

ABSTRACT

A systematic process is introduced to compare (13)C NMR spectra of two (or more) candidate samples of known structure to a natural product sample of unknown structure. The process is designed for the case where the spectra involved can reasonably be expected to be very similar, perhaps even identical. It is first validated by using published (13)C NMR data sets for the natural product 4,6,8,10,16,18-hexamethyldocosane. Then the stereoselective total syntheses of two candidate isomers of the related 4,6,8,10,16-pentamethyldocosane natural product are described, and the process is applied to confidently assign the configuration of the natural product as (4S,6R,8R,10S,16S). This is accomplished even though the chemical shift differences between this isomer and its (16R)-epimer are only ±5-10 ppb (±0.005-0.01 ppm).


Subject(s)
Alkanes/chemical synthesis , Biological Products/chemistry , Coleoptera/chemistry , Hydrocarbons/chemical synthesis , Alkanes/chemistry , Animals , Hydrocarbons/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Stereoisomerism
14.
Phytochem Anal ; 25(6): 495-507, 2014.
Article in English | MEDLINE | ID: mdl-24737485

ABSTRACT

INTRODUCTION: Sharing traditional knowledge with the scientific community could refine scientific approaches to phytochemical investigation and conservation of ethnomedicinal plants. As such, integration of traditional knowledge with scientific data using a single platform for sharing is greatly needed. However, ethnomedicinal data are available in heterogeneous formats, which depend on cultural aspects, survey methodology and focus of the study. Phytochemical and bioassay data are also available from many open sources in various standards and customised formats. OBJECTIVE: To design a flexible data model that could integrate both primary and curated ethnomedicinal plant data from multiple sources. MATERIALS AND METHODS: The current model is based on MongoDB, one of the Not only Structured Query Language (NoSQL) databases. Although it does not contain schema, modifications were made so that the model could incorporate both standard and customised ethnomedicinal plant data format from different sources. RESULTS: The model presented can integrate both primary and secondary data related to ethnomedicinal plants. Accommodation of disparate data was accomplished by a feature of this database that supported a different set of fields for each document. It also allowed storage of similar data having different properties. CONCLUSION: The model presented is scalable to a highly complex level with continuing maturation of the database, and is applicable for storing, retrieving and sharing ethnomedicinal plant data. It can also serve as a flexible alternative to a relational and normalised database.


Subject(s)
Database Management Systems , Databases, Factual , Medicine, Traditional , Models, Statistical , Plants, Medicinal , Data Interpretation, Statistical , Information Storage and Retrieval , Integrated Advanced Information Management Systems
15.
Phytochem Anal ; 25(5): 399-404, 2014.
Article in English | MEDLINE | ID: mdl-24585378

ABSTRACT

INTRODUCTION: Glycyrrhiza glabra L. (Fabaceae), commonly known as 'liquorice', is one of the most popular ingredients in several traditional herbal medicinal preparations, and glycyrrhizin is the major glycoside present in this plant. The content of glycyrrhizin may vary among G. glabra samples collected from various geographical origins, which may affect the therapeutic efficacy. Thus, quantification of glycyrrhizin in G. glabra samples is important. OBJECTIVE: To develop and validate a simple semi-preparative reversed-phase HPLC with photodiode array (PDA) method for separation and quantification of glycyrrhizin in nine samples of G. glabra root collected from various geographical origins. METHODS: Dried and ground root of G. glabra was Soxhlet-extracted sequentially with n-hexane and methanol (MeOH). The separation and quantification of glycyrrhizin was achieved on a C18 reversed-phase semi-preparative column using a gradient mobile phase, 30-100% solvent B in solvent A in 30 min (solvent A: 0.1% v/v trifluoroacetic acid (TFA) in water and solvent B: 0.1% v/v of TFA in MeOH), at a flow rate of 3.00 mL/min and UV detection at 254 nm. RESULTS: A simple semi-preparative reversed-phase HPLC/PDA method allowing clear separation and quantification of glycyrrhizin content in nine samples has been validated in terms of linearity, selectivity, limits of detection, precision, accuracy and detection. Concentration levels of glycyrrhizin were between 0.177 and 0.688% w/w of dry materials. CONCLUSION: This method is precise, less time consuming and more cost effective, and can be used for the quality control of any G. glabra sample with regard to its glycyrrhizin contents.


Subject(s)
Chromatography, High Pressure Liquid , Glycyrrhiza/chemistry , Glycyrrhizic Acid/chemistry , Plant Roots/chemistry , Demography
16.
Org Biomol Chem ; 11(48): 8476-505, 2013 Dec 28.
Article in English | MEDLINE | ID: mdl-24212203

ABSTRACT

Reactions of 5-benzyloxy-4-methylpent-2-enyl(tributyl)stannane with aldehydes promoted by bismuth(III) iodide were usefully stereoselective in favour of the (E)-1,5-anti-6-benzyloxy-5-methylalk-3-en-1-ols. Similar stereoselectivity was observed for reactions of analogous 5-benzyloxy-4-methylpent-2-enyl bromides with aldehydes when promoted by a low valency bismuth species prepared by reduction of bismuth(III) triiodide with powdered zinc so providing a "tin-free" procedure. The analogous reactions of 4-benzyloxypent-2-enyl(tributyl)stannane with aldehydes promoted by bismuth(III) iodide were also stereoselective but gave lower yields. Attempted 1,6-stereocontrol using these reactions resulted in only modest stereoselectivities. Aspects of the chemistry of the products were studied in particular their stereoselective conversion into aliphatic compounds with methyl bearing stereogenic centres at 1,5,9,13- and 1,3,5-positions along the aliphatic chain. Mechanistically, allylic organobismuth species may be involved in both sets of reactions but this was not confirmed although the similar stereoselectivities observed for both the bismuth(III) iodide mediated reactions of the pent-2-enylstannanes and the low-valency bismuth promoted reactions of the pent-2-enyl bromides are consistent with participation of similar intermediates.

17.
Org Biomol Chem ; 10(9): 1743-5, 2012 Mar 07.
Article in English | MEDLINE | ID: mdl-22274635

ABSTRACT

The stereoselective reaction of an allyl bromide with an aldehyde mediated by a low valency bismuth species was the key reaction in stereoselective syntheses of (4S,6R,8R,10S,16S)- and (4S,6R,8R,10S,16R)-4,6,8,10,16-pentamethyldocosanes. (13)C NMR data for these compounds confirmed that the cuticular hydrocarbon isolated from the cane beetle Antitrogus parvulus was the (4S,6R,8R,10S,16S)-stereoisomer.


Subject(s)
Coleoptera/chemistry , Hydrocarbons/chemical synthesis , Animals , Coleoptera/anatomy & histology , Molecular Structure , Stereoisomerism
18.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 9): o2300, 2011 Sep 01.
Article in English | MEDLINE | ID: mdl-22058935

ABSTRACT

The reaction of 5,6-(2,2-dimethyl-chroman-yl)-2-hy-droxy-4-meth-oxy-acetophenone and 3,4-bis-(meth-oxy-meth-yloxy)benzaldehyde affords the intense orange title chalcone derivative, C(25)H(30)O(8). The two benzene rings are connected through a -C(=O)-CH=CH- (propenone) unit, which is in an E conformation; the ring with the hy-droxy substitutent is aligned at 19.5 (2)° with respect to this unit, whereas the ring with the meth-oxy-meth-yloxy substituent is aligned at 9.3 (3)°. The dihedral angle between the rings is 19.38 (10)°. The hy-droxy group engages in an intra-molecular O-H⋯O hydrogen bond with the carbonyl O atom of the propenone unit, generating an S(5) ring.

19.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 9): o2301, 2011 Sep 01.
Article in English | MEDLINE | ID: mdl-22058936

ABSTRACT

The reaction of 5,6-(2,2-dimethyl-chromane)-2-hy-droxy-4-meth-oxy-acetophenone and 3,4-methlene-dioxy-benzaldehyde affords the title chalcone derivative, C(22)H(22)O(6). The two benzene rings are connected through a -C(=O)-CH=CH- (propenone) unit, which is in an E conformation; the ring with the hy-droxy substitutent is aligned at 6.2 (1)° with respect to this unit, whereas the ring with the methyl-enedi-oxy substituent is aligned at 8.2 (1)°. The dihdral angle between the rings is 14.32 (7)°. The hy-droxy group engages in an intra-molecular hydrogen bond with the carbonyl O atom of the propenone unit, generating an S(5) ring.

20.
Nat Prod Res ; 25(10): 982-6, 2011 Jun.
Article in English | MEDLINE | ID: mdl-21644178

ABSTRACT

The essential oils obtained by hydrodistillation of the rhizomes of Alpinia aquatica Rosc. syn. Alpinia melanocarpa and Alpinia malaccensis Roscoe were analysed by capillary gas chromatography and gas chromatography-mass spectrometry. Eighteen compounds, representing 98.4% of the essential oil were identified in A. aquatica rhizome oil, with ß-sesquiphellandrene in 36.5% being the major constituent, while 20 compounds representing 99.7% of the rhizome oil of A. malaccensis were identified, among which methyl (E)-cinnamate (78.2%) was the major constituent.


Subject(s)
Alpinia/chemistry , Plant Oils/chemistry , Rhizome/chemistry , Chromatography, Gas , Malaysia
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