Carbon-13 NMR study of (20,24)-epoxydammarane triterpenes

Assignments of the ¹³C NMR signals of the dammarane triterpenes, 3β,25,30-trihydroxy-(20R,24R)-epoxydammaran-16-one 3,30-diacetate (trevoagenin A diacetate) (2), its 20S-isomer (trevoagenin B diacetate) (3) and their related (20R)-3β,30-diacetoxy-16-oxo-25,26,27-trisnordammarane-24,20-lactone (4) and its 20S-isomer (5) have been achieved. Suitable tetrahydrofuran models have been synthesized in order to aid the ¹³C NMR assignments of the side-chain carbons of the above-mentioned compounds. The remarkable chemical shift differences observed for C-21 and C-22 between each pair of the C-20 epimers (2, 3 and 4, 5) allowed the confirmation of the C-20 stereochemistry of these ocotillol-type dammarane triterpenes.     

New Epoxydammarane Triterpenes from Salvia santolinifolia

Three new 20,24‐epoxydammarane triterpenes, santolins A–C ( 1 – 3 ), were isolated from the AcOEt‐soluble fraction of the MeOH extract of Salvia santolinifolia (whole plant). Their structures were assigned based on ¹H‐NMR, ¹³C‐NMR (DEPT), and 2D‐NMR analyses, in combination with HR‐MS experiments and comparison with literature data of related compounds.     

Computer-aided carbon-13 nuclear magnetic resonance spectroscopy for identification of terpenoid mixtures

The procedure for identifying triterpenes in mixtures is based on the simulation of ¹³C-NMR spectra for probable mixtures and comparison of these with a specialized spectral data bank. The system was designed to facilitate the analysis of complex mixtures of terpenoid compounds. A special matching procedure was developed and its efficiency is discussed. The method is demonstrated for a mixture of five triterpenes isolated from Vernonia cognata.     

13C NMR spectroscopic data for glutinol and derivatives

The ¹³C NMR chemical shifts of the triterpenes glutinol, glutinone and acetylglutinol were measured and analysed.     

Novel monocyclic sester- and triterpenoids from the marine diatom, Rhizosolenia setigera

The structures of two polyunsaturated monocyclic triterpenes have been elucidated using NMR spectroscopy following their isolation from the common marine diatom, Rhizosolenia setigera. The structure of a related monocyclic sesterterpene is proposed on the basis of mass spectral comparisons with the two monocyclic triterpenes.     

Combretins A and B,New Cycloartane‐Type Triterpenes from Combretum fragrans

The phytochemical studies on the leaves of the traditionally used medicinal plant Combretum fragrans F. Hoffm (Combretaceae) from Cameroon have led to the isolation of combretins A and B ( 1 and 2 , resp.), two new cycloartane‐type triterpenes from the AcOEt‐soluble subfraction along with β‐sitosterol ( 3 ), oleanolic acid ( 4 ), ursolic acid ( 5 ), and pratensein ( 6 ). The compounds 4  –  6 are reported for the first time from this species. The structures of the new triterpenes were elucidated by spectroscopic techniques including ¹H‐ and ¹³C‐NMR (DEPT), and 2D‐NMR experiments.     

Analysis of Bioactive Triterpenes from Rubus chingii by Cyclodextrin-Modified Capillary Electrophoresis

A capillary electrophoretic (CE) method with β-cyclodextrin (CD) as modifier has been developed to enable separation, for the first time, of bioactive pentacyclic triterpene acids from the fruits of Rubus chingii. The effects of conditions such as the concentration of the running buffer, amounts of added β-cyclodextrin and organic modifier, applied voltage, and column temperature were systematically investigated to optimize the separation conditions. Baseline separation was achieved for the seven triterpenes by use of background electrolyte consisting of 200 mmol L⁻¹ disodium tetraborate, 15 mmol L⁻¹ β-cyclodextrin, and 12.5% (v/v) methanol. Binding constants between β-cyclodextrin and the triterpenes in the capillary electrophoresis buffer were calculated from the order of migration to elucidate the separation mechanism. The amounts of the triterpenes in the fruits of R. chingii were also determined by use of the method after a relatively simple extraction procedure.Revised: 5 January and 22 April 2005     

Determination of oleanolic and ursolic acid in Chinese herbs using HPLC and γ-CD as mobile phase modifier

To separate and determine oleanolic acid and ursolic acid, a rapid and accurate HPLC using γ‐CD as the mobile phase additive was developed. The effect of CD nature and concentration, and the acidity of the mobile phase on the chromatographic behavior of two bioactive triterpenes were systematically studied. Two bioactive triterpenes were completely separated (R = 3.11) on a Kromasil^® C₁₈ column (150×4.6 mm id, 5 μm) with the mobile phase consisting of acetonitrile/0.1% phosphoric acid with 2 mM γ‐CD as the mobile phase modifier (60:40, v/v). The flow rate was set at 1.0 mL/min and the eluent was detected at 210 nm for two bioactive triterpenes. The linearity of the method was excellent (r=0.9999) over the studied range of 6–300 μg/mL for oleanolic acid, and 12–600 μg/mL for ursolic acid. The LOD and LOQ were 1.5 and 5.0, 1.0 and 3.0 μg/mL for oleanolic acid and ursolic acid, respectively. The optimized method was successfully applied to separate and determine two bioactive triterpenes in five Chinese herbs. It is concluded that this method could be used for rapid and accurate qualitative and quantitative analysis of the two bioactive triterpenes in Chinese herbs.     

Structure assignment by 1H and 13C NMR of two epimers derived from glycyrrhetic acid

A full assignment of the ¹³C signals of four pentacyclic triterpenes confirms the results obtained by ¹H NMR analysis of steroidal methyls, resolving the stereochemistry of the oxidation product of 3-β-acetoxyolean-12-en-30-oic acid methyl ester.     

Maragenins I,II and III,new pentacyclic triterpenes from Marah macrocarpus

Maragenins I, II and III, new pentacyclic triterpenes from Marah macrocapus (Greene) Greene, are shown to be respectively Δ¹²-, Δ^12,17- and Δ¹⁷-3β-hydroxy-16-oxo-28-norloeananes on the basis of chemical and spectroscopic evidence. The structural proposal for maragenin I is confirmed by synthesis from echinocystic acid.     

Triterpenes and limonoids of Cedrela: Distribution,biosynthesis, and 1H and 13C NMR data

Cedrela genus, a member of the Meliaceae family, presents both chemical characteristics associated with and those that distinguish it from the rest of its members. The presence of triterpenes and limonoids is the characteristic of the Meliaceae family, but the class and type of these chemical constituents are distinctive for each genus. Cedrela includes cycloartane, ursane, oleanane, tirucallane, butyrospermane, and apotirucallane triterpenes, and its limonoids belongs to six class and nine types, known as class Ia-type havanensines, class Ib-type delevoyin, class II-type gedunin, class IIIb-type andirobin, class IIIg-type mexicanolide, class IVa-type evoludone, class Va-type obacunol, class V-type limonin, and class VIII. Each of these structural arrangements includes specific traits, defined by their biosynthetic origin, which can be established by means of structural elucidation techniques, particularly ¹H and ¹³C NMR, which assisted by 2D NMR techniques, allowing to deduce their structures unequivocally. The constant presence of these skeletal arrangements in Cedrela ensures that they are its chemophenetic markers and their recurrence is an important criterion for their identity. This review is a compilation of the occurrence of triterpenes and limonoids in Cedrela genus, detailing their biosynthetic association and collecting and organizing their NMR data, with the purpose of facilitating its location, analysis, and use in the phytochemical study of species from this genus.     

A Convenient Synthesis of Hydrophenanthrenes the Synthesis of Ferrugindl and Xanthoperol

We wish to report an approach (equation 1) to hydrophenanthrenes which shows considerable promise of providing a general synthetic route for diterpenes, steroids, triterpenes, and tetraterpenes. Herein we illustrate the utility of this Friedel-Crafts type of procedure^3,6 by describing a synthesis of ferruginol (6) ⁷ and xanthoperol (8).⁸     

1H and 13C chemical shifts and coupling constants of lupane. Application of two-dimensional NMR techniques

2D NMR techniques (J-resolved ¹³C, ¹³C? ¹³C correlated, ¹H? ¹³C correlated) were used to gather more chemical shift and coupling information on the pentacyclic triterpene, lupane. They confirm and complete ¹³C assignments made earlier, and corroborate the constitution and major configurational details of lupane. Lupane is a parent compound and spectral reference in the study of sedimental demethylated triterpenes.     

Anti-Escherichia coli activity of extracts from Schinus terebinthifolius fruits and leaves

Ethanol extracts obtained from Schinus terebinthifolius Raddi fruits and leaves were active against Escherichia coli with MIC of 78 μg mL^?1 for both extracts. Phytochemical analyses revealed a major presence of phenolic acids, tannins, fatty acids and acid triterpenes in the leaves and phenolic acids, fatty acids, acid triterpenes and biflavonoids in the fruits. Major compounds isolated from the plant, such as the acid triterpene schinol, the phenolic acid derivative ethyl gallate and the biflavonoids agathisflavone and tetrahydroamentoflavone, showed very little activity against E. coli. Bioautography of the ethanol extracts on silica gel plate showed inhibition zones for E. coli. They were removed from the plate and the compounds identified as a mixture of myristic, pentadecanoic, palmitic, heptadecanoic, stearic, nonadecanoic, eicosanoic, heneicosanoic and behenic fatty acids.     

A liquid chromatography‐atmospheric pressure photoionization tandem mass spectrometric (LC‐APPI‐MS/MS) method for the determination of triterpenoids in medicinal plant extracts

An analytical method using liquid chromatography‐atmospheric pressure photoionization tandem mass spectrometry with toluene as a dopant was developed for the determination of triterpenes in medicinal plant extracts. The 12 compounds determined have been shown to exhibit biological activity, such as gastroprotective, hepatoprotective, anti‐inflammatory, antiviral and anti‐tumor effects. The parameters of the atmospheric pressure photoionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection and quantification ranged from 0.4 to 157.9 µg l^?1 and 1.3 to 526.4 µg l^?1, respectively. The method was validated and applied to extracts of five medicinal plants species (Mansoa alliacea (Lam.) A.H.Gentry, Bauhinia variegata var variegata, Bauhinia variegata var alboflava, Cecropia obtuse Trécul and Cecropia palmate Willd) from the Amazonian region. The concentrations of the six triterpenes quantified in the samples ranged from 0.424 mg kg^?1 for ursolic acid to 371.96 mg kg^?1 for β‐amyrin, which were quantified by using the standard addition method (n = 3). Copyright © 2016 John Wiley & Sons, Ltd.     

Two New 3,4‐seco‐Cycloartane Triterpenes from Gardenia sootepensis

Two new 3,4‐seco‐cycloartane triterpenes, named sootepin F ( 1 ) and sootepin G ( 2 ), together with two known compounds, coronalolide methyl ester ( 3 ) and sootepin D ( 4 ), were isolated from the leaves and twigs of Gardenia sootepensis. Their structures were elucidated on the basis of 1D‐ and 2D‐NMR experiments, including HMBC, HSQC, ¹H,¹H‐COSY, and ROESY, as well as HR‐MS.     

Methylation of Dimedone

In connection with our synthetic approach to pentacyclic triterpenes,¹ we have required substantial amounts of 2,5,5-trimethyl-1,3-cyclohexanedione (methyldimedone, 2), which is available by methylation of dimedone (1).² However, methylation may also afford the 2,2-dimethyl product 3, the methyl ether 4, and the C, O-dimethyl product 5.     

Three New Pentacyclic Triterpenoids from Lantana camara

Three new pentacyclic triterpenes ursoxy acid ( 1 ), methyl ursoxylate ( 2 ), and ursangilic acid ( 3 ), along with three known compounds dotriacontanoic acid, oleanolic acid acetate, and tetracosanoic acid, were isolated from the aerial parts of Lantana camara Linn . Structures of the new compounds were elucidated by chemical transformation and spectral studies including 1D (¹H‐ and ¹³C‐NMR) and 2D (COSY‐45, NOESY, J‐resolved, HMQC, and HMBC) NMR spectroscopy.     

Ether Fission of 2,5-bis(Dialkylamino)hydroquinone Dimethylethers and O-Alkylation of 2,5-bis(Dialkylamino)hydroquinones

In connection with work underway in these laboratories on the total synthesis of Pentacyciic. triterpenes; guitable methods were sought for the introduction of angular methyl groups into preiormed polynuclear systems. A method of some generality was recognized in the work ofNagata³ on the organoaluminum catalyzed conjugate addition of cyanide to α,β-unsaturated ketones and subsequent conversion of the resulting cyano group to the desired angular methyl substttuent. The total synthesis of dl-alnusenone reported^4a earlier from these laboratories has this synthon as its central feature. Another approach that appeared attractive entailed the 1,6-addition ⁵ of cyanide to the dienone 1, available from intermediates already in hand.^4b     

Changes in Triterpenes in Alismatis rhizoma after Processing Based on Targeted Metabolomics Using UHPLC-QTOF-MS/MS

Alismatis rhizoma (AR) has been used as an herbal medicine in China for over a thousand years. Crude AR, salt-processed AR (SAR), and bran-processed AR (BAR) are recorded in the Pharmacopoeia of the People′s Republic of China. However, the differences of chemical composition between crude AR and its processing products remain limited. In this study, triterpenes were identified from crude AR, SAR, and BAR by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight-mass spectrometer (UHPLC-QTOF-MS/MS). Subsequently, the differences of triterpenes between the crude AR and processed ARs were compared via a targeted metabolomics approach. Finally, a total of 114 triterpenes were identified, of which 83, 100, and 103 triterpenes were found in crude AR, SAR, and BAR, respectively. After salt-processing, there were 17 triterpenes newly generated, 7 triterpenes with trends of increasing, and 37 triterpenes decreased. Meanwhile, 56 triterpenes including 21 newly generated and 35 with significant increases were observed in BAR. This study could be benefit to investigate the processing mechanism of AR, as well as support their clinical applications.