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

Insight into tetrahydrofuran lignans from Isatis indigotica fortune with neuroprotective and acetylcholinesterase inhibitor activity

Nine tetrahydrofuran lignans, including three undescribed spiro-lignans, were isolated from Isatis indigotica Fortune (Brassicaceae). Extensive spectroscopic analyses achieved the structure elucidation of these tetrahydrofuran lignans, and quantum chemical calculation combined with the MAE_ΔΔδ parameter. Notably, isatispironeols A-B have a unique spiro[dienone-tetrahydrofuran] molecular core. These spiro[dienone-tetrahydrofuran] lignans showed comparable neuroprotective effects as the positive control in the H₂O₂-induced SH-SY5Y cells model. In addition, (-)-(7R,8S,1'R,7'R,8'R)-isatispironeol A possessed more significant AChE inhibitory activity, further interact sites were also predicted by the in silico assay.

Phytochemicals targeting nitric oxide signaling in neurodegenerative diseases

Neurodegenerative diseases are a set of diseases in which slow and progressive neuronal loss occurs. Nitric oxide (NO) as a neurotransmitter performs key roles in the stimulation and blockade of various inflammatory processes. Although physiological NO is necessary for protection against a variety of pathogens, reactive oxygen species-mediated oxidative stress induces inflammatory cascades and apoptosis. Activation of glial cells particularly astrocytes and microglia induce overproduction of NO, resulting in neuroinflammation and neurodegenerative disorders. Hence, inhibiting the overproduction of NO is a beneficial therapeutic approach for numerous neuroinflammatory conditions. Several compounds have been explored for the management of neurodegenerative disorders, but they have minor symptomatic benefits and several adverse effects. Phytochemicals have currently gained more consideration owing to their ability to reduce the overproduction of NO in neurodegenerative disorders. Furthermore, phytochemicals are generally considered to be safe and beneficial. The mechanisms of NO generation and their implications in neurodegenerative disorders are explored in this review article, as well as several newly discovered phytochemicals that might have NO inhibitory activity. The current review could aid in the discovery of new anti-neuroinflammatory drugs that can suppress NO generation, particularly during neuroinflammatory and neurodegenerative conditions.

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.

Functional Characterization of UDP-Glycosyltransferases Involved in Anti-viral Lignan Glycosides Biosynthesis in Isatis indigotica

Isatis indigotica is a popular herbal medicine with its noticeable antiviral properties, which are primarily due to its lignan glycosides such as lariciresinol-4-O-β-D-glucoside and lariciresinol-4,4'-bis-O-β-D-glucosides (also called clemastanin B). UDP-glucose-dependent glycosyltransferases are the key enzymes involved in the biosynthesis of these antiviral metabolites. In this study, we systematically characterized the UGT72 family gene IiUGT1 and two UGT71B family genes, IiUGT4 and IiUGT71B5a, with similar enzymatic functions. Kinetic analysis showed that IiUGT4 was more efficient than IiUGT1 or IiUGT71B5a for the glycosylation of lariciresinol. Further knock-down and overexpression of these IiUGTs in I. indigotica's hairy roots indicates that they play different roles in planta: IiUGT71B5a primarily participates in the biosynthesis of coniferin not pinoresinol diglucoside, and IiUGT1 primarily participates in the biosynthesis of pinoresinol diglucoside, while IiUGT4 is responsible for the glycosylation of lariciresinol and plays a dominant role in the biosynthesis of lariciresinol glycosides in I. indigotica. Analysis of the molecular docking and site-mutagenesis of IiUGT4 have found that key residues for its catalytic activity are H373, W376, E397, and that F151 could be associated with substrate preference. This study elucidates the biosynthetic route of anti-viral lignan glycosides in I. indigotica, and provides the foundation for the production of anti-viral lignan glycosides via synthetic biology under the heterologous model.

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.

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.

Indole-3-carboxaldehyde regulates RSV-induced inflammatory response in RAW264.7 cells by moderate inhibition of the TLR7 signaling pathway

Human respiratory syncytial virus (RSV) is highly contagious and the leading cause of severe respiratory tract illness in infants, elderly, and immunocompromised individuals. Toll-like receptor 7 (TLR7), a pattern recognition receptor recognising the ssRNA of RSV, activates proinflammatory pathways and triggers secretion of interferons (IFNs). On the one hand, the inflammatory responses help clear out virus. On the other hand, they lead to severe lung damage. Banlangen is a traditional Chinese herbal medicine commonly prescribed for respiratory virus infection treatment, but the mechanisms of action and active components remain largely unknown. In the present study, we investigated the effects of the main active components of total alkaloids from banlangen (epigoitrin, indole-3-carboxaldehyde, indole-3-acetonitrile and 4-methoxyindole-3-acetonitrile) on the RSV-induced inflammatory responses in mouse macrophage cells (RAW264.7). Our results demonstrated that RSV-induced IFN-α excessive secretion was moderately inhibited by indole-3-carboxaldehyde through downregulation of mRNA expression in a dose-dependent manner, in comparison, the inhibitory effects of ribavirin were too strong. Furthermore, we revealed that indole-3-carboxaldehyde suppressed transcription of IFN-α by inhibiting RSV-induced TLR7 expression in RAW264.7 cells. Additionally, indole-3-carboxaldehyde inhibited RSV-induced NF-κB signalling activation in a TLR7-MyD88-dependent manner. Together, our findings suggest that indole-3-carboxaldehyde inhibited RSV-induced inflammatory injury by moderate regulation of TLR7 signaling pathway and did not significantly affect the viral clearance competence of the innate immune system.