Indole alkaloids from the roots of Isatis indigotica and their inhibitory effects on nitric oxide production

Exploring the chemical compositions of Fufang Yinhua Jiedu granules based on ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry combined with multistage intelligent data annotation strategy

Fufang Yinhua Jiedu granules (FYJG) is a Traditional Chinese Medicine (TCM) compound formulae preparation comprising ten herbal drugs, which has been widely used for the treatment of influenza with wind-heat type and upper respiratory tract infections. However, the phytochemical constituents of FYJG have rarely been reported, and its constituent composition still needs to be elucidated. The complexity of the natural ingredients of TCMs and the diversity of preparations are the major obstacles to fully characterizing their constituents. In this study, an innovative and intelligent analysis strategy was built to comprehensively characterize the constituents of FYJG and assign source attribution to all components. Firstly, a simple and highly efficient ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MSE) method was established to analyze the FYJG and ten single herbs. High-accuracy MS/MS data were acquired under two collision energies using high-definition MSE in the negative and positive modes. Secondly, a multistage intelligent data annotation strategy was developed and used to rapidly screen out and identify the compounds of FYJG, which was integrated with various online software and data processing platforms. The in-house chemical library of 2949 compounds was created and operated in the UNIFI software to enable automatic peak annotation of the MSE data. Then, the acquired MS data were processed by MS-DIAL, and a feature-based molecular networking (FBMN) was constructed on the Global Natural Product Social Molecular Networking (GNPS) to infer potential compositions of FYJG by rapidly classifying and visualizing. It was simultaneously using the MZmine software to recognize the source attribution of ingredients. On this basis, the unique chemical categories and characteristics of herbaceous plant species are utilized further to verify the accuracy of the source attribution of multi-components. This comprehensive analysis successfully identified or tentatively characterized 279 compounds in FYJG, including flavonoids, phenolic acids, coumarins, saponins, alkaloids, lignans, and phenylethanoids. Notably, twelve indole alkaloids and four organic acids from Isatidis Folium were characterized in this formula for the first time. This study demonstrates a potential superiority to identify compounds in complex TCM formulas using high-definition MSE and computer software-assisted structural analysis tools, which can obtain high-quality MS/MS spectra, effectively distinguish isomers, and improve the coverage of trace components. This study elucidates the various components and sources of FYJG and provides a theoretical basis for its further clinical development and application.

TMSOTf-Catalyzed C2-Sulfenylation of Indole Alkaloids Using N-Sulfenylsuccinimides: An Approach for the Total Synthesis of Isatindigotindolosides

A TMSOTf-catalyzed C2-sulfenylation of indole alkaloids with N-sulfenylsuccinimides has been developed. This straightforward, metal-free, and cost-effective catalytic system produces valuable 2-thioindole derivatives with yields ranging from moderate to excellent. The synthetic applicability demonstrated includes the total syntheses of isatindigotindolosides I-IV.

Chemical composition and antioxidant properties of native Ecuadorian fruits: Rubus glabratus Kunth, Vaccinium floribundum Kunth, and Opuntia soederstromiana

The native berries of South America present promising marketing opportunities owing to their high antioxidant content, notably rich in anthocyanin and phenolic compounds. However, Ecuador's endemic fruits, primarily found in the wild, lack comprehensive data regarding their phytochemical composition and antioxidant capacity, underscoring the need for research in this area. Accordingly, this study evaluated the total phenolic, anthocyanin, flavonoid, resveratrol, ascorbic acid, citric acid, sugars, and antioxidant content of three native Ecuadorian fruits: mora de monte (Rubus glabratus Kunth), mortiño (Vaccinium floribundum Kunth), and tuna de monte (Opuntia soederstromiana). Determination of resveratrol, ascorbic acid, citric acid, and sugars was determined by HPLC analysis, and UPLC analysis was used to determine tentative metabolites with nutraceutical properties. Antioxidant capacity was assessed using cyclic voltammetry and the DPPH method; differential pulse voltammetry was used to evaluate antioxidant power. Analysis of results through UPLC-QTOF mass spectrometry indicated that R. glabratus Kunth and V. floribundum Kunth are important sources of various compounds with potential health-promoting functions in the body. The DPPH results showed the following antioxidant capacities for the three fruits: R. glabratus Kunth > O. soederstromiana > V. floribundum Kunth; this trend was consistent with the antioxidant capacity results determined using the electrochemical methods.

A Method for the Synthesis of Thioindoles through Copper-Catalyzed C-S Bond Coupling Reaction

We herein report the copper-catalyzed C-S bond coupling reaction of indoles with N-thiosuccinimides, resulting in moderate to excellent yields of mono- and bis-sulfenylated compounds such as arylthioindoles, alkylthioindoles, selenylated indoles, and cysteine-substituted indoles. Thioarylation and thioglycosylation at the C2 position of indole alkaloids in the Radix Isatidis were achieved via structural modification. The first total syntheses of isatindigotindolosides III and IV have been successfully carried out. The electrophilic sulfenyl bromides generated in situ can play an important role in the catalytic cycle.

Copper-Catalyzed C2- or C3-Thioglycosylation of Indoles with N-(Thioglycosides)succinimides: An Effective Strategy for the Total Synthesis of Isatindigotindolosides

Isatindigotindolosides, indoles containing a 1-S-β-glucopyranosyl unit at position C2, show promising bioactivity. Here, we report a copper-catalyzed C2- or C3-thioglycosylation of indoles with N-(thioglycosides)succinimides to construct indole alkaloid glucosides. This reaction is widely tolerant of functional groups, as various indoles and thioglycosides are suitable. It also provides a reliable method for performing late-stage modifications of natural products, such as gramine and melatonin. Total syntheses of isatindigotindolosides I and II were successfully accomplished using the C2-thioglycosylation reaction as a key step.

Eight Indole Alkaloids from the Roots of Maerua siamensis and Their Nitric Oxide Inhibitory Effects

Maerua siamensis (Capparaceae) roots are used for treating pain and inflammation in traditional Thai medicine. Eight new indole alkaloids, named maeruanitriles A and B, maeroximes A-C, and maeruabisindoles A-C, were isolated from them. Spectroscopic methods and computational analysis were applied to determine the structure of the isolated compounds. Maeroximes A-C possesses an unusual O-methyloxime moiety. The bisindole alkaloid maeruabisindoles A and B possess a rare azete ring, whereas maeruabisindole C is the first indolo[3,2-b]carbazole derivative found in this plant family. Five compounds [maeruanitriles A and B, maeroxime C, maeruabisindoles B, and C] displayed anti-inflammatory activity by inhibiting nitric oxide (NO) production in the lipopolysaccharide-induced RAW 264.7 cells. Maeruabisindole B was the most active inhibitor of NO production, with an IC50 of 31.1 ± 1.8 μM compared to indomethacin (IC50 = 150.0 ± 16.0 μM) as the positive control.

Hydroalcoholic Leaf Extract of Isatis tinctoria L. via Antioxidative and Anti-Inflammatory Effects Reduces Stress-Induced Behavioral and Cellular Disorders in Mice

Stress that can occur at different levels of a person’s life can cause and exacerbate various diseases. Oxidative stress and inflammation underlie this process at the cellular level. There is an urgent need to identify new and more effective therapeutic targets for the treatment of stress-induced behavioral disorders and specific drugs that affect these targets. Isatis tinctoria L. is a herbaceous species in the Brassicaceae family. Due to its potential antioxidant, nitric oxide- (NO-) inhibiting, anti-inflammatory, and neuroprotective properties, I. tinctoria could be used to treat depression, anxiety, and stress resistance. Hence, the present study is aimed at delineating whether administration of I. tinctoria leaf extract may improve stress-induced disorders in mice. A set of four behavioral tests was selected that together are suitable for phenotyping acute restraint stress-associated behaviors in mice, namely locomotor activity, social integration, dark/light box, and splash tests. The plasma and brains were collected. A brain-derived neurotrophic factor, tumor necrosis factor-alpha, C-reactive protein, corticosterone, NO, reactive oxygen species levels, superoxide dismutase and catalase activity, and ferric-reducing antioxidant power were measured. In mice stressed by immobilization, decreased locomotor activity, anxiety-like behavior, and contact with other individuals were observed, as well as increased oxidative stress and increased levels of nitric oxide in the brain and plasma C-reactive protein. A single administration of I. tinctoria leaf extract was able to reverse the behavioral response to restraint by a mechanism partially dependent on the modulation of oxidative stress, neuroinflammation, and NO reduction. In conclusion, Isatis tinctoria hydroalcoholic leaf extract can reduce stress-induced behavioral disturbances by regulating neurooxidative, neuronitrosative, and neuroimmune pathways. Therefore, it could be recommended for further research on clinical efficacy in depression and anxiety disorder treatment.

A Systemic Review for Ethnopharmacological Studies on Isatis indigotica Fortune: Bioactive Compounds and their Therapeutic Insights

Isatis indigotica Fortune is a biennial Chinese woad of the Cruciferae family. It is primarily cultivated in China, where it was a staple in indigo dye manufacture till the end of the 17th century. Today, I. indigotica is used primarily as a therapeutic herb in traditional Chinese medicine (TCM). The medicinal use of the plant is separated into its leaves (Da-Qing-Ye) and roots (Ban-Lan-Gen), whereas its aerial components can be processed into a dried bluish-spruce powder (Qing-Dai), following dehydration for long-term preservation. Over the past several decades, I. indigotica has been generally utilized for its heat-clearing effects and bodily detoxification in TCM, attributed to the presence of several classes of bioactive compounds, including organic acids, alkaloids, terpenoids, and flavonoids, as well as lignans, anthraquinones, glucosides, glucosinolates, sphingolipids, tetrapyrroles, and polysaccharides. This paper aims to delineate I. indigotica from its closely-related species (Isatis tinctoria and Isatis glauca) while highlighting the ethnomedicinal uses of I. indigotica from the perspectives of modern and traditional medicine. A systematic search of PubMed, Embase, PMC, Web of Science, and Google Scholar databases was done for articles on all aspects of the plant, emphasizing those analyzing the bioactivity of constituents of the plant. The various key bioactive compounds of I. indigotica that have been found to exhibit anti-inflammatory, antimicrobial, anticancer, and anti-allergic properties, along with the protective effects against neuronal injury and bone fracture, will be discussed. Collectively, the review hopes to draw attention to the therapeutic potential of I. indigotica not only as a TCM, but also as a potential source of bioactive compounds for disease management and treatment.

Isatidis Radix and Isatidis Folium: A systematic review on ethnopharmacology, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Isatidis Radix (called Banlangen, BLG in Chinese) and Isatidis Folium (called Daqingye, DQY in Chinese) are common traditional edible-medicinal herbs in detoxifying for thousands of years, have been traditionally applied in traditional Chinese medicine for centuries. Both of them are bitter in taste, coolness in nature, acting on the heart and stomach channels. They are often used to treat influenza and other viral infectious diseases in clinic, as well as could treat fever, dizziness, and cough and sore throat caused by lung heat.

AIMS OF THE REVIEW

This review aimed at summarizing the latest and comprehensive information of BLG and DQY on the ethnopharmacology, phytochemistry, pharmacology, toxicity and clinical application to explore the therapeutic potential of them. In addition, outlooks and perspective for possible future researches that related are also discussed.

MATERIALS AND METHODS

Related information concerning BLG and DQY were gathered from the internet database of Google Scholar, PubMed, Baidu Scholar, GeenMedical, CNKI and Web of Science, as well as other relevant textbooks, reviews, and documents (e.g., Chinese Pharmacopoeia, 2020 edition, Chinese herbal classic books and PhD and MSc thesis, etc.). Among of them with the keywords including "Isatis indigotica" "Isatidis Radix", "Isatidis Folium", "phytochemistry", "pharmacology", "toxicology", "clinical application" etc. and their combinations.

RESULTS

To date, 39 Chinese patent medicines containing BLG and/or DQY have been developed on basis of the data of NMPA. Besides, 304 and 142 compounds have been found in BLG and DQY, respectively. The main chemical differences between BLG and DQY were concentrated on alkaloids and lignans, such as indican, indirubin, (R, S)-epigoitrin, 4(3H)-quinazolinone, clemastanin B and isatindigotindolines A-D. In 2020 Edition ChP, (R, S)-goitrin and indirubin are now used as the official marker to monitor the quality of BLG and DQY, respectively. Modern pharmacology has mainly studied some monomer components such as 4(3H)-quinazolinone, clemastanin B, erucic acid and adenosine, etc., all of which have shown good effects. These active compounds can resist various viruses, such as influenza virus, respiratory syncytial virus, herpes simplex virus, etc.. By regulating the level of immunity and a variety of inflammatory factors, inhibit the growth and reproduction of the virus. At the same time, it is worth noting that different components of BLG and DQY lead to BLG is more powerful in antiviral and immunomodulatory activity than DQY, while DQY possesses a higher intensity than BLG in anti-oxidant activity.

CONCLUSION

By collecting and collating a large number of literature and various data websites, we concluded that the common compounds are mainly alkaloids. Recent findings regarding the phytochemical and pharmacological properties of BLG and DQY have confirmed their traditional uses in antiviral, antibacterial and treatment immune diseases. Without doubt, their significant differences on ethnopharmacology, phytochemistry and pharmacology can be used as evidence of separate list of BLG and DQY. For shortcomings, some comprehensive studies should be well designed for further utilization of BLG and DQY.

Potential therapeutic effect of Shufeng Jiedu capsule and its major herbs on coronavirus disease 2019 (COVID-19): A review

The outbreak and rapid spread of coronavirus disease 2019 (COVID-19) poses a huge threat to human health and social stability. Shufeng Jiedu capsule (SFJDC), a patented herbal drug composed of eight medicinal plants, is used to treat different viral respiratory tract infectious diseases. Based on its antiviral, anti-inflammatory, and immunoregulatory activities in acute lung injury, SFJDC can be effectively used as a treatment for COVID-19 patients according to the diagnosis and treatment plan issued in China and existing clinical data. SFJDC has been recommended in 15 therapeutic regimens for COVID-19 in China. This review summarizes current data on the ingredients, chemical composition, pharmacological properties, clinical efficacy, and potential therapeutic effect of SFJDC on COVID-19, to provide a theoretical basis for its anti-viral mechanism and the clinical treatment of COVID-19.

Synthesis and evaluation of fosfomycin group end-capped packing materials for hydrophilic interaction liquid chromatography

Hydrophilic interaction liquid chromatography (HILIC) plays an important role in the analysis of compounds having high polarity. In this study, fosfomycin (F) was chosen as a new end-capping reagent, owing to the facile hydrolysis reaction of its epoxy group. Zirconia coated silica (ZrO₂/SiO₂) materials having good chemical and physical stability were prepared. D-glucose-6-phosphate (G) and D-fructose1,6-bisphosphate (FDP) were modified onto the inner and outer surfaces of the ZrO₂/SiO₂ microbeads. The new end-capping reagent (F) was then bonded onto the surface of the modified material through Lewis acid-base interactions. The properties (morphology, Zr content, pore size, pore volume, and carbon content) of the stationary phases (SPs) were characterized. Finally, the resulting end-capped SPs were employed to separate alkaloids and benzoic acids. Multiple interactions, including HILIC, electrostatic repulsion, ion exchange and hydrogen bonding, contributed to the retention of the analytes on the SPs. On the F-FDP-ZrO₂/SiO₂ column, a theoretical plate number of 31,700 plates/m and an asymmetry factor of 1.63 were achieved for berberine, exhibiting good chromatographic performance. Furthermore, the FDP-ZrO₂/SiO₂ column showed good acid-base stability and good potential for the analysis of benzoic acid in Sprite and ginsenoside separations. Thus, the results indicated the significant potential of using F as an end-capping reagent.

Determination of Free Amino Acids in Banlangen Granule and its Fractions by Solid Phase Extraction Combined with Ion-pair Hig-h Perfor mance Liquid Chromatography using a Corona-charged Aerosol Detector (SPE-HPLC-CAD)

Background:

Banlangen granules are broad-spectrum effective antiviral drugs, and have a large clinical demand in China. Free amino acid is one of the main antiviral active ingredients of Banlangen granules. The pre-processing of samples by the existing pre-column derivatization reversed- HPLC method is complicated. Therefore, the determination of free amino acids (AAs) by underivatized ion-pair HPLC-CAD is advantageous for simplifying the preparation process and improving sensitivity.

Objective:

To better optimize AAs analysis methods, here a sensitive SPE-HPLC-CAD method with a better resolution was established for the determination of underivatized AAs in Banlangen Granule for the first time.

Method:

The analytes were separated only by HPLC using a Hypercarb column with gradient elution of solvent A (20 mM nonafluorovaleric Acid in water) and solvent B (0.3% trifluoroacetic acid in acetonitrile-0.3% trifluoroacetic acid in water (1:9, v/v)) at a flow rate of 0.15 mL/min. N2 gas pressure and evaporation temperature of CAD were held at a constant 58.6 psi and 60 ℃, respectively.

Results:

This method was linear over the respective concentration range of six amino acids. The precision, accuracy, stability and recovery were satisfactory in all samples examined. And the method was successfully applied to determination of free amino acids in Banlangen granules and its fractions. The total contents of six amino acids in 28 batches of Banlangen Granule were between 1.36 mg/g-11.62 mg/g.

Conclusion:

The proposed method could be a simple, accurate and sensitive alternative approach for the determination of free AAs in Banlangen Granule.

Microscopic Mass Spectrometry Imaging Reveals the Distribution of Phytochemicals in the Dried Root of Isatis tinctoria

The dried root of Isatis tinctoria L. (Brassicaceae) is one of the most popular traditional Chinese medicines with well-recognized prevention and treatment effects against viral infections. Above 300 components have been isolated from this herb, but their spatial distribution in the root tissue remains unknown. In recent years, mass spectrometry imaging (MSI) has become a booming technology for capturing the spatial accumulation and localization of molecules in fresh plants, animal, or human tissues. However, few studies were conducted on the dried herbal materials due to the obstacles in cryosectioning. In this study, distribution of phytochemicals in the dried root of Isatis tinctoria was revealed by microscopic mass spectrometry imaging, with application of atmospheric pressure-matrix-assisted laser desorption/ionization (AP-MALDI) and ion trap-time-of-flight mass spectrometry (IT-TOF/MS). After optimization of the slice preparation and matrix application, 118 ions were identified without extraction and isolation, and the locations of some metabolites in the dried root of Isatis tinctoria were comprehensively visualized for the first time. Combining with partial least square (PLS) regression, samples collected from four habitats were differentiated unambiguously based on their mass spectrometry imaging.

Synthetic Studies toward Bisindigotin: Polyheteroaromatic Scaffolds via Skeletal Rearrangements of a Diacetoxytetraindole

The deacetylation of a diacetoxytetraindole formed the basis of a first-generation synthetic route toward the alkaloid bisindigotin. However, this conceptually straightforward plan led to unexpected results. Acid-mediated hydrolysis initiated skeletal rearrangement processes that resulted in the formation of two novel heteroaromatic scaffolds, both of which contain nine rings. Upon treating the same diacetoxytetraindole with base followed by a silica-mediated autoxidation, a distinct cascade process occurred, generating another novel scaffold also comprising nine rings. A mechanistic rationale for these observations is provided.

Multigram Scale Synthesis and Anti-Influenza Activity of 3-Indoleacetonitrile Glucosides

Indole-3-acetonitrile-6- O-β-d-glucopyranoside 1 is a simple alkaloid with anti-influenza A virus activity extracted from Radix isatidis. Herein, a concise and practical total synthetic route of 1 was presented, starting from 6-benzyloxyindole on a multigram scale. The pivotal reaction sequence involved the Mannich reaction, the fluoride ion-induced elimination-addition reaction, and phase-transfer-catalyzed glycosylation reaction as key steps. In addition, compounds 1 and two modified derivatives 8 and 16 were tested for anti-influenza efficacy and cytotoxicity in vitro performed on Madin-Darby canine kidney cells. The results revealed that the compounds exerted antiviral activity against the influenza A virus to a certain extent and displayed no cytotoxicity. These findings could contribute to the development of traditional Chinese medicine R. isatidis for treating the influenza virus.

Four new indole alkaloids from the roots of Isatis tinctoria

Chemical fractionation of the ethanolic extract of the roots of Isatis tinctoria L. (I. tinctoria) yielded fourteen indole alkaloids including four new ones, isatisindigoticanine L-N and isatindigoside M. Their structures were established on the basis of extensive spectroscopic techniques including NMR, HRESIMS and IR as well as chemical methods. The absolute configuration of 1 was confirmed by ECD experiments. All the compounds were tested for their inhibitory effects on NO production in mouse mononuclear macrophages (RAW264.7) induced by lipopolysaccharide (LPS). The results showed that only compound 5 exhibited inhibitory effects with IC₅₀ value of 18.5 μM.

Bisindole alkaloids with nitric oxide inhibitory activities from an alcohol extract of the Isatis indigotica roots

Eight bisindole alkaloids including six undescribed ones (1a/1b-5) were isolated from an alcohol extract of the Isatis indigotica roots. Their structures and absolute configurations were supported by extensive spectroscopic data analysis, including 1D, 2D NMR, HRESIMS data, specific rotation data, and comparison of the experimental and calculated ECD data. Compounds 1a and 1b were determined to be a pair of enantiomers with a ratio of approximately 1:1 by chiral-phase chromatography analysis while compound 4 was elucidated as a new type of bisindole alkaloid with the aglycone categorized as bis(indole-1'/3″-yl)methane. All the isolated compounds were tested for their nitric oxide (NO) inhibitory effects and 1-4 and 6 exhibited inhibitory effects with IC₅₀ values ranging from 11.0 to 37.6 μM.

Four undescribed sulfur-containing indole alkaloids with nitric oxide inhibitory activities from Isatis tinctoria L. roots

Four undescribed sulfur-containing indole alkaloids, isatisindigoticanines H, I and isatindigosides F, G along with three known analogues were obtained from Isatis tinctoria L. roots. Isatisindigoticanines H and I contained an unusual 1-(thiazol-4-yl)butane-1,2,3,4-tetraol moiety while isatindigosides F and G possessed a new 3-[3-(1H-indole-2-yl)azet-2-yl]-1H-indole skeleton. The putative biosynthetic pathways of isatisindigoticanines H, I and isatindigosides F, G are proposed. The isolated compounds showed nitric oxide inhibitory effects with IC₅₀ values ranging from 4.3 to 70.3 μM.

Indole alkaloid glycosides with a 1'-(phenyl)ethyl unit from Isatis indigotica leaves

Seven indole alkaloid glycosides containing a 1′-(4″-hydroxy-3″,5″-dimethoxyphenyl)ethyl unit (1–7) were isolated from an aqueous extract of Isatis indigotica leaves (da qing ye). Their structures were determined by spectroscopic data analysis combined with enzymatic hydrolysis as well as comparison of their experimental CD (circular dichroism) and calculated ECD (electrostatic circular dichroism) spectra. Based on analysis of [α]D20 and/or Cotton effect (CE) data of 1–7, two simple roles to assign location and/or configuration of β-glycopyranosyloxy and 1′-(phenyl)ethyl units in the indole alkaloid glycosides are proposed. Stereoselectivity in plausible biosynthetic pathways of 1–7 is discussed. Compounds 3 and 4 and their mixture in a 3:2 ratio showed activity against KCNQ2 in CHO cells. The mixture of 5 and 6 (3:2) exhibited antiviral activity against influenza virus H1N1 PR8 with IC₅₀ 64.7 μmol/L (ribavirin, IC₅₀ 54.3 μmol/L), however, the individual 5 or 6 was inactive. Preliminary structure–activity relationships were observed.

Inhibitory Effects of Indole-3-Acetonitrile-4-Methoxy-2-S-Β-d-Glucopyranoside From Nasturtium officinale R. Br on Human Kallikrein 5 and 7 Protease

The stratum corneum tryptic enzyme kallikrein 5 (KLK5) is a serine protease that is involved in the cell renewal and maintenance of the skin barrier functions. The excessive activation of KLK5 causes an exacerbation of dermatoses, such as rosacea and atopic dermatitis. Nasturtium officinale R. Br. (Brassicaceae) is a hardy perennial plant native to Europe and commonly called “Watercress” or “Cresson,” which is one of the brassica vegetables. We aimed to investigate whether the bioactive sulfur-containing compound inhibits the KLK5 protease. The sulfur-containing compounds were evaluated using an enzymatic assay to measure the anti-KLK5 activity. Our study revealed that the sulfur-containing compound inhibits the KLK5 and 7 protease activity. Indole-3-acetonitrile-4-methoxy-2-S-β-d-glucopyranoside may affect the skin barrier and atopic function via the regulation of proteases.

Metal-free oxidative C(sp3)–H functionalization: a facile route to quinoline formaldehydes from methyl-azaheteroarenes

A facile protocol for the synthesis of quinoline formaldehydes via direct oxidative C–H bonds functionalization of methyl-azaheteroarenes in the presence of I2–DMSO has been described. This method is metal-free and easy to operate. This reaction provided a convenient route for the preparation of a range of important quinoline formaldehydes.

Indole alkaloids: 2012 until now, highlighting the new chemical structures and biological activities

Indole alkaloids have attracted attention because of their therapeutic properties, being anti-inflammatory, antinociceptive, antitumoural, antioxidant and antimicrobial. These compounds present a wide structural diversity, which is directly related to the genera of the producing plants, as well as the biological activities. Indole alkaloids have attracted attention over the last decade because of this combination of bioactivity and structural diversity. Therefore, this review presented recent (2012-2018) advances in alkaloids, focusing on new compounds, extraction methods and biological activities. As such, approximately 70 articles were identified, which showed 261 new compounds produced by plants of the families Apocynaceae, Rubiaceae, Annonaceae and Loganiaceae. In addition, different extraction methods were identified, and the structures of the new compounds were analysed. In addition to indole molecules, there were mono-indole-, di-indole-, vinblastine-, vimblastine-, gelsedine-, geissospermidine-, koumine-, geissospermidine-, iboga-, perakine-, corynanthe-, vincamine-, ajmaline-, aspidorpema-, strychnos-type, β-carboline alkaloids and indole alkaloid glucosides. The reported biological activities are mainly anticancer, antibacterial, antimalarial, antifungal, antiparasitic, and antiviral, as well as anti-acetylcholinesterase and anti-butyrylcolinesterase properties. This review serves as a guide for those wishing to find the most recently identified alkaloid structures and their associated activities.

A chromosome-scale genome assembly of Isatis indigotica, an important medicinal plant used in traditional Chinese medicine: An Isatis genome

Isatis indigotica (2n = 14) is an important medicinal plant in China. Its dried leaves and roots (called Isatidis Folium and Isatidis Radix, respectively) are broadly used in traditional Chinese medicine for curing diseases caused by bacteria and viruses such as influenza and viral pneumonia. Various classes of compounds isolated from this species have been identified as effective ingredients. Previous studies based on transcriptomes revealed only a few candidate genes for the biosynthesis of these active compounds in this medicinal plant. Here, we report a high-quality chromosome-scale genome assembly of I. indigotica with a total size of 293.88 Mb and scaffold N50 = 36.16 Mb using single-molecule real-time long reads and high-throughput chromosome conformation capture techniques. We annotated 30,323 high-confidence protein-coding genes. Based on homolog searching and functional annotations, we identified many candidate genes involved in the biosynthesis of main active components such as indoles, terpenoids, and phenylpropanoids. In addition, we found that some key enzyme-coding gene families related to the biosynthesis of these components were expanded due to tandem duplications, which likely drove the production of these major active compounds and explained why I. indigotica has excellent antibacterial and antiviral activities. Our results highlighted the importance of genome sequencing in identifying candidate genes for metabolite synthesis in medicinal plants.

Alkaloids with Nitric Oxide Inhibitory Activities from the Roots of Isatis tinctoria

As our ongoing research project on Ban Lan Gen (Isatis tinctoria roots), a total of 23 alkaloids were obtained. Compounds 1 and 2 contain an unusual C–C bond between the 2(1H)-quinolinone moiety and the phenol moiety and between the 2(1H)-quinolinone moiety and the 1H-indole moiety, respectively. Compound 3 possesses an unusual carbon skeleton and its putative biosynthetic pathway was discussed, and Compound 23 was deduced as a new indole alkaloid glycoside. Compounds 4–7 were identified as four new natural products by extensive spectroscopic experiments. Additionally, the anti-inflammatory activity was assessed based on nitric oxide (NO) production using Lipopolysaccharide-stimulated RAW264.7 macrophages. Compounds 9, 15, and 17 showed inhibitory effects with IC₅₀ values of 1.2, 5.0, and 74.4 μM.

Untargeted liquid chromatography coupled with mass spectrometry reveals metabolic changes in nitrogen-deficient Isatis indigotica Fortune

Isatis indigotica Fortune is a popular herb in traditional Chinese medicine, and various types of metabolites are the basis for its pharmacological efficacy. The biosynthesis and accumulation of these metabolites are closely linked to nitrogen availability; the benefits of low nitrogen application on the environment and herb quality are increasingly prominent. To analyze metabolic changes in the leaves and roots of I.indigotica in nitrogen deficiency conditions, and to identify the pathways and metabolites induced by low nitrogen availability, we used untargeted liquid chromatography coupled with mass spectrometry (UHPLC-TripleTOF) to obtain metabolomics profiling of I.indigotica under two N-deficiency treatments (0 kg/hm²; 337.5 kg/hm²) and normal nitrogen treatment (675 kg/hm²). A total of 447 metabolites were annotated. Principal component analysis separated the three nitrogen treatments. A greater diversity of metabolites was observed in roots than in leaves under N-deficiency treatments, suggesting that roots have a more important function in low N tolerance. Differential metabolites were mainly enriched in purine metabolism, phenylpropanoid biosynthesis, the shikimate pathway, tryptophan metabolism, and flavonoid biosynthesis that notably induced only in leaves in low nitrogen stress. Moderate N-deficiency benefits carbohydrate accumulation, whereas accumulation of most amino acids decreases. Uniquely, L-tryptophan was maintained at a high concentration in N-deficiency conditions. Low nitrogen stress induced the accumulation of some specialized metabolites (matairesinol, dictamnine, 5-hydroxyindoleacetate (serotonin) in roots and vitexin, xanthohumol, sinapyl alcohol in leaves). N-deficiency also increased the accumulation of adenosine and quality indicators of I.indigotica (indirubin-indigo, epigoitrin and anthranilic acid) in a certain degree. Our findings showed that nitrogen deficiency modified roots and leaves conditions of I.indigotica, affecting both the primary and secondary metabolism. Moderate nitrogen reduction was beneficial to the accumulation of active ingredients. Our methods and analysis are expected to provide an insight regarding the diversity of metabolites and regulation of their synthesis in low nitrogen application, and better investigate the nitrogen deficiency effect on I.indigotica.

Alkaloid Enantiomers from the Roots of Isatis indigotica

Five pairs of alkaloid enantiomers (1a/1b–5a/5b) were obtained from Isatis indigotica (I. indigotica) roots. Among them, 1a/1b, 2a/2b and 3a/3b were determined as three pairs of new alkaloid enantiomers. Their structures were elucidated by physicochemical properties and spectroscopic methods. The absolute configurations were deduced by comparison of their experimental circular dichroism (CD) and calculated electronic circular dichroism (ECD) spectra, as well as by single-crystal X-ray crystallography using anomalous scattering of Cu Kα radiation. Alkaloids 1a and 1b possess an unpresented carbon skeleton and their putative biosynthetic pathways are discussed. Moreover, all of the alkaloids were tested for their nitric oxide (NO) inhibitory effects in RAW 264.7 cells, and 4a and 4b showed inhibitory effects with IC₅₀ values of 76.97 μM and 65.88 μM, respectively.

Protective Effects of Indole 3-Acetonitrile-4-Methoxy-2-S-β-d-Glucopyranoside From Nasturtium officinale R. Br. Against Ultraviolet B-Induced Photodamage in Normal Human Dermal Fibroblasts

Ultraviolet radiation induces skin photoaging, which is associated with the elevation of matrix metalloproteinase-1 (MMP-1) and the decrease of procollagen. Nasturtium officinale plays a well-known role in the treatment of sulfur-containing compounds and their important role in protecting human health. However, their skin protective activity toward UVB-induced photodamage remains unclear. In the present study, we investigated the protective effect of indole 3-acetonitrile-4-methoxy-2- S-β-d-glucopyranoside (IAMG) from N. officinale on UVB-irradiated normal human dermal fibroblasts (NHDF). Our results show that IAMG enhanced NHDF cell migration. The UVB-induced increases in MMP-1 and decrease in type I procollagen were ameliorated by IAMG treatment. Taken together, our data strongly suggest that IAMG from N. officinale could reduce UVB-induced photodamage.

Isatisindigoticanine A, a novel indole alkaloid with an unpresented carbon skeleton from the roots of Isatis tinctoria

Isatisindigoticanine A (1), a new indole alkaloid with an unusual carbon skeleton of a benzofuran-3-one unit connected with a 1H-indole-3-yl unit and a 4-(1,2-dihydroxyethyl)-6-oxa-3-azabicyclo[3.1.0]hexan-2-one unit via a C-3－C-8'' bond and a C-4'－C-8'' bond, was obtained from the roots of Isatis tinctoria. Its structure was determined by physicochemical properties and spectroscopic methods including 1 D, 2 D NMR, IR, HRESIMS data. The absolutely configurations were deduced by comparison of its experimental CD and calculated ECD spectra. Nitric oxide (NO) inhibitory activities of isatisindigoticanine A was also evaluated in the LPS-stimulated RAW 264.7 cells, however, no inhibitory effect was presented.

Indole alkaloid glycosides from Isatis tinctoria roots

Isatindigoside A and B (1 - 2), two new indole alkaloid glycosides along with five known ones (3 - 7) were obtained from the roots of I. tinctoria. Their structures were determined as isatindigoside A (1), isatindigoside B (2), isatindosulfonicacid A 3-O-β-D-glucopyranoside (3), indole-3-acetonitrile 6-O-β-D-glucopyranoside (4), isatindigobisindoloside A (5), isatindigobisindoloside B (6) isatindigobisindoloside F (7), by physicochemical properties and spectroscopic methods including 1 D, 2 D NMR, IR, HR-ESI-MS data. Nitric oxide (NO) inhibitory activities of all of the isolated compounds (1 - 7) were also evaluated. Compounds 2 and 7 showed inhibitory effects against LPS-stimulated RAW 264.7 cells with IC₅₀ values of 27.6 μM and 18.8 μM, respectively.

Selection of reference genes for the quantitative real-time PCR normalization of gene expression in Isatis indigotica fortune

Background

Isatis indigotica, a traditional Chinese medicine, produces a variety of active ingredients. However, little is known about the key genes and corresponding expression profiling involved in the biosynthesis pathways of these ingredients. Quantitative real-time polymerase chain reaction (qRT-PCR) is a powerful, commonly-used method for gene expression analysis, but the accuracy of the quantitative data produced depends on the appropriate selection of reference genes.

Results

In this study, the systematic analysis of the reference genes was performed for quantitative real-Time PCR normalization in I. indigotica. We selected nine candidate reference genes, including six traditional housekeeping genes (ACT, α-TUB, β-TUB, UBC, CYP, and EF1-α), and three newly stable internal control genes (MUB, TIP41, and RPL) from a transcriptome dataset of I. indigotica, and evaluated their expression stabilities in different tissues (root, stem, leaf, and petiole) and leaves exposed to three abiotic treatments (low-nitrogen, ABA, and MeJA) using geNorm, NormFinder, BestKeeper, and comprehensive RefFind algorithms. The results demonstrated that MUB and EF1-α were the two most stable reference genes for all samples. TIP41 as the optimal reference gene for low-nitrogen stress and MeJA treatment, while ACT had the highest ranking for ABA treatment and CYP was the most suitable for different tissues.

Conclusions

The results revealed that the selection and validation of appropriate reference genes for normalizing data is mandatory to acquire accurate quantification results. The necessity of specific internal control for specific conditions was also emphasized. Furthermore, this work will provide valuable information to enhance further research in gene function and molecular biology on I. indigotica and other related species.

Electronic supplementary material

The online version of this article (10.1186/s12867-019-0126-y) contains supplementary material, which is available to authorized users.

Bio-guided search of active indole alkaloids from Tabernaemontana catharinensis: Antitumour activity, toxicity in silico and molecular modelling studies

Active plant metabolites have been used as prototype drugs. In this context, Tabernaemontana catharinensis (Apocynaceae) has been highlighted because of the presence of active indole alkaloids. Thus, this study aims the bio-guided search of T. catharinensis cytotoxic alkaloids. The chemical composition was identified by high-resolution mass spectrometry, and fractionation was performed by open column and preparative thin-layer chromatography, from plant stems. The enriched fractions were tested in vitro in tumour cells A375 (melanoma cell line) and A549 (adenocarcinomic human alveolar basal epithelial cells), and non-tumour Vero cells (African green monkey kidney epithelial cells). The alkaloids identified as active were submitted to in silico toxicity prediction by ADME-Tox and OSIRIS programs and, also, to molecular docking, using topoisomerase I (PDB ID: 1SC7) by iGEMDOCK. As a result, six sub-fractions were obtained, which were identified as containing 16-epi-affinine, 12-methoxy-n-methyl-voachalotine, affinisine, voachalotine, coronaridine hydroxyindoline and ibogamine, respectively. The affinisine-containing sub-fraction showed selective toxicity against A375, with an IC₅₀ of 11.73 µg mL^-1, and no cytotoxicity against normal cells (Vero). From the in silico toxicity test results, all indole alkaloid compounds had a low toxicity risk. The molecular docking data provided structural models and binding affinities of the plant's indole alkaloids and topoisomerase I. In summary, this bio-guided search revealed that the indole alkaloids from T. catharinensis display selective cytotoxicity in A375 tumour cells and toxicity in silico. Particularly, affinisine might be a chemotherapeutic for A375 melanoma cells.

Rare Thioglycosides from the Roots of Wasabia japonica

Six new thioglycosides (1-6) were characterized from the roots of Wasabia japonica along with a known analogue (7). Of these compounds, 1-3 possess a disulfide bridge connecting the carbohydrate motif and the aglycone, which is extremely rare in Nature. In particular, compound 1 forms an unusual 1,4,5-oxadithiocane ring system. The structures of the isolated compounds were determined through conventional NMR and HRMS data analysis procedure, and computational methods with advanced statistics were used for the configurational assignments of 1 and two pairs of inseparable epimers, 2/3 and 4/5. All compounds were evaluated for their anti-inflammatory, neuroprotective, and cytotoxic activities, with 1 showing weak anti-inflammatory activity (IC₅₀ 41.2 μM).

Alkaloids with neuroprotective effects from the leaves of Isatis indigotica collected in the Anhui Province, China

Six undescribed alkaloids, indiforine A-F, together with four known ones, were isolated from the leaves of Isatis indigotica Fortune. Their structures were elucidated on the basis of extensive spectroscopic analyses. The absolute configurations of indiforine A and B were determined by comparison of the experimental and calculated electronic circular dichroism spectra, as well as experimental and calculated optical rotations. The isolated alkaloids were evaluated for their neuroprotective activities against H₂O₂-induced cell injury in human neuroblastoma SH-SY5Y cells. The results showed that in H₂O₂-induced SH-SY5Y cell injury models, indiforine A and B exhibited potent neuroprotective activities. Further investigation of the most potent indiforine A by Hoechst 33258 staining and Annexin V/PI analysis demonstrated that it could protect SH-SY5Y cells from oxidative damage through inhibiting cell apoptosis.

Bioactive spiropyrrolizidine oxindole alkaloid enantiomers from Isatis indigotica Fortune

Four pairs of new alkaloids, isatindigotindoline A–D, were isolated from Isatis indigotica, and were evaluated for their anti-Aβ1–42 aggregation effects.

8,4'-Oxyneolignane glucosides from an aqueous extract of "ban lan gen" (Isatis indigotica root) and their absolute configurations

Three pairs of glycosidic 8,4'-oxyneolignane diastereoisomers, named isatioxyneolignosides A-F (1-6), were isolated from an aqueous extract of Isatis indigotica roots. Their structures and absolute configurations were elucidated by comprehensive spectroscopic data analysis and enzyme hydrolysis. The validity of ΔδC8-C7 values to distinguish threo and erythro aryl glycerol units and Cotton effects at 235±5 nm to determine absolute configurations at C-8 in 1-6 and their aglycones (1a-6a) are discussed.

Diglycosidic indole alkaloid derivatives from an aqueous extract of Isatis indigotica roots

Six new indole alkaloid diglycosides named isatigotindolediosides A-F (1-6), along with three known analogs (7-9), were isolated from an aqueous extract of the Isatis indigotica roots (ban lan gen). Their structures including the absolute configurations were determined by comprehensive spectroscopic data analysis, combined with enzyme or acid hydrolysis, and comparison of experimental circular dichroism (CD) and calculated electronic circular dichroism (ECD) spectra. In the preliminary assays, compounds 3, 5, and 8 showed antiviral activity against Coxsackie virus B3.

Indole alkaloid sulfonic acids from an aqueous extract of Isatis indigotica roots and their antiviral activity

Six new indole alkaloid sulfonic acids (1-6), together with two analogues (7 and 8) that were previously reported as synthetic products, were isolated from an aqueous extract of the Isatis indigotica root. Their structures including the absolute configurations were determined by spectroscopic data analysis, combined with enzyme hydrolysis and comparison of experimental circular dichroism and calculated electronic circular dichroism spectra. In the preliminary assay, compounds 2 and 4 showed antiviral activity against Coxsackie virus B3 and influenza virus A/Hanfang/359/95 (H3N2), respectively.

Aromatic compounds from an aqueous extract of "ban lan gen" and their antiviral activities

A pair of new diphenyl glycerol ether enantiomers (−)-1 and (+)-1 and two new methyl benzamidobenzoates 2 and 3, named (−)-(R)- and (+)-(S)-isatindigotrioic acid [(−)-1 and (+)-1] and isatindigoticamides A (2) and B (3), respectively, were isolated from an aqueous decoction of the roots of Isatis indigotica (ban lan gen). Their structures were elucidated by spectroscopic data analysis including 2D NMR experiments. The absolute configurations of (−)-1 and (+)-1 were assigned based on the CD exciton chirality method. Compounds 2 and 3 exhibited antiviral activities against HSV-1 with IC₅₀ values of 4.87 and 25.87 μmol/L, respectively. Compound 2 was also found active against Coxsackie virus B3 and LPS-induced NO production.

Phthalide derivatives from Ligusticum chuanxiong

Eleven new phthalide derivatives (1–11) have been isolated from the rhizome of Ligusticum chuanxiong.