Interrogation of spatial metabolome of Ginkgo biloba with high-resolution matrix-assisted laser desorption/ionization and laser desorption/ionization mass spectrometry imaging

Differential distribution of characteristic constituents in peel and pulp of Aurantii Fructus Immaturus (Citrus aurantium L.) using MALDI mass spectrometry imaging

Aurantii Fructus Immaturus (AFI) was structurally divided into two parts named "peel" and "pulp". The exocarp and mesocarp of materials named "peel". The endocarp separated into multiple compartments and the cystic hair attached to it named "pulp". In order to explore the distribution and content of constituents in AFI, an efficient method to explore the distribution of constituents was developed based on matrix assisted laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry imaging (MALDI-FTICR-MSI). After simple processing, thirty-two constituents with distinct localization in the mass range of 101-1200 Da were identified by MALDI-FTICR-MSI. In addition, the identified four flavnoids (poncirin, sinensetin, 3,5,6,7,8,3',4'-heptemthoxyflavone, and tangeritin) were analyzed for differences between using LC-MS. Quantitative analysis results supported the quantitative results from MALDI-FT-ICR-MSI. The results implied that different parts had different constituents in AFI, and demonstrated MALDI-MSI have high potential in the direct analysis of constituents.

Mass spectrometry imaging as a promising analytical technique for herbal medicines: an updated review

Herbal medicines (HMs) have long played a pivotal role in preventing and treating various human diseases and have been studied widely. However, the complexities present in HM metabolites and their unclear mechanisms of action have posed significant challenges in the modernization of traditional Chinese medicine (TCM). Over the past two decades, mass spectrometry imaging (MSI) has garnered increasing attention as a robust analytical technique that enables the simultaneous execution of qualitative, quantitative, and localization analyses without complex sample pretreatment. With advances in technical solutions, MSI has been extensively applied in the field of HMs. MSI, a label-free ion imaging technique can comprehensively map the spatial distribution of HM metabolites in plant native tissues, thereby facilitating the effective quality control of HMs. Furthermore, the spatial dimension information of small molecule endogenous metabolites within animal tissues provided by MSI can also serve as a supplement to uncover pharmacological and toxicological mechanisms of HMs. In the review, we provide an overview of the three most common MSI techniques. In addition, representative applications in HM are highlighted. Finally, we discuss the current challenges and propose several potential solutions. We hope that the summary of recent findings will contribute to the application of MSI in exploring metabolites and mechanisms of action of HMs.

Electromagnetic Field-Assisted Frozen Tissue Planarization Enhances MALDI-MSI in Plant Spatial Omics

Plant samples with irregular morphology are challenging for longitudinal tissue sectioning. This has restricted the ability to gain insight into some plants using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Herein, we develop a novel technique termed electromagnetic field-assisted frozen tissue planarization (EMFAFTP). This technique involves using a pair of adjustable electromagnets on both sides of a plant tissue. Under an optimized electromagnetic field strength, nondestructive planarization and regularization of the frozen tissue is induced, allowing the longitudinal tissue sectioning that favors subsequent molecular profiling by MALDI-MSI. As a proof of concept, flowers, leaves and roots with irregular morphology from six plant species are chosen to evaluate the performance of EMFAFTP for MALDI-MSI of secondary metabolites, amino acids, lipids, and proteins among others in the plant samples. The significantly enhanced MALDI-MSI capabilities of these endogenous molecules demonstrate the robustness of EMFAFTP and suggest it has the potential to become a standard technique for advancing MALDI-MSI into a new era of plant spatial omics.

Matrix-assisted laser desorption ionization mass spectrometry imaging reveals the spatial distribution of compounds that may exacerbate inflammation in garden ginseng and ginseng under forest

Ginseng, a highly esteemed herbal medicine, has been utilized over 5000 years, predominantly in Far Eastern countries. Ginseng is categorized into garden ginseng (GG) and ginseng under forest (FG). However, in contrast to FG, excessive intake of GG may lead to potential adverse effects due to disruption of epithelial cell integrity, and the specific population groups that may be at higher risk. In this work, untargeted metabolomics were used to determine the heterogeneity between GG and FG, the data indicates that the content of Ethyl caffeate, Homoorientin, Citric acid and Quinic acid in GG were higher than in FG. Mass spectrometry imaging showed that ethyl caffeate and Homoorientin were concentrated on the brownish yellow exocarp of the primary root. Our experiments demonstrated that excessive exposure to ethyl caffeate and Homoorientin exacerbated the inflammatory response of HUVECs and reduced the expression of cell junctions. This suggest that the compounds causing adverse effects from excessive intake of GG are mainly concentrated in the yellow exocarp of the primary root of GG. These results suggest that untargeted metabolomics coupled with MALDI-MSI can visualize the spatial distribution of endogenous differential molecules of the same herb in different growth environments or developmental stages.

Study on the Anti-Inflammatory Mechanism of Coumarins in Peucedanum decursivum Based on Spatial Metabolomics Combined with Network Pharmacology

Peucedanum decursivum (Miq.) Maxim (P. decursivum) is a traditional Chinese medicinal plant with pharmacological effects such as anti-inflammatory and anti-tumor effects, the root of which is widely used as medicine. Determining the spatial distribution and pharmacological mechanisms of metabolites is necessary when studying the effective substances of medicinal plants. As a means of obtaining spatial distribution information of metabolites, mass spectrometry imaging has high sensitivity and allows for molecule visualization. In this study, matrix-assisted laser desorption mass spectrometry (MALDI-TOF-MSI) and network pharmacology were used for the first time to visually study the spatial distribution and anti-inflammatory mechanism of coumarins, which are metabolites of P. decursivum, to determine their tissue localization and mechanism of action. A total of 27 coumarins were identified by MALDI-TOF-MSI, which mainly concentrated in the cortex, periderm, and phloem of the root of P. decursivum. Network pharmacology studies have identified key targets for the anti-inflammatory effect of P. decursivum, such as TNF, PTGS2, and PRAKA. GO enrichment and KEGG pathway analyses indicated that coumarins in P. decursivum mainly participated in biological processes such as inflammatory response, positive regulation of protein kinase B signaling, chemical carcinogenesis receptor activation, pathways in cancer, and other biological pathways. The molecular docking results indicated that there was good binding between components and targets. This study provides a basis for understanding the spatial distribution and anti-inflammatory mechanism of coumarins in P. decursivum.

Advances in mass spectrometry imaging for plant metabolomics-Expanding the analytical toolbox

Mass spectrometry imaging (MSI) has become increasingly popular in plant science due to its ability to characterize complex chemical, spatial, and temporal aspects of plant metabolism. Over the past decade, as the emerging and unique features of various MSI techniques have continued to support new discoveries in studies of plant metabolism closely associated with various aspects of plant function and physiology, spatial metabolomics based on MSI techniques has positioned it at the forefront of plant metabolic studies, providing the opportunity for far higher resolution than was previously available. Despite these efforts, profound challenges at the levels of spatial resolution, sensitivity, quantitative ability, chemical confidence, isomer discrimination, and spatial multi-omics integration, undoubtedly remain. In this Perspective, we provide a contemporary overview of the emergent MSI techniques widely used in the plant sciences, with particular emphasis on recent advances in methodological breakthroughs. Having established the detailed context of MSI, we outline both the golden opportunities and key challenges currently facing plant metabolomics, presenting our vision as to how the enormous potential of MSI technologies will contribute to progress in plant science in the coming years.

Cell type-specific control and post-translational regulation of specialized metabolism: opening new avenues for plant metabolic engineering

Although plant metabolic engineering enables the sustainable production of valuable metabolites with many applications, we still lack a good understanding of many multi-layered regulatory networks that govern metabolic pathways at the metabolite, protein, transcriptional and cellular level. As transcriptional regulation is better understood and often reviewed, here we highlight recent advances in the cell type-specific and post-translational regulation of plant specialized metabolism. With the advent of single-cell technologies, we are now able to characterize metabolites and their transcriptional regulators at the cellular level, which can refine our searches for missing biosynthetic enzymes and cell type-specific regulators. Post-translational regulation through enzyme inhibition, protein phosphorylation and ubiquitination are clearly evident in specialized metabolism regulation, but not frequently studied or considered in metabolic engineering efforts. Finally, we contemplate how advances in cell type-specific and post-translational regulation can be applied in metabolic engineering efforts in planta, leading to optimization of plants as metabolite production vehicles.

Desorption Electrospray Ionization Mass Spectrometry Imaging Techniques Depict a Reprogramming of Energy and Purine Metabolism in the Core Brain Regions of Chronic Social Defeat Stress Mice

Depression is associated with pathological changes and metabolic abnormalities in multiple brain regions. The simultaneous comprehensive and in situ detection of endogenous molecules in all brain regions is essential for a comprehensive understanding of depression pathology, which is described in this paper. A method based on desorption electrospray ionization mass spectrometry imaging (DESI-MSI) technology was developed to classify mouse brain regions using characteristic lipid molecules and to detect the metabolites in mouse brain tissue samples simultaneously. The results showed that characteristic lipid molecules can be used to clearly distinguish each subdivision of the mouse brain, and the accuracy of this method is higher than that of the conventional staining method. The cerebellar cortex, medial prefrontal cortex, hippocampus, striatum, nucleus accumbens-core, and nucleus accumbens-shell exhibited the most significant differences in the chronic social defeat stress model. An analysis of metabolic pathways revealed that 13 kinds of molecules related to energy metabolism and purine metabolism exhibited significant changes. A DESI-MSI method was developed for the detection of pathological brain sections. We found, for the first time, that there are characteristic changes in the energy metabolism in the cortex and purine metabolism in the striatum, which is highly important for obtaining a deeper and more comprehensive understanding of the pathology of depression and discovering regulatory targets.

Imaging plant metabolism in situ

Mass spectrometry imaging (MSI) has emerged as an invaluable analytical technique for investigating the spatial distribution of molecules within biological systems. In the realm of plant science, MSI is increasingly employed to explore metabolic processes across a wide array of plant tissues, including those in leaves, fruits, stems, roots, and seeds, spanning various plant systems such as model species, staple and energy crops, and medicinal plants. By generating spatial maps of metabolites, MSI has elucidated the distribution patterns of diverse metabolites and phytochemicals, encompassing lipids, carbohydrates, amino acids, organic acids, phenolics, terpenes, alkaloids, vitamins, pigments, and others, thereby providing insights into their metabolic pathways and functional roles. In this review, we present recent MSI studies that demonstrate the advances made in visualizing the plant spatial metabolome. Moreover, we emphasize the technical progress that enhances the identification and interpretation of spatial metabolite maps. Within a mere decade since the inception of plant MSI studies, this robust technology is poised to continue as a vital tool for tackling complex challenges in plant metabolism.

Tissue distribution of metabolites in Cordyceps cicadae determined by DESI-MSI analysis

In this paper, we establish an in situ visualization analysis method to image the spatial distribution of metabolites in different parts (sclerotium, coremium) and different microregions of Cordyceps cicadae (C. cicadae) to achieve the in situ visual characterization of tissues for a variety of metabolites such as nucleosides, amino acids, polysaccharides, organic acids, fatty acids, and so on. The study included LC-MS chemical composition identification, preparation of C. cicadae tissue sections, DEDI-MSI analysis, DESI combined with Q-TOF/MS to obtain high-resolution imaging of mass-to-charge ratio and space, imaging of C. cicadae in positive-negative ion mode with a spatial resolution of 100 μm, and localizing and identifying its chemical compositions based on its precise mass. A total of 62 compounds were identified; nucleosides were mainly distributed in the coremium, L-threonine and DL-isoleucine, and other essential amino acids; peptides were mainly distributed in the sclerotium of C. cicadae; and the rest of the amino acids did not have a clear pattern; sugars and sugar alcohols were mainly distributed in the coremium of C. cicadae; organic acids and fatty acids were distributed in the nucleus of C. cicadae more than in the sclerotium, and the mass spectrometry imaging method is established in the research. The mass spectrometry imaging method established in this study is simple and fast and can visualize and analyse the spatial distribution of metabolites of C. cicadae, which is of great significance in characterizing the metabolic network of C. cicadae, and provides support for the quality evaluation of C. cicadae and the study of the temporal and spatial metabolic network of chemical compounds.

Exposure to Light of the Abaxial versus Adaxial Side of Detached Kalanchoë blossfeldiana Leaves Affects Anthocyanin Content and Composition Differently

The accumulation and composition of anthocyanins in leaves of Kalanchoë blossfeldiana, detached and kept for five days under natural light conditions, were investigated. The presence of fifteen derivatives of cyanidin, petunidin, and delphinidin was found. Changes in the content of each anthocyanin in the leaves before and after exposure to light on the abaxial (naturally upper) and adaxial (naturally lower) sides of the leaves were compared. When the adaxial side was exposed to light, the anthocyanin contents of the leaves did not change. In contrast, when the abaxial side of detached leaves was exposed to light, there was enhanced accumulation of delphinidin-rhamnoside-glucoside, cyanidin-rhamnoside-glucoside, cyanidin-glucoside-glucoside, and two unknown derivatives of petunidin and delphinidin. Application of methyl jasmonate (JA-Me) on the abaxial side exposed to light inhibited the accumulation of these anthocyanins. This effect could probably be due to the presence of these anthocyanins in the epidermal cells of K. blossfeldiana leaves and was visible in the microscopic view of its cross-section. These anthocyanins were directly exposed to JA-Me, leading to inhibition of their formation and/or accumulation. The lack of significant effects of JA-Me on anthocyanin mono- and tri-glycosides may indicate that they are mainly present in the mesophyll tissue of the leaf.

Comprehensive analysis of JAZ family members in Ginkgo biloba reveals the regulatory role of the GbCOI1/GbJAZs/GbMYC2 module in ginkgolide biosynthesis

Ginkgo biloba L., an ancient relict plant known as a 'living fossil', has a high medicinal and nutritional value in its kernels and leaves. Ginkgolides are unique diterpene lactone compounds in G. biloba, with favorable therapeutic effects on cardiovascular and cerebrovascular diseases. Thus, it is essential to study the biosynthesis and regulatory mechanism of ginkgolide, which will contribute to quality improvement and medication requirements. In this study, the regulatory roles of the JAZ gene family and GbCOI1/GbJAZs/GbMYC2 module in ginkgolide biosynthesis were explored based on genome and methyl jasmonate-induced transcriptome. Firstly, 18 JAZ proteins were identified from G. biloba, and the gene characteristics and expansion patterns along with evolutionary relationships of these GbJAZs were analyzed systematically. Expression patterns analysis indicated that most GbJAZs expressed highly in the fibrous root and were induced significantly by methyl jasmonate. Mechanistically, yeast two-hybrid assays suggested that GbJAZ3/11 interacted with both GbMYC2 and GbCOI1, and several GbJAZ proteins could form homodimers or heterodimers between the GbJAZ family. Moreover, GbMYC2 is directly bound to the G-box element in the promoter of GbLPS, to regulate the biosynthesis of ginkgolide. Collectively, these results systematically characterized the JAZ gene family in G. biloba and demonstrated that the GbCOI1/GbJAZs/GbMYC2 module could regulate ginkgolides biosynthesis, which provides a novel insight for studying the mechanism of JA regulating ginkgolide biosynthesis.

Nitro Indole Derivatives as Novel Dual-Polarity Matrices for MALDI Mass Spectrometry and Imaging with Broad Applications

A new matrix framework is presented in this study for the improved ionization efficiency of complex mixtures by matrix-assisted laser desorption ionization (MALDI) mass spectrometry/imaging. Five nitro indole (NI) derivatives [3-methyl-4-nitro-1H-indole (3,4-MNI), 3-methyl-6-nitro-1H-indole (3,6-MNI), 2,3-dimethyl-4-nitro-1H-indole (2,3,4-DMNI), 2,3-dimethyl-6-nitro-1H-indole (2,3,6-DMNI), and 4-nitro-1H-indole (4-NI)] were synthesized and shown to produce both positive and negative ions with a broad class of analytes as MALDI matrices. NI matrices were compared to several common matrices, such as 2,5-dihydroxybenzoic acid (DHB), alpha-cyano-4-hydroxylcinnamic acid (CHCA), sinapinic acid (SA), 1,5-diaminonaphthelene (1,5-DAN), and 9-aminoacridine (9-AA), for the analysis of lipid, peptide, protein, glycan, and perfluorooctanesulfonic acid (PFOS) compounds. 3,4-MNI demonstrated the best performance among the NI matrices. This matrix resulted in reduced ion suppression and better detection sensitivity for complex mixtures, for example, egg lipids/milk proteins/PFOS in tap water, while 2,3,6-DMNI was the best matrix for blueberry tissue imaging. Several important aspects of this work are reported: (1) dual-polarity ion production with NI matrices and complex mixtures; (2) quantitative analysis of PFOS with a LOQ of 0.5 ppb in tap water and 0.05 ppb in MQ water (without solid phase extraction enrichment), with accuracy and precision within 5%; (3) MALDI imaging with 2,3,6-DMNI as a matrix for plant metabolite/lipid identification with ionization enhancement in the negative ion mode m/z 600-900 region; and (4) development of a thin film deposition under/above tissue method for MALDI imaging with a vacuum sublimation matrix on a high-vacuum MALDI instrument.

Combined Widely Targeted Metabolomic, Transcriptomic, and Spatial Metabolomic Analysis Reveals the Potential Mechanism of Coloration and Fruit Quality Formation in Actinidia chinensis cv. Hongyang

Postharvest kiwifruit (Actinidia chinensis cv. Hongyang) pulp is mainly composed of outer yellow-flesh (LR) and inner red-flesh (HR). However, information about the differences in coloration and fruit quality between these two parts are limited. In this study, widely targeted metabolomic, transcriptomic, and spatial metabolomic analyses were used to reveal the potential mechanism of coloration and fruit quality formation. The results show that a total of 1001 metabolites were identified in Hongyang kiwifruit, and the accumulation of 211 metabolites were significantly higher in the HR than LR, including 69 flavonoids, 53 phenolic acids, and 38 terpenoids. There were no significant differences in the content of citric acid, quinic acid, glucose, fructose, or sucrose between the LR and HR. These results were consistent with the results from the RNA-seq profile and spatial metabolomic analysis. In addition, a total of 23 key candidate genes related to flesh color and fruit quality formation were identified and validated by qRT-PCR analysis. This study provides a theoretical basis for elucidating the underlying mechanism of the formation of kiwifruit flesh color and fruit quality.

Unveiling targeted spatial metabolome of rice seed at the dough stage using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry imaging

Rice (Oryza sativa) seeds contain a variety of metabolites, which not only provide energy for their own growth and development, but also are an important source of nutrition for humans. It is crucial to study the distribution of metabolites in rice seeds, but the spatial metabolome of rice seeds is rarely investigated. In this study, Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) imaging was used to reveal the spatial distribution of free soluble sugars (glucose, fructose, sucrose, and maltose), amino acids (9 essential amino acids and 2 amino acids affecting rice eating quality: L-aspartic acid and L-glutamic acid), and 4 metabolites in the flavonoids synthesis pathway (cinnamic acid, naringenin chalcone, naringenin, and dihydrokaempferol) in rice seed at the dough stage. It was found that the 4 free soluble sugars present similar spatial distribution, mainly distributed in the seed cortex and embryo with high abundance. The majority of amino acids are also concentrated in the rice cortex and embryo, while the others are abundant in the whole seed. Besides cinnamic acid distributed in the seed cortex and embryo, the naringenin chalcone, naringenin, and dihydrokaempferol were also found in the endosperm and had lower content. Furthermore, a colocalization phylogenetic tree according to the spatial distribution imaging of each metabolite was constructed. This study revealed the distribution diversity of metabolites in different segmentations of rice seed at the dough stage, providing clues for the nutritional differences between brown rice and white rice, and serving as a reference for people to target a healthy diet.

Changes in physical architecture and lipids compounds in skeletal muscle from Pekin duck and Liancheng white duck

As a complex food, meat displays various biochemical properties that are determined to a great extent by physical architecture and lipid metabolites. Pekin duck and Liancheng white duck are elite breeds with distinct characteristics. Here, we explored the development of the muscle fibers from embryonic stage to 10-wk after birth, and muscle fibers grow slowly after 8-wk. We investigated the meat quality, ultrastructure, lipidomics profiling, and lipids spatial distribution of skeletal muscle at 8 wk. Pekin duck has lower Warner-Bratzler shear force (WBSF) (P < 0.05), high intramuscular fat (IMF) (P < 0.01), longer and wider sarcomere, and higher mitochondrial density (P < 0.001). Liancheng white duck with tighter collagen architecture. A total of 950 lipids from 6 lipid classes identified with lipidomics were analyzed, the levels of GP, GL, and PR were significantly higher in Pekin duck (P < 0.05), SL and ST were significantly higher in Liancheng white duck (P < 0.05). There were 333 significantly different lipids (|log2(Fold Change)| ≥ 1 and FDR < 0.05) screened, most lipids distributed in the muscle tissue were uniform, but some specifically distributed in connective tissue. To some extent, the results demonstrate the high lipid deposition capacity of Pekin duck and the high medicinal function of Liancheng white duck. Our study provides new insights into the relationship between skeletal muscle architecture and meat toughness, which increased the knowledge of lipidomic characteristics and provide a basis for duck meat authentication.

A bibliometric and thematic analysis of the trends in the research on ginkgo biloba extract from 1985 to 2022

Background

Ginkgo biloba extract (GBE), a complementary and alternative medicine, has been widely used for disorders such as brain infarction, dementia, and coronary heart disease, in recent decades. Given its widespread clinical use, GBE has always been a vital research topic. However, there are no bibliometric analyses on this topic; furthermore, published reviews of GBE focus only on a specific research field or lack scientific and systematic evaluation. This study combined bibliometrics with thematic reviews by visual analysis to identify the current status of GBE research and to better identify research hotspots and trends in the past 40 years to understand future developments in basic and clinical research.

Methods

Articles and reviews on GBE were retrieved by topic from the Web of Science Core Collection from inception to 2022.12.01. Countries, institutions, authors, journals, references, and keywords in the field were visually analyzed using CiteSpace, Scimago Graphica, and VOSviewer software; then, these visualization results for references and keywords were clarified in detail by thematic reviews in subdivisions of the fields.

Results

In total, 2015 publications were included. The GBE-related literature has high volumes of publications and citations. The majority of literature is from China, and the USA cooperates most closely with other countries. In GBE research, Christen Yves is the most cited author, Phytotherapy Research is the most prolific journal, and the Journal of Ethnopharmacology is the most co-cited journal. Through a comprehensive analysis of keywords, references, and reviews, the quality of the meta-analysis of randomized controlled clinical trials of GBE in treating dementia was evaluated by the Risk of Bias in Systematic Reviews scale (ROBIS). Current research on GBE focuses on its pharmacological mechanisms, and neuroprotective application in diseases such as Alzheimer's disease, and glaucoma. Randomized controlled trials are the current research hotspot.

Conclusion

Research on GBE is flourishing; using bibliometric and thematic analysis, we identified its hotspots and trends. The pharmacological mechanisms and clinical applications of GBE are the focus of present and likely future research.

In-depth profiling of carbohydrate isomers in biological tissues by chemical derivatization-assisted mass spectrometry imaging

Carbohydrates play crucial regulatory roles in various physiological and pathological processes. However, the low ionization efficiency and the presence of linkage pattern, monosaccharide composition and anomeric configuration isomers make their in-depth analysis very challenging, especially for heterogeneous biological tissues. In this study, we propose a high-sensitive and isomer-specific imaging approach to visualize the spatial distributions of monosaccharide and disaccharide isomers by integrating chemical derivatization and matrix-assisted laser desorption/ionization tandem mass spectrometry imaging (MALDI-MS2I). 2-Pyridinecarbohydrazide (PYD) is developed as a novel derivatization reagent which can not only improves the MS sensitivity of carbohydrates, but also enables the identification and visualization of ketose and aldose monosaccharide isomers, as well as linkage pattern, monosaccharide composition and anomeric configuration disaccharide isomers by mass spectrometry imaging of isomer-specific MS/MS fragment ions. Moreover, we build quantitative MALDI-MS2 and MALDI-MS2I methods for disaccharide isomers based on the diagnostic fragment ions, and good linear relationships could be achieved both in solution and on glass slides. We expect that this study should provide new ideas for in-depth profiling of the spatial signatures of carbohydrates in biological tissues and lay the foundation for a deeper understanding of carbohydrates' structure.

Novel mechanisms for the synthesis of important secondary metabolites in Ginkgo biloba seed revealed by multi-omics data

Although the detailed biosynthetic mechanism is still unclear, the unique secondary metabolites of Ginkgo biloba, including ginkgolic acids (GAs) and terpene trilactones, have attracted increasing attention for their potent medicinal, physiological and biochemical properties. In particular, GAs have shown great potential in the fields of antibacterial and insecticidal activities, making it urgent to elucidate their biosynthetic mechanism. In this study, we systematically revealed the landscape of metabolic-transcriptional regulation across continuous growth stages of G. biloba seeds (GBS) based on multi-omics mining and experimental verification, and successfully identified all major types of GAs and terpene trilactones along with more than a thousand kinds of other metabolites. The phenological changes and the essential gene families associated with these unique metabolites were analyzed in detail, and several potential regulatory factors were successfully identified based on co-expression association analysis. In addition, we unexpectedly found the close relationship between large introns and the biosynthesis of these secondary metabolites. These genes with large introns related to the synthesis of secondary metabolites showed higher gene expression and expression stability in different tissues or growth stages. Our results may provide a new perspective for the study of the regulatory mechanism of these unique secondary metabolites in GBS.

In situ analysis of volatile oil in Angelica sinensis roots by fluorescence imaging combined with mass spectrometry imaging

In this study, the spatial distribution and accumulation dynamics of volatile oil in Angelica sinensis roots was realized by fluorescence imaging combined with mass spectrometry imaging. The laser scanning confocal microscopy was used to determine the optimal excitation wavelength and the fluorescent stability of volatile oil in the sections of Angelica sinensis roots. The results demonstrated that 488 nm was the most suitable excitation wavelength for the identification and quantitative analysis of volatile oil. It was observed that volatile oil accumulated in the oil chamber of the phelloderm and secondary phloem, and the oil canal of the secondary xylem. The results also indicated that there were differences in content during different periods. Furthermore, the MALDI-TOF-MSI technology was used to study the spatial distribution and compare the chemical compositions of different parts of Angelica sinensis roots during the harvest period. A total of 55, 49, 50 and 30 compounds were identified from the head, body, tail of the root and root bark, respectively. The spatial distribution of phthalides, organic acids and other compounds were revealed in Angelica sinensis roots. The method developed in this study could be used for the in situ analysis of volatile oil in Angelica sinensis roots.

MALDI Imaging Assisted Discovery of a Di-O-glycosyltransferase from Platycodon grandiflorum Root

A matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) assisted genome mining strategy was developed for the discovery of glycosyltransferase (GT) from the root of Platycodon grandiflorum. A di-O-glycosyltransferase PgGT1 was discovered and characterized that is capable of catalyzing platycoside E (PE) synthesis through the attachment of two β-1,6-linked glucosyl residues sequentially to the glucosyl residue at the C3 position of platycodin D (PD). Although UDP-glucose is the preferred sugar donor for PgGT1, it could also utilize UDP-xylose and UDP-N-acetylglucosamine as weak donors. Residues S273, E274, and H350 played important roles in stabilizing the glucose donor and positioning the glucose in the optimal orientation for the glycosylation reaction. This study clarified two key steps involved in the biosynthetic pathway of PE and could greatly contribute to improving its industrial biotransformation.

Visualizing the distribution of flavonoids in litchi (Litchi chinenis) seeds through matrix-assisted laser desorption/ionization mass spectrometry imaging

Flavonoids are one of the most important bioactive components in litchi (Litchi chinensis Sonn.) seeds and have broad-spectrum antiviral and antitumor activities. Litchi seeds have been shown to inhibit the proliferation of cancer cells and induce apoptosis, particularly effective against breast and liver cancers. Elucidating the distribution of flavonoids is important for understanding their physiological and biochemical functions and facilitating their efficient extraction and utilization. However, the spatial distribution patterns and expression states of flavonoids in litchi seeds remain unclear. Herein, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used for in situ detection and imaging of the distribution of flavonoids in litchi seed tissue sections for the first time. Fifteen flavonoid ion signals, including liquiritigenin, apigenin, naringenin, luteolin, dihydrokaempferol, daidzein, quercetin, taxifolin, kaempferol, isorhamnetin, myricetin, catechin, quercetin 3-β-d-glucoside, baicalin, and rutin, were successfully detected and imaged in situ through MALDI-MSI in the positive ion mode using 2-mercaptobenzothiazole as a matrix. The results clearly showed the heterogeneous distribution of flavonoids, indicating the potential of litchi seeds for flavonoid compound extraction. MALDI-MS-based multi-imaging enhanced the visualization of spatial distribution and expression states of flavonoids. Thus, apart from improving our understanding of the spatial distribution of flavonoids in litchi seeds, our findings also facilitate the development of MALDI-MSI-based metabolomics as a novel effective molecular imaging tool for evaluating the spatial distribution of endogenous compounds.

Spatial segmentation of mass spectrometry imaging data featuring selected principal components

Spatial segmentation aims to find homogeneous/heterogeneous subgroups of spectra or ion images in mass spectrometry imaging (MSI) data. The maps it generated inform researchers of vital characteristics of the data and thus provide the basis for strategizing further biological analysis. Dimensional reduction and clustering are two basic steps of segmentation. Due to the variations in the quality, resolution, density of spectral information, and sizes, not all datasets could be segmented ideally with combinations of different dimensional reduction and clustering algorithms. Here, we proposed a segmentation pipeline that utilized pattern compression by principal component analysis (PCA) and represented by principal components. Instead of preprocessed or raw MSI data, normalized principal components were used for the segmentation process. Multiple datasets of rat brains and mouse kidneys were tested, and the proposed segmentation pipeline presented the obvious advantage of easy-to-use and can be readily intergraded with other existing innovative pipelines.

Prefabricated platinum nanomaterial matrix for MALDI-MS imaging of oligosaccharides and lipids in plant tissues

Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) can visualize the spatial distribution characteristics of molecules in tissues in situ, in which the matrix plays a key role. In this paper, we propose a platinum nanomaterial pre-coated matrix, which can be prepared in bulk by sputtering platinum nanoparticles onto slides using an ion sputterer and then used for MALDI-MS analysis by placing tissue sections on the matrix. We used this matrix for MALDI-MS imaging analysis of corn kernels and germinated wheat sections, and the results show that triacylglycerides were mainly distributed in the embryo of corn kernels and germinated wheat, and sugars were mainly distributed in the endosperm, with the highest content of disaccharides.It provides a simple and reliable experimental condition for analyzing the distribution of oligosaccharide and lipid components in plant tissues.

Metabolomics-centered mining of plant metabolic diversity and function: Past decade and future perspectives

Plants are natural experts in organic synthesis, being able to generate large numbers of specific metabolites with widely varying structures that help them adapt to variable survival challenges. Metabolomics is a research discipline that integrates the capabilities of several types of research including analytical chemistry, statistics, and biochemistry. Its ongoing development provides strategies for gaining a systematic understanding of quantitative changes in the levels of metabolites. Metabolomics is usually performed by targeting either a specific cell, a specific tissue, or the entire organism. Considerable advances in science and technology over the last three decades have propelled us into the era of multi-omics, in which metabolomics, despite at an earlier developmental stage than genomics, transcriptomics, and proteomics, offers the distinct advantage of studying the cellular entities that have the greatest influence on end phenotype. Here, we summarize the state of the art of metabolite detection and identification, and illustrate these techniques with four case study applications: (i) comparing metabolite composition within and between species, (ii) assessing spatio-temporal metabolic changes during plant development, (iii) mining characteristic metabolites of plants in different ecological environments and upon exposure to various stresses, and (iv) assessing the performance of metabolomics as a means of functional gene identification , metabolic pathway elucidation, and metabolomics-assisted breeding through analyzing plant populations with diverse genetic variations. In addition, we highlight the prominent contributions of joint analyses of plant metabolomics and other omics datasets, including those from genomics, transcriptomics, proteomics, epigenomics, phenomics, microbiomes, and ion-omics studies. Finally, we discuss future directions and challenges exploiting metabolomics-centered approaches in understanding plant metabolic diversity.

Study on the spatial distribution of coumarins in Angelica dahurica root by MALDI-TOF-MSI

INTRODUCTION

The main chemical components of Angelica dahurica (Hoffm.) Benth. & Hook.f. ex Franch. & Sav. are coumarins and volatile oils, and coumarins are regarded as the representative constituents with various pharmacological effects.

OBJECTIVE

Based on matrix-assisted laser desorption/ionization time of flight mass spectrometry imaging (MALDI-TOF-MSI), a method for spatial distribution analysis of coumarins in primary root and lateral root of A. dahurica was established. Also, spatial visualization of coumarins in the roots of A. dahurica was realized.

MATERIALS AND METHODS

α-Cyano-4-hydroxycinnamic acid (CHCA), 2,5-dihydroxybenzoic acid, and 9-aminoacridine were used as matrices. MALDI-TOF-MSI was employed to analyze the standards of imperatorin, oxypeucedanin, and osthole. Based on the higher sensitivity and repeatability of MALDI-TOF-MSI, the CHCA matrix was selected. The matrix was used for MALDI-TOF-MSI in positive mode to analyze the distribution of coumarins in primary root and lateral root of A. dahurica.

RESULTS

In total, 37 coumarins were detected in primary root and 36 coumarins were detected in lateral root by MALDI-TOF-MSI. The results showed that the coumarin content in primary root was higher than that in lateral root. Coumarins in primary root of A. dahurica were concentrated in the periderm, cortex, and phloem, whereas coumarins in lateral roots were concentrated in the phloem.

CONCLUSION

The coumarins in primary root and lateral root of A. dahurica were directly analyzed without extraction and isolation, and the spatial distribution of coumarins was comprehensively visualized for the first time by MALDI-TOF-MSI, which provided a basis for distinguishing primary root and lateral root.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

Imaging tools for plant nanobiotechnology

The successful application of nanobiotechnology in biomedicine has greatly changed the traditional way of diagnosis and treating of disease, and is promising for revolutionizing the traditional plant nanobiotechnology. Over the past few years, nanobiotechnology has increasingly expanded into plant research area. Nanomaterials can be designed as vectors for targeted delivery and controlled release of fertilizers, pesticides, herbicides, nucleotides, proteins, etc. Interestingly, nanomaterials with unique physical and chemical properties can directly affect plant growth and development; improve plant resistance to disease and stress; design as sensors in plant biology; and even be used for plant genetic engineering. Similarly, there have been concerns about the potential biological toxicity of nanomaterials. Selecting appropriate characterization methods will help understand how nanomaterials interact with plants and promote advances in plant nanobiotechnology. However, there are relatively few reviews of tools for characterizing nanomaterials in plant nanobiotechnology. In this review, we present relevant imaging tools that have been used in plant nanobiotechnology to monitor nanomaterial migration, interaction with and internalization into plants at three-dimensional lengths. Including: 1) Migration of nanomaterial into plant organs 2) Penetration of nanomaterial into plant tissues (iii)Internalization of nanomaterials by plant cells and interactions with plant subcellular structures. We compare the advantages and disadvantages of current characterization tools and propose future optimal characterization methods for plant nanobiotechnology.

Mass spectrometry imaging: new eyes on natural products for drug research and development

Natural products (NPs) and their structural analogs represent a major source of novel drug development for disease prevention and treatment. The development of new drugs from NPs includes two crucial aspects. One is the discovery of NPs from medicinal plants/microorganisms, and the other is the evaluation of the NPs in vivo at various physiological and pathological states. The heterogeneous spatial distribution of NPs in medicinal plants/microorganisms or in vivo can provide valuable information for drug development. However, few molecular imaging technologies can detect thousands of compounds simultaneously on a label-free basis. Over the last two decades, mass spectrometry imaging (MSI) methods have progressively improved and diversified, thereby allowing for the development of various applications of NPs in plants/microorganisms and in vivo NP research. Because MSI allows for the spatial mapping of the production and distribution of numerous molecules in situ without labeling, it provides a visualization tool for NP research. Therefore, we have focused this mini-review on summarizing the applications of MSI technology in discovering NPs from medicinal plants and evaluating NPs in preclinical studies from the perspective of new drug research and development (R&D). Additionally, we briefly reviewed the factors that should be carefully considered to obtain the desired MSI results. Finally, the future development of MSI in new drug R&D is proposed.

A mass spectrometry imaging approach on spatiotemporal distribution of multiple alkaloids in Gelsemium elegans

Gelsemium elegans contains multiple alkaloids with pharmacological effects, thus researchers focus on the identification and application of alkaloids extracted from G. elegans. Regretfully, the spatiotemporal distribution of alkaloids in G. elegans is still unclear. In this study, the desorption electrospray ionization mass spectrometry imaging (DESI-MSI) was applied to simultaneously analyze the distribution of pharmacologically important alkaloids in different organ/tissue sections of G. elegans at different growth stages. Finally, 23 alkaloids were visualized in roots, stems and leaves at seedling stage and 19 alkaloids were observed at mature stage. In mature G. elegans, 16 alkaloids were distributed in vascular bundle region of mature roots, 15 alkaloids were mainly located in the pith region of mature stems and 2 alkaloids were enriched in epidermis region of mature stems. A total of 16 alkaloids were detected in leaf veins of mature leaves and 17 alkaloids were detected in shoots. Interestingly, diffusion and transfer of multiple alkaloids in tissues have been observed along with the development and maturation. This study comprehensively characterized the spatial metabolomics of G. elegans alkaloids, and the spatiotemporal distribution of alkaloid synthesis. In addition, the results also have reference value for the development and application of Gelsemium elegans and other medicinal plants.

Genome-wide transcriptome analysis reveals the regulatory network governing terpene trilactones biosynthesis in Ginkgo biloba

Ginkgo biloba L. is currently the only remaining gymnosperm of the Ginkgoaceae Ginkgo genus, and its history can be traced back to the Carboniferous 200 million years ago. Terpene trilactones (TTLs) are one of the main active ingredients in G. biloba, including ginkgolides and bilobalide. They have a good curative effect on cardiovascular and cerebrovascular diseases because of their special antagonistic effect on platelet-activating factors. Therefore, it is necessary to deeply mine genes related to TTLs and to analyze their transcriptional regulation mechanism, which will hold vitally important scientific and practical significance for quality improvement and regulation of G. biloba. In this study, we performed RNA-Seq on the root, stem, immature leaf, mature leaf, microstrobilus, ovulate strobilus, immature fruit and mature fruit of G. biloba. The TTL regulatory network of G. biloba in different organs was revealed by different transcriptomic analysis strategies. Weighted gene co-expression network analysis (WGCNA) revealed that the five modules were closely correlated with organs. The 12 transcription factors, 5 structural genes and 24 Cytochrome P450 (CYP450) were identified as candidate regulators for TTL accumulation by WGCNA and cytoscape visualization. Finally, 6 APETALA2/ethylene response factors, 2 CYP450s and bHLH were inferred to regulate the metabolism of TTLs by correlation analysis. This study is the comprehensive in authenticating transcription factors, structural genes and CYP450 involved in TTL biosynthesis, thereby providing molecular evidence for revealing the comprehensive regulatory network involved in TTL metabolism in G. biloba.

Enhanced Coverage and Sensitivity of Imprint DESI Mass Spectrometry Imaging for Plant Leaf Metabolites by Post-photoionization

Plant metabolites exhibit a variety of different chemical properties, physiological activities, and biological functions. However, untargeted imaging of highly diverse metabolic profiles is still a great challenge. Here, metabolites in plant leaves were imaged via imprint, followed by desorption electrospray ionization/post-photoionization (imprint DESI/PI) mass spectrometry imaging. In contrast to the traditional imprint DESI method, quite a few metabolites, such as terpenoids, flavonoids, glycosides, alkylphenols, amino acids, phenolic acids, tannins, and lipids, in fresh sage leaves, ginkgo leaves, and tea leaves were well detected and imaged by imprint DESI/PI. More than 80 metabolites were additionally identified, and more than 1 order of magnitude higher signal intensities were obtained for most metabolites in the negative ion mode. By virtue of the significant improvement of coverage and sensitivity of PI, the catechin biosynthesis network in fresh tea leaves could be clearly illustrated, indicating the potential applicability of imprint DESI/PI in exploring the sites and pathways of plant metabolic conversion.

Uncovering the pharmacology of Ginkgo biloba folium in the cell-type-specific targets of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease with a fast-growing prevalence. Developing disease-modifying therapies for PD remains an enormous challenge. Current drug treatment will lose efficacy and bring about severe side effects as the disease progresses. Extracts from Ginkgo biloba folium (GBE) have been shown neuroprotective in PD models. However, the complex GBE extracts intertwingled with complicated PD targets hinder further drug development. In this study, we have pioneered using single-nuclei RNA sequencing data in network pharmacology analysis. Furthermore, high-throughput screening for potent drug-target interaction (DTI) was conducted with a deep learning algorithm, DeepPurpose. The strongest DTIs between ginkgolides and MAPK14 were further validated by molecular docking. This work should help advance the network pharmacology analysis procedure to tackle the limitation of conventional research. Meanwhile, these results should contribute to a better understanding of the complicated mechanisms of GBE in treating PD and lay the theoretical ground for future drug development in PD.

On-tissue derivatization for isomer-specific mass spectrometry imaging and relative quantification of monosaccharides in biological tissues

Spatially-resolved profiling of tissue monosaccharides not only gives an insight into the spatial heterogeneity of monosaccharides, but also helps to decipher the possible roles of monosaccharides in biological processes. Here, we develop an on-tissue derivatization method, coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to image and quantify the aldose and ketose isomers of monosaccharide in biological tissues. A new derivatization reagent, 1-naphthaleneacethydrazide (NAH) was synthesized for the on-tissue derivatization of monosaccharides, and it significantly enhanced the imaging sensitivity of monosaccharides. Moreover, the NAH-derivatized aldose and ketose can generate isomer-specific diagnostic ions during MALDI-MS/MS analysis, and thus paves way for the isomer-specific MS imaging of aldose and ketose monosaccharides. On this basis, we further constructed a quantitative MALDI-MS imaging model based on isomer-specific diagnostic ions, and calculated the expression contents of aldose and ketose monosaccharide isomers in different tissue regions of carrot section. We expect that the development of this method should provide more precise view on the spatial distributions and contents of different monosaccharides in heterogeneous biological tissues.

Recent advances in proteomics and metabolomics in plants

Over the past decade, systems biology and plant-omics have increasingly become the main stream in plant biology research. New developments in mass spectrometry and bioinformatics tools, and methodological schema to integrate multi-omics data have leveraged recent advances in proteomics and metabolomics. These progresses are driving a rapid evolution in the field of plant research, greatly facilitating our understanding of the mechanistic aspects of plant metabolisms and the interactions of plants with their external environment. Here, we review the recent progresses in MS-based proteomics and metabolomics tools and workflows with a special focus on their applications to plant biology research using several case studies related to mechanistic understanding of stress response, gene/protein function characterization, metabolic and signaling pathways exploration, and natural product discovery. We also present a projection concerning future perspectives in MS-based proteomics and metabolomics development including their applications to and challenges for system biology. This review is intended to provide readers with an overview of how advanced MS technology, and integrated application of proteomics and metabolomics can be used to advance plant system biology research.

Mass Spectrometry Imaging for Spatial Chemical Profiling of Vegetative Parts of Plants

The detection of chemical species and understanding their respective localisations in tissues have important implications in plant science. The conventional methods for imaging spatial localisation of chemical species are often restricted by the number of species that can be identified and is mostly done in a targeted manner. Mass spectrometry imaging combines the ability of traditional mass spectrometry to detect numerous chemical species in a sample with their spatial localisation information by analysing the specimen in a 2D manner. This article details the popular mass spectrometry imaging methodologies which are widely pursued along with their respective sample preparation and the data analysis methods that are commonly used. We also review the advancements through the years in the usage of the technique for the spatial profiling of endogenous metabolites, detection of xenobiotic agrochemicals and disease detection in plants. As an actively pursued area of research, we also address the hurdles in the analysis of plant tissues, the future scopes and an integrated approach to analyse samples combining different mass spectrometry imaging methods to obtain the most information from a sample of interest.

Research Progress and Trends in Metabolomics of Fruit Trees

Metabolomics is an indispensable part of modern systems biotechnology, applied in the diseases' diagnosis, pharmacological mechanism, and quality monitoring of crops, vegetables, fruits, etc. Metabolomics of fruit trees has developed rapidly in recent years, and many important research results have been achieved in combination with transcriptomics, genomics, proteomics, quantitative trait locus (QTL), and genome-wide association study (GWAS). These research results mainly focus on the mechanism of fruit quality formation, metabolite markers of special quality or physiological period, the mechanism of fruit tree's response to biotic/abiotic stress and environment, and the genetics mechanism of fruit trait. According to different experimental purposes, different metabolomic strategies could be selected, such as targeted metabolomics, non-targeted metabolomics, pseudo-targeted metabolomics, and widely targeted metabolomics. This article presents metabolomics strategies, key techniques in metabolomics, main applications in fruit trees, and prospects for the future. With the improvement of instruments, analysis platforms, and metabolite databases and decrease in the cost of the experiment, metabolomics will prompt the fruit tree research to achieve more breakthrough results.

The application of mass spectrometry imaging in traditional Chinese medicine: a review

Mass spectrometry imaging is a frontier technique which connects classical mass spectrometry with ion imaging. Various types of chemicals could be visualized in their native tissues using mass spectrometry imaging. Up to now, the most commonly applied mass spectrometry imaging techniques are matrix assisted laser desorption ionization mass spectrometry imaging, desorption electrospray ionization mass spectrometry imaging and secondary ion mass spectrometry imaging. This review gives an introduction to the principles, development and applications of commonly applied mass spectrometry imaging techniques, and then illustrates the application of mass spectrometry imaging in the investigation of traditional Chinese medicine. Recently, mass spectrometry imaging has been adopted to explore the spatial distribution of endogenous metabolites in traditional Chinese medicine. Data collected from mass spectrometry imaging can be further utilized to search for marker components of traditional Chinese medicine, discover new compounds from traditional herbs, and differentiate between medicinal plants that are similar in botanical features. Moreover, mass spectrometry imaging also plays a role in revealing the pharmacological and toxicological mechanisms of traditional Chinese medicine.

Submicron 3,4-dihydroxybenzoic acid–TiO2 composite particles for enhanced MALDI MS imaging of secondary metabolites in the root of differently aged baical skullcap

This work provides a high-efficient organic-inorganic hybrid matrix for MALDI MSI of secondary metabolites in plant tissues.

Nanoscale Three-Dimensional Imaging of Drug Distributions in Single Cells via Laser Desorption Post-Ionization Mass Spectrometry

Exploring the three-dimensional (3D) drug distribution within a single cell at nanoscale resolution with mass spectrometry imaging (MSI) techniques is crucial in cellular biology, yet it remains a great challenge due to limited lateral resolution, detection sensitivities, and reconstruction problems. Herein, a microlensed fiber laser desorption post-ionization time-of-flight mass spectrometer (MLF-LDPI-TOFMS) was developed for the 3D imaging of two anticancer drugs within single cells at a 500 × 500 × 500 nm³ voxel resolution. Nanoscale desorption was obtained with a microlensed fiber (MLF), and a 157 nm post-ionization laser was introduced to enhance the ionization yield. Furthermore, a new type of alignment method for 3D reconstruction was developed on the basis of our embedded uniform circular polystyrene microspheres (PMs). Our findings demonstrate that this 3D imaging technique has the potential to provide information about the 3D distributions of specific molecules at the nanoscale level.

Visualizing the spatial distribution of metabolites in Clausena lansium (Lour.) skeels using matrix-assisted laser desorption/ionization mass spectrometry imaging

Clausena lansium (Lour.) Skeels (Rutaceae) is a natural bioactive plant. Its roots, stems, leaves, and seeds are widely used in Chinese traditional and folk medicine. Although the characterization and functional analysis of bioactive components in Clausena lansium (Lour.) Skeels has been widely reported, the spatial distribution of these compounds within the main plant tissues remains undefined. Here, we adopted matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) to reveal the spatial distribution of active alkaloids, coumarins, sugars and organic acids in C. lansium. Using a combined wet and dry matrix covering method to enhance sensitivity, we detected alkaloids throughout the fruit including 3-methylcarbazole and murrastinine which were especially rich in the kernel tissues but were restricted to the stem xylem and medulla and in the leaf epidermal region. Interestingly, murrayanine and heptaphylline were mainly found in pulp tissues with very low content in the stems and leaves while girinimbine was only distributed within the outer kernel skin. Coumarins were mainly distributed in the fruit pericarp and leaf vein tissues but with no clear spatial specificity in stems. Lastly, hexoses were mainly evident in the fruit pulp, although sucrose was also found in the pericarp, pulp, and pulp fibers with citric acid being distributed throughout the fruit. The accurate spatial and chemical information obtained provides new insights into the specific accumulation of metabolites in individual tissues.

Visualizing the distributions and spatiotemporal changes of metabolites in Panax notoginseng by MALDI mass spectrometry imaging

Background

Panax notoginseng is a highly valued medicinal herb used widely in China and many Asian countries. Its root and rhizome have long been used for the treatment of cardiovascular and hematological diseases. Imaging the spatial distributions and dynamics of metabolites in heterogeneous plant tissues is significant for characterizing the metabolic networks of Panax notoginseng, and this will also provide a highly informative approach to understand the complex molecular changes in the processing of Panax notoginseng.

Methods

Here, a high-sensitive MALDI-MS imaging method was developed and adopted to visualize the spatial distributions and spatiotemporal changes of metabolites in different botanical parts of Panax notoginseng.

Results

A wide spectrum of metabolites including notoginsenosides, ginsenosides, amino acids, dencichine, gluconic acid, and low-molecular-weight organic acids were imaged in Panax notoginseng rhizome and root tissues for the first time. Moreover, the spatiotemporal alterations of metabolites during the steaming of Panax notoginseng root were also characterized in this study. And, a series of metabolites such as dencichine, arginine and glutamine that changed with the steaming of Panax notoginseng were successfully screened out and imaged.

Conclusion

These spatially-resolved metabolite data not only enhance our understanding of the Panax notoginseng metabolic networks, but also provide direct evidence that a serious of metabolic alterations occurred during the steaming of Panax notoginseng.

Visualizing the spatial distribution of endogenous molecules in wolfberry fruit at different development stages by matrix-assisted laser desorption/ionization mass spectrometry imaging

Wolfberry fruit has been attracting attention for centuries in Asian countries as a traditional herbal medicine and valuable nourishing tonic. Revealing the spatial distribution changes of important endogenous molecules during plant development is of great significance for investigating the physiological roles, nutritional and potential functional values of phytochemicals in wolfberry fruit. However, their spatial distribution information during fruit development has not been extensively explored due to the lack of efficient analytical techniques. In this work, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was performed to visualize the spatial distribution of the endogenous molecules during fruit development. From the mass spectrum imaging, the choline, betaine and citric acid were distributed evenly throughout the entire fruit at all development stages. The hexose was distributed in the endocarp and flesh tissue, while sucrose was located in the seeds. Additionally, several phenolic acids and flavonoids were accumulated in the exocarp during fruit development, which indicated that they seemingly played protective roles in wolfberry fruit growth progress against abiotic and biotic stress. From the collected data, we found that the signal intensities of citric acid were decreased, while choline, betaine, hexose and sucrose were increased with fruit development. These results indicate that MALDI-MSI may become a favorable tool for studying of the spatial distribution and effective use of endogenous molecules, which provide a simple and intuitive way for authenticity identification, classification of drug food homologous foods and further understanding the physiological roles of endogenous molecules.

Structure, synthesis, biosynthesis, and activity of the characteristic compounds from Ginkgo biloba L

Covering: 1928-2021Ginkgo biloba L. is one of the most distinctive plants to have emerged on earth and has no close living relatives. Owing to its phylogenetic divergence from other plants, G. biloba contains many compounds with unique structures that have served to broaden the chemical diversity of herbal medicine. Examples of such compounds include terpene trilactones (ginkgolides), acylated flavonol glycosides (ginkgoghrelins), biflavones (ginkgetin), ginkgotides and ginkgolic acids. The extract of G. biloba leaf is used to prevent and/or treat cardiovascular diseases, while many ginkgo-derived compounds are currently at various stages of preclinical and clinical trials worldwide. The global annual sales of G. biloba products are estimated to total US$10 billion. However, the content and purity of the active compounds isolated by traditional methods are usually low and subject to varying environmental factors, making it difficult to meet the huge demand of the international market. This highlights the need to develop new strategies for the preparation of these characteristic compounds from G. biloba. In this review, we provide a detailed description of the structures and bioactivities of these compounds and summarize the recent research on the development of strategies for the synthesis, biosynthesis, and biotechnological production of the characteristic terpenoids, flavonoids, and alkylphenols/alkylphenolic acids of G. biloba. Our aim is to provide an important point of reference for all scientists who research ginkgo-related compounds for medicinal or other purposes.

Mass spectrometry imaging for direct visualization of components in plants tissues

Mass spectrometry is considered the most informative technique for components identification and has been widely adopted in plant sciences. However, the spatial distribution of compounds in the plant, which is vital for the exploration of plant physiological mechanisms, is missed in MS analysis. In recent years, mass spectrometry imaging has brought a great breakthrough in plant analysis because it can determine both the molecular compositions and spatial distributions, which is conducive to understand functions and regulation pathways of specific components in plants. Mass spectrometry imaging analysis of plant tissue is toward high sensitivity, high spatial resolution, and even single-cell analysis. Despite many challenges and technical barriers, such as difficulties of sample pretreatment caused by morphological diversity of plant tissues, obstacles for high spatial resolution imaging, and so on, lots of researches have contributed to remarkable progress, including improvement in tissue preparation, matrix innovation, and ionization mode development. This review focuses on the advances of mass spectrometry imaging analysis of plants in the last 5 years, including commonly used ionization techniques, technical advances, and recent applications of mass spectrometry imaging in plants.

Unveiling spatial metabolome of Paeonia suffruticosa and Paeonia lactiflora roots using MALDI MS imaging

Paeonia suffruticosa (PS) and Paeonia lactiflora (PL) belong to the only genus in the family Paeoniaceae. Comparative analysis of the spatial metabolomes of PS and PL has rarely been performed. In this work, combined with multiple matrixes and dual-polarity detection, high mass resolution matrix-assisted laser desorption/ionization MS imaging (MALDI MSI) and MALDI tandem MSI were performed on the root sections of the two Paeonia species. The spatial distributions of many metabolites including monoterpene and paeonol glycosides, tannins, flavonoids, saccharides and lipids were systematically characterized. The ambiguous tissue distribution of the two isomers paeoniflorin and albiflorin were distinguished by tandem MSI using lithium salt doped 2,5-dihydroxybenzoate matrix. In addition, the major intermediates involved in the biosynthetic pathway of gallotannins were successfully localized and visualized in the root sections. High-mass resolution MALDI full-scan MSI provides comprehensive and accurate spatial distribution of metabolites. The analytical power of the technique was further tested in the tandem MSI of two isomers. The ion images of individual metabolites provide chemical and microscopic characteristics beyond morphological identification, and the detailed spatiochemical information could not only improve our understanding of the biosynthetic pathway of hydrolyzable tannins, but also ensure the safety and effectiveness of their medicinal use.

Light and CO2 Modulate the Accumulation and Localization of Phenolic Compounds in Barley Leaves

Barley (Hordeum vulgare) accumulates phenolic compounds (PhCs), which play a key role in plant defense against environmental stressors as antioxidants or UV screening compounds. The influence of light and atmospheric CO2 concentration ([CO2]) on the accumulation and localization of PhCs in barley leaves was examined for two varieties with different tolerances to oxidative stress. PhC localization was visualized in vivo using fluorescence microscopy. Close relationships were found between fluorescence-determined localization of PhCs in barley leaves and PhC content estimated using liquid chromatography coupled with mass spectroscopy detection. Light intensity had the strongest effect on the accumulation of PhCs, but the total PhC content was similar at elevated [CO2], minimizing the differences between high and low light. PhCs localized preferentially near the surfaces of leaves, but under low light, an increasing allocation of PhCs in deeper mesophyll layers was observed. The PhC profile was significantly different between barley varieties. The relatively tolerant variety accumulated significantly more hydroxycinnamic acids, indicating that these PhCs may play a more prominent role in oxidative stress prevention. Our research presents novel evidence that [CO2] modulates the accumulation of PhCs in barley leaves. Mesophyll cells, rather than epidermal cells, were most responsive to environmental stimuli in terms of PhC accumulation.