Vibrational microspectroscopic identification of powdered traditional medicines: chemical micromorphology of Poria observed by infrared and Raman microspectroscopy

Surface-enhanced Raman spectroscopy as a powerful method for the analysis of Chinese herbal medicines

Chinese herbal medicines (CHMs) derived from nature have received increasing attention and become more popular. Due to their diverse production processes, complex ingredients, and different storage conditions, it is highly desirable to develop simple, rapid, efficient and trace detection methods to ensure the drug quality. Surface-enhanced Raman spectroscopy has the advantages of being time-saving, non-destructive, usable in aqueous environments, and highly compatible with various biomolecular samples, providing a promising analytical method for CHM. In this review, we outline the major advances in the application of SERS to the identification of raw materials, detection of bioactive constituents, characterization of adulterants, and detection of contaminants. This clearly shows that SERS has strong potential in the quality control of CHM, which greatly promotes the modernization of CHM.

Attenuated Total Reflection Fourier Transform Infrared Mapping for the Identification of the Prescribed and Abnormal Ingredients of Herbal Powder Preparations

Herbal powder preparations (HPPs) are common forms of traditional medicine made by blending the powder of two or more ingredients. The first step to ensure the safety and efficacy of HPPs is to confirm the prescribed ingredients and screen the abnormal ingredients. With the help of attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) imaging or mapping, the particles of different ingredients in an HPP sample can be measured individually. In this way, the overlapped absorption signals of different ingredients in the ATR FT-IR spectrum of the bulk sample can be isolated in the ATR FT-IR spectra of the microscopic particles, which leads to the substantial increase of the specificity and sensitivity of the infrared spectral identification method. The characteristic particles of each ingredient can be identified by the objective comparison of the microscopic ATR FT-IR spectra against the reference spectra based on the correlation coefficients. Since the ATR FT-IR imaging or mapping tests of HPPs are free of the separation preprocess, multiple organic and inorganic ingredients are able to be recognized by a single identification procedure simultaneously rather than by different separation and identification procedures. As an example, the ATR FT-IR mapping method was used in this research to successfully identify three prescribed ingredients and two abnormal ingredients in oral ulcer pulvis, which is a classic HPP for oral ulcer in traditional Chinese medicine. The results show the feasibility of the ATR FT-IR microspectroscopic identification method for the objective and simultaneous identification of the prescribed and abnormal ingredients of HPPs.

Geographical traceability and multielement analysis of edible and medicinal fungi: Taking Wolfiporia cocos (F.A. Wolf) Ryvarden and Gilb. as an example

Different geographical environment has a certain influence on the accumulation of fungi elements and chemical components. However, our knowledge is limited to elucidate the fungi elements in response to heterogeneous environmental and the quality differences among different habitats. Here, multielement analysis, FTIR spectrum, and feature-level fusion technique combined with chemometrics were used to study Wolfiporia cocos from different geographical areas, different sampling sites and different altitude sources. From the results, (1) there is significant difference in element content of samples from different sampling sites and no positive correlation with geographical ranges. (2) There is a correlation between elevation and elements, and relatively low elevation (<1,800 m) is conducive to the enrichment of elements. (3) From the perspective of elements, the W. cocos in Yuxi have relatively better quality. (4) FTIR and feature-level models can well realize origin identification. The SVM models are better than the PLS-DA models, and the feature-level model is better than the single FTIR models. In summary, this study demonstrated that the developed method was reliable and could realize the genuineness evaluation and origin identification of W. cocos. The results have implications for the establishment of the technology system of geographical traceability and the development of high-quality geographical indication products of W. cocos.

Pd-based catalysts promoted by hierarchical porous Al2O3 and ZnO microsphere supports/coatings for ethyl acetate highly active and stable destruction

Developing economical and active materials is of great significance for VOC purification. Here, hierarchical porous Al₂O₃ and ZnO microspheres (Al₂O₃-pm and ZnO-pm) were synthesized by a facile hydrothermal strategy. The urchin-like Al₂O₃-pm and flower-like ZnO-pm possess high specific surface area (especially; external surface area) obviously boost the dispersion of Pd with 29.3 % and 30.1 % over Pd/Al₂O₃-pm and Pd/ZnO-pm, respectively, over 3.4 times higher than those of commercial Al₂O₃- and ZnO-supported counterparts. Pd/Al₂O₃-pm possesses excellent activity and CO₂ yield in ethyl acetate (EA) degradation, with TOF reaches 7.76 × 10^-3 s^-1 at 160 °C under GHSV of 50,000 h^-1. Moreover, Pd/Al₂O₃-pm exhibits satisfied performance in EA-contained binary VOCs oxidation and has high long-term stability under both dry and humid conditions. Both Pd sites and Brønsted acid sites participated in reaction process and initially react with EA to form ethylene and ethanol, respectively. Larger amount Brønsted acid sites over Pd/Al₂O₃-pm promote ethanol formation and C-C cleavage, resulting in different CO₂ yields and EA activation mechanisms. The coating greatly enhances Pd dispersion over Pd supported monolithic catalyst, endowing its desired activity and stability even with a much lower Pd loading. This work promotes the potential application of noble-metal-based monolithic materials in VOC degradation.

Extraction assisted by far infrared radiation and hot air circulation with deep eutectic solvent for bioactive polysaccharides from Poria cocos (Schw.) wolf

In this study, a new ternary choline chloride-deep eutectic solvent was used to efficiently extract bioactive polysaccharides from poria cocos assisted by the new tool of the far infrared radiation (FIR) together with hot air circulation (HAC).

Comparison and quantitative analysis of wild and cultivated Macrohyporia cocos using attenuated total refection-Fourier transform infrared spectroscopy combined with ultra-fast liquid chromatography

Dried sclerotium of Macrohyporia cocos is a well-known and widely-consumed traditional Chinese medicine and is also used as dietary supplement. According to the differential treatment between cultivation and wild habitats in the market, the comparison and quantitative analysis of wild and cultivated M. cocos were performed using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and ultra-fast liquid chromatography combined with partial least squares discriminant analysis and partial least squares regression (PLSR). 636 samples were used for the spectral scan and chromatographic analysis. Results indicated that contents of dehydrotumulosic acid, poricoic acid A and dehydrotrametenolic acid in cultivated samples were significantly different from wild samples in two medicinal parts. Differences of dehydropachymic acid and pachymic acid just existed in inner part samples (P < 0.05). Wild M. cocos samples could be discriminated with cultivated samples with >95.14% efficiency using spectral data. ATR-FTIR combined with PLSR provided satisfactory performance for content predictions of poricoic acid A and dehydrotrametenolic acid. This study demonstrated that growth patterns could affect the quality of inner part and epidermis of M. cocos, and ATR-FTIR was a promising technique for the identification of wild and cultivated M. cocos and the rapid determination of triterpene acids contents.

Isolation of two sesquiterpene glycosides from Sapindus mukorossi Gaertn. with cytotoxic properties and analysis of their mechanism based on network pharmacology

The anti-tumor effects of two compounds purified from Sapindus mukorossi Gaertn. (S. mukorossi.) on breast cancer in vitro were observed. Their chemical structures were identified as sesquiterpene glycosides, namely, Mukurozioside IIa and Mukurozioside IIb. The results of XTT assay indicated that their inhibition rates against three cancer cell lines (MCF-7, MDA-MB-231 and MDA-MB-435s) reached approximately 80% at a concentration of 200 μg/mL, which were higher than that of cyclophosphamide (below 40% at 200 μg/mL), and their 50% inhibiting concentrations were ranged from 120.73 to 154.01 μg/mL, indicating their inhibition were weaker than their parent fraction. Furthermore, the mechanism on breast cancer was predicted, and 22 targets including PTPN1, IL2 and VEGFA were relatively important. These results illustrated the anti-breast cancer activity of S. mukorossi was related to the two compounds with the structure of sesquiterpene glycosides, but they did not represent the full activity of their parent fraction.

Integrated recognition and quantitative detection of starch in surimi by infrared spectroscopy and spectroscopic imaging

Surimi products have become increasingly-consumed food with prominent characteristics of high nutrition and convenience and its supply falls short of demand. However, due to exhausted fishery resource in recent years, surimi adulteration, such as addition of plant proteins, starch and other animal origin meat, is becoming serious, so recognition of these exogenous substances has become an urgent issue. In this study, Fourier transform infrared spectroscopy (FT-IR) combined with infrared spectroscopic imaging could distinguish heterogeneity in surimi qualitatively and quantitatively and obtain integral chemical images so that spatial distribution of each component in surimi could be visually displayed, thus a rapid recognition method and a prediction model were developed. The different starch contents in surimi had been primarily identified through intensity change of infrared absorption peaks at 1045cm^-1 and 988cm^-1, specifically with peak shifts to 1041cm^-1 and to 992cm^-1, respectively. In infrared imaging analysis, principal components (PCs) were separated and one key PC was confirmed as starch by characteristic peaks comparison at 1147cm^-1, 1075cm^-1, 997cm^-1 and 930cm^-1. Meanwhile, an established statistic model could predict starch content in surimi correctly with a reliable correlation coefficient (R=0.9856) and root mean square error of prediction (RMSEP=5.64). Therefore, FT-IR combined with infrared spectroscopic imaging could be applicable to integrally recognize and quantitatively detect starch in surimi.

Geographical Authentication of Macrohyporia cocos by a Data Fusion Method Combining Ultra-Fast Liquid Chromatography and Fourier Transform Infrared Spectroscopy

Macrohyporia cocos is a medicinal and edible fungi, which is consumed widely. The epidermis and inner part of its sclerotium are used separately. M. cocos quality is influenced by geographical origins, so an effective and accurate geographical authentication method is required. Liquid chromatograms at 242 nm and 210 nm (LC₂₄₂ and LC₂₁₀) and Fourier transform infrared (FTIR) spectra of two parts were applied to authenticate the geographical origin of cultivated M. cocos combined with low and mid-level data fusion strategies, and partial least squares discriminant analysis. Data pretreatment involved correlation optimized warping and second derivative. The results showed that the potential of the chromatographic fingerprint was greater than that of five triterpene acids contents. LC₂₄₂-FTIR low-level fusion took full advantage of information synergy and showed good performance. Further, the predictive ability of the FTIR low-level fusion model of two parts was satisfactory. The performance of the low-level fusion strategy preceded those of the single technique and mid-level fusion strategy. The inner parts were more suitable for origin identification than the epidermis. This study proved the feasibility of the data fusion of chromatograms and spectra, and the data fusion of different parts for the accurate authentication of geographical origin. This method is meaningful for the quality control of food and the protection of geographical indication products.

Enhanced chemical and spatial recognition of fish bones in surimi by Tri-step infrared spectroscopy and infrared microspectroscopic imaging

Surimi is an intermediate product with an increasing popularity worldwide. Discrimination of impurities like fish bones in surimi has become an urgent issue owing to the food safety and the improved requirements for assessment methods in identification of surimi quality and grades. A Tri-step infrared spectroscopy, including Fourier transform infrared spectroscopy (FT-IR), second derivative infrared spectroscopy (SD-IR) and two-dimensional correlation infrared spectroscopy (2DCOS-IR) has been applied to integrally discriminate different contents (1%-8%) of fish bones in surimi at macro-scale. Meanwhile, attenuated total reflection infrared spectroscopy (ATR-IR) microspectroscopic imaging has been employed to recognize and identify the location of fish bones (less than 1.0 mm in size) in micro-scale. Fishbone characteristic infrared absorption peak at 1011 cm^-1 contributes to surimi peaks at 1045 cm^-1 and 988 cm^-1 confirmed by calculation of their peak heights and ratios of peak areas in original spectra. SD-IR spectra enhance the difference in range of 1440-500 cm^-1, and specifically peak intensity at 599 cm^-1 is significantly increased in surimi with 3%-8% fish bones. Moreover, 2DCOS-IR spectra reveal that surimi containing fish bones have increased intensity of auto-peaks at 525 cm^-1, 519 cm^-1, 512 cm^-1 and 505 cm^-1 mainly contributed by hydroxyapatite and collagen. In ATR-IR microspectroscopic images, a clear fishbone shape (800 × 200 μm) corresponding to its visible image is clearly observed in principal component (PC) score image, which is confirmed as a fish bone by corresponding pixel spectra. Furthermore, the single-wavenumber image shows the spatial chemical distribution of various components for both the fish bone and surimi. Consequently, fish bones can be integrally recognized by physical and chemical imaging manners. It has been demonstrated that the developed Tri-step infrared spectroscopy and ATR-IR microspectroscopic imaging could be applicable for rapidly recognizing impurities and adulterants in surimi.

Recent Development of Quality Control Methods for Herbal Derived Drug Preparations

Pharmaceutical industries should apply rigorous QC (quality control) to ensure the consistency, safety, and efficacy of their herbal derived drug-preparations. QC must be performed at every stage of the production line i.e. incoming raw materials, extractions, in-process control, finished products and keeping samples. Due to the complex nature of the chemical content of herbal drugs, two approaches to QC should be taken, that is quantitative determination of the selected marker(s) compound(s), and metabolite profiling. Contamination of herbal medicines by heavy metals, pesticides, toxic metabolites, microbial toxins, pathogenic microorganisms and other foreign matter should also be evaluated. A combination of chemical profiling and multivariate analysis (MVA) is recommended as the QC tool for the botanical identification method (BIM) of herbs, extracts, herb materials, and herbal drug preparations. Microscopic methods, DNA profiling or chemical marker(s) are not recommended for use as the sole BIM due to the lack of specificity. Only markers that meet certain criteria i.e. quality active (QA) markers can be utilized as a QC tool. The limit specification range of markers used as QC tools should be described in the analytical target profile (ATP). To gain reliable results of any analysis that has been performed at any QC laboratory, the analysis method must be validated according to the newest guidance. Sample detection limit of any toxic compound(s) should be lower than its cut-off value and MPL. The reliability of any results of analysis of a QC laboratory must be evaluated by using QC-samples for each series of measurements.

Application of variable selection in the origin discrimination of Wolfiporia cocos (F.A. Wolf) Ryvarden & Gilb. based on near infrared spectroscopy

Dried sclerotium of Wolfiporia cocos (F.A. Wolf) Ryvarden & Gilb. is a traditional Chinese medicine. Its chemical components showed difference among geographical origins, which made it difficult to keep therapeutic potency consistent. The identification of the geographical origin of W. cocos is the fundamental prerequisite for its worldwide recognition and acceptance. Four variable selection methods were employed for near infrared spectroscopy (NIR) variable selection and the characteristic variables were screened for the establishment of Fisher function models in further identification of the origin of W. cocos from Yunnan, China. For the obvious differences between poriae cutis (fu-ling-pi in Chinese, or FLP) and the inner part (bai-fu-ling in Chinese, or BFL) of the sclerotia of W. cocos in the pattern space of principal component analysis (PCA), we established discriminant models for FLP and BFL separately. Through variable selection, the models were significant improved and also the models were simplified by using only a small part of the variables. The characteristic variables were screened (13 for BFL and 10 for FLP) to build Fisher discriminant function models and the validation results showed the models were reliable and effective. Additionally, the characteristic variables were interpreted.

Direct and model-free detection of carbohydrate excipients in traditional Chinese medicine formula granules by ATR-FTIR microspectroscopic imaging

A formula granule is a traditional Chinese medicine preparation made from the decoction of a single herbal medicinal. Because of the flexibility for combination and the convenience for utilization, formula granules are becoming popular in clinical applications. However, the efficacy and safety of commercial formula granules often suffer from the improper addition of carbohydrate excipients. Therefore, the detection of carbohydrate excipients is indispensable for the quality control of formula granules. FTIR spectroscopy has been used for the detection of carbohydrate excipients in formula granules. But the overlapped absorption signals limit the sensitivity and specificity of detection. Besides, a large number of multivariate calibration models are needed for quantitative determination. To overcome the above disadvantages, this research utilizes FTIR microspectroscopy for the model-free and universal detection of carbohydrate excipients in formula granules. Using ATR-FTIR imaging, excipient particles and herbal extract particles in formula granules can be measured individually, which resolves the absorption signals of excipients and herbal extract spatially and thus improves the sensitivity and specificity of detection. The content of excipients can be estimated directly from the number of excipient particles, which is robust to the variations of herb extracts and free of calibration models. The case study of Gardeniae Fructus formula granules shows the potential of FTIR microspectroscopy in the direct and rapid detection of carbohydrate excipients in formula granules. Graphical Abstract Excipient particles in TCM formula granules can be measured and recognized individually by FTIR microspectroscopy.

A Review of Mid-Infrared and Near-Infrared Imaging: Principles, Concepts and Applications in Plant Tissue Analysis

Plant cells, tissues and organs are composed of various biomolecules arranged as structurally diverse units, which represent heterogeneity at microscopic levels. Molecular knowledge about those constituents with their localization in such complexity is very crucial for both basic and applied plant sciences. In this context, infrared imaging techniques have advantages over conventional methods to investigate heterogeneous plant structures in providing quantitative and qualitative analyses with spatial distribution of the components. Thus, particularly, with the use of proper analytical approaches and sampling methods, these technologies offer significant information for the studies on plant classification, physiology, ecology, genetics, pathology and other related disciplines. This review aims to present a general perspective about near-infrared and mid-infrared imaging/microspectroscopy in plant research. It is addressed to compare potentialities of these methodologies with their advantages and limitations. With regard to the organization of the document, the first section will introduce the respective underlying principles followed by instrumentation, sampling techniques, sample preparations, measurement, and an overview of spectral pre-processing and multivariate analysis. The last section will review selected applications in the literature.

Rapid and simple determination of polyphyllin I, II, VI, and VII in different harvest times of cultivated Paris polyphylla Smith var. yunnanensis (Franch.) Hand.-Mazz by UPLC-MS/MS and FT-IR

Paris Polyphylla Smith var. yunnanensis (Franch.) Hand.-Mazz ("Dian Chonglou" in Chinese) is a famous herbal medicine in China, which is usually well known for activities of anti-cancer, hemolysis, and cytotoxicity. In this study, Fourier transform infrared (FT-IR) spectroscopy coupled with principal component analysis (PCA) and partial least-squares regression (PLSR) was applied to discriminate samples of P. polyphylla var. yunnanensis harvested in different years and determine the content of polyphyllin I, II, VI, and VII in P. polyphylla var. yunnanensis. Meanwhile, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to study the dynamic changes of P. polyphylla var. yunnanensis harvested in different years (4, 5, 7, 8, 9, 12, and 13 years old). According to the UPLC-MS/MS result, the optimum harvest time of P. polyphylla var. yunnanensis is 8 years, due to the highest yield of four active components. By the PCA model, P. polyphylla var. yunnanensis could be exactly discriminated, except that two 8-year-old samples were misclassified as 9-year-old samples. For the prediction of polyphyllin I, II, VI, and VII, the quantitative results are satisfactory, with a high value for the determination coefficient (R ²) and low values for the root-mean-square error of estimation (RMSEE), root-mean-square error of cross-validation (RMSECV), and root-mean-square error of prediction (RMSEP). In conclusion, FT-IR combined with chemometrics is a promising method to accurately discriminate samples of P. polyphylla var. yunnanensis harvested in different years and determine the content of polyphyllin I, II, VI, and VII in P. polyphylla var. yunnanensis.

Direct and simultaneous detection of organic and inorganic ingredients in herbal powder preparations by Fourier transform infrared microspectroscopic imaging

Herbal powder preparation is a kind of widely-used herbal product in the form of powder mixture of herbal ingredients. Identification of herbal ingredients is the first and foremost step in assuring the quality, safety and efficacy of herbal powder preparations. In this research, Fourier transform infrared (FT-IR) microspectroscopic identification method is proposed for the direct and simultaneous recognition of multiple organic and inorganic ingredients in herbal powder preparations. First, the reference spectrum of characteristic particles of each herbal ingredient is assigned according to FT-IR results and other available information. Next, a statistical correlation threshold is determined as the lower limit of correlation coefficients between the reference spectrum and a larger number of calibration characteristic particles. After validation, the reference spectrum and correlation threshold can be used to identify herbal ingredient in mixture preparations. A herbal ingredient is supposed to be present if correlation coefficients between the reference spectrum and some sample particles are above the threshold. Using this method, all kinds of herbal materials in powder preparation Kouqiang Kuiyang San are identified successfully. This research shows the potential of FT-IR microspectroscopic identification method for the accurate and quick identification of ingredients in herbal powder preparations.

In-situ micro-FTIR spectroscopic observation on the hydration process of Poria cocos

In Poria cocos, triterpene compound and polysaccharides are the main compositions. The heteropolysaccharide was identified as a linear chain of β-(1→3)-d-glucan, which has the strong water absorbing capacity. In order to investigate the effect of water on the structure of Poria cocos, which belongs to a kind of Polyporaceae, the Micro-Fourier transform infrared spectroscopy (micro-FTIR) technique has been employed with the ambient relative humidity (RH) increasing. The gained IR spectra are measured and analyzed in detail. Because of strong overlaps between some bands, the differential spectra and band decompositions have been applied to analyze the structural change. IR spectra show the transformation of hydrogen bonds with the RH. The blue shift of the CH2 bending vibration from 1417 to 1424cm(-1) with the increase in RH means that the hydrogen bonds are formed between CH2 groups and water molecules at lower RH and some transferred to weak hydrogen bonds. The further study suggests that the C1OH, C2OH, and C3OH groups from polysaccharide bond formed C1OH⋯H2O, C2OH⋯H2O, and C3OH⋯H2O steady modes, respectively, with water molecules.

Chemical morphology of Areca nut characterized directly by Fourier transform near-infrared and mid-infrared microspectroscopic imaging in reflection modes

Fourier transform near-infrared (NIR) and mid-infrared (MIR) imaging techniques are essential tools to characterize the chemical morphology of plant. The transmission imaging mode is mostly used to obtain easy-to-interpret spectra with high signal-to-noise ratio. However, the native chemical compositions and physical structures of plant samples may be altered when they are microtomed for the transmission tests. For the direct characterization of thick plant samples, the combination of the reflection NIR imaging and the attenuated total reflection (ATR) MIR imaging is proposed in this research. First, the reflection NIR imaging method can explore the whole sample quickly to find out typical regions in small sizes. Next, each small typical region can be measured by the ATR-MIR imaging method to reveal the molecular structures and spatial distributions of compounds of interest. As an example, the chemical morphology of Areca nut section is characterized directly by the above approach.

Characteristic Fingerprint Based on Low Polar Constituents for Discrimination of Wolfiporia extensa according to Geographical Origin Using UV Spectroscopy and Chemometrics Methods

The fungus species Wolfiporia extensa has a long history of medicinal usage and has also been commercially used to formulate nutraceuticals and functional foods in certain Asian countries. In the present study, a practical and promising method has been developed to discriminate the dried sclerotium of W. extensa collected from different geographical sites based on UV spectroscopy together with chemometrics methods. Characteristic fingerprint of low polar constituents of sample extracts that originated from chloroform has been obtained in the interval 250-400 nm. Chemometric pattern recognition methods such as partial least squares discriminant analysis (PLS-DA) and hierarchical cluster analysis (HCA) were applied to enhance the authenticity of discrimination of the specimens. The results showed that W. extensa samples were well classified according to their geographical origins. The proposed method can fully utilize diversified fingerprint characteristics of sclerotium of W. extensa and requires low-cost equipment and short-time analysis in comparison with other techniques. Meanwhile, this simple and efficient method may serve as a basis for the authentication of other medicinal fungi.