Mapping the genetic and tissular diversity of 64 phenolic compounds in Citrus species using a UPLC-MS approach

Metabolite Variations during the First Weeks of Growth of Immature Citrus sinensis and Citrus reticulata by Untargeted Liquid Chromatography-Mass Spectrometry/Mass Spectrometry Metabolomics

Immature citruses are an important resource for the pharmaceutical industry due to their high levels of metabolites with health benefits. In this study, we used untargeted liquid chromatography-mass spectrometry (LC-MS) metabolomics to investigate the changes associated with fruit size in immature citrus fruits in the first weeks of growth. Three orange cultivars (Citrus sinensis 'Navel', Citrus sinensis 'Valencia', and Citrus sinensis 'Valencia Late') and a mandarin (Citrus reticulata Blanco 'Fremont') were separated into eight fruit sizes, extracted, and analyzed. Statistical analyses revealed a distinct separation between the mandarin and the oranges based on 56 metabolites, with an additional separation between the 'Navel' orange and the 'Valencia' and 'Valencia Late' oranges based on 21 metabolites. Then, metabolites that evolved significantly with fruit size growth were identified, including 40 up-regulated and 31 down-regulated metabolites. This study provides new insights into the metabolite modifications of immature Citrus sinensis and Citrus reticulata in the first weeks of growth and emphasizes the significance of including early sampled fruits in citrus maturation studies.

Anti-staphylococcal activity of a polyphenol-rich citrus extract: synergy with β-lactams and low proficiency to induce resistance

Introduction

Antibiotic resistance represents one of the most significant threats to public health in the 21st century. Polyphenols, natural molecules with antibacterial activity produced by plants, are being considered as alternative antimicrobial strategies to manage infections caused by drug-resistant bacteria. In this study, we investigated the antibacterial activity of a polyphenol mixture extracted from citrus fruits, against both antibiotic-susceptible and resistant strains of Staphylococcus aureus and Staphylococcus epidermidis.

Methods

Broth microdilution and time-kill curve experiments were used to test the extract anti-staphylococcal activity. Cytotoxicity was assessed by the hemolysis assay. The interaction between the mixture and antibiotics was investigated by the checkerboard assay. The effect of B alone and in combination with oxacillin on the membrane potential was investigated by the 3,3'-dipropylthiadicarbocyanine iodide assay. The ability of the extract to induce the development of resistance was verified by propagating S. aureus for 10 transfers in the presence of sub-inhibitory concentrations.

Results

The citrus extract was found to be active against all Staphylococcus strains at remarkably low concentrations (0.0031 and 0.0063%), displaying rapid bactericidal effects without being toxic on erythrocytes. In particular, B was found to rapidly cause membrane depolarization. When combined with methicillin, meropenem, and oxacillin, the mixture displayed synergistic activity exclusively against methicillin-resistant strains. We additionally show that the sequential exposure of S. aureus to sub-inhibitory concentrations did not induce the development of resistance against the extract.

Discussion

Overall, these findings support the potential use of the citrus extract as promising option to manage staphylococcal infections and suggest that it may counteract the mechanism behind methicillin-resistance.

Advances in extraction and purification of citrus flavonoids

Flavonoids are the representative active substances of citrus with various biological activities and high nutritional value. In order to evaluate and utilize citrus flavonoids, isolation and purification are necessary steps. This manuscript reviewed the research advances in the extraction and purification of citrus flavonoids. The structure classification, the plant and nutritional functions, and the biosynthesis of citrus flavonoids were summarized. The characteristics of citrus flavonoids and the selection of separation strategies were explained. The technical system of extraction and purification of citrus flavonoids was systematically described. Finally, outlook and research directions were proposed.

3D-QSAR studies on the structure-bitterness analysis of citrus flavonoids

Despite their important bioactivities, the unpleasant bitter taste of citrus derived flavonoids limits their applications in the food industry, and the structure-bitterness relationship of flavonoids is still far from clear. In this study, 26 flavonoids were characterized by their bitterness threshold and their common skeleton using sensory evaluation and molecular superposition, respectively. The quantitative conformational relationship of the structure-bitterness of flavonoids was explored using 3D-QSAR based on comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA). The results showed that increases of a hydrogen bond donor at A-5 or B-3', a bulky group at A-8, or an electron-withdrawing group at B-4' would enhance the bitterness of flavonoids. The bitterness of some flavonoids was predicted and evaluated, and the results were similar to the bitter intensity of the counterparts from the 3D-QSAR and contour plots, confirming the validation of 3D-QSAR. This study explains the theory of the structure-bitterness relationship of flavonoids, by showing potential information for understanding the bitterness in citrus flavonoids and developing a debittering process.

Recent developments in citrus bioflavonoid encapsulation to reinforce controlled antioxidant delivery and generate therapeutic uses: Review

Citrus fruits contain numerous antioxidative biomolecules including phenolic acids, flavonols, flavanones, polymethoxyflavones (PMFs), and their derivatives. Previous in vitro and in vivo studies thoroughly investigated the antioxidant and therapeutic potential of bioflavonoids extracted from different citrus varieties and fruit fractions. Major bioflavonoids such as hesperidin, naringin, naringenin, and PMFs, had restricted their incorporation into food and health products due to their poor solubility, chemical stability and bioavailability. Considering these limitations, modern encapsulation methodologies such as hydrogelation, liposomal interactions, emulsifications, and nanoparticles have been designed to shield bioflavonoids with improved target distribution for therapeutic enhancements. The size, durability, and binding efficiency of bioflavonoid-loaded encapsulates were acquired by the optimized chemical and instrumental parameters such as solubility, gelation, dispersion, extrusion, and drying. Bioflavonoid-enriched encapsulates have been also proven to be effective against cancer, inflammation, neurodegeneration, and various other illnesses. However, in the future, newer natural binding agents with higher binding capacity might accelerate the encapsulating potential, controlled release, and enhanced bioavailability of citrus bioflavonoids. Overall, these modern encapsulation systems are currently leading to a new era of diet-based medicine, as demand for citrus fruit-based nutritional supplements and edibles grows.

Amino acid, sugar, phenolic, and terpenoid profiles are capable of distinguishing Citrus tristeza virus infection status in citrus cultivars: Grapefruit, lemon, mandarin, and sweet orange

Citrus tristeza virus (CTV) is the most severe viral disease for citrus production. Many strains of CTV have been characterized and their symptomology widely varies, ranging from asymptomatic or mild infections to severe symptomology that results in substantial yield loss or host death. The capacity of the different CTV strains to affect the biochemistry of different citrus species has remained largely unstudied, despite that associated metabolomic shifts would be relevant toward symptom development. Thus, amino acid, sugar, phenolic, and terpenoid levels were assessed in leaves of healthy and CTV-infected grapefruit, lemon, mandarin, and two different sweet orange cultivars. Both mild [VT-negative (VT-)] and severe [VT-positive (VT+)] CTV genotype strains were utilized. When looking at overall totals of these metabolite classes, only amino acid levels were significantly increased by infection of citrus with severe CTV strains, relative to mild CTV strains or healthy plants. No significant trends of CTV infection on summed amounts of all sugar, phenolic, or terpenoid compounds were observed. However, individual compound levels were affected by CTV infections. Subsequent canonical discriminant analysis (CDA) that utilized profiles of individual amino acids, terpenoids, or phenolics successfully distinguished leaf samples to specific citrus varieties and identified infection status with good accuracy. Collectively, this study reveals biochemical patterns associated with severity of CTV infections that can potentially be utilized to help identify in-field CTV infections of economic relevance.

Optimization of Naringin and Naringenin Extraction from Citrus × paradisi L. Using Hydrolysis and Excipients as Adsorbent

While flavanones exist in a variety of chemical forms, their favorable health effects are most prominent in their free form—aglycones. Their concentrations in grapefruit (Citrus × paradisi L.) extracts vary according to the extraction and hydrolysis methods used. The primary aim of this work was to maximize the yields of naringin and naringenin from various parts of fresh grapefruit fruits (flavedo, albedo, and segmental) using different extraction and hydrolysis methods. In addition, we aimed to evaluate the excipient—magnesium aluminometasilicate—and determine its influence on the qualitative composition of grapefruit extracts. Extracts were obtained by heat reflux extraction (HRE), ultrasound-assisted extraction with an ultrasonic homogenizer (UAE*), and ultrasound-assisted extraction with a bath (UAE). Ultrasound-assisted extraction using a bath (UAE) was modulated using acidic, thermal, and alkaline hydrolysis. The highest yield of naringin 8A (17.45 ± 0.872 mg/g) was obtained from an albedo sample under optimal conditions using ultrasound-assisted extraction; a high yield of naringenin 23-SHR (35.80 ± 1.79 µg/g) was produced using the heat reflux method from the segmental part. Meanwhile, ultrasonic combined with thermal hydrolysis significantly increased flavanone extraction from the albedo and segmental parts: naringin from sample 9-A (from 17.45 ± 0.872 mg/g to 25.05 ± 1.25 mg/g) and naringenin from sample 15-S (from 0 to 4.21 ± 0.55 µg/g). Additionally, magnesium aluminometasilicate demonstrated significant increases of naringenin from all treated grapefruit parts. To our knowledge, this is the first report of magnesium aluminometasilicate used as an adsorbent in flavanone extractions.

Parallel evolution of UbiA superfamily proteins into aromatic O-prenyltransferases in plants

Plants produce ∼300 aromatic compounds enzymatically linked to prenyl side chains via C-O bonds. These O-prenylated aromatic compounds have been found in taxonomically distant plant taxa, with some of them being beneficial or detrimental to human health. Although their O-prenyl moieties often play crucial roles in the biological activities of these compounds, no plant gene encoding an aromatic O-prenyltransferase (O-PT) has been isolated to date. This study describes the isolation of an aromatic O-PT gene, CpPT1, belonging to the UbiA superfamily, from grapefruit (Citrus × paradisi, Rutaceae). This gene was shown responsible for the biosynthesis of O-prenylated coumarin derivatives that alter drug pharmacokinetics in the human body. Another coumarin O-PT gene encoding a protein of the same family was identified in Angelica keiskei, an apiaceous medicinal plant containing pharmaceutically active O-prenylated coumarins. Phylogenetic analysis of these O-PTs suggested that aromatic O-prenylation activity evolved independently from the same ancestral gene in these distant plant taxa. These findings shed light on understanding the evolution of plant secondary (specialized) metabolites via the UbiA superfamily.

Comparative profiling and natural variation of polymethoxylated flavones in various citrus germplasms

Citrus fruits are the main dietary source of polymethoxylated flavones (PMFs) with significant effects on consumer health. In this study, eleven main PMFs were evaluated in the fruit flavedo or leaves of 116 citrus accessions via UPLC-DAD-ESI-QTOF-MS/MS combined with HPLC-DAD analysis, which revealed significant species-specific and spatiotemporal characteristics. All Citrus reticulata and their natural or artificial hybrids were found to have detectable PMFs, especially in the fruit flavedo of the wild or early-cultivated mandarins at early fruit development stages. However, PMFs were not detected in citrons, pummelos, kumquats, trifoliata oranges, papedas, Chinese box oranges and 'Mangshanyegan'. The results enlightened that PMF accumulation only in mandarins and mandarin hybrids is a phenotype inherited from mandarin ancestors. This study provides a comprehensive PMF profile in various citrus germplasms and will benefit future functional citrus breeding practices aimed at designing plants rich in total or specific PMFs for health benefits.

Multiomics-based dissection of citrus flavonoid metabolism using a Citrus reticulata × Poncirus trifoliata population

Deciphering the genetic basis of plant secondary metabolism will provide useful insights for genetic improvement and enhance our fundamental understanding of plant biological processes. Although citrus plants are among the most important fruit crops worldwide, the genetic basis of secondary metabolism in these plants is largely unknown. Here, we use a high-density linkage map to dissect large-scale flavonoid metabolic traits measured in different tissues (young leaf, old leaf, mature pericarp, and mature pulp) of an F₁ pseudo-testcross citrus population. We detected 80 flavonoids in this population and identified 138 quantitative trait loci (QTLs) for 57 flavonoids in these four tissues. Based on transcriptional profiling and functional annotation, twenty-one candidate genes were identified, and one gene encoding flavanone 3-hydroxylase (F3H) was functionally verified to result in naturally occurring variation in dihydrokaempferol content through genetic variations in its promoter and coding regions. The abundant data resources collected for diverse citrus germplasms here lay the foundation for complete characterization of the citrus flavonoid biosynthetic pathway and will thereby promote efficient utilization of metabolites in citrus quality improvement.

Diversification and selection pattern of CYP6B genes in Japanese Papilio butterflies and their association with host plant spectra

Herbivorous insects are thought to have evolved counteradaptations to conquer chemical defenses in their host plants in a stepwise co-evolutionary process. Papilio butterflies use CYP6B gene family members to metabolize furanocoumarins in their Rutaceae or Apiaceae host plants. CYP6Bs have functionally diverged among Papilio species to be able to metabolite diverse types of furanocoumarins in their host plants. In this study, we examined the diversification and selection patterns of CYP6B among nine Papilio species in Japan (eight Rutaceae specialists and one Apiaceae specialist) and their association with host plant spectra and furanocoumarin profiles. We compared host plant spectrum of eight Rutaceae feeding Papilio species and also performed a furanocoumarin profiling of their host plants. In addition, we reconstructed CYP6B gene phylogeny and performed selection analysis based on the transcriptome data of those nine Papilio species. Among Rutaceae-feeding Papilio species, host plant spectrum differences were correlated with their furanocoumarin profiles. However, all tested Papilio species had similar duplicated sets of CYP6B, with no apparent lineage-specific or host plant-specific pattern of CYP6B diversification. Selection analysis showed a signature of positive selection on a CYP6B branch. The positively selected sites located at predicted substrate recognition sites and we also found that these CYP6B genes were observed only in Rutaceae-feeding species. These findings indicate that most CYP6B diversification occurred in ancestral species of these Papilio species, possibly in association with specific host plant chemical defenses and subsequent gene loss due to host specialization. These processes would have shaped the complex diversification patterns of the CYP6B gene family in Papilio butterflies. Our results also show potentially important CYP6B clades among Papilio species which likely to have diverged functions and associated with host plant phytochemicals in ancestral Papilio species.

Role of Oak Coumarins in the Taste of Wines and Spirits: Identification, Quantitation, and Sensory Contribution through Perceptive Interactions

During barrel aging, wines and spirits undergo sensory changes as a result of the release of aroma and taste molecules. Among the nonvolatile compounds, various coumarins have already been identified in oak wood but their sensory role remained unclear. In this study, the presence of coumarins in oak wood extract, wine, and spirits was first assessed by targeted screening. Fraxetin was identified for the first time in these matrices. After development and validation of a liquid chromatography-high-resolution mass spectrometry quantitation method, esculetin, scopoletin, fraxetin, umbelliferone, 4-methylumbelliferone, and coumarin were assayed in various wines and spirits. The concentrations measured were generally below the gustatory detection thresholds determined in wines and spirits. Nevertheless, by adding a mixture of coumarins in wines and spirits, a significant increase in bitterness was observed, thus demonstrating their potential contribution to the taste of wines and spirits through perceptive interactions.

Profiling of Flavonoid and Antioxidant Activity of Fruit Tissues from 27 Chinese Local Citrus Cultivars

Flavonoid profile and antioxidant activity of citrus peels, pulps, and juices from 27 local citrus cultivars in China were investigated. Flavonoid composition and content were determined using UPLC-PDA. Total phenolic content (TPC) and total flavonoid content (TFC) were measured using a Folin-Ciocalteau reagent and Al(NO3)-NaNO2 complexometry, respectively. The antioxidant capacities of the extracts were evaluated by DPPH, ABTS and FRAP method, respectively. Citrus peel not only exhibited better antioxidant potential, but also presented more composition diversity and contained higher concentrations of flavonoids than pulp and juice. Different citrus species were characterized by their individual predominant flavonoids, contributing largely to the antioxidant activity, such as mandarin was characterized by hesperidin, nobiletin and tangeretin, while pummelo and papeda were characterized by naringin. The peel of Guihuadinanfeng (Citrus reticulata) had the highest TPC of 23.46 mg equivalent gallic acid/g DW (dry weight) and TFC of 21.37 mg equivalent rutin/g DW. Shiyueju (C. reticulata) peel showed the highest antioxidant capacity based on the antioxidant potency composite (APC) analysis. Overall, mandarin (C. reticulata) fruits peel contained more TPC and TFC, exhibiting higher antioxidant capacities than other species, and were good natural sources of flavonoids and antioxidants.

Evolution of phytochemical diversity in Pilocarpus (Rutaceae)

The evolution of phytochemical diversity and biosynthetic pathways in plants can be evaluated from a phylogenetic and environmental perspective. Pilocarpus Vahl (Rutaceae), an economically important medicinal plant in the family Rutaceae, has a great diversity of imidazole alkaloids and coumarins. In this study, we used phylogenetic comparative methods to determine whether there is a phylogenetic signal for chemical traits across the genus Pilocarpus; this included ancestral reconstructions of continuous and discrete chemical traits. Bioclimatic variables found to be associated with the distribution of this genus were used to perform OLS regressions between chemical traits and bioclimatic variables. Next, these regression models were evaluated to test whether bioclimatic traits could significantly predict compound concentrations. Our study found that in terms of compound concentration, variation is most significantly associated with adaptive environmental convergence rather than phylogenetic relationships. The best predictive model of chemical traits was the OLS regression that modeled the relationship between coumarin and precipitation in the coldest quarter. However, we also found one chemical trait was dependent on phylogenetic history and bioclimatic factors. These findings emphasize that consideration of both environmental and phylogenetic factors is essential to tease out the intricate processes in the evolution of chemical diversity in plants. These methods can benefit fields such as conservation management, ecology, and evolutionary biology.

Characterisation and classification of Citri Reticulatae Pericarpium varieties based on UHPLC-Q-TOF-MS/MS combined with multivariate statistical analyses

INTRODUCTION

Citri Reticulatae Pericarpium (CRP), comprising dried pericarps of Citrus reticulata Blanco and its cultivars, is popularly used for its great medicinal and dietary values. Generally, the pericarps from C. reticulate "Chachi" ("Guangchenpi" in Chinese, GCP) is considered to have superior qualities and merit premium price compared with CRP derived from other cultivars (collectively called "Chenpi" in Chinese, CP). Since its multiple origins and derived economic adulteration, it is significant to systematically compare the chemical profiles of different CRP varieties.

OBJECTIVE

The main objective of this work was to identify the chemical profiles of CRP from different varieties and find out potential chemical markers for differentiating GCP and CP.

METHODS

In the present study, a total of 42 CRP samples from 10 varieties (including GCP and CP) were analysed by ultra-high performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS) for chemical profiling. Obtained MS/MS data were further employed in multivariate statistical methods to screen the main compounds which contributed to the characterisation and classification of CRP.

RESULTS

As a result, 73 compounds (mainly flavonoids) were identified or tentatively characterised in these CRP samples. Based on the obtained chemical profiles data, GCP and CP samples could be easily discriminated from each other by statistical analyses. Moreover, seven compounds were selected as having the most discriminating features which contributed to the classification of CRP.

CONCLUSION

This work obtains a better understanding of the chemical profiles of different CRP varieties and provides a practical strategy for the authentication of GCP and CP.

Development of a sensitive monoclonal antibody-based indirect competitive enzyme-linked immunosorbent assay for analysing nobiletin in citrus and herb samples

Nobiletin, a polymethoxyflavone mainly found in citrus fruits, have been reported to exhibit various beneficial biological activities for human health. It is an important bioactive compound in traditional Chinese medicine, Pericarpium Citri Reticulatae and Fructus Aurantii. To detect the contents of nobiletin in citrus and herb samples, we developed an indirect competitive enzyme-linked immunosorbent assay (icELISA) based on monoclonal antibodies. It possessed a median inhibition concentration (IC₅₀) of 2.43 ± 0.19 ng/mL and a working range of 0.52-12.3 ng/mL. The assay exhibited the average recoveries of 72.5-85.3% in citrus peel, pulp and juice samples. Moreover, eleven citrus cultivars samples and four herb samples were also detected by the icELISA. The nobiletin content varied in different citrus cultivars samples and herb samples, which were confirmed by the ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS). These results indicated that the developed immunoassay was suitable for detecting nobiletin in citrus and herb samples.

Developmental Stage- and Genotype-Dependent Regulation of Specialized Metabolite Accumulation in Fruit Tissues of Different Citrus Varieties

Flavor traits in citrus are the result of a blend of low molecular weight metabolites including sugars, acids, flavonoids and limonoids, these latter being mainly responsible for the characteristic bitter flavor in citrus. In this work, the genotype- and developmental stage-dependent accumulation of flavonoids and limonoids is addressed. To fulfill this goal, three models for citrus bitterness: bitter Duncan grapefruit, bittersweet Thomson orange and sweet Wase mandarin were selected from a total of eight different varieties. Compounds were annotated from LC/ESI-QqTOF-MS non-targeted metabolite profiles from albedo and pulp tissues. Results indicated that the specific blend of compounds providing the characteristic flavor trait is genotype-specific and hence under genetic control, but it is also regulated at the developmental level. Metabolite profiles in albedo mirrored those found in pulp, the edible part of the fruit, despite differences in the concentration and accumulation/depletion rates being found. This is particularly relevant for polymethoxylated flavones and glycosylated limonoids that showed a clear partitioning towards albedo and pulp tissues, respectively. Fruit ripening was characterized by a reduction in flavonoids and the accumulation of limonoid glycosides. However, bitter grapefruit showed higher levels of limonin A-ring lactone and naringin in contrast to sweeter orange and mandarin. Data indicated that the accumulation profile was compound class-specific and conserved among the studied varieties despite differing in the respective accumulation and/or depletion rate, leading to different specialized metabolite concentration at the full ripe stage, consistent with the flavor trait output.

Ecometabolomic Analysis of Wild Populations of Pilocarpus pennatifolius (Rutaceae) Using Unimodal Analyses

Studies examining the diversity of plant specialized metabolites suggest that biotic and abiotic pressures greatly influence the qualitative and quantitative diversity found in a species. Large geographic distributions expose a species to a great variety of environmental pressures, thus providing an enormous opportunity for expression of environmental plasticity. Pilocarpus, a neotropical genus of Rutaceae, is rich in alkaloids, terpenoids, and coumarins, and is the only commercial source of the alkaloid pilocarpine for the treatment of glaucoma. Overharvesting of species in this genus for pilocarpine, has threatened natural populations of the species. The aim of this research was to understand how adaptation to environmental variation shapes the metabolome in multiple populations of the widespread species Pilocarpus pennatifolius. LCMS data from alkaloid and phenolic extracts of leaf tissue were analyzed with environmental predictors using unimodal unconstrained and constrained ordination methods for an untargeted metabolomics analysis. PLS-DA was used to further confirm the chemoecotypes of each site. The most important variables contributing to the alkaloid variation between the sites: mean temperature of wettest quarter, as well as the soil content of phosphorus, magnesium, and base saturation (V%). The most important contributing to the phenolic variation between the sites: mean temperature of the wettest quarter, temperature seasonality, calcium and soil electrical conductivity. This research will have broad implications in a variety of areas including biocontrol for pests, environmental and ecological plant physiology, and strategies for species conservation maximizing phytochemical diversity.

A new approach to examining the extraction process of Zhishi and Zhiqiao considering the synergistic effect of complex mixtures by PAMPA

Zhishi (ZS) and Zhiqiao (ZQ) are two important traditional Chinese medicines (TCMs) that exert various pharmacological functions due to their active ingredients. However, the oral absorption of these ingredients requires further study. At the early drug discovery stage, the high-throughput parallel artificial membrane permeability assay (PAMPA) is one of the most frequently used to predict transcellular passive absorption in in-vitro models. This study aims to establish a new approach to examine an optimal extraction process that can take into account not only the concentration of active ingredients but also the overall absorption properties of the mixtures extracted from TCMs. A high-performance liquid chromatography triple-quadrupole mass spectrometry (HPLC-QqQ-MS/MS) method was validated for the determination of the effective permeability value (P_e) applied to the above experimental medium. The PAMPA experiment showed that certain active ingredients such as diosmin, rhoifolin, eriocitrin, narirutin, naringin, hesperidin and neohesperidin were not detected in the permeability assay of mono-constituents but were well detected and achieved a better absorption in the permeability assay of the mixture, indicating that certain unknown ingredients may act as cosolvents to improve the solubility or permeability of other ingredients. Furthermore, solid phase extraction (SPE) as an enrichment and purification process enhances absorption. In the present study, a novel in vitro approach was developed to decipher the potential role of TCMs in global absorption, and the extraction process for complex TCMs was described and systematically optimized.

Chemical Profiles and Simultaneous Quantification of Aurantii fructus by Use of HPLC-Q-TOF-MS Combined with GC-MS and HPLC Methods

Aurantii fructus (AF) is a traditional Chinese medicine that has been used to improve gastrointestinal motility disorders for over a thousand years, but there is no exhaustive identification of the basic chemical components and comprehensive quality control of this herb. In this study, high-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (HPLC-Q-TOF-MS) and gas chromatography coupled mass spectrometry (GC-MS) were employed to identify the basic chemical compounds, and high-performance liquid chromatography (HPLC) was developed to determine the major biochemical markers from AF extract. There were 104 compounds belonging to eight structure types, including 13 amino acids or peptides, seven alkaloids, 18 flavanones, 14 flavones, 15 polymethoxyflavonoids, six triterpenoids, nine coumarins, and 18 volatile oils, as well as four other compounds that were systematically identified as the basic components from AF, and among them, 41 compounds were reported for the first time. Twelve bioactive ingredients were chosen as the benchmark markers to evaluate the quality of AF. The analysis was completed with a gradient elution at a flow rate of 0.7 mL/min within 55 min. This efficient method was validated showing good linearity, precision, stability, repeatability and recovery. Furthermore, the method was successfully applied to the simultaneous determination of 12 chemical markers in different samples of AF. This study could be applied to the identification of multiple bioactive substances and improve the quality control of AF.

Determination of citrus juice coumarins, furanocoumarins and methoxylated flavones using solid phase extraction and HPLC with photodiode array and fluorescence detection

A synergistic combination of analytical techniques was developed for the simultaneous determination of the three most biologically active chemical families in citrus juices: methoxylated flavones, coumarins, and furanocoumarins. No rapid methodology has been available to determine them together. A solid phase extraction concentrated these groups and a ternary reverse phase HPLC gradient completely resolved them from other juice components. Two coumarins, isomeranzin and osthole, were identified in a sweet orange (C. sinensis) cultivar, Changyecheng, for the first time. Pummelo juice was characterized by coumarin and furanocoumarin epoxides such as meranzin and epoxybergamottin. No epoxides were observed in the more acidic juices. Added furanocoumarin epoxides hydrolyzed rapidly in the most acidic juices. The ratios of the UV peak areas at 320 nm to the fluorescence emission peaks as well as the ratio of fluorescence emission peaks at 450-400 nm could be used to identify chromatographic peaks.

Rapid Investigation and Screening of Bioactive Components in Simo Decoction via LC-Q-TOF-MS and UF-HPLC-MD Methods

Simo decoction (SMD), as a traditional medicine, is widely used in the treatment of gastrointestinal dysmotility in China. In this study, a combined method of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) and ultrafiltration high-performance liquid chromatography molecular docking (UF-HPLC-MD) was efficiently employed to identify and screen bioactive ingredients in SMD. Ninety-four major constituents were identified or tentatively characterized by comparing their retention times and mass spectra with standards or literature data by using LC-Q-TOF-MS, and the ascription of those compounds were classified for the first time. Among them, 13 bioactive ingredients, including norisoboldine, eriocitrin, neoeriocitrin, narirutin, hesperidin, naringin, neohesperidin, hesperitin-7-O-glucoside, linderane, poncirin, costunolide, nobiletin, and tangeretin, were primarily identified as the human serum albumin (HSA) ligands at a range of docking scores from −29.7 to −40.6 kJ/mol by UF-HPLC-MD. The results indicate the systematic identification and screening of HSA ligands from Simo decoction guided by LC-Q-TOF-MS and UF-HPLC-MD represents a feasible and efficient method that could be extended for the identification and screening of other bioactive ingredients from natural medicines.

Characterization of active antiplatelet chemical compositions of edible Citrus limon through ultra-performance liquid chromatography single quadrupole mass spectrometry-based chemometrics

UPLC-SQD-MS-based chemometrics was applied for antiplatelet active compounds screening for the first time, and seven potential biomarkers were found in lemon extract.

Chemotaxonomic Classification Applied to the Identification of Two Closely-Related Citrus TCMs Using UPLC-Q-TOF-MS-Based Metabolomics

This manuscript elaborates on the establishment of a chemotaxonomic classification strategy for closely-related Citrus fruits in Traditional Chinese Medicines (TCMs). UPLC-Q-TOF-MS-based metabolomics was applied to depict the variable chemotaxonomic markers and elucidate the metabolic mechanism of Citrus TCMs from different species and at different ripening stages. Metabolomics can capture a comprehensive analysis of small molecule metabolites and can provide a powerful approach to establish metabolic profiling, creating a bridge between genotype and phenotype. To further investigate the different metabolites in four closely-related Citrus TCMs, non-targeted metabolite profiling analysis was employed as an efficient technique to profile the primary and secondary metabolites. The results presented in this manuscript indicate that primary metabolites enable the discrimination of species, whereas secondary metabolites are associated with species and the ripening process. In addition, analysis of the biosynthetic pathway highlighted that the syntheses of flavone and flavone glycosides are deeply affected in Citrus ripening stages. Ultimately, this work might provide a feasible strategy for the authentication of Citrus fruits from different species and ripening stages and facilitate a better understanding of their different medicinal uses.

Characterization and Metabolic Diversity of Flavonoids in Citrus Species

Flavonoids are widely distributed in plants and play important roles in many biological processes. Citrus fruits are rich dietary sources of flavonoids. However, there have been very few reports about the comprehensive metabolic profile and natural diversity of flavonoids in different tissues of various Citrus cultivars. In this study, based on the 7416 metabolic signals detected with non-targeted metabolomics approach, Principal Component Analysis revealed the flavedo has the largest differences from other tissues in metabolite levels; as many as 198 flavonoid signals were then detected in 62 Citrus germplasms from 5 species mainly cultivated worldwide, while 117 flavonoids were identified, including 39 polymethoxylated flavonoids (PMFs), 7 flavones, 10 C-O-glycosylflavonoids, 44 O-glycosylflavonoids, 10 C-glycosylflavonoids and 7 newly annotated O-glycosylpolymethoxylated flavonoids. Tissue-specific accumulations were observed: O-glycosylated flavonoids were abundant in all fruit tissues, while PMFs were accumulated preferentially in the flavedo. Among different species, mandarins had the highest levels of PMFs and O-glycosylpolymethoxylated flavonoids, followed by sweet oranges. Based on the flavonoid profiles, 62 germplasms could be clearly grouped into five distinct clusters via hierarchical clustering analysis, which were perfectly matched with their species, with sweet oranges and mandarins clustering closely and being further away from other three species.

The Distribution of Coumarins and Furanocoumarins in Citrus Species Closely Matches Citrus Phylogeny and Reflects the Organization of Biosynthetic Pathways

Citrus plants are able to produce defense compounds such as coumarins and furanocoumarins to cope with herbivorous insects and pathogens. In humans, these chemical compounds are strong photosensitizers and can interact with medications, leading to the "grapefruit juice effect". Removing coumarins and furanocoumarins from food and cosmetics imply additional costs and might alter product quality. Thus, the selection of Citrus cultivars displaying low coumarin and furanocoumarin contents constitutes a valuable alternative. In this study, we performed ultra-performance liquid chromatography coupled with mass spectrometry analyses to determine the contents of these compounds within the peel and the pulp of 61 Citrus species representative of the genetic diversity all Citrus. Generally, Citrus peel contains larger diversity and higher concentrations of coumarin/furanocoumarin than the pulp of the same fruits. According to the chemotypes found in the peel, Citrus species can be separated into 4 groups that correspond to the 4 ancestral taxa (pummelos, mandarins, citrons and papedas) and extended with their respective secondary species descendants. Three of the 4 ancestral taxa (pummelos, citrons and papedas) synthesize high amounts of these compounds, whereas mandarins appear practically devoid of them. Additionally, all ancestral taxa and their hybrids are logically organized according to the coumarin and furanocoumarin pathways described in the literature. This organization allows hypotheses to be drawn regarding the biosynthetic origin of compounds for which the biogenesis remains unresolved. Determining coumarin and furanocoumarin contents is also helpful for hypothesizing the origin of Citrus species for which the phylogeny is presently not firmly established. Finally, this work also notes favorable hybridization schemes that will lead to low coumarin and furanocoumarin contents, and we propose to select mandarins and Ichang papeda as Citrus varieties for use in creating species devoid of these toxic compounds in future breeding programs.