Indole alkaloid glucosides from the roots of Isatis indigotica

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.

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.

Lignans and a neolignan from an aqueous extract of Isatis indigotica roots

Four new lignans (1-4) and one new neolignan (5), along with two known lignan derivatives (6 and 7), were isolated from an aqueous extract of the Isatis indigotica root (ban lan gen). Their structures were determined by spectroscopic data analysis, chemical method, and theoretical calculation, for which 1 was proved by single-crystal X-ray diffraction. Compound 2 exhibited antiviral activity against influenza virus A/Hanfang/359/95 (H3N2) with an IC50 value of 11.1 µM and a selective index (SI) > 9, while 1 and 5 are the first examples of sulfonated lignan and neolignan from nature.

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.

Sulfonated alkaloids from an aqueous extract of Isatis indigotica roots

Eleven new sulfonated alkaloids (1 - 11) having diverse structures were isolated from an aqueous extract of the Isatis indigotica root (ban lan gen). Their structures were determined by spectroscopic data analysis, chemical method, and theoretical calculation, of which (-)-4 was proved by single crystal X-ray diffraction.

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.

Synthesis of Medicinally Important Indole Derivatives: A Review

Indoles constitute a widely occurring functional group in nature and are present in an extensive number of bioactive natural products and medicinally important compounds. As a result, exponential increases in the development of novel methods for the formation of indole core along with site-specific indoles have been established. Conventional methods for the synthesis of indoles are getting replaced with green methods involving ionic liquids, water as a solvent, solid acid catalyst, microwave irradiation and the use of nanoparticles under solvent-free conditions. In addition, there are immense applications of the substituted indoles in diverse fields.

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.

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.

Discovery, synthesis, and optimization of an N-alkoxy indolylacetamide against HIV-1 carrying NNRTI-resistant mutations from the Isatis indigotica root

From an aqueous decoction of the traditional Chinese medicine "ban lan gen" (the Isatis indigotica root), an antiviral natural product CI - 39 was isolated as an NNRTI (non-nucleoside reverse transcriptase inhibitor) (EC50 = 3.40 μM). Its novel structure was determined as methyl (1-methoxy-1H-indol-3-yl)acetamidobenzoate by spectroscopic data and confirmed by single crystal X-ray diffraction. Through synthesis and structure-activity relationship (SAR) investigation of CI - 39 and 57 new derivatives (24 with EC50 values of 0.06-8.55 μM), two optimized derivatives 10f and 10i (EC50: 0.06 μM and 0.06 μM) having activity comparable to that of NVP (EC50 = 0.03 μM) were obtained. Further evaluation verified that 10f and 10i were RT DNA polymerase inhibitors and exhibited better activities and drug resistance folds compared to NVP against seven NNRTI-resistant strains carrying different mutations. Especially, 10i (EC50 = 0.43 μM) was more active to the L100I/K103N double-mutant strain as compared to both NVP (EC50 = 0.76 μM) and EFV (EC50 = 1.08 μM). The molecular docking demonstrated a possible binding pattern between 10i and RT and revealed activity mechanism of 10i against the NNRTI-resistant strains.

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.

Sulfur-enriched alkaloids from the root of Isatis indigotica

Five new sulfur-enriched alkaloids isatithioetherins A-E (1-5), and two pairs of scalemic enantiomers (+)- and (-)-isatithiopyrin B (6a and 6b) and isoepigoitrin and isogoitrin (7a and 7b), along with the known scalemic enantiomers epigoitrin and goitrin (8a and 8b), were isolated and characterized from an aqueous extract of the Isatis indigotica roots. Their structures were determined by extensive spectroscopic data analysis, including 2D NMR and theoretical calculations of electronic circular dichroism (ECD) spectra based on the quantum-mechanical time-dependent density functional theory (TDDFT). Compounds 1-5 represent a novel group of sulfur-enriched alkaloids, biogenetically originating from stereoselective assemblies of epigoitrin-derived units. Isolation and structure characterization of 6a and 6b support the postulated biosynthetic pathways for the diastereomers 9a and 9b via a rare thio-Diels-Alder reaction. Compounds 2 and 4 showed antiviral activity against the influenza virus A/Hanfang/359/95 (H3N2, IC50 0.60 and 1.92 μmol/L) and the herpes simplex virus 1 (HSV-1, IC50 3.70 and 2.87 μmol/L), and 2 also inhibited Coxsackie virus B3 (IC50 0.71 μmol/L).

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).

C19-Diterpenoid alkaloid arabinosides from an aqueous extract of the lateral root of Aconitum carmichaelii and their analgesic activities

Eight new C₁₉-diterpenoid alkaloid arabinosides, named aconicarmichosides E–L (1–8), were isolated from an aqueous extract of the lateral roots of Aconitum carmichaelii (Fu Zi). Their structures were determined by spectroscopic and chemical methods including 2D NMR experiments and acid hydrolysis. Compounds 1–8, together with the previously reported four neoline 14-O-arabinosides from the same plant, represent the only examples of glycosidic diterpenoid alkaloids so far. At a dose of 1.0 mg/kg (i.p.), as compared with the black control, compounds 1, 2, and 4–6 exhibited analgesic effects with >65.6% inhibitions against acetic acid-induced writhing of mice. Structure–activity relationship was also discussed.

Tomentodione E, a new sec-pentyl syncarpic acid-based meroterpenoid from the leaves of Rhodomyrtus tomentosa

A new meroterpenoid, tomentodione E (1), along with four known ones (2-5) were isolated from the leaves of Rhodomyrtus tomentosa. Their structures were elucidated based on extensive spectroscopic data as well as computational methods. Compound 1 represents the first example of meroterpenoid possessing a sec-pentyl syncarpic acid motif coupled with a caryophyllene. Compounds 1-4 were evaluated for their in vitro antiviral activity against respiratory syncytial virus (RSV) with cytopathic effect (CPE) reduction assay, and 2 showed potent in vitro anti-RSV effect.

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.

Survey of natural products reported by Asian research groups in 2016

The new natural products reported in peer-reviewed articles in 2016 in journals with good reputations were reviewed and analyzed. The advances that Asian research groups made in the field of natural products chemistry in 2016 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on structural classification.

New iridoid glycosides from the fruits of Forsythia suspensa and their hepatoprotective activities

A novel iridoid glycoside trimer named forsydoitriside A (1) and five new iridoid glycosides (2-6) were isolated from the fruits of Forsythia suspensa together with two known compounds (7, 8). These new structures were elucidated by comprehensive spectroscopic data and the comparison of experimental and calculated electronic circular dichroism spectra. Compounds 1-8 were all assayed on acetaminophen-induced HepG2 cell damage. The results exhibited that compounds 2, 3, 5 and 6 possessed strong hepatoprotective activities against the damage in HepG2 cell.

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.