The tandem of full spin analysis and qHNMR for the quality control of botanicals exemplified with Ginkgo biloba

Botanical dietary supplements and herbal remedies are widely used for health promotion and disease prevention. Due to the high chemical complexity of these natural products, it is essential to develop new analytical strategies to guarantee their quality and consistency. In particular, the precise characterization of multiple botanical markers remains a challenge. This study demonstrates how a combination of computer-aided spectral analysis and 1D quantitative 1H NMR spectroscopy (qHNMR) generates the analytical foundation for innovative means of simultaneously identifying and quantifying botanical markers in complex mixtures. First, comprehensive 1H NMR profiles (fingerprints) of selected botanical markers were generated via 1H iterative full spin analysis (HiFSA) with PERCH. Next, the 1H fingerprints were used to assign specific 1H resonances in the NMR spectra of reference materials, enriched fractions, and crude extracts of Ginkgo biloba leaves. These 1H fingerprints were then used to verify the assignments by 2D NMR. Subsequently, a complete purity and composition assessment by means of 1D qHNMR was conducted. As its major strengths, this tandem approach enables the simultaneous quantification of multiple constituents without the need for identical reference materials, the semiquantitative determination of particular subclasses of components, and the detection of impurities and adulterants.     

Dynamic nature of the ligustilide complex

Monomeric phthalides such as Z-ligustilide (1) and Z-butylidenephthalide (2) are major constituents of medicinal plants of the Apiaceae family. While 1 has been associated with a variety of observed biological effects, it is also known for its instability and rapid chemical degradation. For the purpose of isolating pure 1 and 2, a gentle and rapid two-step countercurrent isolation procedure was developed. From a supercritical CO2 fluid extract of Angelica sinensis roots, the phthalides were isolated with high GC-MS purities of 99.4% for 1 and 98.9% for 2 and consistently lower qHNMR purities of 98.1% and 96.4%, respectively. Taking advantage of molarity-based qHNMR methodology, a time-resolved study of the dynamic changes and residual complexity of pure 1 was conducted. GC-MS and (qH)NMR analysis of artificially degraded 1 provided evidence for the phthalide degradation pathways and optimized storing conditions. Parallel qHNMR analysis led to the recognition of variations in time- and process-dependent sample purity and has impact on the overall assessment of time-dependent changes in complex natural products systems. The study underscores the importance of independent quantitative monitoring as a prerequisite for the biological evaluation of labile natural products such as monomeric phthalides.     

A routine experimental protocol for qHNMR illustrated with Taxol

Quantitative 1H NMR (qHNMR) provides a value-added dimension to the standard spectroscopic data set involved in structure analysis, especially when analyzing bioactive molecules and elucidating new natural products. The qHNMR method can be integrated into any routine qualitative workflow without much additional effort by simply establishing quantitative conditions for the standard solution 1H NMR experiments. Moreover, examination of different chemical lots of taxol (paclitaxel) and a Taxus brevifolia extract as working examples led to a blueprint for a generic approach to performing a routinely practiced 13C-decoupled qHNMR experiment and for recognizing its potential and main limitations. The proposed protocol is based on a newly assembled 13C GARP broadband decoupled proton acquisition sequence that reduces spectroscopic complexity by removal of carbon satellites. The method is capable of providing qualitative and quantitative NMR data simultaneously and covers various analytes from pure compounds to complex mixtures such as metabolomes. Due to a routinely achievable dynamic range of 300:1 (0.3%) or better, qHNMR qualifies for applications ranging from reference standards to biologically active compounds to metabolome analysis. Providing a "cookbook" approach to qHNMR, acquisition conditions are described that can be adapted for contemporary NMR spectrometers of all major manufacturers.     

Quantitative 1H NMR: development and potential of a method for natural products analysis

Based on a brief revision of what constitutes state-of-the-art "quantitative experimental conditions" for (1)H quantitative NMR (qHNMR), this comprehensive review contains almost 200 references and covers the literature since 1982 with emphasis on natural products. It provides an overview of the background and applications of qHNMR in natural products research, new methods such as decoupling and hyphenation, and analytical potential and limitations, and compiles information on reference materials used for and studied by qHNMR. The dual status of natural products, being single chemical entities and valuable biologically active agents that need to be purified from complex matrixes, results in an increased analytical demand when testing their deviation from the singleton composition ideal. The outcome and versatility of reported applications lead to the conclusion that qHNMR is currently the principal analytical method to meet this demand. Considering both 1D and 2D (1)H NMR experiments, qHNMR has proved to be highly suitable for the simultaneous selective recognition and quantitative determination of metabolites in complex biological matrixes. This is manifested by the prior publication of over 80 reports on applications involving the quantitation of single natural products in plant extracts, dietary materials, and materials representing different metabolic stages of (micro)organisms. In summary, qHNMR has great potential as an analytical tool in both the discovery of new bioactive natural products and the field of metabolome analysis.     

Bacterial biofilm inhibitors from Diospyros dendo

One new (1) and four known (2-5) ursene triterpenes with potent inhibition of the formation of the bacterial biofilm Pseudomonas aeruginosa PA01 were obtained from Diospyros dendo using a high-throughput natural products chemistry procedure. These compounds were isolated as mass-limited samples. The miniaturization of the structure elucidation and dereplication was performed primarily utilizing a capillary-scale NMR probe.     

Quantitative 1H NMR. Development and potential of an analytical method: an update

Covering the literature from mid-2004 until the end of 2011, this review continues a previous literature overview on quantitative (1)H NMR (qHNMR) methodology and its applications in the analysis of natural products. Among the foremost advantages of qHNMR is its accurate function with external calibration, the lack of any requirement for identical reference materials, a high precision and accuracy when properly validated, and an ability to quantitate multiple analytes simultaneously. As a result of the inclusion of over 170 new references, this updated review summarizes a wealth of detailed experiential evidence and newly developed methodology that supports qHNMR as a valuable and unbiased analytical tool for natural product and other areas of research.     

Purity-activity relationships of natural products: the case of anti-TB active ursolic acid

The present study explores the variability of biological responses from the perspective of sample purity and introduces the concept of purity-activity relationships (PARs) in natural product research. The abundant plant triterpene ursolic acid (1) was selected as an exemplary natural product due to the overwhelming number yet inconsistent nature of its approximate 120 reported biological activities, which include anti-TB potential. Nine different samples of ursolic acid with purity certifications were obtained, and their purity was independently assessed by means of quantitative 1H NMR (qHNMR). Biological evaluation consisted of determining MICs against two strains of virulent Mycobacterium tuberculosis and IC50 values in Vero cells. Ab initio structure elucidation provided unequivocal structural confirmation and included an extensive 1H NMR spin system analysis, determination of nearly all J couplings and the complete NOE pattern, and led to the revision of earlier reports. As a net result, a sigmoid PAR profile of 1 was obtained, demonstrating the inverse correlation of purity and anti-TB bioactivity. The results imply that synergistic effects of 1 and its varying impurities are the likely cause of previously reported antimycobacterial potential. Generating PARs is a powerful extension of the routinely performed quantitative correlation of structure and activity ([Q]SAR). Advanced by the use of primary analytical methods such as qHNMR, PARs enable the elucidation of cases like 1 when increasing purity voids biological activity. This underlines the potential of PARs as a tool in drug discovery and synergy research and accentuates the need to routinely combine biological testing with purity assessment.     

Actaeaepoxide 3-O-beta-D-xylopyranoside, a new cycloartane glycoside from the rhizomes of Actaea racemosa (Cimicifuga racemosa)

A new cycloartane glycoside (1) was obtained from a minor triterpene fraction of the rhizome extract of Actaea racemosa (synonym: Cimicifuga racemosa) along with a known compound, cimigenol 3-O-beta-D-xylopyranoside. The structure of 1 was elucidated as 20(S),22(R),23(R),24(S)-12beta-acetoxy-16beta:23,23alpha:24-diepoxy-3beta,22beta,25-trihydroxy-9,19-cyclolanost-7-ene 3-O-beta-D-xylopyranoside (actaeaepoxide 3-O-beta-D-xylopyranoside) on the basis of spectral and chemical evidence.     

The value of plant collections in ethnopharmacology: a case study of an 85-year-old black cohosh (Actaea racemosa L.) sample

Ethnopharmacological collections of plants used in traditional medical systems are a valuable but often underappreciated resource for scientific investigation. These collections contain many samples of plants currently employed in herbal and pharmaceutical medicine, and questions on stability and storage life can be examined using these historic collections as vouchers. A sample of black cohosh (Actaea racemosa L.), collected in 1919 by the physician and plant explorer Henry Hurd Rusby, was recently identified in the collections of The New York Botanical Garden and analyzed for its triterpene glycosidic and phenolic constituents qualitatively and quantitatively by high-performance liquid chromatography-photodiode array detector (HPLC-PDA) and liquid chromatography-mass spectrophotometry (LC-MS). A comparison of the triterpene glycosidic and phenolic constituents of the 85-year-old plant sample with those of a modern collection of Actaea racemosa showed the similarity of the two samples, confirming the stability of the older sample, despite its curation over the years under a variety of conditions. Quantitative analyses indicated that both plant samples have similar amounts of the four major triterpene glycosides, but the total amount of the six major phenolic constituents measured in the 85-year-old plant material is lower than the amount measured in the modern plant material. Methanol extracts of the two plant materials were tested for their antioxidant activity, and both extracts showed similar antioxidant activity.     

Euphane and tirucallane triterpenes from the roots of Euphorbia kansui and their in vitro effects on the cell division of Xenopus

Four new euphane-type triterpenes, kansenone (1), kansenonol (3), 11-oxo-kansenonol (4), kansenol (5), and a new tirucallane-type triterpene, epi-kansenone (2), were isolated from a 60% EtOH extract of Euphorbia kansui, together with alpha-euphol. Their structures were elucidated on the basis of extensive analysis of their 1D and 2D NMR spectral data. This appears to be the first report of the natural occurrence of euphane/tirucallane-type triterpenes with a ketone at C-7. In vitro treatment of cultured individual Xenopus laevis cells at the blastular stage with 1-4 significantly arrested cleavage of the cells (10 microg/mL of each compound resulted in >50% cleavage arrest).     

A study on major chemical components of Uvaria grandiflora]

OBJECTIVE: To make clear the chemical constituents of Uvaria grandiflora (Annonaceae). METHODS: Purification was performed using sephadex LH-20 permeation and silica gel chromatography. Structures of the purified components were determined on the basis of 1H, 13C NMR analysis and also by comparison with those of authentic compounds. RESULTS: Two major triterpenes, suberosol and lupeol, were identified. CONCLUSION: This paper is the first report on the identification of suberosol and lupeol from the gunus Uvaria.     

Evolving trends in the dereplication of natural product extracts: new methodology for rapid, small-scale investigation of natural product extracts

The use of an HPLC bioactivity profiling/microtiter plate technique in conjunction with capillary probe NMR instrumentation and access to appropriate databases effectively short-circuits conventional dereplication procedures, necessarily based on multimilligram extracts, to a single, more rapid submilligram operation. This approach to dereplication is illustrated using fungal or bacterial extracts that contain known compounds. In each case the dereplication steps were carried out on microgram quantities of extract and demonstrate the discriminating power of (1)H NMR spectroscopy as a definitive dereplication tool.     

Rapid extract dereplication using HPLC-SPE-NMR: analysis of isoflavonoids from Smirnowia iranica

A novel hyphenated technique, HPLC-SPE-NMR, was used for accelerated identification of isoflavonoids from the roots of Smirnowia iranica. The extract constituents eluted from a HPLC column were automatically trapped on solid-phase extraction (SPE) cartridges, and NMR spectra were acquired with concentrated solutions after solvent change. The structures of 10 new isoflavonoids (1, 4, 5, 7-10, 12, 13, 16) and of seven previously described constituents (2, 3, 6, 11, 14, 15, 17) were elucidated from NMR spectra acquired in the HPLC-SPE-NMR mode. Multiple peak trapping on the same SPE cartridge increased analyte amounts and provided access to 2D NMR data. It was demonstrated that linear accumulation of material is possible in up to seven repeated trapping steps. The use of HPLC-SPE-NMR speeded up dereplication of the S. iranica extract considerably by providing detailed information about the constituents of a complex, essentially crude extract prior to their preparative-scale isolation or extract pre-fractionation, and the information obtained could be used to direct preparative isolation work. In connection with structure elucidation of isoflavonoids containing O-methylated 1,2,3-benzenetriol moieties as the B-ring, O-methylation-induced changes of chemical shifts of aromatic hydrogens were found to depend on the conformation of the resulting methoxy group, i.e., on the number of its ortho substituents. The recognized regularities will be useful in structure determination of partially O-methylated polyphenols based on 1D (1)H NMR spectra obtainable from HPLC-SPE-NMR experiments, diminishing dependence on 2D NMR data and (13)C NMR chemical shifts.     

绿升麻中1个新环阿屯烷型三萜皂苷

目的：研究绿升麻中对肿瘤细胞有细胞毒活性的化学成分。方法：以硅胶柱、凝胶等多种柱色谱分离，制备高效液相色谱纯化，以各种波谱鉴定化合物结构。结果：分离得到1个环阿屯烷型三萜类化合物，鉴定其结构为(23R)-16β,23∶23α,26∶24α∶25-triepoxy-9,19-cyclolanost-7-en-3-O-β-D-xylopyranoside。结论：化合物1是新化合物，命名为(23R)-26-deoxycimicifugoside。化合物1对宫颈癌细胞(Hela)和小鼠成纤维细胞(L929)具有一定的细胞毒作用，IC₅₀分别为72.24，55.97 mg·L^-1。     

Cytotoxic cycloartane triterpene saponins from Actaea asiatica

Three new 9,19-cycloartane triterpene glycosides, asiaticoside A (1), asiaticoside B (2), and 25-O-ethylcimigenol-3-O-beta-D-xylopyranoside (3), together with cimiacemoside I (4), 25-O-acetylcimigenol-3-beta-O-D-xyloside (5), and 25-anhydrocimigenol-beta-O-D-xyloside (6) were isolated from the roots/rhizomes extract of Actaea asiatica, and their structures were established by spectroscopic methods (IR, HRESIMS, and NMR). Compounds 1-3, 5, and 6 had notable cytotoxicity against HepG2 and MCF-7 cancer cell lines.     

Identification of major and minor constituents of Harpagophytum procumbens (Devil's claw) using HPLC-SPE-NMR and HPLC-ESIMS/APCIMS

The HPLC-SPE-NMR technique, supported by HPLC-MS measurements, was used to determine structures of major as well as some minor constituents of ethanol and petroleum ether extracts of Harpagophytum procumbens (Devil's claw) roots. This method was also shown to be applicable for rapid and precise on-line identification of secondary metabolites present in commercial herbal products of H. procumbens. A total of 15 compounds (1-14 and 17) were identified from the ethanol and petroleum ether extracts, including a novel Diels-Alder dimer 14. Optimization of the HPLC-SPE-NMR experiments included quantitative (1)H NMR measurements, determination of trapping and elution efficiency, effect of multiple trapping of analytes, use of various deuterated solvents for SPE cartridge elution, and effect of post-column dilution ratio of eluent with water. Linear accumulation of apolar and relatively polar analytes was demonstrated for at least 8-10 repeated trappings, resulting in greatly improved signal-to-noise ratios in NMR spectra and reduced acquisition times. Thus, the HPLC-SPE-NMR technique provides an efficient means of identification of multiple components of crude extracts. By allowing on-line generation of high-quality 2D NMR data without traditional purification of extract components, the HPLC-SPE-NMR methodology represents a paradigm shift in natural products research with respect to structure elucidation.     

Eranthisaponins A and B,two new bisdesmosidic triterpene saponins from the tubers of Eranthis cilicica

The present investigation aimed at the glycoside constituents of the tubers of Eranthis cilicica has resulted in the isolation of two new bisdesmosidic triterpene saponins based upon hederagenin, named eranthisaponins A (1) and B (2), along with four known triterpene saponins. The structures of the new saponins 1 and 2 were determined on the basis of spectroscopic analysis, including extensive 1D and 2D NMR data, and acid hydrolysis followed by chromatographic analysis. This is the first report concerning the secondary metabolites of E. cilicica.     

Absolute stereostructures of new arborinane-type triterpenoids and inhibitors of nitric oxide production from Rubia yunnanensis

The aqueous acetone extract from the roots of a Chinese herbal medicine, Rubia yunnanensis, showed a potent inhibitory effect on nitric oxide production in lipopolysaccharide-activated macrophages. Five new arborinane-type triterpenes, rubianols-a (1), -b (2), -c (3), -d (4), and -e (5), and a new arborinane-type triterpene glycoside, rubianoside I (6), were isolated from the herbal crude extract together with 10 known compounds. The absolute stereostructures of 1-6 were determined on the basis of chemical and physicochemical evidence, including the application of the modified Mosher's method. The effects of the isolated constituents on nitric oxide production in lipopolysaccharide-activated macrophages were examined, and several triterpenes were found to show inhibitory activity.     

山椒子主要化学成分的研究

目的：了解山椒子的化学成分。方法：分离纯化采用ＳｅｐｈａｄｅｘＬＨ２０凝胶过滤及硅胶柱色谱方法,结构鉴定采用ＨＮＭＲ,^１３ＣＮＭＲ分析及与文献有关数据比较。结果：从山椒子树皮中鉴定出２个三萜类化合物,ｓｕｂｅｒｏｓｏｌ和ｌｕｐｅｏｌ。结论：为首次从该属植物中分得。     

The antimycobacterial components of hops (Humulus lupulus) and their dereplication

Bioassay-guided fractionation of a hexane extract of strobile hops (Humulus lupulus) was undertaken to isolate and characterize the antimycobacterial constituents using the fast-growing mycobacterial species Mycobacterium fortuitum. Activity was associated with a low polarity fraction and 1H NMR spectra indicated the presence of a fatty acid mixture with unsaturated components. GC-MS of the derivatives indicated the presence of palmitic, stearic and oleic acids with small quantities of lignoceric, arachidic, behenic and linoleic acids. These compounds were assessed against M. fortuitum and all saturated fatty acids were inactive at concentrations greater than 256 microg/ml, whereas the unsaturated fats oleic and linoleic acids displayed minimum inhibitory concentrations of between 4 and 16 microg/ml against the fast-growing species tested. The widespread occurrence of these components could render screening for antimycobacterials from natural sources highly problematic without adequate dereplication. We propose that GC-MS of derivatised components of lipophilic extracts be a first step before any antimycobacterial bioassay-guided study, as this technique is the method of choice for dereplication of fatty acids.